HMT Machine Tools Summer Training Report

ACKNOWLEDGEMENT

I would like to thank the entire HMT limited who has provided me this six weeks training. I am thankful to the HRD officer of training centre who organized my training schedule and also the DGM’s and AGM’s of various shop departments who have provided me the various knowledge about their respective shops.

I also thanks to the workers of their respective departments, who were always ready to clarify our doubts and helped us to increase our knowledge by illustrating us to the finer points.

I wish to express my deep gratitude to all the concerned persons, whose co-operation and co-ordination have given me the success to complete my training in organization.

I hope that my report will reflect our technical knowledge and innovativeness, which we gained at HMT Pinjore.

[1]

PREFACE

Industrial training is part and parcel of every technical course and gives a face or form to all the theoretical knowledge we gain in our classroom. We get to have a virtual experience of the processes, methods, objects and phenomenon which used to be just an imaginary picture in our minds. It also gives an exposure to the environment of the industries and workshops which are virtual components of our professional life. We too were provided with this opportunity this summer.

We are thankful to our college administration that handed this invaluable chance to us and at the same time we pay our regards to the administration of HMT Pinjore (Machine Tools Division) that proved to be a great supporting force for the fulfillment of the purpose. The officials and the workers of the firm provided us with the best of their attention and share ample of knowledge of their concerned field with us.

[2]

INTRODUCTION

Fulcrum of Indian Industrial Development:

HMT synonymous with excellence in precision engineering is a multi product company established in 1953. Built on a strong foundation of technical know how acquired from world leaders in machine tools such as Oerlikon, Manurhin, Glidemeister, Liebherr, Rino Berardi, Fritz Werner, Pegard, Waldrich Coburg etc. HMT’s machine tools expertise has been developed to such an extent that HMT can design and develop any kind machine. Having established as a machine tool manufacturer, HMT diversified into other product lines.

From simple lathes to multi-station transfer lines from stand alone CNC machine to flexible manufacturing systems, leading to factory automation, HMT’s broad range of machine tools cover General Purpose Machine, Special Purpose Machines and CNC machines, meetings the application needs to every engineering industry.

Pioneering the concept of CNC technology in India HMT has the destination of being the first company to successfully manufacture its own CNC system in association with Siemens.

HMT’s commitment to the development of the machine tools technology is clearly reflected in the fact that HMT has as many as seven exclusive machine tool units,

[3]

spread across the country. Each superbly equipped to meet the most challenging demand for machine tools. These units are in Banglore, Pinjore, Kalamassery, Hyderabad, and Ajmer are all ISO 9000 certified.

Today HMT is well positioned at the fore front of the precision engineering field. Its manufacturing plants employ highly skilled workforces strongly supported by R&D. Today over 780000 machine tools manufactured by HMT are in used in India and elsewhere.

In tune with changing business environment, HMT limited restructured into holding company tractors as its core business and the following subsidiaries:

HMT Machine Tools Limited, HMT Watch Limited, HMT Bearings Limited, HMT Chinar Watches Limited, HMT (International) Limited, Praga Machine Tools Limited.

[4]

The Pinjore Unit:

After having established two machine tools factories and a watch factory in Bangalore, the Pinjore Unit was established as the third machine tools factory. It went into production on 1st Oct. 1963. This factory has been designed, built and commissioned entirely by Indian talent in a record period of 17 months of breaking the ground on May 2, 1962. Pundit Jawaharlal Nehru, The first Prime minister of free India, inaugurated it on Oct. 28, 1963. Later in June 1971, HMT’s Tractor project commenced its operation here.

Machine Tools Division:

The unit was initially planned for manufacturing Milling Machines. To begin with, foreign designed capabilities, HMT’s self designed machines were introduced. Today the range includes carious types of knee as well as turret ram types of Milling machines Rugged and versatile, these machines offer wide spindle speeds and feeds. With high contents mechatronics, Milling machine with predefined programme upto 40 steps have been introduced.

In 1969 manufacture of Broaching Machines was taken up as import substitution. Available in horizontal and vertical versions, these ruggedly constructed machines have infinitely variable cutting speeds with dead constant speeds ensuring optimum tool life and fine surface finish.

[5]

In tune with HMT’s commitment to usher in the latest technologies to the country’s fast developing industrial base, in 1976 the unit introduced the state of art computerized numerically controlled machine offering unlimited option in unmanned manufacturing concept.

The unit has designed a wide range of both Horizontal and Vertical CNC Machining Centre to meet the stringent accuracy standards, providing high flexibility and productivity with enough muscle to remove large quantities of material at low RPM for steel and high RPM for light metal alloys. High processing speed is ensured through CNC Systems that have powerful graphics and user-friendly features. The machine can be integrated with other machine tools into flexible manufacturing line. The unit also manufactures moving column type Special Purpose Machines which can perform milling, drilling, tapping, boring and reaming operation with re-circulating linear motion bearing for high position accuracy with the encoder ‘x’, ‘y’, and ‘z’ axis.

Beyond Machine Tools:

HMT also manufactures metal forming presses and press brakes, die casting & plastic injection moulding machine, printing presses, wrist watches, tractors, bearings, food processing machinery and a host of other engineering products. Besides, HMT has proven expertise in Turkey projects both within the country and outsides.

[6]

PATTERN SHOP

A pattern may be defined as a replica or facsimile model of the desired casting which, when packed or embedded in a suitable moulding material, produces a cavity called mould. This cavity, when filled with molten metal, produces the desired casting after solidification of the poured metal. Since it is a direct duplication, the pattern very closely conforms to the shape and size of the desired casting, except for a few variations due to the necessary allowances.

The most commonly used pattern materials in the industry are 1) wood (e.g. teak, deodar etc.), 2) metal (e.g. aluminium, cast iron, bronze etc.), 3) thermocol, 4)rubber, 5)epoxy resin.

Wood:-

Wood are used for pattern making are of either teak or deodar or both of them. When both of them are used, then teak is generally used on the inner sides because teak is harder and retains it’s shape for longer times as compared to deodar which secretes a resign that on solidification can effect the shape of the pattern which when used gives defective casting.

[7]

Comparison of Teak and Deodar:

1. Teak is easier to work in milling operation.2. Teak is harder in comparison with deodar.3. Teak has longer life so it is used in making patterns of

those tools which are to be manufactured in large numbers.

[8]

FOUNDARY SHOP

HMT’s foundary shop comprises of two units:

One is the captive foundary, meant for the small production of casting having weight upto 4 tonnes. The capacity of this foundary is 1000 MT per annum.

And the other is meant for mass production of comparatively smaller tractor and machine components. The capacity of this foundary is 2000 MT per annum.

Melting Department:

The process of melting in HMT is carried out in induction furnaces at a temperature of about 1400°-1450° C

Process:

At first the induction furnaces are coated with fine cement clay. Now metal scrap is inserted in the furnace and slag coagulant is added to it. The requisite amount of coke is added to it. The current is supplied to copper coils provided in the furnace which induce current in the metal scrap and the scrap gets heated up, when the melting temperature is reached the molten metal is collected in ladles and taken to the pouring zone. When this process is being carried out the copper coils are regularly cooled with

[9]

coolant (water) so that the coils do’not melt due to the high temperature generated in the coils.

The foundary of HMT has three furnaces, two, each having capacity of 3MT and one of 1.5MT. The two types of induction furnaces are:-

Main frequency Induction Furnace(50Hz) Medium frequency Induction Furnace(250Hz)

Melting of metal ion medium frequency furnaces are faster than the main frequency furnaces.

Specifications of 1.5 tonne capacity furnace:-

Line Voltage : 11000 Volts

Primary Voltage : 440 Volts

Power Voltage : 440 KW

Power Rating : 5 KA

Melting Power : 1 tonne per hour

Frequency : 50 Hz

Lining Thickness : 95 mm

Power Factor : 0.9

After the melting process is complete, the molten metal is carried quickly to the moulds to prevent solidification. The inversion of Induction Furnaces is

[10]

carried out by hydraulic lifts fitted just below the whole apparatus.

Moulding and Core Making:

In HMT due to complex structure of components (such as gear box) are produced with the help of master pattern. Here core is first made with the help of master pattern after which the core is allowed to be baked.

The core is made with the help of sand such as

Rigid coated sand in shell core machining. Air setting sand or no bake sand. Green sand.

Here the gear box is made with no bake/air setting sand which is prepared by mixing different constituents.

Here the prepared core (made from master pattern) is allowed to solidify.

Smaller core is baked with the help of shell core machine, which has a box containing rigid coated sand. When allowed to operate the front assembly rotates and the box moves upward from which the sand falls in the die (die used according to shape of core required) here die can be changed.

Now the core is put in cope, drag and the molten metal is poured after which pattern can be easily obtained.

[11]

Fettling:

Fettling is the process by which the pattern obtained is given the desired finish by various processes. Before fettling, the casting obtained is subjected to removal of projections, chips, core, runner, riser etc. by the following processes:

Decoring Chipping Shot blasting (for heavy pattern) Wheel abrasion (for small pattern)

Decoring:

Decoring is the process of removing the fused sand.

Chipping:

Chipping is the process of removing the runner, riser etc.

Shot Blasting & Wheel Abrasion:

Shot blasting or wheel abrasion is used for removing the sand particles by the usage of air.

After this fettling is done by the following process:

Pneumatic gun- to remove corner sand. Angle grinder- to give corner finish. Die grinder- to give finish to inner portion. Pedestal grinder- to give surface finish.

[12]

While making casting for gears, surface finish is not required because gear has to be cut on it with the help of milling machine after which it is grinded.

PRIMING & PAINTING:

After clean and fettling, the casting is subjected to priming and painting to prevent corrosion.

[13]

SMALL PARTS AND HEAT TREATMENT

This section of machine tool, HMT is primarily concerned with the manufacturer of small parts of machine tools. The machines concerned are CNC machines, lathe machines, milling machines, drilling machines etc. This department requires precision work.

Since there are number of small parts for number of machines and of different shapes, therefore this department is further divided into different subsections. They are:

1 Spindle section

2 Turret section

3 Round section

4 Gearing section

5 Non round section

6 Sheet metals section

Spindle Section:

This section is concerned with the manufacturing of small cylindrical parts or spindles which may be hollow, solid, shell type etc. according to machine’s requirement. The jobs concerned are larger in size as compared to other sections. This section manufactures all the head related obs. This machine requires for the purpose include lathe

[14]

machines like LB26 lathe, centre lathe, turret lathe. Also use of drilling machine is there .Thread cutting operation is also carried out in this section. The job to be worked upon is supplied by the foundry department.

Examples of the parts manufactured:- Bearing housing ,main spindle , shafts, cam, sleeves etc.

Turret Section:-

This section is concerned with small job construction. These jobs requires precision works since these parts are to be fitted in small areas and generally screwed up the machines involved in this process are lathe machine and use of precision measuring instrunments like digital micrometer, dial vernier calliper etc.

Examples of parts manufactured:- nut, bolts, clamping screw, pins, holder, micro nuts etc.

Round Section:-

This section concerned with the round job construction and working. The section involves operation like grinding, slotting, drilling etc.

Following are the lists of machines and operations concerned with them:-

[15]

Internal Grinding Machines:-

Concerned with grinding of inner surface of job.

Surface Grinding Machines:-

Concerned with outer surface of job. It uses magnetic chuck and shows only horizontal motion of the table at the bed.

Rotary Grinding Machines:-

Concerned with horizontal as well as rotational movement of the table. It also uses magnetic chuck.

Cylindrical Grinding Machine:-

This is used to grind cylindrical jobs with the motion of grinder itself. This job is held in the jaw chuck.

Slotter:-

This machine is concerned with slot cutting. It uses carbide tip and shows vertical motion of the tool for slot cutting.

The other machines concerned with this section are lathes, drilling machines etc.

[16]

Gearing Section:-

Gear is used for power transmission of different parts of machines. This section is concerned with teeth cutting. Proper indexing is maintained in the process with fixtures on the machines concerned. There are four types of gears used in manufactured here:-

1. Spur gear2. Worm gear3. Helical gear 4. Bevel gear

The various machines involved are:-

Milling Machine:-

Generally used for manufacturing of spur gears. Cutters of prescribed sizes are used.

Gear Hobbing Machines:-

Gear hobbing machine is used for manufacture of worm gear. It uses hydraulic action.

Broaching Machine:-

Broaching machine is used to put splines in gear.

[17]

Gear Teeth Grinding Machines:-

It is used for grinding the teeth of the gears. In this machine gear teeth are grinded by a worm type grinding wheel. Here the tooth profile are checked with a machine called gear tooth profile tester.

Non- Round Section:

All the non-round jobs that are to be used in machines are machined here.

Components Manufacturing:

Blocks, rectangular strips, gibs, pump body, stop block, adjustable plate, clump levers etc.

Operations Performed:-

1. Marking2. Vertical milling3. Drilling4. Fitting5. Grinding

[18]

Machines Used in Section:-

Horizontal milling machine Vertical milling machine Surface grinding machine

Sheet Metal Section:

This section includes the cutting of sheets, bending of sheets at various angles. Various operations like drilling, bending, shearing etc, are completed in this section. Some of the areas where sheet metal are used are:

1. For outer body manufacture.

2. For making junction boxes in CNC machines.

Machines Used in Section:-

Radial arm drilling machine Nibbling machine Bending machine Shearing machine Nc machine

[19]

MATERIAL TESTING

1) UNIVERSAL TESTING MACHINE :

It has component load scale, oil pump, hydraulic press, main piston, fixed cross head, & movable cross head. It has range according to load applied:

a) 0-1 tonsb) 0-4 tonsc) 0-10 tons

It is generally used to determine:

Proportional & elastic limit Yield point Ultimate tensile strength Percentage elongation & reduction of area

Working:

It is generally used to perform tensile test which is widely used in the design of material for structure & other purposes. Here, test piece is pulled out at a constant rate gradually increasing the axial pull, till the rupture take place. The tensile test for ductile material is generally, carried out with the help of a Universal Testing Machine on the specimen made from material to be tested.

[20]

2)SPECTROSCOPE:

It is a method of qualitative analysis of material with the help of electricity. Argon gas is being used as it prevents oxidizing of piece. Here piece is not destroyed. This is used for chromium, ammonium, nickel, tungsten, manganese, zinc, tin, lead etc. the spectrum is directly compared with a chart as it is moved by caliper & is then compared. It is used to find what materials are present.

3)SPRING TESTING MACHINE:

In this machine, spring test is done. We will find out compression or extension of spring & the load applied which is noted from load indicator. Then we calculate spring stiffness.

4)POLISHING MACHINE:

In this machine polishing of material is done. In this belts are present on which abrasive powder is applied. In this machine belt is passed over two pulleys & which is driven by motor.

5)MAGNETIC CRACKING TEST:

[21]

In this method, magnetic crack test machine is used. It is to check cracks b/w two pieces. We take two pieces which are magnetized followed by spraying the iron chips. The ultra violet light marked & fluorescent color is produced. Then Iron piece is glows due to ultra violet light.

6)SPECTOMETER:

It is basically computerized control program in which material is kept under observation than software is there which give composition of each element present in the material.

7)PORTABLE MICROSCOPE:

It is a method used for analysis of the structure without cutting. And also it is used for determining the composition of element present in the material. It is used for the analysis of the structure.

8)CARBON TASTING APPRATUS:

It is chemical method of analysis of the material. In this, we take test sample of 1gm of carbon in the silica boat which is put in silica pipe. This is now passed through furnace which is at 1000 deg Celsius. Now oxygen gas is passed & then carbon dioxide (CO2) is

[22]

formed which dissolves in alkaline solution than value is raised to corresponding exhaust temperature. Then carbon content is determined as:

CARBON CONTENT = 0.3×CORRECTION FACTOR×VOLUME READING

9)ROCKWELL HARDNESS TEST:

The Rockwell hardness test is generally performed when quick & direct reading is desirable. This test is also performed when the material have hardness beyond the range of Brinell hardness test. In this test the load for making indent are smaller & thus make smaller shallower indent. It is because of this reason that the Rockwell hardness test is widely used in industry. This test has nine scales of hardness (A to H & K). But B & C scales are widely used. The ball indenters are generally made of hardened tool steel or tungsten carbide. During the test, the specimen is placed on anvil, & raised till it comes in contact with indenter. A minor load of 100 KN is applied on the specimen & the small pointer indicates set. Now the main pointer is also brought to the set position. The major load is then applied & is allowed to continue for one second. The depth of indentation in mm is read from the smaller pointer.

[23]

10)VICKER HARDNESS TEST:

The Vicker Hardness Test is the most accurate test which has a fairly continuous scale of hardness. The test makes the use of a diamond square based pyramid indenter. A piston & a dashpot of oils used for controlling the rate & duration of the loading. The test is performed by placing the specimen on an anvil & raised till it is close to the indenter point. The load is then gradually applied to the indenter & then removed. This test is very suitable for testing polished & hardened material or nitride surface due to small impression made on the test specimen.

PRECAUTION:

The indenter & anvil should be clean & well placed. The surface of the specimen should be flat, clean, dry,

& smooth &should be placed perpendicular to the indenter.

[24]

M CODES

M00 Program Stop

M01 Optional (Planned) Stop

M02 End of program

M03 Spindle CW

M04 Spindle CCW

M05 Spindle OFF

M06 Tool change

M07 Coolant #2 ON

M08 Coolant #1 ON

M09 Coolant OFF

M10 Clamp

M11 Unclamp

M12 Unassigned

M13 Spindle CW & Coolant ON

M14 Spindle CCW & Coolant ON

M15 Motion +

M16 Motion -

M17 Unassigned

M18 Unassigned

M19 Oriented spindle stop[25]

M20-M29 Permanently Unassigned

M30 End of tape

M31 Interlock bypass

M32-M35 Unassigned

M36-M39 Permanently Unassigned

M40-M45 Gear changes if used, otherwise unassigned

M46-M47 Unassigned

M48 Cancel M49

M49 Bypass override

M50-M89 Unassigned

M90-M99 Reserved for user

[26]

G CODES

G00 Rapid Positioning

G01 Linear Interpolation

G02 CW circular Interpolation

G03 CCW circular Interpolation

G04 Dwell

G05.1 Q1 Ai Nano contour control

G05 P10000 HPCC

G07 Imaginary axis designation

G09 Exact stop check

G10/G11 Programmable Data input/ Data write cancel

G12 CW Circle Cutting

G13 CCW Circle Cutting

G17 X-Y Plane selection

G18 X-Z Plane selection

G19 Y-Z Plane selection

G20 Programming in inches

G21 Programming in mm

G28 Return to home position

G30 2nd reference point return

G31 Skip function[27]

G33 Constant pitch threading

G34 Variable pitch threading

G40 Tool radius compensation off

G41 Tool radius compensation left

G92 Programming of absolute zero point

G94/G95 Inch per minute/ Inch per revolution feed

G96 Constant surface speed

G97 Constant spindle speed

G98/G99 Return to initial Z plane/ R plane in canned cycle

[28]

HEAVY PARTS AND TOOL ROOM

INTRODUCTION:-

It is the shop which gives the shape to the largest castings which come from the foundary after being painted rough. In this section various operations are performed by the help of planers, boring and planning-boring machines.

In this section, first of all the jobs are checked for the castings to be over-size or undersize. If they are undersize, they are sent to scrap. If they are oversize, they are marked and sent for machining.

Different types of operations are done by using different machines including various measuring devices.

This section also includes in itself a high technology section in which advanced machines are placed to machine crucial parts generally guide ways etc. It accommodates a tool preset device which is used to set the tool of all machines and CNC machines. It is used to measure the length and diameter of the tool with the help of leases.

This section is generally divided into two sections:

Planning Boring

[29]

Planning:-

This section consists essentially of planers mounted on one side of the section. In this section the job planning is one of the basic operations done for machining process. It is primarily intended for machining large flat surfaces.

Machines Installed

Double Housing Planer Open Side Planer Plano Milling Machining Horizontal Turning Centre

1) Double Housing Planer:-

This is the heavy type of planer and is used for heavy cuts by double cutters. Its length is 3000mm. It consists of two columns, one on each side of bed. The cross rail is fitted between the two housings which can accommodate one or two heads, according to the specifications.

2) Open Side Planer:-

This type of planer consists of a single column situated vertically on one side of the bed and other side is left open without any column.

[30]

The cross-rail is wholly supported on the single column. Only one tool head can be located on it as there is only one column.

3) Plano Milling Machine:-

This is similar to a double housing planer but the tool can be milling tool. One of the machines is TNC (three axis turning centre) in which only one axis can be moved at a time. Thus round jobs cannot b machined here.

Another machine is CNC in which two axis can be moved simultaneously to machine round job. The length of the bed is 2800mm.

Boring:-

Boring is the operation of enlarging an already drilled hole. The holes are pre-drilled as in casting only.

Machining time in boring:-

Machining time is the time required to complete the work place in a request period of time.

Time required = Length of cut/(RPM × feed per meter)

Machines installed

Horizontal Boring Machine[31]

Vertical Boring Machine Jig Boring Machine

Horizontal Boring Machine

In the horizontal boring machine, operations are performed on those large components which cannot be rotated. The spindle and the boring bar are horizontal.

It has mechanical system and fixture is attached with table. The work table can be transverse along and across the machine bed.

Vertical Boring Machine

The spindle is vertical and bores vertical holes in the spindle. The size of the machine is determined by maximum length of the job which can be machined on it. The machine can also be used as a drilling machine.

Jig Boring Machine

Jig boring machine is used to accurately enlarge existing holes and make their diameters highly accurate. Jig boring can also maintain high accuracy between multiple holes and surfaces.

[32]

Tolerances can be held readily within ±0.002mm. The machine can also do accurate milling, reaming, drilling and facing,

In general, the vertical jig boring machine employs a precision vertical tools spindle and coordinate work table with a great accuracy. The position measuring system consists of accurate lead screw with micrometer and an optical scale along with a vernier.

The machine are of rail type i.e. they are constructed with a cross rail that is supported and adjusted vertically on two columns. The cross rail serves to carry vertical spindle in its housing along the transverse axis.

[33]

TOOL ROOM

This department keeps various kinds of tools which are useful during manufacturing of heavy pats. Most of the tools are measuring devices such as vernier caliper, micrometer etc.

Vernier Caliper:-

A vernier caliper is a device used to measure the distance between two symmetrically opposing sides.

The tips of the caliper are adjusted to fit across the points to be measured, the caliper is then removed and the distance read by measuring between the tops with a measuring tool, such as a ruler. Vernier calipers can measure internal dimensions (using the uppermost jaws in the picture), external dimensions using the pictured lowered jaws and depending on the manufacturer, depth measurements by the use of a probe that is attached to the movable head and slides along the center of the body. This probe is slender and can get into deep grooves that may prove difficult for other measuring tools.

The vernier scale may include both metric and inch measurements on the upper and lower part of the scale.

Vernier calipers commonly used in industry to provide a precision to a hundredth of a millimeter (10 micrometers), or one thousandth of an inch.

[34]

Parts of Vernier caliper

Outside Jaws: used to measure external diameter or width of an object

Inside Jaws: used to measure internal diameter of an object

Depth Probe: used to measure depth of an object or an hole

Main Scale: gives measurements of up to one decimal place (in cm)

Main Scale: gives measurements in fraction (in inch) Vernier gives measurements up to two decimal places

(in cm) Vernier gives measurements in fraction (in inch) Retainer: Used to block movable part to allow the

easy transferring a measurement.

Micrometer:-

A micrometer sometimes known as a “Micrometer Screw Gauge”, is a device used widely in mechanical engineering and machining as well as most mechanical trades for precision measurement, along with other metrological instruments such as dial calipers and vernier calipers. Micrometers are often, but not always, in the form of calipers.

[35]

Types of Micrometer:

Outside Micrometer (aka micrometer caliper), typically used to measure wires, spheres, shafts and blocks.

Inside Micrometer, used to measure the diameter of holes.

Depth Micrometer, measures depths of slot and steps. Bore Micrometer, typically a three-anvil head on a

micrometer base used to accurately measure inside diameters.

Tube Micrometer, used to measure the thickness of tubes.

Dial Indicator:

Dial indicators, also known as dial gauge and probe indicators, are instruments used to accurately measure small linear distances, and are frequently used in industrial and mechanical processes. They are named as so because the measurement results are displayed in a magnified way by means of a dial.

Dial Indicator may be used to check the variation in tolerance during the inspection process of a machined part, measure the deflection of a beam or ring under laboratory conditions, as well as many other situations where a small measurement needs to be registered or indicated. Dial indicators typically measure ranges from 0.25mm to 300mm (0.015in to 12.0in), with graduations of 0.001mm to 0.01mm (metric) or 0.00005in to 0.001in (imperical).

[36]

GPM ASSEMBLY & CNC ASSEMBLY

GPM Section:-

GPM stands for general purpose machines.These are generally manually worked machines involving no computerized or numerical control. These machines are semiautomatic in nature and some of its operation like table movement, job movement, tool movement etc. can be carried out either automatically or even manually. These are operated by concerned operations only. The concept of modern days machines originated from GPMs itself. These are the simplest from of the metal working machines.

Examples of these machines- Lathe machines, milling machines, drilling machines, grinding machines etc.

In HMT, Pinjore unit primarly four types of GPM are manufactured-

1. FN2 milling machines

2. FN3 milling machines

3. Turret Ram milling machines

4. Broaching machines.

The machines are further classified into horizontal, vertical and universal milling machines.

a) When the rotating spindle lies vertical w.r.t. the table the machine is termed as vertical (V) milling machine.

[37]

b) When the rotating spindle lies horizontal w.r.t. the table the machine is as horizontal (H) milling machine.

c) When the cutting can be done at any angle of the job with the help of rotary motion of tile table the machine is termed as universal (U) milling machine.

Thus, these machines are named as FN2V, FN2H, FN2U, FN3H, FN3V, FN3U, TRM3V, and TRM3H.Now here we would discuss the features of the three types of milling machines with their properties:-

Swivel is contained only in universal milling machine, since the table can turn at different angles with its help.

[38]

Assembly of Milling Machines:-

1) First of all the parts are obtained from the foundary and machined accordingly to give the desired shape to them.

2) The base is leveled properly with proper instruments .

3) Then the column is aligned w.r.t. the base. The column is attached to the base with the help of guide pins which form a right fit and later with the help of screws.

4) The knee is then aligned with the base keeping in mind that the face of the saddle is parallel with the base.

5) Then the saddle is mounted on the knee and aligned properly.

6) The table is then mounted on the saddle with the help of guides which form a proper fixture with each other.

7) The ball screw is then attached which is responsible for the vertical movement.

8) The gears and the pulleys are then assembled inside the column along with other basic components.

9) The electrical assembly is carried out with proper earthing facility.

10) Then all the accessories are attached to it.

11) Final inspection is done and machine is dispatched.

[39]

BROACHING MACHINE :-

A broach is a multi- point cutting tool consisting of a bar having a surface containing a series of cutting teeth or edges which gradually increases in size from starting and to the rear end. The basic purpose of the machine is to form splines to hollow jobs. Splines are multiple slots on the hollow surface of the job. The surface may be flat, circular, or any intricate shape. In broaching , the broach is pushed or pulled over/through a surface of workpiece. Each tooth of the tool takes a slice from the surface. Broaching of inside surface is called internal or hole broaching and that of outside surface is called surface broaching.

Material:-

High speed steel, brazed carbides or disposable inserts are sometimes used for cutting edges for machining of cast iron parts. Carbide tools are used to an advantage on steel.

HMT manufacturers two types of broaching machine:-

a) Vertical Broaching Machines.

b) Horizontal Broaching Machines.

Reconditioning of Machine (RCM):-

This section is concerned with the reconditioning of machine i.e. repair and maintenance of the worn out or faulty mahines. First of ll the defect is detected and then worked upon accordingly. If the fault is of small scale then it is dealt here itself or sent for re-machining or as scrap in the foundary.

[40]

CNC SECTION

Introduction

We know that GPMs are semi - automatic machines. They require an operator for each work piece loaded on machine and in a limited period. Mass production is not possible in these machines. Moreover complex shaped jobs require high precision. They need for flexible automation has always been felt. And this is an era of machine tool automation. So, flexible automation is implemented in machine tools in the form of NC and CNC (Computerized Numerical Control) technology . Today HMT is producing a lot of CNC variants of conventional machine tools with the specialized functions and mostly CNC products.

CNC machines are part of the field named mechatronics. This field is the combination of electronics and mechanical engineering fields. When they work in combination they are termed as above. A single CNC machine can perform variety of machining operations in a sequential order (based upon the programme). For example drilling , tapping , slotting, milling, etc. operator is used only for clamping and declamping purpose ( after feeding the programme ). These machines ensure repeatability of the dimensions (precision). Accuracy of these machines is in microns.

A CNC machine may be of three dimensional coordinate system with XYZ axis. Rest two are available on machines whose table can rotate and tilt. These are 4th and 5th axis. The axis of the spindle is termed as Z axis. The axis which crosses Z axis

[41]

perpendicularly is X axis and the other mutually perpendicular axis is Y axis. CNC machines differ in orientation of the main spindle. If spindle is horizontal it is termed as HMC (horizontal machining centre) and if the spindle is vertical it is termed as VMC (vertical machining centre). Model number of machine depends upon capacity of machine. Capacity means traverse length along various axis or maximum size of the pallet. Thus a VTC 1000 designates a CNC machines whose spindle is vertical with pallet size or traverse length of 1000mm.

Various CNCs produced here:- HMC 320M, HMC 400M, HMC 500M, HMC 600M, HMC 800M, VMC 400M, VMC 500M, VMC 800M, VMC 1000M etc.

Assembly:-

Main parts of the CNC machine are:-

1. Bed

2. Column

3. Saddle

4. Table

5. Pallet chaner (optional)

6. Magazine

7. AC servo motors

8. Tool changer arm

9. Head[42]

10. Main spindle

The different processes of assembly are:-

1. Procurement of various parts.

2. Bed is leveled.

3. Column is fixed on bed.

4. Ball screws and drive motors are installed.

5. Alignment of column w.r.t. bed.

6. Fixing table on saddle.

7. Installing ball screws and drive motor.

8. Alignment of saddle w.r.t. column.

9. Fixing table on saddle.

10. Laser test:- In this test the laser beam is thrown on the pairs of prism one attached to the table and other on the spindle of the machine and reflected back through the same part and data is collected on the computer and thus can be corrected.

11. Tool magazine is assembled and attached to the machine.

12. The oiling system is attached to the machine as separate apparatus and solves the purpose of lubrication .

13. All electrical and electronics appliances are installed.

14. The body of the machine is and rest of the accessories are attached to it.

15. Final inspection is done.[43]

Machine Description:-

Salient features of CNC machines are as follows:-

1) Bed type machine configuration :-

Bed type construction with longitudinal and cross movement to work table and vertical movement to head , provides stable cutting condition and maximum rigidity. Box type construction of bed and column with properly ribbed reinforcement minimizes torsion and flexural deflection.

2) Linear motion with guide ways :-

Preloaded anti - friction linear motion type. Guide ways in the entire three provide clearance free guidance for slides during cutting. Their use significantly reduces the coefficient of friction and eliminates stick slip and thermal generation during high speed positioning. In addition they offer high positioning and outstanding contouring capability.

3) One package design :-

One package design i.e. integral mechanical- electrical construction with CNC unit mounted on machine guarding, substantially cuts down floor space requirements. This enhances productivity per unit area and assures easy machine movement when production line is changed.

4) Long nose quill type spindle :-[44]

Cylindrically shaped head end and prevents any interference with the work complicated shape. This configuration also eliminates interference even with large steep work. Machining of deep holes in the work are also possible with full power and without compromising tool rigidity.

5) Spindle cooling( for machine with spindle speed of 6000 rpm):-

Circulation of cooled oil through the oil jacket around the main spindle bearing, maintains precision even in long and continuous runs.

6) Stepless AC spindle motor :-

AC spindle motor eliminates the troublesome brush inspections and replacements required in case of DC motors. Another advantage of DC motor is that it reduces electricaly consumption.

7) Electronic spindle orientation :-

The spindle motor has build in encoder for position feedback of the spindle. Spindle orientation stops spindle in a particular position. This helps in retracting bars without damaging bores in boring operations and counter-boring/Facing. Automatic tool change is also achieved through the features.

8) AC servomotors :-

All the three axes are driven through AC servomotors. Their [45]

use provides a higher rapid rate of revolution with minimum maintenance. They also provide high acceleration and deceleration property and subsequently increase the machining efficiency.

9) Lubrication :-

Automatic lubrication is provided for minimal operator attention. Main spindle bearing and all axes drive bearing are fitted with synthetic grease, requiring no attention for long periods . All axes ball screws and linear re-circulating bearings are also lubricated.

10)Automatic chip collection :-

Flushing coolant with discharge of 100lpm is used for automatic flushing of chips and is collected in tray at rear of machine. Wide channels with sufficient scope are provided in both sides of bed for easy disposal of chips at rear of machine.

11)Guide protection :-

Guide ways protection with telescopic cover protects guide ways against external damages and chips.

12)Automatic Tool Changer(ATC) :-

Machine is equipped with a suitable number of tool

[46]

station/pocket (mainly12,30,60,120) . Using cam the automatic tool changer changes a tool accurately and swiftly.

13)Numeric head counter balance:-

It offsets the natural weight of spindle head and guarantees consistent cutting , high speed and highly accurate positioning . It eliminates head falling.

Machining Features (Optional):-

1. External coolant on spindle:- External coolant facilities the machining of steel/aluminium. It also helps in taking away chips from machining zone with its large flow.

2. Mist coolant:- Machining of light metals is faciliated with mist coolant. Mist coolant takes away heat from work zone, with change of state. It does not require any return path.

3. Chip conveyor:- It takes away large volume of chips produced out of the machine continuously with its independent drive.

4. Refrigeration type of spindle coolant:- Coolant of cooled oil with heat exchanger(refrigeration type), through spindle jacket provides higher spindle stability which results in improved working accuracy.

5. Spindle mounted probe:- Spindle mounted probe with auto measuring cycle and datum cycle makes fixture/job setting simple.

[47]

6. Higher speed spindle upto 8000 rpm :- It facilitates machining of light metals with latest tool technology.

7. Pallet changer:- This part is concerned with handling of additional table on which the next job can be mounted for machining meanwhile machining of the current job is going on which considerably reduces the mounting time.

[48]