Fyp Report Dpe 080001k Liang Yue

PROJECT TITLE

Development and Optimizing of Machining Process for CNC Turning with Appropriate Technologies and

Methodology

PROJECT NO: DPE034-02-10

SCHOOL OF ENGINEERING (MANUFACTURING)

Development and Optimizing of Machining Process for CNC Turning with Appropriate

Technologies and Methodology

NANYANG POLYTECHNICPROJECT REPORT

COURSE: DIPLOMA IN DIGITAL AND PRECISION ENGINEERING

PROJECT TITLE: Development and Optimizing of Machining Process for CNC Turning with Appropriate Technologies and Methodology

PROJECT NO: DPE034-02-10

PROJECT DURATION: 06-12-10 TO 25-02-11

PROJECT MEMBER(S):

NAME ADMIN. NO. ELECTIVELiang Yue 080001K

SUPERVISORS: Mr. Wong Kim TuckMr. Lim Siok Khing

Proposed by:

SEG (M): [ √ ]

COMPANY: [ ]

DATE OF SUBMISSION:


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CNC Technology&Product Innovation and Rapid Prototyping




SUMMARY


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This project is carried out for 12 weeks from 7th of September to 25th of December.

During this time, I attended the structural training at the first week and I started my

final year project during the following 11 weeks.

My project title is Development and Optimizing of Machining Process for CNC

Turning with Appropriate Technologies and Methodology. The objectives of my

project are to be able to operate CNC Turning machine and further optimize the

machining process to get a high quality product.

Firstly, I developed the three-dimensional model of my project components using

UG software, including one steel component and two aluminum components which

can be assembled together. Then I did the part programs of the three project

components by the aid of Mastercam software. And lastly, I machined the project

components out using OKUMA LB3000 CNC Turning machine.

This report will cover what I have learned during the project weeks. Firstly, I will

introduce some general concept of CNC Turning. Then I will introduce the

important concept of cutting tool technology followed by step by step Mastercam

programming procedure. And the most important part is the machining process and

the optimization of the machining process based on the problem I encountered. The

main objectives of optimization are to get a better surface finishing of the workpiece

and reduce the time consumed. So I will explain the optimization of the machining

process in four aspects: selection of tool insert, selection of cutting parameters,

optimal toolpath planning and controlling during machine process.

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ACKNOWLEDGEMENTS


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First of all, I would like to take this opportunity to give my special thanks to all the

stuffs in NYP who have given me support and help during my project.

Firstly, I would like to express my sincere thanks to Mr. Wong Kim Tuck, my

supervisor of final year project, for giving me the strength and guidance to do this

project and helping me with my preparation of presentation.

I also would like to thank my co-supervisor, Mr. Lim Siok Khing, for kindly

teaching me to do Mastercam Programming, setup of the machine and machining

operation.

I deeply express my sincere thanks to Mr. James Liang Hao Jie, Mr. Xu Jia Lu,

and Mr. Yeo Teck Cher for direcly or indirecly support of my project whenever I

have troubles, especiall when I have machining problem.

My deep thanks to my accessors Mr. Lau Foo Yew and Mr. Tan Kah Lock for

making time for my presentation and giving judgement.

Last but not least, I would like to express thanks for all my lab mates and friends,

especially who had given their support and encouragement to me. They always gave

me a hand when I was in need. Finally, my most sincere and warmest thanks to all

the people mentioned as above, who help me complete this project successfully.

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TABLE OF CONTENTS


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Chapter 1 Introduction

1.1 – What is CNC 11

1.2 – CNC Turning 12

1.3 – General Turning Operation 13

1.4 – Jaws 15

1.5 – Toolholder 16

1.6 – Flow of CNC Process 17

Chapter 2 Project Components

2.1 – Steel Component 19

2.2 – Aluminium Component – Part A 21

2.3 – Aluminium Component – Part B 23

Chapter 3 Cutting Tool Technology

3.1 – Tool Geometry 26

3.2 – Cutting Data 27

3.3 – Tool Life 28

3.5 – Tool Materials 31

Chapter 4 Mastercam Programming

4.1 – Mastercam Software 34

4.2 – Mastercam Programming 35

Chapter 5 Machining Process of Project Components

5.1 – Machine Specification 53

5.2 – Machining Preparation 55

5.3 – Machining Process 57

5.4 – Finished Project Components 62

Chapter 6 Optimization of Machining Process

6.1 – Cutting Tool Selection 66

6.2 – Cutting Parameters Selection 68

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6.3 – Toolpath Planning 69

6.4 – Machining Process 75

Conclusion 80

Appendix 82

Gantt Chart 85

References 87

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CHAPTER 1

INTRODUCTION


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1.1 What is CNC

Previously, machines are operated manually by skilled machinists and it requires a great

deal of operator skills and training to achieve high quality product. Manual machining is

also relatively slow and expensive.

Today, manual machine tools have been largely replaced by computer numerical control

machine tools. The machines still perform the essentially the same functions, but

movements of the machine tool are controlled electronically rather than by hand.

So what is CNC? CNC is automated control of machine tools by a computer and computer

program. In other word, a computer rather than a person will directly control the machine

tool.

A CNC machine tool differs from a conventional machine tool only in respect to the

specialized components that make up the CNC system. The CNC system can be further

divided into three subsystems: control, drive and feedback system. All of these subsystems

must work together to form a complete CNC system.

The heart of the CNC system is the control unit. This is the computer that stores and reads

the program and tells the other components what to do. The control also acts as the user

interface so that the operator can set up and operate the machine.

The drive system comprises of the motors and screws that will finally turn the part program

into motion.

The function of feedback system is to provide the control with information about the status

of the motion control system. The control can compare the desired condition to the actual

condition and make corrections.

Compared with manual machining, the CNC machining has many advantages:

Reduce the setup time and lead time

Programs are easy to edit, so programming process time is reduced

Greater flexibility in complexity of components produced

Higher accuracy and repeatability

Simplified tooling and work holding system

Able to achieve high productivity

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However, there are still some limitations in CNC machining:

CNC is slightly more expensive

Depending on the complexity of machine tool, possibly more training is required for

machine operators

Greater maintenance cost

1.2 CNC Turning

CNC turning is the process whereby a single point cutting tool is parallel to the surface of

the workpiece. It is used to produce an object which has rotational symmetry about an axis

of rotation and in most cases the tool is stationary with the workpiece rotating. The cutting

tool follows the contour of the programmed tool path.

CNC Turning uses the Cartesian coordinate system for programmed coordinates. The axis

aligned with the spindle should be designated “Z”. The axis that is at a right angle to the

spindle is designated “X”. Positive Z points to the right of the spindle, and the positive X

direction points toward the back of the machine. This is done because the typical CNC

turning center is constructed with the tool mounted on the back side.

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Chuck jawsWorkpiece

X+

X–

Z+Z–



1.3 General Turning Operations

A variety of machining operations can be performed on a CNC turning machine:

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Remove material from outer diameter of a rotating cylindrical workpiece to reduce the diameter of the workpiece

Remove material from the end face of the workpiece to produce a flat surface

Use a blade-like cutting tool to plunge directly into the workpiece to cut off the workpiece at a specific length

Enlarge a hole made by previous process and machine the internal cylindrical forms



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Produce a hole by feeding the drill into the rotating workpiece along its axis

Metal forming operation used to produce a regular cross-hatched pattern in workpiece surfaces

Widen an existing hole and make the holes dimensionally more accurate and to improve surface finish

A pointed tool is fed linearly across the outside or inside surface of rotating parts to produce external or internal threads



1.4 Jaws

Generally, there are two types of jaws for CNC turning – hard jaws and soft jaws. Hard

jaws are generally used for roughing and semifinishing toolpaths, whereby soft jaws are

used for semifinishing and finishing toolpaths.

The main reason why hard jaws are not suitable for clamping finished surfaces is because

the hard material used for hard jaws will leave a physical mark on the part diameter.

Another reason is that hard jaws do no guarantee concentricity of the workpiece as well as

soft jaws do.

Soft jaws are made from mild steel. The main advantage of soft jaws is that they can be

bored to the exact diameter required with excellent concentricity of the clamped part.

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Hard jaws Soft jaws

http://www.google.com.sg/imgres?q=soft+jaws&um=1&hl=en&biw=1349&bih=566&tbs=isch:1&tbnid=3NnkILI6yq1BbM:&imgrefurl=http://www.samchully.com/eng/pd_info/pd_info2.asp?lgroup_number=007&imgurl=http://www.samchully.com/upload/product/Soft--Jaw-2.gif&ei=CatHTYGpMoyjcfnDlMwD&zoom=1&w=200&h=200&iact=rc&dur=264&oei=6qpHTdizJtDHrQfAlYCoBA&esq=3&page=3&tbnh=126&tbnw=152&start=40&ndsp=22&ved=1t:429,r:21,s:40&tx=80&ty=53



1.5 Toolholder

Modern toolholders have been designed to provide optimum machining performance in

different applications and area.

The selection of toolholder style is influenced by insert shape used and feed direction,

depth of cut, workpiece and toolholding in machines as well as the accessibility required.

For stability during machining process, the largest possible toolholder size should be

chosen to suit the application. This provides the most advantageous tool-overhang ratio and

the most rigid base for the insert. There are few types of toolholders:

Standard Tool Holders

Standard tool holders are made of heavy metal and have a long slide where they are

fastened to the tool post, and a shorter side with rigidly fixed angles and a space for

insertion of the cutting tool. A clamp screw securely fastens the standard tool holders to the

tool post. Standard tool holders are commonly used for high-speed metal cutting at low

forces because of their tendency to move at higher pressures. They come in right-hand,

straight and left-hand shapes.

Quick-change Tool Holders

Quick-change toolholders are used mostly in conjunction with carbide tools. The quick-

change toolholders are constructed with a dovetail. The tool post also has a dovetail. A

large clamp wedges both dovetails together so they are more rigid than standard tool

holders and tool posts. Quick-change toolholders are much faster and more accurate than

standard toolholders and they come in a large variety: turning, boring, knurling and parting.

Parting Tool Holders

Parting tools use a blade to cut off the material at a specific length. After the workpiece is

finished, a parting tool removes it from the part that is clamped into the chuck. They also

can be used to cut off the heads of bolts. Parting toolholders have an adjustment collar to

adjust the height of the tool used.

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Boring Tool Holders

There are different types of toolholders for boring tools. The light duty boring toolholder

works well with the standard-style tool post. The clamp-type boring toolholder can also be

used on the standard post, but it is used for heavier kinds of boring operations. Clamp-style

boring toolholders are adjustable, while quick-change boring toolholders are more rigid and

are perfect for carbide boring, but are not as adjustable for various sizes.

Tailstock Tool Holders

The tailstock of the lathe has a self-holding Morse taper, a device which allows for an

angle of only 2 or 3 degrees. Tailstock toolholders connect to the Morse taper so tightly

that it takes a lot of friction to keep the tool from spinning. Tailstock toolholders usually

hold drill chucks, drill sleeves and reamers.

1.6 Flow of CNC Process

In order to achieve the final product that cut out from the CNC machine, a few steps are

required to follow:

Develop the three-dimensional geometric model of the part using CAD software

Decide the required machining operations to produce the part

Choose the proper tools to be used

Generate the CNC part program using CAM software

Verify and edit the program

Download the part program to the appropriate machine over the network

Verify the program on the actual machine and edit them if necessary

Run the program and produce the part

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CHAPTER 2

PROJECT COMPONENTS


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2.1 Steel Component

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2.2 Aluminium Component – Part A

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2.3 Aluminium Component – Part B

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CHAPTER 3

CUTTING TOOL TECHNOLOGY


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3.1 Tool Geometry

Nearly all turning processes use single point cutting tools. The tools cut with only a single edge in contact with the work. The geometry of an insert includes:

The insert’s basic shapeIn turning, insert shape selection is based on the trade-off between strength and versatility. For example, larger point angles are stronger, such as round inserts for contouring and square inserts for roughing and finishing. The smaller angles (35º and 55º) are the most versatile for intricate work.A large point angle is strong but needs more machine power and has a higher tendency to vibrate due to having a large cutting edge engaged in cut. The small point angle is weaker and has a smaller cutting edge engagement, which can make it more sensitive to the effects of heat. Each insert shape has a set maximum effective cutting edge length which influences the depth of cut possible.

The insert’s nose radiusThe nose radius is a key factor in many turning operations and one that needs consideration as the right choice affects cutting edge strength to surface finish of the component. An insert is available in several nose radii where the smallest nose radius is theoretically zero but where 0.2mm is more commonly the smallest. The largest is normally 2.4mm, although the full range is not available for one and the same insert shape or size.In rough turning, the nose radius can be as large as possible for strength, without giving rise to vibration tendencies. The feed rate of the tool is also affected by the nose radius or vice versa. A large nose radius provides a strong edge, capable and dependent upon high feeds for proper cutting edge engagement. The small nose radius means a weaker point but one capable of fine cuts.

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3.2 Cutting Data

Cutting speed

The workpiece rotates in the lathe, with a certain spindle speed at a certain number of revolutions per minute. In relation to the diameter of the workpiece, at the point it is being machined, this will give rise to a cutting speed, or surface speed. This is the speed at which the cutting edge machines the surface of the workpiece and it is the speed at which the periphery of the cut diameter passes the cutting edge.

The cutting speed is only constant for as long as the spindle speed and /or part diameter remains the same. In a facing operation, where the tool is fed in towards the centre, the cutting speed will change progressively if the workpiece rotates at a fixed spindle speed. On most modern CNC Turning machine, the spindle speed is increased as the tool moves in towards the centre.

For a given material there will be an optimum cutting speed for a certain set of machining conditions, and from this speed the spindle speed (RPM) can be calculated. Factors affecting the calculation of cutting speed are:

The material being machined The material the cutter is made from (Carbon steel, high speed steel (HSS), carbide,

ceramics) The economical life of the cutter (the cost to regrind or purchase new, compared to

the quantity of parts produced)

Feed rate

The feed in mm/rev is the movement of the tool in relation to the revolving workpiece. This is a key value in determining the quality of the surface being machined and for ensuring that the chip formation is within the scope of the tool geometry. This value influences, not only how thick the chip is, but also how the chip forms against the insert geometry.

Feedrate is dependent on the:o Type of toolo Surface finish desiredo Power available at the spindle (to prevent stalling of the cutter or workpiece)o Rigidity of the machine and tooling setup (ability to withstand vibration or chatter)o Strength of the workpieceo Characteristics of the material being cut, chip flow depends on material type and

feed rate. The ideal chip shape is small and breaks free early, carrying heat away from the tool and work

o Threads per inch for taps, die heads and threading tools

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http://en.wikipedia.org/wiki/Ceramic

http://en.wikipedia.org/wiki/Tungsten_carbide

http://en.wikipedia.org/wiki/High_speed_steel

http://en.wikipedia.org/wiki/Carbon_steel

http://en.wikipedia.org/wiki/Revolutions_per_minute



Depth of cut

The depth of cut in mm is the difference between un-cut and cut surface. It is always measured at right angles to the feed direction of the tool.

3.3 Tool Life

All cutting tools have a finite working life. It is not a good practice to use worn, dull tools until they break. This is a safety hazard which creates scrap, impacts tool and part costs, and reduces productivity. Cutting tools wear in many different ways, including:

Excessive flank wear and notch wear

Rapid flank wear causing poor surface finish or out of tolerance. Notch wears causing poor surface finish and risk of edge breakage. This is caused by high cutting speed or insufficient wear resistance. Reduce the cutting speed and select a more wear resistant grade tool can eliminate the problem.

Crater wear

Excessive crater wear causing a weakened edge. Cutting edge breakthrough on the training edge causes poor surface finish. This is caused due to too high cutting temperatures on the rake face. The solution is to select positive insert geometry. First reduce the speed to obtain a lower temperature, and then reduce the feed.

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Plastic deformation

It leads to poor chip control and poor surface finish. The risks of excessive flank wear leading to insert breakage. It is caused by high cutting temperature combined with a high pressure. The solution is to select a harder grade with better resistance to plastic deformation or to reduce feed and speed.

Build-up-edge

Build-up-edge causes poor surface finish and cutting edge frittering when the B.U.E. is torn away. This is caused by low cutting speed and negative cutting geometry. The solution is to increase cutting speed and select a positive geometry.

Chip hammering

The part of the cutting edge not in cut is damaged through chip hammering. Both the top side and the support for the insert can be damaged. This is because the chips are deflected against the cutting edge. The solution is to change the feed and select alternative insert geometry.

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Frittering

This is small cutting edge fractures causing poor surface finish and excessive flank wear. This is occurred due to brittle grade, weak insert geometry and built-up-edge. The solution is to select tougher grade and an insert with a stronger geometry and increase cutting speed or select a positive geometry. And also can reduce feed at beginning of cut.

Thermal cracks

This is small cracks perpendicular to the cutting edge causing frittering and poor surface finish. Thermal cracks are due to temperature variations caused by intermittent machining and varying coolant supply. The solution is to select a tougher grade with better resistance to thermal shocks and coolant should be applied copiously or not at all.

Insert breakage

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Insert breakage damages not only the insert but also the shim and workpiece. This is due to brittle grade, excessive load on the insert, weak insert geometry and small insert size. The solutions are to select a tougher grade, reduce the feed and/or the depth of cut, select a stronger geometry and select a thicker/larger insert.

3.4 Tool Materials

Different machining applications require different cutting tool materials. The ideal cutting tool material should have all of the following characteristics: Harder than the work it is cutting High temperature stability Resists wear and thermal shock Impact resistant Chemically insert to the work material and cutting fluid

As rates of metal removal have increased, so has the need for heat resistant cutting tools. The result has been a progression from high-speed steels to carbide, and on to ceramics and other superhard materials.

High speed steelThere are over 30 grades of high-speed steel, in three main categories: tungsten, molybdenum, and molybdenum-cobalt based grades. The use of coatings, particularly titanium nitride, allows high-speed steel tools to cut faster and last longer. Titanium nitride provides a high surface hardness, resists corrosion, and it minimizes friction.

CarbideIn industry today, carbide tools have replaced high-speed steels in most applications. These carbide and coated carbide tools cut about 3 to 5 times faster than high-speed steels. Cemented carbide is a powder metal product consisting of fine carbide particles cemented together with a binder of cobalt. The major categories of hard carbide include tungsten carbide, titanium carbide, tantalum carbide, and niobium carbide. Each type of carbide affects the cutting tool’s characteristics differently. The carbide is used in solid round tools or in the form of replaceable inserts. Every manufacturer of carbide tools offers a variety for specific applications. The proper choice can double tool life or double the cutting speed of the same tool. Shock-resistant types are used for interrupted cutting. Harder, chemically-stable types are required for high speed finishing of steel. More heat-resistant tools are needed for machining the superalloys, like Inconel and Hastelloy.

CeramicCeramic cutting tools are hard and more heat-resistant than carbides, but more brittle. They are well suited for machining cast iron, hard steels, and the superalloys. Two types of ceramic cutting tools are available: the alumina-based and the silicon nitride-based ceramics. The alumina-based ceramics are used for high speed semi- and final-finishing of ferrous and some non-ferrous materials. The silicon nitride-based ceramics are generally used for rougher and heavier machining of cast iron and the superalloys.

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Superhard Superhard tool materials are divided into two categories: cubic boron nitride, or “CBN”, and polycrystalline diamond, or “PCD”. Their cost can be 30 times that of a carbide insert, so their use is limited to well-chosen, cost effective applications. Cubic boron nitride is used for machining very hard ferrous materials such as steel dies, alloy steels and hard0facing materials. Polycrystalline diamond is used for non-ferrous machining and for machining abrasive materials such as glass and some plastics. In some high volume applications, polycrystalline diamond inserts have outlasted carbide inserts by up to 100 times.

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CHAPTER 4

MASTERCAM PROGRAMMING


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4.1 Mastercam Software

Mastercam helps provide the CNC programmer with a valuable productivity tool for both the generation of CNC part programs and process planning. It helps reduce the time it takes to generate accurate machine-ready NC programs.

Mastercam supports many types of machines, each with a choice of levels of functionality, as well as offers optional add-ins for solid modeling, 4-axis machining, and 5-axis machining. The following list describes the Mastercam product levels:

Design—3D wireframe geometry creation, dimensioning, importing and exporting of non-Mastercam CAD files (such as AutoCAD, SolidWorks, Solid Edge, Inventor, Parasolid, etc.).

Mill Entry—Includes Design, plus various toolpaths (top construction and tool planes only), posting, backplot, verify.

Mill, Level 1—Includes Mill Entry, plus surface creation, many additional toolpaths (for all construction and tool planes), high feed machining, toolpath editor, toolpath transforms, stock definition.

Mill, Level 2—Includes Mill, Level 1, plus additional toolpaths, toolpath projection, surface rough and finish machining, surface pocketing, containment boundaries, check surfaces.

Mill, Level 3—Includes Mill, Level 2, plus 5-axis wireframe toolpaths, more powerful surface rough and finish machining, multi-axis toolpaths.

5-Axis add-on—5-Axis roughing, finishing, flowline multi-surface, contour, depth cuts, drilling, advanced gouge checking.

Lathe Entry—3D wireframe geometry creation, dimensioning, importing and exporting of non-Mastercam CAD files (such as AutoCAD, SolidWorks, Solid Edge, Inventor, Parasolid, etc.), various toolpaths, backplot, posting.

Lathe, Level 1—Includes Lathe Entry, plus surface creation, C-axis toolpaths, stock definition, stock view utility.

Router Entry—3D wireframe geometry creation, dimensioning, importing and exporting of non-Mastercam CAD files (such as AutoCAD, SolidWorks, Solid Edge, Inventor, Parasolid, etc.), various toolpaths (top construction and tool planes only), toolpath transformation in top plane, backplot, verify, posting.

Router—Includes Router Entry, plus surface creation, rectangular geometry nesting, additional toolpaths (for all construction and tool planes), high feed machining, toolpath editor, full toolpath transformations, stock definition.

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Router Plus—Includes Router, plus additional toolpaths, toolpath projection, surface rough and finish machining, surface pocketing, containment boundaries, check surfaces.

Router Pro—Includes Router Plus, plus True Shape geometry nesting, 5-axis toolpath functionality, multiple surface rough and finish machining, multi-axis toolpaths, toolpath nesting.

Wire—2D and 3D geometry creation, dimensioning, various 2-axis and 4-axis wirepaths, customizable power libraries, tabs.

Art—Quick 3D design, 2D outlines into 3D shapes, shape blending, conversion of 2D artwork into machinable geometry, plus exclusive fast toolpaths, rough and finish strategies, on-screen part cutting.

4.2 Mastercam Programming

There are three distinct steps in the CAM process, as follows:1. Input or define the part geometry2. Describe the cutter toolpath3. Generate the final CNC program

Before do the part program, we need to decide which side of the component should be machined first according to the part drawing. After the first side of part is done, we need to do a part program for soft jaw to clamp the machined side of the workpiece to machine the second half of the part. Therefore, there are at least three programs are needed in order to machine the part out.

I will use Aluminium – A project component as an example to illustrate the steps to do the Mastercam programming:

1. Plug-in the MastercamX4 license.

2. Double click the MastercamX4 icon on the desktop. 3. Select the machine definition – OKUMA LB3000EX-R MM.LMD from the Machine

Type menu.

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4. From the status bar appears along the bottom of the Mastercam window, select the working planes: D+ Z+.

5. Use the sketcher toolbar to create the geometry of the part according to the part drawing and save the drawing as Part2 (second half).

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Points

Lines

Arcs

Geometric shapes

Fillets/Chamfers

Splines

Primitives



6. Use Transforming Entities (Xform) to mirror the profile and translate to the zero location. Save the file as Part1 (first half).

7. Set the machine group properties. Click on Stock setup.

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Stock properties

Chuck jaws

properties



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Define raw material size

Define material to be faced off

Adjust chuck jaws diameter and location



8. Use the following guidelines to create toolpaths and apply them to geometry:a. Choose a toolpath type from the Toolpaths menub. Using the dialog boxes and prompts that display, chain geometry or select

points or other entities, as necessary.c. Select the tool and refine the tool parameters.

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Select tool

Set tool number

Check the tool shape

Check the corner radius



d. Set toolpath parameters to define and create the toolpath operation.

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Width of the grooving tool

Corner radius

Set cutting parameters



e. Verify and edit the toolpaths using the Toolpath manager, Backplot, and Verify functions.

Toolpath for first halfo Facing

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Depth of cut

Stock to leave

Stock recognition

Lead in/out



o External roughing

o External groove roughing

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o Internal roughing

o Internal groove roughing

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o External finishing

o External groove finishing

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o Internal groove finishing

o Internal finishing

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Toolpath for soft jaw

Toolpath for second half

o Facing

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o External roughing

o External groove roughing

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o Internal roughing

o External finishing

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o Internal finishing

o Threading

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9. Post process the selected machine group operations to create the NC code output for the machine control.

10. Go to website: 172.17.192.34 and upload the part files to the correct machine station.

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Post process icon

Machine control station: T1, T2, T3, T4




CHAPTER 5

MACHINING PROCESS OF PROJECT COMPONENTS


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5.1 Machine Specification

The machine I used for my project is OKUMA LB3000 EX CNC turning machine. It is a 2-axis lathe machine built on the high performance standards set by the successful LB series product and offering high accuracy with enhanced multi-tasking capacity. It is able to achieve machining dimensional change over time of less than Ø5µm.

It is very important to get to know the machine specifications and features of the machine tool. Many features relate to the control system, many others to the machine tool itself. In CNC programming, many important decisions are based on one or several of these features.

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CAPA

CITY

SPECIFICATIONS LB3000 EXDistance Between Centres

mm (in) 500 / 1000

Spec Line-up mm (in) M - W - MW - MYW

Swing Over Bed / Cover mm (in) Ø580 (22.83)

Saddle mm (in) Ø470 (18.5)

Max Machining Diameter mm (in) LØ410, MØ340 (16.14, 13.39)

Max Machining Length mm (in) 300 (11.81)

TRAV

ELS

X Axis mm (in) 260 (10.24)

Z Axis mm (in) 565 / 1,065 (22.24 / 41.93)

Y Axis mm (in) 120 ( / -50) (4.72 (.76 / -1.97))

Tailstock mm (in) 515 / 1,015 (20.28 / 39.96)

W Axis mm (in) 595 / 895 (23.43 / 35.24)

MAI

N S

PIN

DLE

Spindle Nose JIS A2-6 <JIS A2-8>

Thru Hole / Bearing Diameter

mm (in) 80 <91> / 120 <140> (3.15<3.58> / 4.72 <5.51>)

Spindle Speeds 45～5,000, 42～4,200

TURR

ET

Type V12

Tool Shank Height / ID mm (in) 25 / Ø40 (1 / Ø1.57)

Indexing Time sec 0.15

Live Tool Shank mm (in) 20 (0.79)

Live Tool Spindle Speeds 45～6,000

TAIL

STO

CK Live Centre Bore MT 5

Built-In Centre Bore MT 4

Quill Diameter mm (in) 90 (3.54)

SUB-

SPIN

DLE Spindle Nose Ø140 flats

Thru Hole / Bearing Diameter

mm (in) 62 / 100 (2.44 / 3.94)

Spindle Speeds 50～6,000

MO

TORS

RAPID TRAVERSE X-Z-Y m/min (ipm)

25, 30, 12.5 (984, 1,181, 492)

Main Spindle KW (hp) 22 / 15 [30 / 22] <30 / 22> (30 / 20 [40 / 30] <40 / 30>)

Live Tool Spindle KW (hp) 7.1 / 4.1 (25 min / cont) (9.6 / 5.5)

Sub-Spindle KW (hp) 11 / 7.5 (15 / 10)

Axis Drives KW (hp) X-Y-Z: 2.8, 2.8, 3.5 (3.8, 3.8, 4.8)Coolant Pump (side / rear)

KW (hp) 0.25 / 0.8 (0.34 / 1.09)

SIZE

Height mm (in) 1,839 / 1,950 (72.4 / 76.77)

Floor Space mm 500: 2,200X1,734, 1000: 3,310X1,895

Weight kg (lb) 4,400 / 5,900 (9,700 / 13,007)



5.2 Machining Preparation

Check the lubricant oil level of the machine before start operation.

Check the coolant level of the machine before start operation.

Switch on the main switch on the back of the machine.

Press start button on the machine panel.

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Start Button



Release the emergency stop button and press start button again.

Select the correct toolholders and inserts. Mount the required tools onto the machine turret. The internal tools must separate one slot with each other to avoid crashing into the chuck or workpiece.

Adjust the three jaw chuck location to clamp the raw material rigidly.

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Emergency stop button

Steel:T1 – OD RoughT2 – OD FinishT3 – OD Groove (R0.2)T4 – OD ThreadT6 – ID RoughT8 – ID FinishT10 – Face Groove (R0.3)

Aluminium:T1 – OD RoughT2 – OD FinishT3 – OD Groove (R0.4)T4 – OD ThreadT6 – ID RoughT8 – ID FinishT10 – ID Groove (R0.3) / ID Thread



5.3 Machining Process

1. Tool Length CalibrationBefore doing any machining, we need to calibrate the tools using the sensor mounted at the side of the machine. This is a procedure that corrects the difference between the programmed length of the tool and its actual length. The most significant benefit of tool length offset in CNC programming is that it enables the programmer to design a complete program, using as many tools as necessary, without actually knowing the actual length of any tool.

Pull out the probe on the side of the machine under manual mode. The machine display will automatically change to tool offset table.

Use the master tool – external finishing tool as a reference tool. Bring the master tool near to the probe and calibrate the length in X and Z axis.

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Pull out the probe

Tool offset table

Calibrate in X-axis Calibrate in Z-axis



Back to the tool offset table and calibrate all the tools required. External tools are calibrated by touching the upper and right side of the sensor which is the same as the master tool illustrated above. Internal tools are calibrated by touching the right and lower side of the sensor which is illustrated below.

2. Pre-drill Hole

In order to machine the internal profile of the components, we need to pre-drill a hole to leave space for boring bar to go in: Clamp the raw material into the three jaw chuck Go to MDI (Manual Data Input) mode and key in S1300M3 press enter.

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Calibrate in X-axis Calibrate in Z-axis

MDI Mode



Call the drilling tool and set the X offset value of drilling tool as 0. Move the drilling tool to X0 under MDI mode and near the right surface of the workpiece. Slowly move the drilling tool until it touches the right surface of the workpiece. Go to zero point set window on the control panel and calculate this location as Z0 so that we can roughly know how deep we should go in at the first side of the workpiece.

Turn on the coolant and use hand wheel to control the movement of drilling tool. After cut half of the length of the workpiece, stop the spindle and turn the

workpiece to the other side and drill again until a through hole is drilled.

3. Set Part Zero Point Use external roughing tool to touch the right surface of the workpiece and calculate this position as the amount of material need to be faced off. For example, the amount of material to be faced off is 4mm, then press calculate and key in 4 enter.

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X zero point – fixed at the center

of the chuck

Z zero point



4. Load Program for First Side and Do Simulation Go to program selection window on the machine panel → select TC → select the

correct program file → copy the file to MDI Go to program execution mode and select the program Click on display change → ANIMATED SIMULATION. Press Machine Lock button while holding Interlock button to lock the machine and

then press cycle start button. We can simulate the program without any movement of the machine.

5. Run the Program for First SideIf the simulation is done and no problem occurred, we can start to run the program. Turn on the optional stop and single block button first. Turn off the coolant for ease of observing the movement of the tool. Control the machine feed until it slowly reaches the start point of the program. If the start point location is correct, we can turn off the single block and on the coolant to start machining.

6. Soft Jaw Machining

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Machine lock

Cycle start

InterlockRelease

Feed rate

Coolant offSingle block

Optional stop



The workpiece should be like the figure shown below after machining the first side.

Take out the machined workpiece from the hard jaw. Select the appropriate ring size and clamp the ring with soft jaw.

Load the soft jaw program. Use thickness gauge to set the part zero point as the right surface of the soft jaw then run the program.

7. Machine Second Side

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Thickness Gauge



Clamp the workpiece into the soft jaw.

Use roughing tool to face off the rough surface of the workpiece then change to finishing tool to set part zero point.

Repeat the steps as illustrated for first side and machine the part out.

5.4 Finished Project Components

Steel Component

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Aluminium Component – A

Aluminium Component – B

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Assembled Aluminium Component – A and B

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CHAPTER 6

OPTIMISATION OF MACHINING PROCESS


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6.1 Cutting Tool Selection

The number one error when selecting tooling is calculating monetary savings based on lowest cost per tool, rather than on maximized productivity and extended tool life. To effectively select tools for machining, a machinist or engineer must have specific information about: Component design and limitations

Large or small, demanding form, long or short, diameter variation, vibration prone, close tolerances and surface finish, fixturing possibilities, etc.

Machining operations neededExternal and/or internal cuts, roughing, semi-finishing, finishing and complimentary operations, best tool paths, optimization possibilities, set-ups needed, additional operations with rotating tools, etc.

Stability and machining conditionsTool engagement, intermittent cuts, tool clamping, tool overhang, tool size, workpiece shape and condition, vibration tendencies, machine tool condition, power and drive, etc

Machine tool availability and choiceNumber of tool positions, power, capacity, possibilities of performing additional operations, driven tools, multi-axis and multi-task requirements, batch size suitability, coolant supply, tool holding, etc.

Component materialHardness, condition, strength, machinability, bar, casting, forging, pre-machined, variability, dry or wet machining, etc.

Tool program and inventoryOptimization, new types of tools, toolholding system, necessary tool variation/coverage, tool administration possibilities, select and apply strategy, standardization, tool supplier delivery, etc.

Machining economic aspectsOptimization of machining, cycle time, tool-life, continuous improvement, latest development, reliability, method choices, work-in-progress, cell machining, lean-manufacturing, cost-per-piece priority, focus areas, down-time minimization, etc.

The inserts I used are listed below:

80º OD Roughing with corner radius 0.8mm

35º OD Finishing with corner radius 0.4mm

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80º ID Roughing with corner radius 0.8mm

55º ID Finishing with corner radius 0.4mm

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OD Groove with corner radius 0.4mm, length 10mm/15mm depend upon the deep of the groove

ID Groove with corner radius 0.3mm

Face Groove with corner radius 0.3mm

Metric 60º thread



6.2 Cutting Parameters Selection

The controlled parameters in a turning operation that under normal conditions affect surface finish most profoundly are feed rate and cutting speed. The controlled parameters would play an important role in optimizing surface roughness. Inappropriate feed rate, cutting speed or depth of cut may cause the tool insert to wear or even break.

The cutting parameters are different for different materials. The physical properties of steel include high strength, low weight, durability, flexibility and corrosive resistance while the properties of aluminium include light weight, corrosion resistance, electrical and thermal conductivity, reflectivity, ductility and recyclability.

The cutting parameters I used for machining steel and aluminium components are listed below:

Steel component

Feed rate (mm/rev) Cutting speed (CSS)Face 0.15 300OD Rough 0.2 250ID Rough 0.15 250OD Groove Rough 0.05 150Face Groove Rough 0.05 150Groove Finish 0.1 350OD Finish 0.1 350ID Finish 0.1 350Thread - 400

Aluminium component

Feed rate (mm/rev) Cutting speed (CSS)Face 0.15 300OD Rough 0.2 275ID Rough 0.15 250Groove Rough 0.05 300Groove Finish 0.05 500OD Finish 0.05 500ID Finish 0.05 500Thread - 600

6.3 Toolpath P lanning

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In order to achieve the optimal performance of machining, we need to analyze the drawing and edit the program to decide the optimal toolpaths.

1. Toolpath for Steel Component

First Sideo Face o External rougho External groove rougho Face groove rougho Internal rougho Face and external finisho External groove finisho Face groove finisho Internal finish

Second Side

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o Faceo External rougho External groove rougho Internal rougho Face and external finisho Internal finisho External thread

2. Toolpath for Aluminium Component A

First Sideo Faceo External rougho External groove rougho Internal rougho Internal groove rougho Face and external finisho External groove finisho Internal groove finisho Internal finish

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Second Sideo Faceo External rougho External groove rougho Internal rougho Face and external finisho Internal finisho External thread

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3. Toolpath for Aluminium Component B

First Sideo Faceo External rougho External groove rougho Internal rougho Internal undercuto Face and external finisho External groove finisho Internal finisho Internal thread

Second Sideo Faceo External rougho External groove rougho Face and external finisho External groove finish

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When doing facing operation, I leave 2mm overcut to make sure that no redundant material is left on right surface of the material. This is critical if there is no internal profile to be machined on that surface.

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Overcut Amount



I use internal finishing tool to slowly cut the small internal groove instead of using internal grooving tool. This is to reduce the number of tools used due to limited space in machine turret and it shortens the tool setup time as well.

In order to achieve better surface finishing, the toolpaths for external finishing and groove finishing cannot be overlapped.

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Finishing cut of the outer surface

Internal groove



6.4 Machining Process

To get better surface finishing and dimensional accuracy of the final product, control during machining process is essential.

Although we have calibrated all the tools using the sensor on the machine, the sensor may not be very accurate. This is not a big problem for external tools, but when comes to internal tools consideration should be taken. The error may cause the boring bar takes a rather deep cut or crashes with the workpiece. Hence, I do manually calibration for the internal tools by taking light cut of the internal profile and measure the diameter. Then go to tool offset table and change the X– offset value.

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Groove finishing

X–offset value for internal tool



The hole pre-drilled for the access of internal tool should be a through hole if the workpiece is to be machined on both sides. The hole should be deep enough if the workpiece is only machined in one side. If the depth of the hole is not given an enough tolerance, the tool tip may crash into the workpiece and break the insert. When it comes to machining of non-through hole, chip may stick inside the workpiece. The solution to overcome this problem is to take few cut then move the cutter out and clean the chip then restart.

When a tight dimensional tolerance and a fine surface finishing of the workpiece are needed, the program itself is no necessary to be changed but a tool wear offset for the selected tool is applied. Tool wear offset value is the difference between the programmed value and the actual measured size of the part. The principle of the wear offset adjustment is logical. If the machined diameter is larger than the drawing dimension allows, the wear offset is changed into the minus direction, towards the spindle center line, and vice versa. This principle applies equally to external and internal diameters. The only practical difference is that on oversized external diameter and undersize internal diameter can be recut. The figure below illustrated the principle of the tool wear offset.

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Spoiled workpiece with chip stuck inside

Program path

Offset path



To adjust the tool wear offset value, go to tool offset table and change the tool wear offset value of the finishing tool before the finishing operation to control the dimension of the workpiece. I left 0.1mm and 0.05mm for external and internal finishing tool on X axis and Z axis respectively. For groove finishing, I left 0.05mm on X axis.

After the modified finishing toolpath is done, measure the length as well as the external and internal diameter of the workpiece. And then modify the tool wear offset value based on the measured dimension.Restart the program to do the finishing cut again by selecting Main Program Selection→ Restart → Key in the block number → Press Sequence Restart button on the control panel → Press Cycle Start button.

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X offset value

Z offset value

Sequence Restart



We need to edit the block number to ensure that the program can be restarted at the required operation. Take the following program as an example:

(OD GROOVE RIGHT - NARROW)G50 S3000G00 G97 S800 X500. Z500.NAT3T0303 M4 M8 ( ROUGH GROOVING )G96 S150G00 X74.4 Z-25.55G01 X54.4 F.05G00 X74.4 Z-25.55X74.4 Z-27.133G01 X54.4X54.717 Z-26.975G00 X74.4 Z-26.975X74.4 Z-23.967G01 X54.4X54.717 Z-24.125G00 X74.4 Z-24.125X74.4 Z-23.2G01 X54.4X54.717 Z-23.358G00 X74.4 Z-23.358X74.4 Z-28.717G01 X54.195G00 X74.4 Z-28.717X74.4 Z-22.383G01 X69.207G03 X65.6 Z-23.2 I-1.803 K1.584G01 X54.4X54.717 Z-23.358G00 X74.4 Z-23.358X74.4 Z-29.2G01 X42.4G00 X56.543 Z-29.2X56.543 Z-27.734G02 X54.195 Z-28.717 I.599 K-1.908G03 X52.6 Z-29.2 I-.797 K.416G01 X42.4G00 X74.4 Z-29.2X74.4 Z-29.8G01 X42.4X42.717 Z-29.642G00 X74.4 Z-29.642X74.4 Z-30.3G01 X59.512G02 X57.9 Z-29.8 I-.806 K-.4

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Change to NAT33



G01 X42.4X42.717 Z-29.642G00 X74.4 Z-29.642X74.4 Z-20.8G01 X70.4G03 X69.207 Z-22.384 I-2.4G00 X74.4 Z-22.383M9G00 G97 S800 X500. Z500.M5M1 (OD GROOVE RIGHT - NARROW)G50 S3000G00 G97 S800 X500. Z500.NAT3T0303 M4 M8 ( FINISH GROOVING )G96 S350G00 X72.828 Z-19.386G01 X70. Z-20.8 F.1G03 X65.6 Z-23. I-2.2G01 X54.Z-25.7Z-28.3G03 X52.6 Z-29. I-.7G01 X42.Z-30.X57.9X57.945X58.245 Z-29.85G00 X74.4 Z-29.85X74.4 Z-30.5G01 X70.4X59.242G02 X57.9 Z-30. I-.671 K-.2G01 X42.Z-29.321G00 X74. Z-29.321M9G00 G97 S800 X500. Z500.M5M1

The program contains two grooving operations using the same tool, but the first one is groove roughing while second one is groove finishing. If we remain both the block number as NAT3, the program will jump to the first block which is groove roughing operation. This is inconvenience if we want to restart at groove finishing operation. So we need to edit one of the block numbers to differentiate them.

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Remain unchanged




CONCLUSION


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During the 12 weeks time, I have gained the skills of producing a high quality product using CNC

Turning machine.

I have faced some difficulties and machining problems when doing my project, for example,

difficulty of cleaning the chip in the machine, inappropriate cutting parameters lead to

unsatisfactory surface finishing of the workpiece, improper clamping of the boring bar lead to bad

surface finishing of the soft jaw, insert break due to inadequate depth of the pre-drilled hole.

However, with teachers’ guidance, I have overcome these difficulties and trained my technical

skills through the process of machining.

I learned a lot of things during this project. I refreshed the knowledge I learned previously and

designed my project component using UG software. I learned how to use Mastercam software and

generate the toolpath. I gained the skills of operating the CNC Turning machine as well as adjusted

the tool wear offset value to control the dimension of the component and get a better surface

finishing part.

Overall, I absorbed a lot of information about CNC Turning by doing this project and it’s really a

significant experience for me.

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APPENDIX


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I. List of Preparatory Functions (G Codes)

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G code DescriptionG00 Rapid positioningG01 Linear interpolationG02 Circular interpolation clockwiseG03 Circular interpolation counterclockwiseG04 Dwell (as a separate block)G09 Exact stop check – one block onlyG10 Programmable data input (Data Setting)G11 Data Setting mode cancelG20 English units of inputG21 Metric units of inputG22 Stored stroke check ONG23 Stored stroke check OFFG25 Spindle speed fluctuation detection ONG26 Spindle speed fluctuation detection OFFG27 Machine zero position checkG28 Machine zero return (reference point 1)G29 Return from machine zeroG30 Machine zero return (reference point 2)G31 Skip functionG32 Threading – constant leadG35 Circular threading CWG36 Circular threading CCWG40 Tool nose radius offset cancelG41 Tool nose radius offset leftG42 Tool nose radius compensation rightG50 Tool position register / Maximum r/min presetG52 Local coordinate system settingG53 Machine coordinate system settingG54 Work coordinate offset 1G55 Work coordinate offset 2G56 Work coordinate offset 3G57 Work coordinate offset 4G58 Work coordinate offset 5G59 Work coordinate offset 6G61 Exact stop modeG62 Automatic corner override modeG64 Cutting modeG65 Custom macro callG66 Custom macro modal callG67 Custom macro modal call cancelG68 Mirror image for double turretsG69 Mirror image for double turrets cancelG70 Profile finishing cycle



II. List of Miscellaneous Functions (M Codes)

M code DescriptionM01 Optional program stopM02 Program endM03 Spindle on clockwiseM04 Spindle on counterclockwiseM05 Spindle stopM07 Coolant 1 onM08 Coolant 2 onM09 Coolant offM30 End of program, Reset to start


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G71 Profile roughing cycle – Z axis directionG72 Profile roughing cycle – X axis direction G73 Pattern repetition cycleG74 Drilling cycleG75 Grooving cycleG76 Threading cycleG90 Cutting cycle A (Group type A)G90 Absolute command (Group type B)G91 Incremental command (Group type B)G92 Thread cutting cycle (Group type A)G92 Tool position register (Group type B)G94 Cutting cycle B (Group type A)G94 Feedrate per minute (Group type B)G95 Feedrate per revolution (Group type B)G96 Constant surface speed mode (CSS)G97 Direct r/min input (CSS mode cancel)G98 Feedrate per minute (Group type A)G99 Feedrate per revolution (Group type A)



GANTT CHART


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REFERENCES


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http://books.google.com.sg/books?

id=6M1E8ydzAgkC&printsec=frontcover#v=onepage&q&f=false

http://books.google.com.sg/books?

id=JNnQ8r5merMC&pg=PA132&lpg=PA132&dq=tool+length+offset&source=bl&ots=P

XVFRN4PwS&sig=MDXopZyFTDBoDUJoNb5y9__Cy9Q&hl=en&ei=20c-

Tcm7EZG3rAee2bCbCA&sa=X&oi=book_result&ct=result&resnum=11&ved=0CF4Q6A

EwCg#v=onepage&q=tool%20length%20offset&f=false

http://www.mini-lathe.com/Mini_lathe/Operation/Turning/turning.htm

http://www2.coromant.sandvik.com/coromant/pdf/metalworking_products_061/

tech_a_2.pdf

http://www.ehow.com/list_7467149_types-lathe-tool-holders.html

http://en.wikipedia.org/wiki/CNC_Software/Mastercam

http://en.wikipedia.org/wiki/Speeds_and_feeds#Feed_rate

MCAMX4_RefGuide

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http://en.wikipedia.org/wiki/Speeds_and_feeds#Feed_rate

http://en.wikipedia.org/wiki/CNC_Software/Mastercam

http://www.ehow.com/list_7467149_types-lathe-tool-holders.html

http://www2.coromant.sandvik.com/coromant/pdf/metalworking_products_061/tech_a_2.pdf

http://www2.coromant.sandvik.com/coromant/pdf/metalworking_products_061/tech_a_2.pdf

http://www.mini-lathe.com/Mini_lathe/Operation/Turning/turning.htm

http://books.google.com.sg/books?id=JNnQ8r5merMC&pg=PA132&lpg=PA132&dq=tool+length+offset&source=bl&ots=PXVFRN4PwS&sig=MDXopZyFTDBoDUJoNb5y9__Cy9Q&hl=en&ei=20c-Tcm7EZG3rAee2bCbCA&sa=X&oi=book_result&ct=result&resnum=11&ved=0CF4Q6AEwCg#v=onepage&q=tool%20length%20offset&f=false



http://books.google.com.sg/books?id=6M1E8ydzAgkC&printsec=frontcover#v=onepage&q&f=false

http://books.google.com.sg/books?id=6M1E8ydzAgkC&printsec=frontcover#v=onepage&q&f=false

Fyp Report Dpe 080001k Liang Yue

Documents

lim siok khing

excessive

stored stroke

mastercam

emergency

press start

increase cutting

poor surface