CNC PROGRAMMING & MACHINING. CONTEXT. 1.0 NC/CNC/DNC system 2.0 CNC Systems 3.0 CNC part programming (Fanuc & Siemens) 4.0 Speed and Feed 5.0 Cutting Tools 6.0 Inserts and Tool Holders 7.0 Clamping devices 8.0 3D programming and CAM 9.0 High speed machining 1
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CNC PROGRAMMING & MACHINING.
CONTEXT.
1.0 NC/CNC/DNC system
2.0 CNC Systems
3.0 CNC part programming (Fanuc & Siemens)
4.0 Speed and Feed
5.0 Cutting Tools
6.0 Inserts and Tool Holders
7.0 Clamping devices
8.0 3D programming and CAM
9.0 High speed machining
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1. NC/CNC/DNC SYSTEMS
NC TECHNOLOGY
1.1 INTRODUCTION
1.1.1 HISTORY OF NC TECHNOLOGY
We all know and heard the word automation. These machine works with primitive mechanical control system. The operating systems controlled by mechanical devices had their own advantages. As the industrial growth immersed the research and development of each company all over the world there engrossed with new ideas to bring out better machines which can deliver quality product in less time and with very little human effort. Scientists in Massachusetts institute of technology in the year 1948 started working on U.S. Air force concept projects to develop a computer packed controlling system for machine tools. The first ever numerically controlled (NC) machine, a hydraulic vertical spindle machine was built by Cincinnati Company in the year 1948. Then onwards a rapid technological advancement in the area of NC technology began.
In the year 1960, the NC machines built by Germans were displayed at the Hanover international trade fair. In the year 1965 the first batch of NC machines with automatic tool changer had appeared in the world market. In the year 1969, NC machines with pallet changing system was marketed. In the year 1972 the first batch of CNC incorporated system came in the world market.
In the year 1978 onwards the fast growth of CNC techniques was noticed. The features like graphic assisted path movements, interactive program inputs, scaling factors, mirror imaging etc. were incorporated in the machine memory system and side by side the computer integrated manufacturing developed and introduced.
1.1.2 NC TECHNOLOGY
Numerical control can be defined as an operation of machine tools by means of specifically coded instructions to the machine control system. The instructions are combinations of alphabet, digits and selected symbols. All instructions are written in a logical order and in a predetermined form. The collection of all instructions necessary to machine a part is called an NC program, CNC program or a part program. Such a program can be stored for future use and are used repeatedly to achieve identical machining results at any time.
The modern NC system uses internal micro processor. (i.e. a computer) this computer contains memory registers storing a variety of instructions that are capable of manipulating logical functions. That means the part programmer or the machine operator can change the program on the control itself. (At the machine). This flexibility is the greatest advantage of CNC system and probably the key element that contributed to such a wide use of technology in modern manufacturing.
The CNC program and logical functions are stored on special computer chips as software instructions.
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When describing a particular subject that related to the numerically controlled technologies, it is customary to use either the term NC or CNC, NC can also mean CNC but CNC can never refer to the term NC the old technology.
1.1.3 APPLICATIONS OF CNC MACHINES
CNC can be applied to all types of machines ranging from simple sawing machine to complex contour grinding machines. Major application areas as follows:
1. Metal cutting machines: CNC milling, CNC turning, CNC drilling/jig boring, gear cutting CNC grinding etc.
2. Metal forming machines: Press tools, Injection/ Blow Moldings / Die casting machines tube bending etc.
3. Non – Conventional machining processes such as, EDM Die- sinking and EDM wire cut machines, Plasma Arc cutting machines. Electron beam machining, Laser beam machining, Ion beam machining, Ultrasonic Machining, etc.
4. Welding machines: TIG, MIG, Submerged Arc welding, etc.5. Inspection and quality control systems: CMM, LMM6. Assembly, Testing and Des-patch equipment and7. Tool and work handling systems.
Today the CNC concepts are applied to every aspect of manufacturing and its area of applications is widening day-by-day. The well known statement saying CNC machines are ideal for small and medium batch production is no-longer valid and now-a-days CNC is finding increasing applications in transfer lines, special purpose machines and even in single purpose machines producing one-off components.The rapid evolution of CNC technology transformed the complete manufacturing technology and leads to modern concepts of CIM- Computer integrated Manufacturing and Engineering.
1.1.4 ADVANTAGES AND DISADVANTAGES OF CNC MACHINE
ADVANTAGES:
i).REDUCED NON PRODUCTIVE TIME:It accomplishes this by means of fewer set ups, less time in setting up, reduce work piece handling time, automatic tool changes on some machines etc.
ii).CONSISTENT CUTTING TIME (Cutting time):CNC machining is under the control of a computer. The main benefit of a consistent cutting time is for repetitive jobs where the production scheduling and work allocation to individual machine tools can be done very accurately.
iii).GREAT MANUFACTURING FLEXIBILITY:Can easy to modify engineering changes, alterations of production schedule etc.
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iv).IMPROVED QUALITY CONTROL:
CNC produces part greater accuracy, reduced scrap and inspection frequencies.
v).REDUCED INVENTORY:
Due to fewer setups and more operation using same tool, the amount of inventory carried by the company is reduced.
vi).REDUCE FLOOR SPACE REQUIREMENTS:
Since one CNC machine can often accomplish the production of several conventional machines, reduce floor space .
DISADVANTAGES:
i).HIGHER INVESTMENT COST:
The capital investment cost is high ,because of advanced design.
ii).HIGHER MAINTENANCE COST:
Because CNC is a more complex technology the maintenance problems become more acute. Maintenance cost for CNC machines will generally be higher than conventional machine tools.
ii). SKILLED PERSONNEL:
For effective utilization of cnc machine requires skilled programmer,setter,and maintenance personnel.
2. CNC SYSTEM
The advantages derived from CNC machines are due to their salient constructional features listed below.
2.1MACHINE STRUCTURE
High rigidity High stiffness to weight ratio Thermal stability Good damping characteristics
2.1.1SLIDE WAYS
Antifriction bearing elements like re-circulating ball packs, re-circulating ball bushings. Hydrostatic or Aerostatic slide ways. Plastic or non-metallic liners like PTFE (Poly Tetra Fluro Ethylene), Turcite B, etc.
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2.1.2 SPINDLE DRIVE
Wide spindle speed range to meet cutting parameters DC motors with silicon controlled rectifier drive or AC motors with variable frequency. Spindle orientation for Automatic Tool change and fine boring applications.
2.1.3FEED DRIVE
Slides are actuated by precision re-circulating ball screw mechanism driven by servo motors. DC motors with silicon controlled rectifier drive or AC motors with variable frequency.
2.1.3 FEED-BACK SYSTEMS
The accuracy of positioning in any CNC machine achieved by measuring the position or displacement of the slide and comparing it with the commanded position as per the part program. The servo system then actuates the slide such that the error, which is the difference between actual position and commanded position, is brought to zero. That is why CNC is called “Error driven systems”. The position measuring devices could be direct or indirect depending upon whether the device is fitted directly in the slides or at the end of the ball screw.
Some of the measuring devices are linear inductosyns, Optical scales with gratings, rotary encoders, rotary inductosyns, brush less synchro resolvers, etc.
2.1.4 AUTOMATIC TOOL CHANGER (ATC)
Automatic Tool Changer (ATC) is an important element of machining centers responsible for increase in productivity by reduction of idle time during tool change. Present day CNC machines are equipped with ATC units capable of performing tool changes within 3 to 7 seconds.
In act ATC unit, the tool magazine can be drum type with capacity up to 40 tools or chain type with capacity up to 132 tools.
The tool change arm can be of single gripper type or of double gripper type.
The tool selection can be of Sequential type (applicable for less no, of tools and consuming more time) or of Random type (applicable for more no. of tools and consuming less time).
The latter type is more commonly used.
2.1.5 AUTOMATIC PALLET CHANGER (APC)
Similar to ATC the Automatic pallet changer (APC) aids in increase of productivity by reducing the job setup time considerably. The function of the pallet changer is to
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interchange the pallet on the machine that one pallet has the finished component and the other pallet with newly loaded component. The pallet when transferred from the Pallet changer on the machine gets located and clamped with heavy clamping force either hydraulically or mechanically.
APC could be of dual pallet type or multiple pallet pool type.
2.1.6 SOME OF THE OTHER SALIENT FEATURES
Thermal stabilization of headstock, feed drive elements and machine structural elements by re-circulating refrigerated oil.
Axial calibration for all fixed mechanical elements.
Lost motion compensation for backlash, axial and torsional deflections.
Usage of Touch trigger probes for post process metrology purpose, tool condition monitoring. Tool measurement and setting of tool offsets and thermal error compensation.
Centralized lubrication of slides, etc, controlled by timer or soft ware.
Coolant systems of either flood type or mist type.
Chip conveyors for collection and disposal of chips.
Auto diagnostic facilities to aid for maintenance and service personnel.
2.2 SLIDE ACTUATION IN CNC MACHINES:
In a conventional machine hand wheels actuate slides. Occasionally when automatic feed is needed the slides are power driven from the machine spindle.
BASIC ELEMENTS OF SLIDE MECHANISM IN CNC
A
A
A
B BB
PULSESAMPLIFIER
SLIDE
LEAD SCREW
MOTOR
MCU (Machine control unit)
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But in a CNC machine the story is quite different. Here the hand wheels are replaced by motors and each slide has its won independent motor. The motor speed can be infinitely varied to get the desired feed rate. A schematic diagram of the slide actuation mechanism of a CNC machine is shown. This diagram is rather an oversimplified one and is given only to understand the fundamental principle of slide actuation. The following description will help understand its working.
MCU reads the program as soon as it receives the start signal from the operator. It processes the instruction and sends out low-level electrical pulses. (voltage) An amplifier magnifies these low voltage pulses high enough to drive the motor. The motor rotates and drives the lead screw and this in turn causes the slide to move.
The number of pulses sent by the MCU would depend on the following facts.
M/c. resolution Feed rate Distance to be traveled
2.3 MACHINE RESOLUTION:
Every single pulse sent out by the MCU causes the slide to move a specific distance and machine resolution is the distance moved by the slide for a single pulse. Thus a resolution of 0.001 would mean that the slide would move 0.001mm for every pulse. In other words for a travel of 1mm the MCU will send out 1000 pulses.
2.3.1 PULSE FREQUENCY:
The number of pulses sent out by the MCU every second is called pulse frequency and the input voltage to motor depends directly on this factor. The pulse frequency is not a constant value. It depends on the required feed rate and the machine resolution.
Pulse frequency = Feed rate in mm/min / M/c resolution x 60. pulse / second.
As the resolution is constant for a given machine the pulse frequency may be taken as directly proportional to the feed rate.
It may thus be concluded that as the MCU read the instruction it sends out pulses at frequencies corresponding to the desired feed rates. Since the input voltage to the motor is proportional to the pulse frequency, the motor speed is automatically adjusted to achieve the desired feed rate.
Example1. Determine the pulse frequency for a feed rate of 30mm/min if the M/c resolution is 0,001 mm.Solution: Pulse frequency = Feed rate in mm/min
----------------------------- M/c resolution x 60
= 30 / 0.001 x 60
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MACHINECONTROL UNIT
DRIVE MOTOR
MACHINE SLIDEDISPLACEMENT
OPEN LOOP SYSTEM
ENCODER
TRAVERESEMEASUREMENTSLIDEDRIVE MOTOR
COMPARATORCOMMAND VALUE
ACTUAL VALUE
FEED BACK SIGNALS
CONTROL COMPUTER
PROGRAM INPUT
CLOSED LOOP SYSTEM
= 500 pulses/sec.Example2. Determine the number of pulses in the above example for a travel of 40mm.
Solution: No. of pulses = Distance to travel -------------------------
Resolution
= 40 / 0.001= 40,000 pulses.
2.4 FEED BACK CONTROL SYSTEM
Based on feed back control NC system is classified as follows:
2.4.1 OPEN LOOP SYSTEM:
In an open loop control system hsa no provisions for detecting or comparing the cutting tool movement with the commanded value.These systems are not used where extremely accurate positioning is required.
2.4.2 CLOSED LOOP CONTROL:
In closed loop control system has provisions for detecting or comparing the cutting tool movement with the commanded value. A closed loop control has a device called encoder and this can continuously ascertain the distance actually travelled by the tool and then monitor the same by feedback signals to the control. The control takes corrective action in case any error is detected .
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2.5 MOTION CONTROL SYSTEM
Based on the motion control system the NC machine is classified as follows:
NC MOTION CONTROL SYSTEM:
There are three basic type of motion control systems.1. Point to point2. Straight cut3. Contouring
2.5.1 Point to point: Machines with point-to-point control provide only one feed axis while the other two axes can perform only rapid motion. E.g.: Drilling
POINT TO POINT CONTROL
2.5.2 Straight cut: This system provides feed motion in two axes (but not simultaneously) and hence their capability is limited to performing operation either along X-axis and Y-axis.
STRAIGHT CUT CONTROL
2.5.3 Contouring: This can provide feed control in three axes. They are also capable of providing simultaneous feed in 2 or 3 axes. Milling machine with contouring control can mill contours made up of straight lines and arc/circular elements. Depending on the number
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of axes that can be simultaneously fed, contouring controls are further classified as 2D control, 21/2D control and 3D control.
CONTOURING CONTROL
2.5.3.1 2D control: Machines with 2D control can have simultaneous feed only in two or three axes. They can mill only contours with constant depth that too in just one plane. (X,Y)
2-D CONTOURING CONTROL
2.5.3.2 21/2D control: Machines with 21/2D control can have simultaneous feed of any of the two axes X-Y, X-Z, Y-Z and hence they can mill contours (of constant depth) in any one of the three planes.
2-1 DCONTOURING CONTROL
2.5.3.3 3D control: Machines with 3D control can have simultaneous feed in 3 axes. These controls can performs contours of increasing or decreasing depth, such as is required in helical milling.
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3-D CONTOURING CONTROL
2.6 Co Ordination of slide movement (INTERPOLATION)Interpolation is the technique by which a cnc machine axes (minimum two) simultaneously moves to facilitate machining in angular or circular paths, in mathematical sense “it means to manipulate the axes in between two given values”.
The system execute the given axes co-ordinates in order to decide the correct pulse rate/feed rate for individual axis. To do this the system divides the tool path into short straight line segments as shown below.
2.7 AXIS DRIVE
Servomotors control the entire axis in a CNC machine. The movement along the different axis is required either to move the cutting tool or the work material to the desired positions.
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MCU (Machine control unit)
PULSES FOR PROGRAMMED FEED RATE
PULSES FOR Y-AXIS
PULSES FORX-AXIS
INTERP-OLATOR
PRINCIPLE OF INTER POLATION
1
2
3
4
5
X1
X2
X3
X4
Y1
Y2
Y3
Y4
1
23
45
X1,X2,X3 AND X4 ARE EQUALY1,Y2,Y3 AND Y4 ARE EQUAL
X1,X2,X3 AND X4 ARE NOT EQUALY1,Y2,Y3 AND Y4 ARE NOT EQUAL
X1
X2
X3X4
Y1
Y2Y3
Y4
In order to accomplish accurate control of position and velocity, stepper motors are used for axis drive. The principle of working of a stepper motor is that on receiving a signal i.e. pulse, from the control unit, the motor spindle will rotate through a specified angle called step. The step size depends on the design of the motor and lies between 1.8 degree and 7.5 degree, which means that one rotation of the spindle can be divided into 200 parts. If a single pulse is received from the control system the motor spindle will rotate by one step. The control unit generates pulses corresponding to the programmed value of movement required for the tool or work. The rate of movement of tool or work is controlled by the speed at which the pulses are received by the stepper motor. The rate at which pulses are sent to the stepper motor is accurately governed by the control system. Hence there is no need of providing positional or velocity feedback system. The use of stepper motor considerably simplifies the system, as the feed back devices are not used. The cost of the machine tool is also less. However stepper motors are suitable only for light duty machines due to low power – output.
2.7.1 BALL LEAD SCREW
Reciprocating ball screw and nut
Ground thread screwNut
Recirculating ballsBall return tube
2.7.2 METALLIC & NON-METALLIC GUIDE WAYS
In the conventional machine tools, there is direct metal-to-metal contact between the slide way and the moving slides. Since the slide movements are very slow and machine utilization is also low, this arrangement is adequate for conventional machine tools. However, the demand on slide ways is much more in CNC machines because of rapid movements and higher machine utilization. The conventional type of arrangement with
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metal-to-metal contact does not meet the requirement of numerically controlled machine tools. The design of slide way in CNC machine tools should:
(a) Reduce friction(b) Reduce wear(c) Satisfy the requirements of the movement of the slides(d) Improve smoothness of the drive.
To meet these requirements in CNC machine tool slide ways, the techniques used include hydrostatic slide ways, linear bearing with balls, rollers or needles and surface coating.
2.8 THE ADVANTAGES OF USING BALL SCREW AND NUT ASSEMBLY :
i).HIGH EFFICIENCY:
As compared to conventional lead screw the efficiency of ball screw and nut assembly is very high (over 90%). The power requirement for the ball screw arrangement is also less due to reduced friction.
ii). REVERSIBILITY: The ball screw and nut assembly is reversible which makes it possible to back drive the unit i.e. by applying axial force to either nut or screw, the unconstrained member can be made to rotate.
iii). WEAR AND LIFE:
The re-circulating rollers reduce wear to a minimum and the ball screw, therefore, has longer life without loss of accuracy.
iv).NO STICK SLIP:
Stick slip is the phenomenon, which occurs when small movements between two lubricated elements. The lubricating medium tries to cause the mating elements to stick to each other to resist motion and results in a jerky motion as the mating elements try to stick and then slip during their relative movement. Since the sliding metal-to-metal contact is substituted by rolling contact, the stick-up phenomenon is eliminated in the ball screw and nut assembly.
2.9 DIFFERENT FEED BACK DEVICES
There are three types of feedback devices being used in CNC machines. They are,
a) Velocity feedback devices.b) Position feedback devices.
c) Linear position measuring transducers.
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2.9.1 VELOCITY FEEDBACK DEVICES
A device called Tachogenerator normally provides velocity feedback. It generates voltage output, which is proportional to its speed. The tachogenerator is normally built in the servomotor case and is directly fitted on the servomotor shaft. The output voltage from the tachogenerator is used as feedback to monitor the motor speed. Rotary encoders are also used to provide feedback for velocity control.
2.9.2 POSITION FEEDBACK DEVICES
The ideal method of measuring the displacement or position of the cutting tool is to continuously measure the position of the cutting tool edge relative to the datum point The positional feedback is provided by measuring the slide movements with measuring devices. The position measuring devices used are either rotary or linear measuring transducers.
2.9.3 LINEAR POSITION MEASURING TRANSDUCERS
Linear position measuring transducer also operates on the photoelectric principle. The linear measuring system measures the displacement of the machines lies from a fixed datum. A linear measuring system consists of a precision linear scale engraved with close spaced alternate transparent and opaque parallel lines as one unit and a photocell and light source as the second unit. One of the units is fixed on the stationary element of the machine tool and the other unit is fixed to the moving worktable. A pulse is generated by the photocell as it is exposed to light source through the transparent areas of the linear scale. From the known number of the engraved lines per unit length on the linear scale and by counting the pulses, the displacement of the worktable can be established.
The linear system may have either a glass scale in which light passes through the transparent area or a stainless steel scale in which the light is reflected from the transparent areas.
2.9.4 ROTARY OR ANGULAR POSITION MEASURING TRANSDUCERS
Angular position measuring transducers operates by measuring the angular speed of a rotating element, normally of a lead screw, from the known value of lead screw, movement of worktable or machine slide is calculated by control system. Most commonly used angular position measuring transducers operate on the photoelectric principle. The transducer consists of a disc fitted on the axis of lead screw. The disc made up of uniform alternate transparent and opaque areas. A light source is fitted on one side of the disc and photocell on the other side. When the disc rotates with rotation of the lead screw, the photocell and light source. The photocell gives output voltage based on the intensity of light falling on it and the output from photocell resembles a sine-wave, which is converted into square shaped pulses to make it useful for control purposes. the rotary speed of the lead screw is calculated from the known number of lines engraved on the rotating disc. The displacement of the slide is then calculated from the lead of the lead screw. The direction of the rotation of lead screw is sensed by putting a second photocell in the circuit. Position measurement by angular position measuring transducer is indirect as the output of the transducer has to be converted into table displacement.
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2.10 TRANSDUCERS / ENCODERS
Transducers are used in CNC machines to trace the movement of members for feed back information. Transducer converts into electrical signals which in turn are recognized by the comparator for controlling the movement. Movement of liver and rotary movements can use optical or electrical transducers.
Two photocells sense direction of movement by phase difference – figure.Photocell 2
Photocell 1
Angular position measuring transducer
photocellLight source
Leadscrew Radial grating disc
Linear positioning measuring transducer
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Work table
Linear grating
Photocell
Lightsource(fixed)
Photocell Mounting
2.11 AUTOMATIC TOOL CHANGER (ATC):
An automatic tool changer (ATC) is an important part of a machining center. An ATC picks up a tool from the magazine and keeps it ready for swapping with the tool in the spindle, which is presently cutting. The time for tool change varies between 3 to 7 seconds. The ATC plays a significant role in reducing idle time during tool change operations. There are a number of different designs for automatic tool changers.
2.12 AUTOMATIC PALLET CHANGER (APC):
For machine with Automatic pallet changer (APC) the table is replaced by pallets. The function of the pallet changer is to interchange the pallet on the machine, in which one pallet has the finished component, and the other pallet with newly loaded component.
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2.13 AUTOMATIC SCRAP REMOVAL MECHANISM:
CNC machines are designed to work at optimum cutting conditions with the improved cutting tools on a continuous operation basis. Since the cutting time is much more in CNC machines, the volume of scrap generated is also more. Unless the scrap is quickly and efficiently removed from the cutting zone, it can affect the cutting process. In addition some auxiliary function like automatic component loading or automatic tool change may also be affected by accumulation of scrap. To avoid these problems an efficient scrap control system should be provided with CNC machine tools with some mechanism to remove the scrap from the cutter and cutting zone and for the disposal of scrap from the machine tool area itself.
2.14 SINUMERIK [810 D / 840 D/ 840Di]
OPERATION
The control systems 810D/840D/840Di are based on an open control concept which allows the machine manufacturers (and partially also you as the user) to configure the control system according to individual requirements. That’s why it is possible that there will be differences in the manual as regards the sequences of action.
2.14.1OVERVIEW OF THE CONTROL SYSTEM
Structure and handling of the control system components “Keyboard” and “display”
• OP 010C operator panel for nt with TFT color screen, soft key bars and mechanical CNC full keypad with 65 keys
These components are used mainly for the programming and processing of data.
• Machine Control Panel with override potentiometers
This control panel influences the machine movements directly.
To a certain degree, it can also be configured by the machine manufacturer according to the customer’s requirements.
SI.No FEATURE DESCRIPTION
1.0 Turning on After turning on, the control system is in the machine operating area. The main menu is displayed in the active machine operating area.
1.1 Area Switchover
1.1.1 Menu selected By using menu selected on the slim line operator panel <Area switchover>key you can unhide the main menu with six operating areas of the control system.
1.1.2 Parameter Change with the soft key to the parameter operating area. The parameter are extended to manage your tools and the label zero offsets
1.1.3 Program In this operating area you can write & simulate NC programs
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1.1.4 Services In this operating area you can manage files and receive them in and out via the serial interface or a floppy disk
1.1.5 Diagnosis Alarm & service information are displayed & documented here
1.1.6 Startup This operating area is intended for system engineers in order to adapt NC data to the machine.
1.2 Turning off Trip the main switch to disconnect the system from the mains
2.1 Keyboard and screen layout(slim line operator panel)
2.1.1 Key H1-H8 By using horizontal soft keys (numbered for m the left to right) you can change between operating areas, with one operating are, you get into further menu areas and functions which can be called via vertical soft keys.
2.1.2 Key V1-V8 By using the vertical soft keys (numbered for m top to the bottom) you activate functions or branch to further sub functions which are called via vertical soft key bar.
2.1.3 Menu Select By using the area switchover key the main menu with the operating system is displayed.
2.1.4 etc (>) By using the etc key, you extend the horizontal soft key bar.
2.1.5 Machine (M) By using Machine key you can directly go to the operating area (Machine)
2.1.6 Recall (^) The Recall key closes the window on top and lets you return to the higher level
2.1.7 Page up & Page down These keys are used to move the scrollbar of a window allowing you to scroll through long part programs
2.1.8 End By pressing this key, you can move the cursor to the end of the line
2.1.9 Selection or toggle key By pressing these keys on the numeric key groups with NUM LOCK”
2.1.10 Delete By pressing this key you can delete the selected character of the value of the input field.
2.1.11 Backspace You can delete the character to the left of the cursor with this key
2.2 Mechanical control panel
2.2.1 Emergency stop Emergency stop, stops all drives as fast as possible
2.2.2 Cycle start This key is intended mainly to start the execution of program
2.2.3 Cycle stop By pressing this key you stop the execution of the current program. Then you can continue the execution.
2.2.4 Reset By pressing this key, you can interrupt the program execution of the current program, messages are cleared and the control system is reset to the initial state.
2.2.5 Single block This key allows you to execute a program block by block. If the single block function is effective either of the entries SBL1, SBL2 or SBL3 is displayed in the channel.
The program execution stops automatically after each block and can be contained with cycle start. Pressing single block again lets you to return to the following block.
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i) FEED HOLD: When Feed hold button is pressed during a rapid motion, it will immediately stop the motion. This action applies to all the axes active at that time. Operations like threading or tapping cannot be stopped by this way.
ii).EMERGENCY STOP: Every machine has a button marked as emergency stop or E-stop. When this button is pressed all the motions will stop immediately. This top switch is mandatory safety feature on all the CNC Machines.
iii).MANUAL DATA INPUT: [MDI]
A CNC Machine is not always operated by means of a program. During a part setup, the CNC operator has to do a number of operations that require physical movements of the machine slides, rotation of a spindle, tool change etc. There are no mechanical devices on a CNC machine. The handle (Manual pulse Generator) is an electronic, not a mechanical unit. In order to operate a CNC machine without conventional devices the control system offers a feature known as Manual Data Input.
The Manual Data Input enables the input of a program data into the system one program instruction at a time.
To access the MDI mode, the MDI key on the operation panel must be selected. That opens the screen display majority of the programming codes are allowed in the MDI mode.
iv).RAPID FEED RATE OVERRIDE
This switch allows temporary rapid motion settings which modifies the rapid motion of the machine tool. This switch can be set to one of the four settings. Three of them are marked as the percentage of the maximum rate, typically as 100%, 50% and 25%. By switching to one of them, the rapid motion rate changes.
The fourth position of the switch often has no percentage assigned and is identified as an F1 which can be customized for the user needs. In this setting, the rapid motion rate is even slower than 25%.
v).SPINDLE SPEED OVERRIDE
It modifies the programmed spindle r/min. If the programmed spindle sped is too high or too low, it may be changed temporarily by this switch. Overriding the programmed spindle speed on the CNC machine should have only one purpose – to establish the spindle speed rotation for the best cutting conditions.
Vi).FEED RATE OVERRIDE
The most commonly used override switch is one that changes programmed feed rates. The new Feed rate calculation based on the overridden federate setting is
Fn = Fp x p x 0.01
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vii).DRY RUN OPERATION
This is a special kind of override. It only has a direct effect on the federate and allows much higher federate that is used for actual machining. Its purpose is to test the integrity of the program before the CNC operator cuts the first part.
Dry Run can be used in combination with several other features of the operation panel.
viii).Machine Lock
When this function is enabled, the motion of all axes is locked. This gives a chance to test the program with virtually no chance of a collision. When this lock is enabled, only the axis motion is locked but all other functions are executed normally.
CNC MACHINES CONTROL SYSTEM
Feature DescriptionON \ OFF Switch Power and control switch for the main power and
the control unit. Cycle start Starts program execution or MDI commandEmergency stop Stops all machine activity and turns off power to
the control unitFeed hold Temporarily stops motion of all axes Single block Allows program run one block at a time Optional stop Temporarily stops the program execution (M01
required in program)Block skip Ignores blocks preceded with a forward slash (/) in
the programDry run Enables program testing at fast federates (without
a mounted part)Spindle override Overrides the programmed spindle speed, usually
within 50-120% rangeFeed override Overrides the programmed federate, usually
within 0-200% rangeChuck clamp Shows current status of the chuck clamping
(outside / inside clamping)Table clamp Shows current status of table clampingCoolant switch Coolant control ON / OFF / AUTOGear selection Shows current status of working gear range
selectionSpindle rotation Indicates spindle rotation direction (clockwise or
counter clockwise)Spindle orientation Manual orientation of the spindle Tool change Switch allowing a manual tool change Reference position Switches and lights relating to setup of the
machine from reference positionHandle Manual pulse generator (MPG), used for axis
select and handle increment switchesTailstock switch Tailstock and/or quill switch to manually position
the tailstockIndexing table switch
Manually indexes machine table during setup
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MDI mode Manual data input modeAUTO mode Allows automatic operationsMEMORY mode Allows program execution from the memory of the
CNC unit.TAPE mode Allows program execution from an external
device, such as a desktop computer or a punched tape
EDIT mode Allows changes to be made to a program stored in the CNC memory
MANUAL mode Allows manual operations during setupJOG mode Selects the jog mode for setupRAPID mode Selects the rapid mode for setupMemory access Key (switch) to allow program editingError lights Red light indicating an error
2.15 AXES DESIGNATION
2.15.1 Typical configuration of a two axis slant bed CNC lathe – rear type
HEADSTOCK
CHUCK
JAWS
TOOL
TAILSTOCK
CENTRE
QUILL
X+
X-
Z- Z+
Schematic representation of a vertical CNC lathe
Z+
Z-
X- X+
21
AXES OF CNC MACHINES:Z
Y
X
+Y
+Z
+X
+Z
+X
+Y
VERTICAL MILLING MACHINE HORRIZONTAL MILLING MACHINE
3.0 CNC PART PROGRAMMING
3.1 CO-ORDINATE SYSTEMS
3.1.1 DEFINING A POINT IN A PLANE
The point of intersection of two axes is called zero point..
CNC machine has two methods of specifying the zero point.
1. Fixed zero: The origin is always located at the same position on the machine table.
2. Floating zero: The reference point for current dimensions is from previous position. It is called floating zero. The zero point should be located based on part programming convenience.
22
3.1.2 LINEAR AND ROTARY ZERO OFFSET
i).LINEAR ZERO OFFSET:
There are work pieces in which the dimensions are distributed from several points. In such cases the co-ordinate system can be relocated in the course of machining operation. This procedure is called ‘zero offset’.
20
70
2035
22
50
LINEAR ZERO OFFSET
100
ii).ROTARY ZERO OFFSET:
In case of dimensions given in an angular way the co-ordinate system may be rotated about the zero point.
20
70
2030
40
30
R20
40
ROTARY ZERO OFFSET
100
Linear and rotary zero offset save you lot of co-ordinate calculations and avoid mistakes during calculations. The transformation of co-ordinate is carried out by the control system.
3.2 CO-ORDINATE SYSTEM
3.2.1 CARTESIAN CO-ORDINATE SYSTEM (Rectangular):
The method of defining a point in space by specifying its distance in x, y and z axes from a reference point is called Cartesian co-ordinate system.
23
X
Y
0
0
P1
P0
X1
Y1
CARTESIAN COORDINATES
3.2.2 POLAR CO-ORDINATE SYSTEM:
The method of defining a point in space by specifying its distance from a pole and the angle between the line from the pole to the point and the main axis of the co-ordinate system.
ANGLE
P0
P1
0
0J
I
DISTANCE
POLAR COORDINATES
.
3.3 METHOD USED FOR SPECIFYING THE TOOL MOVEMENT:
Absolute positioning & incremental positioning:
Absolute positioning means that the tool locations are always defined in relation to the zero point. But in incremental positioning the next tool location must be defined with reference to the previous tool location.
P1
P2
P3
Absolute & Incremental Positioning
24
POINTS IN ABSOLUTE METHOD POINTS IN INCREMENTAL METHOD
Generally the program is
created with the absolute command. In incremental command, if a co-ordinate value is mistaken, next values become improper. The incremental command is applied for pitch machining of constant interval.
3.4 FUNDAMENTALS OF PROGRAMMING
The control system can move a tool along any straight line or circular path. For this, control system should know,
- The target position. (To define the point using Cartesian co-ordinate X, Y and Z)
- Cutter path (straight line/circular path/rapid traverse rate)- Feed rate- Spindle speed etc.
i).PROGRAM:
A set of machine codes (G, M, axis X, Y, Z) in sequence forms the program. This program command the machine to move correct target position.
ii).SUB PROGRAM:
Sub program or subroutine program means, a separate program will nesting with the main program to minimize main program length, while working with more different operation.
iii).MACRO PROGRAM:
Macro programs are master template programs created to perform a particular task and these programs are used to repeat the operation on many jobs. The macro program can be called from other main programs.
PROGRAM BLOCKS
N10 G01 X50 Y100 Z30 F100 S1000
Block number Type of Target co-ordinate Feed rate Spindle speedMovement
3.5 TERMS IN PROGRAMMING:
Point
X Y
P1 X20 Y20P2 X50 Y50P3 X30 Y70
Point
X Y
P1 X20 Y20P2 X30 Y30P3 X20 Y-20
25
i).PROGRAM NUMBER:
a) The program number functions as addressing symbol for accessing a program.b) The program number is expressed by four digits numerals after the alphabet ‘O’. c) Numerals from 0001 to 9999 can be used. E.g. O4090.d) The program number can be input with numbers of smaller than 4 digits.e) The same number cannot be used twice.
ii).SEQUENCE NUMBER:
a) The sequence number is used to - Search- Callout the position is being executed.- The position you want to edit in the program easily.b) Sequence number is expressed by numerals of 5 digits or less after the alphabet
‘N’.c) Numerals from 1 to 99999 can be used. E.g. N1 or N01 or N001.d) Generally sequence numbers are inserted into important places of the program.
(Beginning of each block). If a program is over memory capacity, eliminate the sequence number to save memory capacity.
iii).PART PROGRAM:
Part program is used to process the machining and movement of machine to achive required shape.
iv).ADDRESS:
The address is expressed by the alphabets.
E.g. G00 X100 Y100
ADDRESSv).DATA:
Numerals (including the sign and decimal point) succeeding to the address are called data.
E.g. G00 X100 Y100
DATAvi).WORD:
Word is minimum unit for specifying the functions. It consists of the numerical values (data) including the address and sign.
E.g. G00 X100 Y100
26
WORDvii).BLOCK:
► Block consists of words.► Block is the minimum unit necessary to operate a machine.► On the program each one line corresponds to one block.
E.g. G00 X100 Y100 Block
3.5 NC WORDS
The different words used in the CNC are
1) G-Code (Preparatory code):
This word is used to prepare the NC controller for instructions that are to follow.For eg: G02 is used to prepare the NC controller unit for circular interpolation along an arc in the clockwise direction. There are two types of G codes modal codes and non model codes. Modal codes remain active until cancelled by a contradictory code. Eg: G01, G02, G03 etc.Non modal codes are active only in the block in which they are programmed.
X, Y & Z codes (Coordinates):
These give the coordinate positions of the tool. In a two-axes system, only two of the words would be used. In a four or five axes machine, additional words would specify the angular position. (A, B & C)
2. F-Code (Feed rate):
This specifies the feed in a machining operation. Units are inches/minutes or mm/minute.
3. S-Code (spindle speed):
This specifies the spindle speed, the rate at which the spindle rotates.
4. T-Code (Tool selection):
This word would be needed only for machines with a tool turret or automatic tool changer. The T-word specifies which tool is to be used in the operation. E.g. T05 might be the designation of tool location 5 on an turret/ magazine.
5. M-Code (Miscellaneous function):
27
The M-code is used to specify certain miscellaneous or auxiliary functions, which may be available on the machine tool.E.g. M03 to start the spindle rotation.
3.6 G CODES FOR TURNING & MILLING
CODE
TURNING MILLING
G00 Rapid Positioning Rapid positioningG01 Linear Interpolation Linear InterpolationG02 Circular interpolation clockwise Circular interpolation clockwiseG03 Circular interpolation counterclockwise Circular interpolation counter clockwiseG04 Dwell (as a separate block) Dwell (as a separate block)G09 Exact stop check – one block only Exact stop check – one block onlyG10 Programmable data input (data setting) Programmable data input (data setting)G11 Data setting mode cancel Data setting mode cancelG15 - Polar coordinate command cancelG16 - Polar coordinate commandG17 - XY plane designationG18 - XZ plane designationG19 - YZ plane designationG20 English units of input English units of inputG21 Metric units of input Metric units of inputG28 Machine zero return (reference point1) Machine zero return (reference point1)G40 Tool nose radius offset cancel Cutter radius compensation cancelG41 Tool nose radius offset left Cutter radius compensation – leftG42 Tool nose radius compensation right Cutter radius compensation – right G43 - Tool length compensation – positive G44 - Tool length compensation – negative G49 - Tool length offset cancelG50 Tool position register/Maximum r /min
presetScaling function cancel
G51 - Scaling functionG52 Local coordinate system setting Local coordinate system settingG53 Machine coordinate system setting Machine coordinate system settingG54 Work coordinate offset 1 Work coordinate offset 1G55 Work coordinate offset 2 Work coordinate offset 2G56 Work coordinate offset 3 Work coordinate offset 3G57 Work coordinate offset 4 Work coordinate offset 4G58 Work coordinate offset 5 Work coordinate offset 5G59 Work coordinate offset 6 Work coordinate offset 6G60 - Single direction positioningG61 Exact stop mode Exact stop modeG62 Automatic corner override mode Automatic corner override modeG63 - Ting modeG65 Custom macro call Custom macro call
28
G66 Custom macro modal call Custom macro modal callG67 Custom macro modal call cancel Custom macro modal call cancelG68 Mirror image for double turrets Mirror image for double turretsG69 Mirror image for double turrets cancel Mirror image for double turrets cancelG70 Profile fishing cycle -G71 Profile roughing cycle – Z axis direction -G72 Profile roughing cycle – X axis direction -G73 Pattern repetition cycle High speed peck drilling cycle(deep
hole)G74 Drilling cycle Left hand threading cycleG75 Grooving cycle -G76 Threading cycle Fine boring cycle G80 - Fixed cycle cancelG81 - Drilling or spot drilling cycleG82 - Dwell or counter boring cycleG83 - Peck-drilling cycle (deep hole drilling
cycle)G84 - Right hand threading cycleG85 - Boring cycleG86 - Boring cycleG87 - Back boring cycleG90 Cutting cycle A [Group type A] Absolute dimensioning modeG90 Absolute command [Group type B] -G91 Incremental command [Group type B] Incremental dimensioning modeG92 Thread cutting cycle [Group type A] Tool position registerG94 Cutting cycle B [Group type A] -G94 - Feed rate per minute [Group type B]G95 - Feed rate per revolution [Group type B]G96 Constant surface speed control -G97 Constant surface speed control cancel -G98 Feed rate per minute Return to initial level in fixed cycleG99 Feed rate per revolution [Group type A] Return to R level in a fixed cycle.
3.7 M-CODES FOR TURNING AND MILLING
MCODE TURNING MILLINGM00 Compulsory program stop Compulsory program stopM01 Optional program stop Optional program stopM02 End of program (usually with reset no
rewind)End of program (usually with reset no rewind)
M03 Spindle rotation normal Spindle rotation normalM04 Spindle rotation reverse Spindle rotation reverseM05 Spindle stop Spindle stopM06 - Automatic tool change (ATC)M07 Coolant mist ON Coolant mist ONM08 Coolant ON (coolant pump motor ON) Coolant ON ( coolant pump motor ON)M09 Coolant OFF (coolant pump motor OFF) Coolant OFF (coolant pump motor OFF)
29
M10 Chuck open -M11 Chuck close -M12 Tailstock quill IN -M13 Tailstock quill OUT -M19 Spindle orientation (optional) Spindle orientationM21 Tailstock forward -M22 Tailstock backward -M30 Program end (always with reset and
rewind)Program end (always with reset and rewind)
M98 Subprogram call Sub program callM99 Subprogram end Subprogram end
3. List of codes
A Specifies rotating angle of the NC rotary table
B Specifies rotating angle of the NC rotary table
C Specifies indexing angle of the coolant nozzle
F Specifies feed rate of the tool
G Specifies machining method and movement of axis on each block of the program
H Specifies tool length offset number
I Specifies component of circular command corresponding to the dimension of X axis
J Specifies component of circular command corresponding to the dimension of Y axis
K Specifies component of circular command corresponding to the dimension of Z axis
M Controls ON/OFF functions of the machine
N Specifies sequence number
O Specifies program number
P Specifies time command in the Dwell function / Program number in subprogram call
Q Specifies depth of cut as per pass at hole machining canned cycle
R Specifies radius of circular command point R in the hole machining canned cycle
S Specified spindle speed
T Specifies tool number
X Specifies position in the direction of X axis
Y Specifies position in the direction of Y axis
Z Specifies position in the direction of Z axis
3.3.5 G – Codes CO-ORDINATE SYSTEMS
i). ABSOLUTE G90
30
The destination of movement is specified with the coordinate value with reference to origin.
G90 X60.0 Y10.0; G90X10.0Y60.0;
ii). INCREMENTAL G91
The movement is specified by the incremental value to the destination referring the current position.
G91 X50.0; G91 Y 50.0;
ABSOLUTE (G90) & INCREMENTAL (G91)
G90 and G91 are abbreviated as ABS & INC respectively
31
10
10 60X+
Y+60
10
10
Y+
X+
6010
10
Y+
X+
2 0
2 0
6 0
6 0X+
Y+
A
B
10X+
10
60
Y+
From point A to point B
ABS G90 X60.0 Y60.0 ;INC G91 X40.0 Y40.0 ;
From point B to point A
ABS G90 X20.0 Y20.0 ;INC G91 X-40.0 Y-40.0ABS is better
• when each hole position is indicated from a reference point, programming is made easy by setting as the origin.
INC is better • when the pitch between the position of each hole is indicated. • when position with the same pitch is repeated.
32
2010 30 40 60
10
20
30
40
50
60
Y+
X+50
Example 1 (G90 &G91)O0001 (ABS) ;G90 G54 (X20.0) Y60.0 ; X60.0 Y10.0 ; (X60.0)Y60.0 ;
O0002 (INC) ;G91 G54 (X0) Y50.0 ; X40.0 Y-50.0 ; (X0)Y50.0 ;
Example 2 (G90 &G91)O0001 (ABS) ;G90 G54 X-60.0 (Y20.0) ; X-20.0 Y60.0 ; X-60.0 (Y60.0) ;O0002 (INC) ;G91 G54 X-40.0 (Y0) ; X40.0 Y40.0 ; X-40.0 (Y0) ;
ABS & INC Command for Z Axis movement• When the cutter is started 100mm above the top of the work piece and driven 10mm
in Z direction.
G90 G54 G00 Z2.0; G91 G54 G00 Z-98.0;G01 Z-10.0 F100; G01 Z-12.0 F100 G00 Z100.0; G00 Z110.0;
3.4 Circular Interpolation G02, G03
• Commands G02, G03 are used to cut circles or arcs. G02 is
Z2.0Z0
Z100.0
Z-10.0G01
G00
100m
m.
2mm
10m
m
work piece
2mm
Work piece1
0.0
100.0 Z-98.0
Z-12.0
33
20
3 0
4 0
5 0
6 0
1 0
1 0203 04 05 06 0X -
Y +
Specified for CW circle motion. G03 for CCW circle motion.
CW CCW Clockwise Counterclockwise ( Right hand ) ( Left hand )
THE CIRCLE CENTRE COORDINATE I AND J G17Vertical Machining Centre
In the plane G17 I and J
34
+Y
+X
I
J
A
E
M
A=start pointE=end pointM=centre
I is a coordinate parallel to the X axisJ is a coordinate parallel to the Yaxis
R
K-
I-
CCW
STARTPOINT
CENTREPOINT
USED IN TURNING
R
I-
J-
CCW
STARTPOINT
CENTREPOINT
USED IN MILLING
Dimension I & J
35
G02 G03
QUADRANTI
QUADRANTII
QUADRANTIII
QUADRANTIV
I0 J - I- J - I- J 0 I- J -
I+J 0 I+ J - I0 J - I+J -
I+ J +I+ J 0I+ J -I0 J +
I- J 0 I- J + I0 J + I- J +
K-
I+R
G03 G01G01
G02G01
G00
G03 G02
• Command I & J specify the distance from the start point of circle arc A to the center. I, J & K must be specified incrementally even under ABS mode, adding plus or minus for the direction of I, J & K.
I : Incremental distance between start point to centre point in X - axis J : Incremental distance between start point to centre point in Y- axis K : Incremental distance between start point to centre point in Z - axis
`
` ABS G90 G30 X20.0 Y40.0 I-30.0 J-10.0 F100 ;
INC G91 G03 X-20.0 Y20.0 I-30.0 J-10.0 F100 ;Specifying radius of circle/arc R
• The radius of circle arc can be directly specified by R instead of specifying the center of circle arc by I, J & K.
• When the center angle of arc is 180 or more, the radius R must be specified with negative (-) sign.
ABS G90 G02 X70.0 Y20.0 R50.0 F100 ; R-50.0 F100 ; INC G91 G02 X50.0 Y-50.0 R50.0 F100 ; R-50.0 F100 ;
A complete circle With I, J & K, a complete circle can be programmed by using one block.
36
G02
Center
Start
End X
Y
I
J
X
Y
G03
10
20
40
10
20 40
A(Start of circular arc)
B(End of circular arc)
J+
I+
J-
I-
R50
70
20
70
20
Y
X
A(Start of arc)
of arc)
R50
180Ø ORMORE
70
20
70
20
X
Y
Start
End
R40.
0
J+
I+
J-
I-
Y+
X+
A
B
From A point From B point ABS G90 G02 J-40.0 F100 ; ABS G90 G02 I-40.0 F100 ; INC G91 G02 J-40.0 F100 ; INC G91 G02 I-40.0 F100 ;
3.4 Machine Zero point & Work Piece Zero point
3.5 WORK ZERO IN MILLING
37
-X
+X
+Z
-X
+X
-Z +Z
-Z
Z REF POINT
ZERO OFFSET (Z)
PART LENGTH
OVER SIZESPINDLE
MACHINE ZERO POINT
CHUCK AND JAW LENGTH
BLANK LENGTH
WORK PIECE ZERO POINT
TOOL ZERO POINT
(POINT COMMANDED BY CNC)
TURRET DISC
TAIL STOCK
L1 = X TOOL
OFFSETL2=Z TOOL
X R
EF.P
OIN
T
TOOL GEOMETRY RADIUS VALUE
L2
MACHINE TABLE TOP AREA
MACHINE ZERO XY AXES
X-MOTION
Y-MOTION
TOP VIEW
W2W1
Work Coordinate System G54~G59What is “work coordinate system”
• The work coordinate system is a coordinate system to be set specifically for a work piece which is fixed on the table. The machining programs are created on the basis of this work coordinate system.
• Setting Procedure for X,Y
3.6 Setting Procedure for Z
CUTTER LENGTH COMPENSATION:
In order to know how far the machine slide has to be down feed the control system must know the length of the tool used. If retrieves the tool length required for a machinery operation from the tool life.
G43 – Tool length compensation +G44 – Tool length compensation –G49 – Cancellation will not takeaway the production time.
PRESETTING TOOL LENGTHS:
Each tool is assigned a specific identification number (H) along with a list of measured tool lengths. The CNC operators must set the tools in their correct location in the tool magazine and register each tool length in the offset register using the proper offset number. Any tool can be recalled by a command in the CNC program whenever a specific tool is required.
38
X-303.444
Y-17
0.12
3
G59
G54
Machine Origin G91 G28 X0 Y0
TOUCH OFF METHOD (FROM ZO GIVING THE VALUE)
Each tool is assigned as H number also called the tool length offset number which usually corresponds to the tool number. The set up procedure is to measure the distance the tool travels from the machine zero position (Hm) to the program zero position (ZO).
This distance always negative in entered into the corresponding H offset numbers under the tool length offset means of the central system. The Z value for any work offset (G54, G59 and the common offset) is normally set to ZO.
39
G 54
G UAG E L INE
H 01 H 02 H 03
P AR T
Z0
H01H03
GUAGE LINE
H02
PART
Z0
MASTER TOOL METHOD:
The master tool method using the largest tool can greatly reduce the amount of time spent in setting tool lengths. The master tool length compensation method is very efficient by following the proper procedure.
1) Install the master tool in the m/c spindle.2) Zero the Z-axis and check that the read cut screen show σ.0003) Measure the length of the master tool from the tool tip to ZO using launch method.
Register it to G54 – G59 work offsets under Z setting (-ve) 4) The touching level of (cutting edge) the cutter is made zero in Z-axis and the other
tool lengths are measured with reference to the material tool.5) The values are centered the H offset number in the tool length offset screen. (The
values are always negative for any tool shorter than the master tool)
3.7 PLANE SELECTION
• It is necessary to select a plane on which the circle interpolation, tool radius compensation, coordinate rotation or drilling carried out.
A plane is signified with a horizontal axis first and then a vertical axis, e.g the left figure is called ‘XY’ plane. This plane is viewed from the positiveside of the Z axis
40
H01 H03
G54
PART
Z0
H02 =0.0
GUAGE LINE
T01
Y
XPlan
e Sign
ifica
tion
G 17(XY PLANE)
41
• The X Y Plane is the plane which is viewed from the positive side of Z axis toward the work piece top surface.
G18(XZ Plane)• The ZX Plane is the plane which is viewed from the positive side of Y axis toward the
work piece Y+direction.
G19 (YZ Plane)• The YZ Plane is the plane which is viewed from the positive side of X axis toward the
work piece x+direction.
42
3.8 CUTTER RADIUS COMPENSATION
Cutter compensation is a method of shifting the tool path so that the actual finished cut is moved to either the left or right of the programmed path. Normally cutter compensation is programmed to shift by exactly the radius of the tool. So that the finished cut matches the programmed path. The offset display is used to enter the amount of tool to be shifted. The offset is entered either the diameter or radius and wear values can be given for both.
The effective value is the sum of wear value and the geometry.
Programming Format G41, G42 & G40
The radius compensation commands used on the CNC lathe are the same preparatory G-codes that are used for programming CNC mills,
• G41 – compensation of the tool-nose radius to the left of the contouring direction.
43
G17G18G19
G00G01
G42G41
G40X_Y_Z_X_Y_Z_
G00G01
X_Y_Z_X_Y_Z_
D_ ;
Canceling
Plane selection Tool compensation Offset number
• G42 - compensation of the tool-nose radius to the right of the contouring direction.• G40 - cancels of the tool-nose radius compensation.
3.5.1 Tool NoseThe tool nose on turning tools is the corner of the cutting tool or insert where the cutting edges blend together. This is the point that is programmed, and is called the command point or the imaginary point. It is referred to as the imaginary point because in reality the cutting-tool insert does not have a sharp point, there is usually a radius on the insert to provide strength and longer life during the cutting operation. Cutting tools for turning have a small radius usually:
.015in. (0.4 mm.030in. (0.8mm).047in. (1.2mm)
44
to Z0
to X
0
a b
to Z0
to X
0
R R
Reference point
Reference point
These codes allow the MCU to accurately produce arcs and tapers on the work piece by automatically accounting for the size of the radius on the tool nose. Without tool-nose radius compensation, the work piece profiles cut by the tool nose would be subject to undercutting and over cutting.
Arbitrary tool tip numbers for tool nose radius compensation. The dot is the point of reference. The tool tip orientation number and the value or size of the tool radius must be entered in the machine control system.
45
PROGRAMMED CONTOUR
TOOL PATH
TOOL NOSE
INSUFFICIENTCUTTING
Compensation not used
PROGRAMMED CONTOUR
TOOL PATH
TOOL NOSECompensation used
Cutter radius compensation, changes a milling cutter’s programmed centerline path to compensate cutter radius.Advantages
allows the use of cutters that have been sharpened to a smaller diameter.
46
Memory aid :G41 = left
Direction of movement=direction of vision G40 cancels G41,G42
Workpiece edge
G41G41
G42
G42
Y
X
Y
X
permits the use of a larger or smaller tool already in the machine’s storage area. allows the tool to be backed away when roughing cuts are required due to excessive
material. permits compensation for unexpected tool or part deflection if the deflection is
constant throughout the programmed path.
Sample of Program for G41, G42& G40.
Effect of cutter radius compensation
47
O 1000 (Ø 20 ENDMILL ) ;T32 M06;
G01 G41 X0 Y-50.0 D32 F100 ; X100.0; Y50.0; X-100.0; Y-50.0 X0; G40 X0 Y0; M30;
100
200
r
R
R
r
2 3
Angle should be
Should not be less than 45°
r R
1
1
3
2 3
4 4
I
I
I
I
r>RI
r
r>2,3I
3.6 TURNING CYCLES (FANUC)
G70 – Finishing Cycle
Format: G70 P__ Q__ F__;
P – Starting block number.Q – Ending block number.F – Feed.
G71 – Rough turning cycle
Format: G71 U__ R__;G71 P__ Q__ U__ W__ F__;
U – Depth of cut per pass in ‘x’ axis. (radial value). R – Tool relief. P – Starting block number.Q – Ending block number.U – Finishing allowance in ‘x’ axis. (Diametric value)W – Finishing allowance in ‘z’ axis.F – Feed.
EXAMPLE: 1
G71 – ROUGH TURNING CYCLE (Profile roughing in z – axis)
20 6 15 10
Ø40 Ø
28
Ø20
O0010;
N10 G28 U0 W0;
N20 T0101 G96S200;
48
N30 G50 S1500 M03;
N40 G00 X50.0 Z0.0 M08;
N50 G01 X0.0 F0.12;
N60 G00 X45.0 Z2.0;
N70 G71 U1.0 R1.0; (Profile roughing in z axis)
N80 G71 P90 Q160 U1.0 W1.0 F0.25;
N90 G01 16.0;
N100 Z0.0;
N110 X20.0 Z-2.0;
N120 Z-10.0;
N130 X28.0;
N140 Z-25.0;
N150 X40.0 Z-31.0;
N160 Z-51.0;
N165 X46.0
N170 G00 X48.0 Z2.0;
N180 G70 P90 Q160 F0.10; (Finishing cycle)
N190 G00 X48.0 Z2.0 M09;
N200 G28 U0 W0 M05;
N210 M30;
G72 – ROUGH TURNING CYCLE (Profile roughing in x – axis)
Format: G72 W__ R__;G72 P__ Q__ U__ W__ F__;
W – Depth of cut per pass in ‘z’ axis. R – Tool relief.
EXAMPLE: 2
G72 – ROUGH TURNING CYCLE (Profile roughing in x – axis)
49
10
10
40
Ø50
Ø25Ø17
16
O0011;
N10 G28 U0 W0;
N20 T0101 G96S250;
N30 G50 S1500 M03;
N40 G00 X55.0 Z0.0 M08;
N50 G01 X0.0 F0.12;
N60 G00 X55.0 Z2.0;
N70 G72 W1.0 R1.0; (Profile roughing in x axis)
N80 G72 P90 Q190 U1.0 W1.0 F0.25;
N90 G01 Z-40.0;
N110 X50.0;
N120 Z-35.0;
N130 G02 X40.0 Z-30.0 R5.0;
N140 G01 X25.0;
N150 Z-20.0;
N160 X17.0 Z-16.0;
N170 Z-1.0;
N180 X15.0 Z0.0;
N190 X0.0;
N200 G00 55.0 Z2.0;
N210 G70 P90 Q190 F0.10;
N220 G00 X100.0 Z50.0 M09;
N230 G28 U0 W0 M05;
N240 M30;
50
G73 – PATTERN REPETITION CYCLE
Format: G73 U__ W__ R__;G73 P__ Q__ U__ W__ F__;
U – Maximum raw material in X-AxisW - Maximum raw material in Z-AxisU – Finishing allowance in X-AxisW – Finishing allowance in Z-AxisR – Number of passes. F - Feed
EXAMPLE: 3
G73 – PATTERN REPETITION CYCLE
20 25 5
Ø50
Ø35 Ø25
20
R6
R2.5
O0012;
N10 G28 U0 W0;
N20 M06 T0101;
N30 M03 S1500;
N40 G00 X55.0 Z0.0 M08;
N50 G01 X0.0 F0.12;
N60 G00 X55.0 Z2.0;
N70 G73 U1.0 W1.0 R5.0; (Pattern repetition cycle)
N80 G73 P90 Q170 U5.0 W5.0 F0.25;
N90 G00 X20.0;
N100 G01 Z0.0;
N110 G03 X25.0 Z-2.5 R2.5;
N120 G01 Z-20.0;
N130 X35.0 Z-25.0;
N140 Z-44.0;
N150 G02 X47.0 Z-50.0 R6.0;
N160 G01 X50.0;
51
N170 Z-70.0
N175 G00 X55.0 Z3.0;
N180 G70 P90 Q170 F0.10;
N190 G00 X55.0 Z2.0 M09;
N200 G28 U0 W0 M05;
N210 M30;
G74 – PECK DRILLING CYCLE
Format: G74 R__;G74 Z__ Q__ F__;
R – Tool relief. Z – Total depth. Q – Depth of cut per pass (in microns). F – Feed.
EXAMPLE: 4G74 – PECK DRILLING CYCLE
Tools:1. Centre drill2. ∅10 mm drill (G74)
O0013;
N5 G28 U0 W0;
N10 T0101; (c.d)
N15 S1000 M03;
N20 G00 X0.0 Z2.0 T0101 M08;
N25 G01 Z-3.0 F0.10;
N30 G00 Z2.0 M09;
N35 G28 U0 W0 M05;
N40 M01;
N45 G28 U0 W0;
N50 T0202; (∅10 mm drill)
N55 S500 M03;
N60 G00 X0.0 Z2.0 M08;
N65 G74 R500.0;
N70 G74 Z-60.0 Q10000 F0.10; (Peck Drilling cycle)
N75 G00 Z10.0 M09;
52
TO
OL
N80 G28 U0 W0 M05;
N85 M30;
G75 – GROOVING CYCLE
Format: G75 R__;G75 X__ Z__ P__ Q__ F__;
R – Tool relief. X – Groove diameter.Z – Groove length from zero point. P – Depth of cut in ‘X’ axis (in microns).Q – Depth of cut in ‘Z’ axis (shifted value). F – Feed.
EXAMPLE: 5
G75 – GROOVING CYCLE
30 20 25
Ø70 Ø60
O0014;
N5 G28 U0 W0;
N10 T0505 G96 S120; (4mm insert)
N15 G50 S1500 M03;
N20 G00 X72.0 Z0.0 M08;
N25 Z-29.0;
N30 G75 R200;
N35 G75 X60.0 Z-45.0 P500 Q3000 F0.12; (Grooving cycle)
N40 G00 X80.0;
N45 Z10.0 M09;
N50 G28 U0 W0 M05;
N55 M30;
53
THREAD CUTTING
d D
Z
H
P
D – Major dia.d – Minor dia.H – Height of thread.P – Pitch.Z – Thread length.
M 30 X 1.5 Pitch Major diameter Metric thread
Formula to calculate diameter
d = D – 2h
h = 0.649 x P (to find the height of the thread)
G76 –THREAD CUTTING CYCLE
Format: G76 P__ Q__ R__;
G76 X__ Z__ P__ Q__ F__;
P – Thread angle Chamfer angle No. of finishing passes
Q – Minimum depth of cut in microns (Radial value) R – Finishing depth of cut in micronsX – Thread diameter Minor dia Z – Thread lengthP – Height of thread in micronsQ – Depth of cut/pass in microns (Radial value)F – Feed (Pitch value)
54
EXAMPLE: 6
G76 –THREAD CUTTING CYCLE
External threading
80505
Using formula, h = 0.649 x P h = 0.649 x 2.5 = 1.6225 d = D – 2h = 40 – (2 x 1.6224) d = 40 – 3.245 = 36.755Minimum No. of passes N = 4 x P = 4 x 2.5 = 10 passes.
O0017;
N5 G28 U0 W0;
N10 T0606;
N15 G97 S500 M03;
N20 G00 X42.0 Z4.5 M08;
N25 G76 P030060 Q150 R25;
N30 G76 X36.755 Z-52.0 P1623 Q500 F2.5;
N35 G00 X50.0;
N40 Z20.0 M09;
N45 G28 U0 W0 M05;
N50 M30;
55
Movement 1
Movement 2
Initial point
Movement 5
Movement 6
Movement 3
Movement 4 Point Z WorkpieceZ-
Z+
Tool
3.7 CANNED CYCLES (milling)
Movement 1 : Positioning to hole machining start position
Movement 2 : Moving of X,Y and Z axis.
Movement 3 : Moving to point R at rapid traverse Hole machining is carried out.
Movement 4 : Movement at hole bottom Specify dwell command if necessary
Movement 5 : Return to point R To return at either rapid traverse or cutting feed varies according
to G code for the hole machining canned cycle.
Movement 6 : Return to initial point at rapid traverse The tool returns to the start point (Initial point) of the movement at rapid traverse.
56
Rapid traverseCutting feed
initial level
R level
G98 G99
R level
3.7.1 DRILLING CYCLES
G81 – DRILLING OR SPOT DRILLING CYCLE
G82 – SPOT DRILLING OR COUNTER BORING CYCLE
G83 – PECK DRILLING CYCLE
G73 – HIGH SPEED PECK DRILLING CYCLE
Format:
G98 or G99 G81 X__ Y__ Z__ R__ F__; (Spotting /Drilling)
G98 or G99 G82 X__ Y__ Z__ R__ P__ F__; (Spotting /Counter Boring)
G98 or G99 G83 X__ Y__ Z__ R__ Q__ F__; (Peck Drilling)
G98 or G99 G73 X__ Y__ Z__ R__ Q__ F__; (High Speed Peck Drilling)
X,Y – Positioning points.Z – Total depth.R – feed starting level.F – cutting feed. P – dwell timeQ – pecking depth
EXAMPLE: (G81, G82, G83,G73)
57
8holesØ14mm drill,depth20mm
150
equallyspaced on a PCD Ø100mm
Tools
1. C.d (centre drill)2. ∅14mm drill
Points
1. X50.0 Y0.02. X35.35 Y35.353. X0.0 Y50.04. X-35.35 Y35.355. X-50.0 Y0.06. X-35.35 Y-35.357. X0.0 Y50.08. X35.35 Y-35.35
O0006;
N5 G00 G91 G28 Z0.0;
N10 G28 X0.0 Y0.0;
N15 M06 T1; (c.d)
N20 G00 G90 G54 X50.0 Y0.0 S2000 M03;
N25 G43 H1 Z100.0;
N30 G00 Z50.0 M08;
N35 G98 G81 X50.0 Y0.0 Z-3.0 R5.0 F100.0; ( Spotting /Drilling)
N35 G98 G82 X50.0 Y0.0 Z-3.0 R5.0 P500 F100.0; ( Spotting /Counter Boring)
N40 X35.35 Y35.35;
58
N45 X0.0 Y50.0;
N50 X-35.0 Y35.35;
N55 X-50.0 Y0.0;
N60 X-35.35 Y-35.35;
N65 X0.0 Y-50.0;
N70 X35.35 Y-35.35;
N75 G00 G80 Z100.0 M09; (Canned cycle cancel)
N80 G00 G91 G28 Z0.0 M05;
N85 G28 X0.0 Y0.0;
N90 M01;
N95 M06 T2; (∅14mm drill)
N100 G00 G90 G54 X50.0 Y0.0 S2000 M03;
N105 G43 H2 Z100.0;
N110 G00 Z50.0 M08;
N115 G98 G83 X50.0 Y0.0 Z-20.0 R5.0 Q3.0 F100.0; (Peck Drilling)
( Tool Retract to Initial Level “R”)
N115 G98 G73 X50.0 Y0.0 Z-20.0 R5.0 Q3.0 F100.0; ( High Speed Peck Drilling)
( Tool Retract set by machine builder”)
N120 X35.35 Y35.35;
N125 X0.0 Y50.0;
N130 X-35.0 Y35.35;
N135 X-50.0 Y0.0;
N140 X-35.35 Y-35.35;
N145 X0.0 Y-50.0;
N150 X35.35 Y-35.35;
N155 G00 G80 Z100.0 M09;
N160 G00 G91 G28 Z0.0 M05;
N165 G28 X0.0 Y0.0;
N170 M30;
59
3.8 TAPPING CYCLES
G84 – RIGHT HAND TAPPING CYCLE
Format:
G98 or G99 G84 X__ Y__ Z__ R__ P__ F__;
X,Y – Positioning points.Z – Total depth.R – Relief.P – Dwell time in milliseconds.F – Feed. (Pitch value)
Note: G84 cycle is used for right hand tapping. In this the tool moves inside in clockwise direction (M03) in feed. At the bottom dwell time is performed, during that time spindle speed, feed stops and spindle automatically reverses its direction (M04). Return movement is also in feed. Spindle speed should be given less (200 – 500).
G74 – LEFT HAND TAPPING CYCLE
Format:
G98 or G99 G74 X__ Y__ Z__ R__ P__ F__;
X,Y – Positioning points.Z – Total depth.R – Relief.P – Dwell time in milliseconds.F – Feed. (Pitch value)
Note: G74 cycle is used for left hand tapping. In this the tool moves inside in counter clockwise direction (M04) in feed. At the bottom dwell time is performed, during that time spindle speed, feed stops and spindle automatically reverses its direction (M03). Return movement is also in feed. Spindle speed should be given less (200 – 500).
G84 – RIGHT HAND TAPPING CYCLE
60
EXAMPLE:
80
100
20
25
Tools
1. C.d (centre drill) – G812. ∅6.8mm drill – G83 or G733. M8 tap – G84
d = D – Pitch value F = S x P where, F = Feed, S = Spindle speed, P = Pitch valued = 8 – 1.25 = 6.75 F = 200 x 1.25 = 250mm/min.d = 6.7 or 6.8mm.
Points
1. X20.0 Y25.02. X60.0 Y25.03. X60.0 Y75.04. X20.0 Y75.0
O0009;
N5 G00 G91 G28 Z0.0;
N10 G28 X0.0 Y0.0;
N15 M06 T1; (c.d)
N20 G00 G90 G54 X20.0 Y25.0 S2000 M03;
N25 G43 H1 Z100.0;
N30 G00 Z5.0 M08;
N35 G98 G81 Z-3.0 R5.0 F100.0;
N40 X60.0 Y25.0;
N45 X60.0 Y75.0;
61
N50 X20.0 Y75.0;
N55 G00 G80 Z100.0 M09;
N60 G00 G91 G28 Z0.0 M05;
N65 G28 X0.0 Y0.0;
N70 M01;
N75 M06 T2; (∅6.8mm drill)
N80 G00 G90 G54 X20.0 Y25.0 S2000 M03;
N85 G43 H2 Z100.0;
N90 G00 Z50.0 M08;
N95 G98 G73 Z-30.0 R5.0 Q10.0 F100.0;
N100 X60.0 Y25.0;
N105 X60.0 Y75.0;
N110 X20.0 Y75.0;
N115 G00 G80 Z100.0 M09;
N120 G00 G91 G28 Z0.0 M05;
N125 G28 X0.0 Y0.0;
N130 M01;
N135 M06 T3; (M8 tap)
N140 G00 G90 G54 X20.0 Y25.0 S200 M03; (Spindle switched ON in cw)
N145 G43 H3 Z100.0;
N150 G00 Z50.0 M08;
N155 G98 G84 Z-30.0 R5.0 P3000 F250.0; (Right hand tapping)
N160 X60.0 Y25.0;
N165 X60.0 Y75.0;
N170 X20.0 Y75.0;
N175 G00 G80 Z100.0 M09;
N180 G00 G91 G28 Z0.0 M05;
N185 G28 X0.0 Y0.0;
N190 M30;
62
G74 – LEFT HAND TAPPING CYCLE
EXAMPLE:
80
100
20
25
M8x1.25,depth 30mm(L.H)
(Above Lines Are Same As G84 Cycle Example)
N135 M06 T3; (M8 tap)
N140 G00 G90 G54 X20.0 Y25.0 S200 M04; (Spindle switched ON in ccw)
N145 G43 H3 Z100.0;
N150 G00 Z5.0 M08;
N155 G98 G74 Z-30.0 R5.0 P3000 F250.0; (Left hand tapping)
N160 X60.0 Y25.0;
N165 X60.0 Y75.0;
N170 X20.0 Y75.0;
N175 G00 G80 Z100.0 M09;
N180 G00 G91 G28 Z0.0 M05;
N185 G28 X0.0 Y0.0;
N190 M30;
63
3.9 BORING CYCLES
G85 – REAMING OR BORING CYCLE (Rough)
Format:
G98 or G99 G85 X__ Y__ Z__ R__ F__;
X,Y – Positioning points.Z – Total depth.R – Relief.F – Feed.
Note: G85 cycle is used for reaming and rough boring operations. This cycle is same as G84 except dwell time.
G86 – BORING CYCLE (Rough)
Format:
G98 or G99 G86 X__ Y__ Z__ R__ F__;
X,Y – Positioning points.Z – Total depth.R – Relief.F – Feed.
Note: G86 cycle is used for rough boring operation. This cycle is same as G81 except spindle orientation.
G76 – BORING CYCLE (Fine)
Format:
G98 or G99 G76 X__ Y__ Z__ R__ Q__ F__;
X,Y – Positioning points.Z – Total depth.R – Relief.Q – Shift amount in mm. (value should be very less between 0.1 – 0.5).F – Feed.
64
OSS
P
PointZ
SpindleCW
q
Initial level
PointR
OSS
P
PointZ
Spindle CW
q
Point R levelPoint R
G 76 (G 99)
G 76 (G 98)
BORING CYCLE
EXAMPLE:
SQ.10035H7
TOOLS
1. c.d (G81)2. Ø15mm drill3. Ø25mm drill (G83 orG73)4. Ø35mm drill5. Ø39mm rough boring (G85 or G86)6. Ø40mm fine boring (G76)
N135 M06 T5; (Ø39mm rough boring tool)
N140 G00 G90 G54 X50.0 Y50.0 S1200 M03;
N145 G43 H5 Z100.0;
65
N150 G00 Z50.0 M08;
N155 G98 G86 Z-35.0 R5.0 F100.0; (Rough boring)
N160 G00 G80 Z100.0 M09;
N165 G00 G91 G28 Z0.0 M05;
N170 G28 X0.0 Y0.0;
N175 M01;
N180 M06 T6; (Ø40mm fine boring tool)
N185 G00 G90 G54 X50.0 Y50.0 S1200 M03;
N190 G43 H6 Z100.0;
N195 G00 Z5.0 M08;
N200 G98 G76 Z-35.0 R5.0 Q0.2 F100.0; (Fine boring)
N205 G00 G80 Z100.0 M09;
N210 G00 G91 G28 Z0.0 M05;
N215 G28 X0.0 Y0.0;
N220 M30;
3.10 SUB PROGRAM
Sub programming or sub routing programming is a means by which we can make one program within the other. Subroutine allows the CNC program to define a series of commands which might be repeated several times in a program. Subroutine call is done by M98 and a P --------(number) which is the name of the subprogram.
Another very important feature of subroutine is that M98 call block also include an L repeat count. If there is an ‘L’ the subroutine call is repeated that number of times before the main program continues with the next block.
To insert a subprogram in a main program, simply write the sub program member in the block where we want the subprogram to work.
66
J ump tosubprogram
End of main program
Return tomain program
O1 O2
M98 P2 L
M30 M99
M98– Sub Program Call
M99 – Sub Program End
M98 – Sub Program Call
Format:
M98 P L
Number of Repeats
Sub program number
PROFILE MACHINING (Using Sub Program)
EXAMPLE: 4
1010
30
20
R30
2015
O0013; Sub program
N5 G00 G91 G28 Z0.0; O0025;
N10 G28 X0.0 Y0.0; N1 G01 G91 Z-5.0 F80.0;
N15 M06 T1; (Ø12mm EM) N2 X60.0;
N20 G00 G90 G54 X0.0 Y0.0 S1200 M03; N3 Y20.0;
N25 G43 H1 Z100.0; N4 G02 X-30.0 Y30.0 R30.0;
N30 G00 Z5.0 M08; N5 G01 X-30.0;
N35 G01 G42 X10.0 Y10.0 D1; N6 Y-50.0;
N40 G01 Z0.0 F80.0; N7 M99; (Subprogram end)
67
N45 M98 P0025 L3;(Sub program call)
N50 G00 G40 X-20.0 Y-20.0;
N55 G00 Z50.0 M09;
N60 G00 G91 G28 Z0.0 M05;
N65 G28 X0.0 Y0.0;
N70 M30;
DRILLING OPERATION (Using Sub Program)
EXAMPLE:
M10x1.5,depth 30mm
60 70 7050
7070
Operations
1. C.d (centre drill) – G812. ∅8.5mm drill – G83 or G733. M10 tap – G84
d = D – Pitch value F = S x P where, F = Feed, S = Spindle speed, P = Pitch valued = 10 – 1.5 = 8.5 F = 200 x 1.5 = 300mm/min.d = 8.5mm.
Points 1. X60.0 Y50.02. X200.0 Y50.03. X200.0 Y190.0
68
4. X60.0 Y190.05. X130.0 Y130.0
O0014;
N5 G00 G91 G28 Z0.0;
N10 G28 X0.0 Y0.0;
N15 M06 T1; (c.d)
N20 G00 G90 G54 X60.0 Y50.0 S2000 M03;
N25 G43 H1 Z100.0;
N30 G00 Z50.0 M08;
N35 G98 G81 Z-3.0 R5.0 F100.0;
N40 M98 P0023;
N45 G00 G80 Z100.0 M09;
N50 G00 G91 G28 Z0.0 M05;
N55 G28 X0.0 Y0.0;
N60 M01;
N65 M06 T2; (∅8.5mm drill)
N70 G00 G90 G54 X60.0 Y50.0 S2000 M03;
N75 G43 H2 Z100.0;
N80 G00 Z50.0 M08;
N85 G98 G83 or G73 Z-30.0 R5.0 Q10.0 F100.0;
N90 M98 P0023;
N95 G00 G80 Z100.0 M09;
N100 G00 G91 G28 Z0.0 M05;
N105 G28 X0.0 Y0.0;
N110 M01;
N115 M06 T3; (M10tap)
N120 G00 G90 G54 X60.0 Y50.0 S200 M03;
N125 G43 H3 Z100.0;
N130 G00 Z50.0 M08;
N135 G98 G84 Z-30.0 R5.0 P2000 F300.0;
N140 M98 P0023;
N145 G00 G80 Z100.0 M09;
N150 G00 G91 G28 Z0.0 M05;
N155 G28 X0.0 Y0.0;
N160 M30;
69
Sub program
O0023;(SUB PROGRAM)
N5 X200.0 Y50.0;
N10 X200.0 Y190.0;
N15 X60.0 Y190.0;
N20 X130.0 Y120.0;
M99;
3.11 LOCAL CO – ORDINATE SYSTEM
EXAMPLE:
100 200 350
200
300
450
4XØ16mm drill equally spaced on PCD Ø70mm,depth15mm
Operations
1. C.d (centre drill) – G812. ∅16mm drill – G83 or G73
Points 1. X35.0 Y0.02. X0.0 Y35.03. X-35.0 Y0.04. X0.0 Y-35.0
70
O0015;
N5 G00 G91 G28 Z0.0;
N10 G28 X0.0 Y0.0; Sub program
N15 M06 T1; (c.d) O0026;
N20 G00 G90 G54 X0.0 Y0.0 S2000 M03; N5 G98 G81 X35.0 Y0.0 R5.0F100.0;
N25 G43 H1 Z100.0; N10 X0.0 Y35.0;
N30 G00 Z5.0 M08; N15 X-35.0 Y0.0;
N35 G52 X100.0 Y950.0; N20 X0.0 Y-35.0;
N40 M98 P0026; N25 G00 G80 Z50.0;
N45 G52 X300.0 Y500.0; N30 M99;
N50 M98 P0026;
N55 G52 X650.0 Y200.0;
N60 M98 P0026;
N65 G52 X0.0 Y0.0;
N70 G00 G91 G28 Z0.0 M05;
N75 G28 X0.0 Y0.0;
N80 M01;
N85 M06 T2; (∅16mm drill)
N90 G00 G90 G54 X0.0 Y0.0 S2000 M03;
N95 G43 H2 Z100.0; Sub program
N100 G00 Z5.0 M08; O0027;
N105 G52 X100.0 Y950.0; N5 G98 G81 X35.0 Y0.0 Z-15.0 R5.0 F100.0;
N110 M98 P0027; N10 X0.0 Y35.0;
N115 G52 X300.0 Y500.0; N15 X-35.0 Y0.0;
N120 M98 P0027; N20 X0.0 Y-35.0;
N125 G52 X650.0 Y200.0; N25 G00 G80 Z100.0;
N130 M98 P0027; N30 M99;
N135 G52 X0.0 Y0.0;
N140 G00 G91 G28 Z0.0 M05;
N145 G28 X0.0 Y0.0;
N150 M30;
3.11.1 SUBROUTINE NESTING
A subprogram may be called not only in a part program but also in a subprogram itself. One subprogram can be called in another subprogram and this may be called in yet another
71
subprogram and so on. This method of calling subprogram is in succession is called subroutine nesting. Sub programming up to 4 levels can be called in subroutine nesting.
It is recommended that the subprograms are programmed under G91 because subprogram under G90 causes the machining to be in the same position.
But if command G52 is used, subprogram can be made with G90.
G52 local co-ordinate system setting
Example:
O00488 (Main)
T01 M06
G90 G00 G54 X-2.5 Y0 S2000 F100. M03
G43 H01 Z10.0 M08
G00 X-2.5Y13.0
G01 Z5 F500
M98 P411 L4
G91 G28 X0 Z0 M09
72
Main program Sub program Sub program Sub program Sub program
O1(MAIN); O10(SUB); O20(SUB); O30(SUB); O40(SUB);
First Second Third Fourth
M98 P10 M98 P20 M98 P30 M98 P40
M30 M99 M99 M99 M99
M30
O00411 (sub)
G0 G90 Z5.0
G0 G91 X21.0
G1G90 Z0.0F100
M98 P420 L3
M99
O00420 (sub nesting)
G1 G91 Z-1.0 F50
G41 D01G01 X7.5
G01 Y22.0
G03 X-15.0 Y0 R7.5
G01 Y-22
G03 X15.0 Y0 R7.5
G1G40 X-7.5
M99
3.12 PROFILE MILLING
I).SLOT (OR) KEYWAY OPERATION
40
20
10 40
50
8
O0002;
N5 G00 G91 G28 Z0.0;
N10 G28 X0.0 Y0.0;
N15 M06 T2; (∅10mm EM)
N20 G00 G90 G54 X45.0 Y-20.0 S1200 M03;
73
N25 G43 H2 Z100.0;
N30 G00 Z5.0 M08;
N35 G01 Z-8.0 F80.0;
N40 Y70.0;
N45 G00 Z100.0 M09;
N50 G00 G91 G28 Z0.0 M05;
N55 G28 X0.0 Y0.0;
N60 M30;
II).PROFILE MILLING (Using cutter compensation)
R10
R20
150
150
R25
Ø40
20X45°
G40 G41 G42
G40 – Cutter compensation cancelG41 – Cutter compensation leftG42 – Cutter compensation right
O0004;
N5 G00 G91 G28 Z0.0;
N10 G28 X0.0 Y0.0;
74
N15 M06 T1; (∅10mm EM)
N20 G00 G90 G54 X-20.0 Y-20.0 S1200 M03;
N25 G43 H1 Z100.0;
N30 G00 Z5.0 M08;
N35 G01 Z-10.0 F80.0;
N37 G01 X-20 Y0;
N40 G42 X140.0Y0.0 D1; (Cutter radius compensation right)
N45 G03 X150.0 Y10.0 R10.0;
N50 G01Y130.0;
N55 G03 X130.0 Y150.0 R20.0;
N60 G01X100.0;
N65 G02 X75.0 Y125.0 R25.0;
N70 G02 X50.0 Y150.0 R25.0;
Instead of writing in two lines, we can write in one line using I, J method
G02 X50.0 Y150.0 I-25.0 J0.0;
N75 G01 X20.0;
N80 X0.0 Y130.0;
N85 Y-20.0;
N87 G00 G40 X-20.0 Y20.0; (Cutter radius compensation cancel)
N90 G00 Z100.0 M09;
N95 G00 G91 G28 Z0.0 M05;
N100 G28 X0.0 Y0.0;
N105 M30;
75
4.0 FEED RATE F & SPINDLE SPEEDS S
Function F and S code
These are given according to the tools to be used and the material of the work piece to be cut.
F01 1mm/min F10 10 mm/min F1000 1000 mm/min
S10 10revolution per min (rpm) S1500 1500 revolution per min S4000 4000 revolution per min
CUTTING SPEED, RPM & FEED FORMULA
Cutting Speed = 3.14 x D x RPM1000
RPM = Cutting Speed x 10003.14 x D
End Mill Feed = Speed x No of tooth x Feed per tooth
Drill Feed = Speed x Feed per revolution
Tap Feed = Speed x Pitch
CUTTING SPEED (Vc) Vs RPM
Vc – dependant on material of work piece / tool & cutting conditions
RPM – dependant on diameter
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Axial Depth of cut
Advance Per Tooth
of Cutter
Chip Thickness
Effective dia
Learning Activity_1
Calculation Speed & Feed• Cutting speed (V)=250 m/min• Cutter Diameter (d)= ø 10 mm
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• No of tooth (z) = 2• Feed per tooth (ft ) = 0.1
RPM: n = 250 x 1000 = 7960rpm
3.14 x 10Feed : F = 7960 x 2 x 0.1 (n x z x f) F = 1592mm/min
Learning Activity_2
Calculation Cutting Speed & Feed Per Tooth• Rpm = 15000 rev/min• Feed = 3000 mm/min• No of tooth = 2• Cutter Diameter = 6 mm
Cutting speed : V = 3.14 x 6 x 15000 = 283m/min.
1000Feed per tooth : = 3000 =0.1mm/min.
2 x 15000
5.0 INSERT & TOOL HOLDERS
5.1 TOOL HOLDING DEVICES
The tool holder system for machining centers shown in the figure is a modular tooling system. It consists of a basic tool holder, extension or reducer and tool adaptors. Tool adaptors are available for receiving various tools like milling cutters, drills reamers etc.Various methods of holding the tools are shown in figures.
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5.2 TOOLS & TOOL MATERIAL USED IN CNC
5.2.1 TOOLS AND TOOL MATERIALS USED IN CNC MACHINE .
The most important properties of the cutting tool material are:
1. The material must withstand excessive wear even though the relative hardness of the tool materials changes.
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2. Ability to retain hardness under severe working condition.3. Ability to withstand cutting forces.4. The frictional coefficient must remain low for minimum wear and reasonable surface
finish.5. Cost and easiness of fabrication should have within reasonable limits.
5.2.2 TYPE OF TOOL MATERIAL
CARBON STEELS
• It may only be used in manufacture of tools operating at low cutting speed (12mt/min).
• Disadvantages of carbon tool steel are they are comparatively low heat and wear resistance.
HIGH-SPEED STEEL (HSS)
• HSS operate at cutting speeds 2 to 3 times higher than for carbon steels and retain their hardness up to 900c.
• Three general types of HSS are high tungsten, high molybdenum and high cobalt.
• Tungsten in HSS provides hot hardness and form stability. Molybdenum maintains keenness of the cutting edge. Cobalt makes the cutting tool more wear resistance.
STELLITES
• Stellite is the trade name of a non-ferrous cast alloy composed of cobalt, chromium and tungsten.
• They are used for non-metal cutting application such as rubbers plastics etc.
CARBIDES
a) Solid Carbidesb) Inserts.
• They are composed principally of carbon mixed with other elements.
The basic ingredient of most carbide is tungsten carbide that is extremely hard, pure tungsten powder is mixed under high hear (1500c) with pure carbon in the ratio of 94% and 6% weight.
The two types of carbides are the tungsten and titanium and both are more wear resistant.
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Carbides are designed for machining tougher materials chiefly for various materials.
COATED CARBIDES
The coated carbide has substrate and coating layer.
Substrate for toughness having hard materials and soft materials (cobalt + carbides)
Coating layer of carbide (very hard)
Better impact strength to resist fracture.
MODERN COATING
This layer of coating reduces friction between chip and tool and time duration is very limited.
Modern coating (Multi Layer)
Coating process
Chemical vapour deposition.
Physical vapour deposition.
Plasma CVD coating.
COATED CEMENTED CARBIDES
The cemented carbides with a very thin coat of carbides. The layers of titanium carbides were only a few microns thick and increase the performance of carbide tools.
COATED CARBIDES (GC)
More than 75% of turning operations and more than 40% of milling operations are today performed with coated carbides.
The main coating materials are
Titanium carbide (Tic)
Titanium nitride (Tin)
Aluminum oxide ceramic (Al203) and
Titanium carbon nitride (TiCN)
5.2.3 OTHER MATERIALS:
CERMETS
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Cermets-Ceramics and metal
Characteristics of Cermets Advantages of cermets
High hardness High efficiency
High hot hardness Long life
Resist oxidation Large batch
Low friction Avoid build up edge
Surface finish control
Cermet has properties to use it for higher cutting speed and wear resistance.
DIAMOND
The diamond is the hardest known material and can be run at cutting speed about 50 times greater than that of HSS tool and 5 to 6 times of life than carbide.
Diamond is incompressible readily conducts heat and has low coefficient of friction.
Diamonds are suitable for cutting very hard material such as glass, plastics etc.
By polycrystalline diamond the tool life is 30 times of carbide.
6.0 ISO DESIGNATION OF CUTTING TOOLS
6.1 INSERT
Inserts of several shapes are used for different application. In the below figure are rhomboidal shapes which are very popular. Shape C is particularly used for rough turning. Shape W is now preferred by many users. Shapes D and V are widely used for finish turning applications. Shape V is useful for contoured parts.
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WTSR
DVCBA
60°
82°
80°
55°
35°
85°6.1.1 CLEARANCE ANGLE
The second alphabet represents clearances angle which varies from 3 degrees to 11 degrees, the figure shows the designation of clearance angle.
PFC
NEB
GDA
25° 11°7°
20°5°
30°15°3°
6.1.2 TOLERANCES
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The tolerances on the insert are important. The third alphabetical character denotes the tolerances.
m
ds
d
d m S
A ± 0.025 ±0.005 ±0.025
C ±0.025 ±0.0125 ±0.025
E ±0.025 ±0.025 ±0.025
G ±0.025 ±0.025 ±0.05
H ±0.0005 ±0.0005 ±0.001
M ±0.002 ±0.003 ±0.0005
6.1.3 LENGTH OF THE INSERT EDGE
The length of the edge of the insert is the next number. Figure shows how the lengths are designated.
06-22 07-1506-1909-19
6.1.4 THICKNESS OF THE INSERT
The next letter refers to the thickness of the insert. The thickness varies as shown in table.
DESIGNATION THICKNESS (MM),S
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02 2.2503 3T3 3.7504 4.505 5.37506 6.2507 8.1309 10
6.1.5 NOSE RADIUS
Corner radius of the cutting edge is an important parameter. The corner radius influences the accuracy in contouring operations in turning. Therefore, tool nose radius compensation has to be called during profile turning operations. Corner radius should be input into the memory of the system to apply tool nose radius compensation. Tool nose usually varies between 0.4 mm to 2.4 mm in standard inserts
Tool Nose radius
Code mm
04 rE=0.4
08 rE=0.8
12 rE=1.2
16 rE=1.6
24 rE=2.4
6.1.6 CUTTING DIRECTION
Inserts may be right hand turning inserts, left hand turning inserts or neutral inserts which may be used either way. This is shown in the figure
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Insert shape
T N M G - 22 04 08
C - Diamond 80D - Diamond 55R - RoundS - Square
clearance angle
T N M G - 22 04 08
R
L
N
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Tolerances
T N M G - 22 04 08
Class s ic
G ±0.13 ±0.025M ±0.13 ±0.05U ±0.13 ±0.08E ±0.025 ±0.25 Insert Type
T N M G - 22 04 08
PFC
NEB
GDA
25° 11°7°
20°5°
30°15°3°
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7.0 CLAMPING SYSTEM
7.1 WORKHOLDING DEVICES
It is important to ensure that a work piece setup is safe. The work piece must be securely fastened, and the setup must be rigid enough to with stand the forces that will be present during the machining operation. If the work piece of the holding device becomes loose during machining, damage can result to the tooling and / or the machine.
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The machine operator should be sure that all work holding devices are free from chips and burrs before use. The work holding devices, generally specified by the programmer, should be located in the proper position on the machine table. Failure to follow these instructions may result in operator injury, damage to the machine, or scrap work pieces.
7.1.1 Types of Work holding Devices
The most important function of any Workholding device is to hold the part so that the surface to be machined is in the correct relationship to other surfaces as indicated on the part drawing. The part must be held securely enough that it can withstand the forces created during the machining operation without becoming loose or moving. Although Workholding devices differ due to the shape and size of the part, the most commonly used are:
7.1.1.1 The Swivel-base vise, fig.7.11.15A, which may be bolted to the machine table or a subplate. The swivel base enables the vise to be swiveled 360° in a horizontal plane.
1
2
34
5
1.Bevel pinion,2.Scroll disc,3.Bevel teeth on scroll disc,4.Chuck body,5.J aw.
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7.1.1.2 Angle plates, fig.7.11.15B, are L-shaped pieces of cast iron or steel accurately machined to a 90° angle. They are made in a variety of sizes and have holes or slots that provide a means for fastening the work piece.
ANGLE PLATE
7.1.1.3 V blocks, fig.7.11.15C are generally used in pairs to support cylindrical work. A U-shaped clamp may be used to fasten the work in a V block.
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12
3
5
USE OF V-BLOCK1.T-bolt, 2.V-block, 3.Work, 4.Nut, 5.Clamp
7.1.1.4 Step blocks, fig.7.11.16A, are used to provide support for strap clamps when work is being fastened to the table or Workholding devices.
Clamp or Straps, fig.7.11.16B are used to fasten work to the table, angle plate, or fixture. They are made in a variety of sizes and are usually supported at the end by a step block and bolted to the table by a T bolt. It is good practice to place the T-bolt in the clamp or strap as close to the work as possible.
Sub plates are generally flat plates that may be fitted to the machine table to provide quick and accurate location of workpieces, Workholding devices, or fixtures. The fixturing holes in these sub
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plates are accurately located and, when set up on the machine table in relation to the machine datum, provide the programmer with known locating positions.
7.2 FIXTURES
CNC eliminates many of the expensive jigs and fixtures that were previously necessary to hold and locate a work piece on conventional machine tools. The repetitive position accuracy of an CNC machine tool also eliminates the need for guide bushings, which were previously required to locate the cutting tool.
In CNC machine fixtures are used to accurately locate a part and hold it securely for machining operations. Fixture design should be kept simple so that the time required to the load and unload a part is kept as short as possible, since this is nonproductive time, the savings here will result in corresponding savings in the cost of producing a part. When designing a fixture to hold a part, it is important to consider the following points:
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Single pin catch plate
Straight tail carrier
Double pin catch plate Double slotted carrier
Double slotted catch plate
Double tail carrier
Bent tail carrier.
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Plain mandrel
1
1.Flattened end
Step mandrel
Screwed mandrel
1 23
Cone mandrel
1
23
4
1.Fixed collar,2. Hollow workpieces,3. Movable collar,4. Nut.
1
2
Expansion mandrel1.Sleeve,2. Tapered pin
Collar mandrel
1. Positive location The fixture must hold a work piece securely enough to prevent the work piece from linear movement in the X, Y, and Z axes, and rotational movement in either direction about each axis.
2. Repeatability
Identical parts should always be held in exactly the same location for every part change.
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3. Ruggedness
Fixtures must be designed to withstand the shock created during the machining and loading/unloading cycles.
4. Rigidity
The work piece must be held securely to prevent any movement due to the forces created by the machining operation.
5. Design
Modular fixtures using standard components are quicker to produce and less costly than custom fixtures. They can also be quickly modified to accommodate differently shaped parts, fig.7.11.18.
6. Low profile
Parts of the fixture or the necessary clamping devices to hold the part should be designed to allow free movement for the cutting tool at any point in the machining cycle.
7. Part loading/unloading
The fixture and its clamping devices should be designed so that they do not interfere with the rapid loading or unloading of a part.
8. Part distortion
The fixture should be designed so that the part being machined is not distorted by gravity, machining forces, or clamping forces. Stress should never be put on a part by the clamping forces; otherwise the machined part will distort when the clamping forces are removed.
MODULAR FIXTURES
Modular fixtures provide many of the advantages of permanent fixtures but are flexible enough to accommodate various shapes of workpieces by changing certain components. A modular fixture can be built from a set of standard components to hold a certain part shape After the production run is complete, the fixture can be disassembled to allow the components to be reused. A manufacturer can thus make fixtures at any time to suit the part to be manufactured.
Clamping Hints
1. Always place the bolt as close to the work as possible.2. Place a piece of soft metal (“packing”) between the clamp and the work piece to prevent damage to the work piece and to spread the clamping force over a wider area.3. Make sure the packing does not extend into the machining path of the cutting tool.4. Use the table slots to prevent round work from moving.5. Use two clamps whenever possible.6. Parts that do not lie flat should be shimmed to prevent the work from rocking. Shimming will also prevent distortion when the work is clamped.7. Tighten clamping bolts evenly to prevent work piece distortion.
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9.0 HIGH SPEED MACHINING (HSM)
High Speed Machining (HSM) of hardened die steels should not be feared but embraced. Many people feel that hard metal machining is a black art, but with a few basic principles it is not only profitable but also a straight forward machining process. There are several components of the process, which include: the effective utilization of the machine tool, cutting tools, tool holders, and programming. If these areas are addressed correctly, hard metal machining loses its mystery and mystique and becomes a predictable process where established formulae and guidelines can be used. In this article, the focus is on the cutting tool but other areas will be addressed as well.
Choosing the Process
There are three major machining methods: soft machining, hard machining, and EDM. The configuration and hardness of the die or mold material determine which method or combination of methods will work best. Soft machining – machining the part prior to heat treatment – should be considered when machining large parts of parts that require deep cuts. Semi – finishing and finishing can then be done in the hardened state. If the part is not very large, or calls for shallow machining, the entire part can be milled in the hardened state. If the part geometry requires thin features and deep cuts, EDM may be the only option.
Tool Selection
Choosing the proper cutting tool is very important when machining hardened metal. There are three basic designs of cutters: ball end, corner radius (bull nose) or square end (Figure 1). The first choice in hard metal machining should be the ball end mill. The ball end mill should be used for roughing operations and most finishing operations. Its large radius dissipates the force and heat that is generated in cutting hard material at high speeds and feeds. The ball end mill allows the user to cut closer to the net three – dimensional shape and allows for higher speeds and feeds.
If a part requires large, flat areas on its floor, a corner radius tool should be used after the ball end tool has roughed out the part. The corner radius tool does not have as large of a radius as the ball, and therefore does not dissipate the heat and force as well as the ball end mill. The square corner radius tool has removed as much materials as possible from the part. The sharp corner of a square end tool acts as a focal point for all the heat and force and will have a tendency to chip. The only time a square end mill should be used is when a sharp corner is required at the transition of a floor and a wall.
Tool rigidity is also an important factor to consider. In small diameter cutters, the shank of the tool should be much larger than the cutting diameter. This increases the stiffness of the cutter, which helps produce better finishes and affords longer tool life.
It is important to choose the tool to fit the application as closely as possible. For example, Robb Jack’s DM and MDM series end mills come with an 8^◦ per side draft angle. Yet, at the factory, it is very easy to modify this angle and it can be done very quickly. If the part has 3^◦ draft, the tool can be modified to 2½ ^◦ draft. Generally, a tool should have 1/2^◦
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less draft than the actual part. This ½^◦ provides for angular clearance while keeping the tool as strong as possible (Figure 2).
Additionally, the tool should not project from the holder any farther than is required. If straight walls are required, a neck can be utilized to strengthen the tool .Both methods allow the short-length-of-cut tool to cut deeper than its cutting length.
Controlling Heat Generation
Excessive heat changes the part’s surface morphology, reducing cutting accuracy. However, one way of minimizing heat generation and retention is by controlling the radial step-over of the cutting tool. Radial step-over is the distance between centerlines of successive, parallel cuts (Figure 4). For roughing operations, the radial step-over should equal 25 to 40 percent of the cutter’s diameter. For finishing with a given cusp height on a flat surface, the radial step-over can be calculated with the following formula:
Radial Step Over = √4 (Cusp Height X Tool Diameter) – 4(Cusp Height^2)
Example: 3/8” tool diameter with a 0.00024” tolerance.
Radial Step over = √ 4(.00024 X .375) – 4(.00024^2) = 0.019”
Example: 3/8” tool diameter with a 0.019” radial step – over.
Radial Step over:
Radial step over determines how much heat is accumulated in the tool and the part by determining the length of time each flute spends in the cut and the amount of time it cools before entering the cut again (Figure 5). The graphical representation illustrates the effects of radial step – over and heat generation.When the step – over is too great, the flute builds up heat because there is insufficient time to cool the flute before it renters the part. By using smaller step – overs, there is a continuous cooling action that controls heat generation. By regulating the heat generation with a continuous cooling action, higher rpms can be used without reaching the fatal temperature of the coating. Once the fatal temperature of the coating is reached, there is a rapid deterioration of the cutting edge; which increases force and temperature to the tool and part. When the proper process is implemented there should be no build up of heat in the part. Excessive heat leads to changes in the surface morphology and loss of cutting accuracy.
By selecting the proper coating, higher temperatures can be reached without compromising the cutting tool. For example, the maximum working temperature for Titanium Carbonitride (TiCN) is 750 degree F (400 degree C) compared to Titanium Aluminium Nitride (TiAIN) with a maximum working temperature of 1470 degree F (800 degree C). Generally, TiAIN is the preferred coating for HSM of hardened die/mold materials because of its high heat resistance. The higher heat resistance of the TiAIN coating enables the use of faster RPMs without damaging the cutting tool.
Heat Generating At The Cutting Edge
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Proper speeds and feeds are essential in controlling heat build up. Large chip loads remove heat with the chip so it does not build up in the tool or part. If the chip load is too light, there is a rubbing or grinding type action which leads to heat build up. Therefore, it is very important for tool life to use the largest chip load possible without damaging the tool or part (Figure 6).
For example, if the chip load per tooth should be 0.008” and the chip load used is 0.002”, a part that should take 20 minutes to machine now takes 80 minutes. This means the tool spent four times as much time in the cut as required.
The geometry of the tool also plays an important role in controlling heat. The geometry of the tool affects the way the chip is formed and evacuated from the cut. Incorrect geometry can result in premature tool failure and poor part finishes. This is why a tool should be designed specifically for hard metal machining.
Flood coolant should not be used in most cases. The result of extensive testing by Robb Jack shows that using flood coolant in materials above 40 HRC reduces
Robb Jack Recommended Chip Loads For Ball End Tools
Chip Load Per ToothSteels 30 – 40 HRc Steels 40 – 50 HRc Steels 50– 60 HRcRoughing Finishing Roughing Finishing Roughing Finishing
DM-201-01 1/32” .0006 -.0008 .0005 -.0006 .0005 -.0006 .0004 -.0005 .0004 - .0005 .0003 -.0004DM-201-02 1/16” .0013 -.0015 .0010 -.0013 .0010 -.0013 .0008 -.0010 .0008 -.0010 .0005 -.0008DM-201-03 3/32” .0019 -.0023 .0015 -.0019 .0015 -.0019 .0011 -.0015 .0011 -.0015 .0008 -.0011DM-201-04 1/8” .0025 -.0030 .0020 -.0025 .0020 -.0025 .0015 -.0020 .0015 -.0020 .0010 -.0015DM-201-06 3/16” .0038 -.0045 .0030 -.0038 .0030 -.0038 .0023 -.0030 .0023 -.0030 .0015 -.0023DM-201-08 1/4” .0050 -.0060 .0040 -.0050 .0040 -.0050 .0030 -.0040 .0030 -.0040 .0020 -.0030DM-201-10 5/16” .0063 -.0075 .0050 -.0063 .0050 -.0063 .0038 -.0050 .0038 -.0050 .0025 -.0038DM-201-12 3/8” .0075 -.0090 .0060 -.0075 .0060 -.0075 .0045 -.0060 .0045 -.0060 .0030 -.0045DM-201-14 7/16” .0088 -.0105 .0070 -.0088 .0070 -.0088 .0053 -.0070 .0053 -.0070 .0035 -.0053DM-201-16 1/2" .0100 -.0120 .0080 -.0100 .0080 -.0100 .0060 -.0080 .0060 -.0080 .0040 -.0060(Speed and Feeds are only general starting points and may vary depending on specific application.)
Robb Jack Recommended RPM for Ball End Tools
Roughing & Semi – Finishing RPM
Steels 30 – 40 HRc Steels 40 – 50 HRc Steels 50– 60 HRc
DM-201-01 1/32” 20,000 – 40,000 20,000 – 40,000 20,000 – 40,000DM-201-02 1/16” 20,000 – 40,000 20,000 – 40,000 20,000 – 16,000DM-201-03 3/32” 20,000 – 32,000 20,000 – 32,000 16,000 – 24,000DM-201-04 1/8” 15,000 – 24,000 18,000 – 24,000 12,000 – 18,000DM-201-06 3/16” 10,000 – 16,000 12,000 – 16,000 8,100 – 12,000 DM-201-08 1/4” 7,600 – 12,000 9,100 – 12,000 6,100 – 9,100DM-201-10 5/16” 6,000 – 9,700 7,300 – 9,700 4,800 – 7,300DM-201-12 3/8” 5,000 – 8,100 6,100 – 8,100 4,000 – 6,100DM-201-14 7/16” 4,300 – 6,900 5,200 – 6,900 3,400 – 5,200DM-201-16 1/2" 3,800 – 6,100 4,500 – 6,100 3,000 – 4,500(Use maximum RPM if suggested RPM is higher than the machine’s capabilities.)
Finishing
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RPM
Steels 30 – 40 HRc Steels 40 – 50 HRc Steels 50– 60 HRc
DM-201-01 1/32” 20,000 – 40,000 20,000 – 40,000 20,000 – 40,000DM-201-02 1/16” 20,000 – 40,000 20,000 – 40,000 20,000 – 40,000DM-201-03 3/32” 20,000 – 40,000 20,000 – 40,000 20,000 – 40,000DM-201-04 1/8” 20,000 – 36,000 20,000 – 40,000 20,000 – 30,500DM-201-06 3/16” 20,000 – 24,000 20,000 – 32,000 16,000 – 20,300 DM-201-08 1/4” 15,000 – 18,000 18,000 – 24,400 12,000 – 15,000DM-201-10 5/16” 12,000 – 14,000 14,600 – 19,000 9,700 – 12,000DM-201-12 3/8” 10,000 – 12,000 12,000 – 16,200 8,100 – 10,000DM-201-14 7/16” 8,700 – 10,400 10,000 – 13,900 6,900 – 8,700DM-201-16 1/2" 7,600 – 9,100 9,100 – 12,200 6,100 – 7,600(Use maximum RPM if suggested RPM is higher than the machine’s capabilities.)
Figure 9
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