UNIT-IV

AUTOMATS

TRANSFER MACHINING

INTRODUCTION

§ The wide spread increase in the quantity of production requiring a multiplicity of

operation such as, milling, 6cing, boring, drilling, etc., has led to the development

of a method of manufacture known as transfer machine.

§ The term transfer refers to the transfer of the job from machining station to the

next as it proceeds through the machining processes involved. Components are

loaded at one end and completed workpieces leave the transfer line at the other

end.

CLASSIFICATION OF AUTOMATS

Automatic lathes are classified in various way as follows

1. Classification according to the type of work material used:

a) Bar stock machine

§ In these machines, collets are used for holding the work. The work material is in

the form of bar or pipe stock

§ Feeding mechanism is used for feeding bar stock Components like screws, nuts,

bushes, rings, studs are produced in this machine

b) Chucking machine:

§ These machines are used to produce components in tl shape of separate blanks

These blanks may be either forgrn or castings.

§ They are held in jaw chuck or special fixture The feeding of the blanks is done by

magazine loadii devices. Hence this machine is otherwise called as magazi)iè loaded

automats.

2. Classification according to the number of Spindles:

a) Single spindle automats:

These machines, machine one component at a time they have only one spindle. Automatic

cutting off machine automatic screw cutting machines and Swiss type machine belong to

this type.

b) Multi spindle automats:

These machines have 2 to 8 spindles. But 4 and 6 spindle machines are commonly used.

Operations are performed simultaneously in all the spindles. Hence the rate of production

is very high. Multi spindle machines are of two types. They are parallel action type and

progressive action type.

3. Classification according to th arrangement of spindles:

a) Horizontal spindle type:

In this type, the spindles are in horizontal position. They are used for machining long jobs

of small diameters.

b) Vertical spindle type:

In this type, the spindles are in vertical position. These machines are heavier and

stronger. They can accommodate larger blank diameter but shorter in length. But they

occupy less floor area.

4. Classification according to the feed control:

a) Single cam shaft rotating at constant speed:

Here a single cam shaft controls the working and idle motions of the tool. The idle motion

and working motions take place at the same speed. Hence cycle time is longer.

b) Single cam shaft with two speeds:

The cam shaft rotates at slow speed for working motions. It rotates at faster speed during

idle motions. Hence idle time is reduced.

c) Two Cam shaft:

This machine consists of two cam shafts.

(i) Main cam shaft.

(ii) Auxiliary cam shaft.

The tool movements during working motions controlled by a main camshaft. The main

camshaft rotates slow speed. The tool movement during idle motion 1. controlled by an

auxiliary camshaft. This camshaft rotates faster speed; Hence idle time is reduced.

5. Classification according to the use:

a) Single purp ose machine:

This machine is designed to produce a single componel of fixed shape and size. This is

used in production lines single product.

b) Genera/purpose machine:

In this machine, a variety of components can produced. The machine can be set for

components with variations in shape and sizes.

SINGLE SPINDLE AUTOMATIC LATHES

§ A single spindle automatic lathe is a modified form of turret lt These machines

have, an addition to a 6-station or 8-station turre maximum of 4 cross slides.

§ These cross slides are operated by C cams. The cams are mounted on a shaft

which draws the power from main spindle through a set of gears called cyclic time

change Turret operation is also synchronized with the cross slide operation is

driven by another cam called main cam.

§ The tools used on the cross slides are usually form tools and I plunged into the

work piece at the desired feed rate. The tools the turret may be turning tool, drilling

tools etc. It is common to U more than one tool on a turret station. External

threading is carried out by a thread chasing attachment. Internal threads are fl

using taps. In addition, milling of slots, flats, grooves, cross.

It can be performed in an automatic lathe with the help of special attachments. This is one

of the outstanding features of automatic lathe.

§ The reduction in number of set ups and total machining time enable Parts to be

produced at an economical cost in an automatic lathe. Because of their application

to produce screws at low cost these are called screw machines.

§ The figure shows the single spindle automatic lathe. The lathe has a geared

headstock. The spindle of the headstock has one slow speed and one fast speed.

The spindle speed is changed by the trip dogs on the drum A.

§ At the end of the bed, a square turret is provided. The travel of the turret slide is

controlled by the adjustable cam drum C. The turret fixed to the next at the end of

each stroke.

1. Automatic cutting off machine.

2. Automatic screw cutting machine.

3. Swiss type automatic screw machine.

Automatic cutting off machine:

§ Two cross slides are situated between the headstock and the the One cross slide is

at the front and the other at the rear side. The c slides have independent

movements.

§ The travel of the cross slides independently controlled by cams B. Overlapping of

operations by tool in the turret and the tools in the cross slide can be done. The

corm feed for each machining operation can be automatically selected by feed

selector pins on the drum D. The following types of single s automatic lathe are

mostly used.

§ These machines are simple in design and is used for produce large quantities of

parts of smaller diameter and shorter Components of simple shapes are produced

in this machine.

§ In this machine, the headstock with the spindle is mounted on the bed. Two cross-

slides are located on the bed at the front end of the spindle- Cams on a camshaft

actuate the working movements of the cross-slides tools can perform the

operations.

Single spindle automatic screw cutting machine:

§ These machines are essentially automatic bar type turret lathes. They are widely

used for production of all sorts of small turned parts. It consists of a cross slide and

a turret. Two cross slides, one front Cross slide and another rear cross slide are

provided for cross feeding tools.

§ An additional vertical slide is also employed in this machine. This third slide is

installed above the work spindle.

§ The turret slide is placed at the right end of the bed. It carries turret having six tool

holes. The various tools used in the machine i mounted around the turret in a

vertical plane in line with the spindle: this machine, the headstock is stationary.

§ It houses the spindle which rotates in either direction. The bar stock is held in a

chuck. It is advanced by a feed finger after each piece is finished and cut off.

§ A camshaft is mounted at the front of the machine. It carries three plate cams.

These plate cams control the travel of cross slides. The turret head rotates about a

horizontal axis. The turret slide travel is controlled by a lead cam. The lead cam

gives a slow forward and fast return movement to the turret slide.

§ The discs cams are used to control the cross slide. All operations such as turning,

drilling, boring, threading, reaming, spot facing, knurling can be done on the

machine. Special attachments are also available to perform slotting work, milling

flats, cross-drilling etc. In this machine, any type of bar stock round, square,

hexagonal can be machined. These machines are made in several sizes for bar work

from 12mm to 60mm diameter. The line diagram of this machine is shown in fig.

9.4.

Applications:

It is used for producing small jobs, screws, stepped pins, taper pins, bolts etc.

Swiss Type Automatic Lathes (Sliding head automatic lathes):

§ The headstock Carrying the bar stock moves back and forth for providing the feed

movement in the longitudinal direction. Hence this type of automatic ‘ athe is also

called a sliding head automatic lathe.

§ This machine is used for producing long accurate parts of (2 to 25mm). In this, the

parts can be machined to an accurate of 0.005mm to 0.0 125mm.

§ There may be as many as five cross slides in the case of automatic lathe. However,

productivity-wise, the conventional automatic lathes aa superior for short work

pieces.

§ The advantage of a sliding he4. automatic lathe is that long slender work pieces can

be machined wi very good surface finish, accuracy and concentricity in sliding hea&

automatic lathes.

§ Further, the Swiss type automatic lathes are capable of completely machining

certain types of parts which may require second and third operations in

conventional automatic machines.

It consists of four major parts:

1. The sliding headstock through which the bar stock passed and gripped by a carbide-

lined guide bush.

2. The camshaft, controlling the bar stock and cutting tO movements.

3. The tool bracket supporting five tool slides and a bush f stock.

4. Auxiliary attachments for performing various operations such as knurling, drilling,

tapping, screwing and slotting, recessing etc.

The description of various parts are given below:

1. Sliding Head stock:

This headstock has a collet. The bar stock is held in the collet. The headstock slides along

the guide ways of the bed. A bell cam connected to the camshaft controls this sliding

motion.

3. Feed Base:

The feed base is mounted at the right hand side of the headstock. This can move along

the bed. Using this attachment operations like drilling, boring, thread cutting etc., are

done. The movement of the feed base is controlled by the plate cam fitted to the

camshaft.

4. Cam shaft:

The camshaft is mounted at the front of the machine. It has a beij cam at the left end.

This controls the sliding movement of the headsto& Plate cams fitted at the centre of the

shaft controls the movement of the tool slides. Plate cam at the right end of the camshaft

controls movement of the feed base.

Parts produced in this machine are shown in fig. 9.8.

Working principle:

§ The bar stock is held in the rotating spindle by a collet chu Headstock slides along

the bed ways with the rotating bar stock.

§ This headstock movement gives longitudinal feed to the work.,1 the tools in the

tool slides remove material from the work piece C’ same time.

§ The tool in the feed base attachment may also do operate. like drilling. After the

work piece is machined, the headstock slides b to the original position. One

revolution of the camshaft produces component.

§ Most of the turning and forming operations are done by the held on the (horizontal)

front and rear tool slides. The vertical tool sli are mainly used for undercutting,

chamfering, knurling and cutting Of

Advantages of Swiss type screw machine:

I. Used to manufacture precision turning of small parts.

2. It has five tool slides.

3. Wide range of speeds.

4. Rigid construction.

5. Micrometer tool setting.

6. Inter changeability of cams.

7. Simple design of cams.

8. Tolerance of 0.005 to 0.0l are obtained.

9. Numerous working stations.

Multiple Spindle Automatic Lathe:

Multiple spindle automatic lathes are machines which can produce larger work pieces than

single spindle automats. The principle advantage of the multi spindle automat is that it

has a tool slide working on the jobs on all spindles simultaneously and hence the time for

producing a piece is the time for the longest cut.

Bar-type automatic machine:

These machines operate on bar stock, usually round. Some bar of hexagonal shape can

also be used. These machines can automats 9.15. specified by the largest diameter of

stock that can be fed through the spindles. The sizes of bars range from about 14mm

diameter. The bar stock may be fed either by gravity or by rollers.

Magazine-loading type or chucking type machine:

These machines are similar to bar type machines. They handle several work pieces held in

several chucks. It can be specified according to the diameter of the work that can be

swung over tool slides. The maximum size of bar stock that can be used in this machine is

250mm.

Parallel action multi spindle automats:

§ These types of automatics are otherwise called as ‘ multiple-flow’ machine. The line

diagram of this machine is shown in fig.9.10. This machine consists of a frame with

a headstock. The axes of work spindles are horizontal.

§ These spindles are arranged in a line one above the other. The work spindles are

housed in the headstock. There are two cross Slides, one on left hand side and the

other on the right hand side.

§ The left hand side cross slide is called as front fool slide. The right hand side

9.16.cross slide is called as rear tool slide. These slides carry the cross feeding

tools. Cams are used to obtain all the working and auxiliary motions of the

machines units.

§ In this type of machine, the same operation is performed on eact spindle. In one

working cycle, each work piece is finished in each spindle. In a five-spindle

machine, five components can be completed a time. Similarly in a eight spindle

machine, eight components can b completed at a time. Hence it is called as parallel

action multi spindle machine.

§ The production rate is very high in this machine. But

simple components can be machined since all the machining processes are donì e at

one position.

Progressive action multi spindle machine:

§ In this type of machine, the work pieces are machined in six-spindle progressive

action multi spindle automatic lathe is shown in fig. 9.11.

§ The headstock is mounted on the base of the machine. headstock has a spindle

carrier. This carrier rotates about a horizC axis through the centre of the machine.

The working spindles mounted in the spindle carrier. Work pieces are held in the

collet in the spindles. The bar stock is fed to the spindle from the rear. Cross slides

are mounted in a frame above the face of the spindle carrier.

§ These tool slides carry forming, chamfering, facing and cutting off tools. These

cross slides travel radially inward for cutting operation. The cross slide movement is

controlled from a cam in the camshaft.

§ The main tool side (or end tool slide) is situated in front of the spindle carrier. It

carries tool slides around its periphery. There is one tool slide corresponding to

each spindle. The tool slides move towards the spindle while machining. Operations

like straight turning, boring and threading are done by the tools mounted on these

tool slides.

§ The Spindle carrier indexes on its own axis by 600 (360.6) at the end of toolreturn.

As the spindle carrier indexes, it carries the work from station to Station. In the

first station, the bar stock is fed. In every station, different Operations are done

progressively (one after another in each station).

COMPARISON OF SINGLE SPINDLE AND MULTI SPINDLE AUTOMATIC LATHES

CAM CONTROLLED AUTOMATS

§ In most of the automatic lathes, the operating cycle is automatic by means of cams

held on a camshaft. That is, the operating mechanism for sliding, feeding and

clamping are actuated by cams through bevel gears .

§ In previous chapters we have discussed various automats which is mostly cam

controlled. The cams are used for the following purposes of automats.

(i) To control purposes in automats screw machine.

(ii) To control movement of the turret for controlling rap approach, working travel, rapid

return.

(iii) To control the movement of cross slide.

(iv) To provide uniform rate of feed to tool during machining.

(v) Some time to clamp the parts.

There are two types of cams used in automats. They are plate cam and cylinder cam or

drum cams.

TRANSFER MACHINES

§ A transfer Machine is an automatic machine. It indexes or transfe the work piece

and its fixture, from station to station while max operations are performed on it. It

is a combined material processing ax material-handling machine.

§ It consists of several machining heads units fastened together by conveying units.

The whole machinery is I one large automatic installation. Work pieces are loaded

at one end ax travel automatically past the machining heads where they a

successively machined on each station.

§ They will finally reach the other end after completion of all operations and

unloaded. A transfer machine once installed is inflexible and can product usually

one product only in large quantities.

Factors to be considered in designing Transfer Machine:

1. Number of operations required in the work piece.

2. Size and weight of parts and total assembly.

3. Weekly, monthly and yearly volume of parts and hourly rate of

production required.

4. Permissible transfer time as a part of cycle time.

5. Accuracy of transfer required.

6. Inertial loads used for acceleration and deceleration of Transfer Machine.

7. Forces to be applied at various stations of machining.

8. Need for variable speed drives to meet.

9. Flexibility of timing the transfer device to permit changing of

operating cycle.

10. Type of Transfer device drive, hydraulic, pneumatic and electric or combination of the

above.

11. Floor space and service facilities available for installation and operation of machine.

12. Initial design built debug and installation cost.

13. Maintenance cost and ease of maintenance.

14. Economy in all aspects.

PRINCIPLE OF TRANFER MACHINE

§ A Transfer Machine is one where several machines are linked together

mechanically, electrically or hydraulically. Two operators run the machine. One

operator loads and controls it while the second Operator unloads the work. He also

stacks it or pushes it on a conveyor for further operation.

§ The controlling operator has a large switch board. It gives him the conditions all

along the switch line. Lights indicate Whether each fixture in each station has

properly been located whether each fixture in each station has properly been

located or not.

§ Another light indicates that the operation has been performed and the tools with

drawn. Other lights may indicate broken or worn out tools and other malfunctions

or when gauges fail to pass the finished operations. Each section can be considered

as a simple work head with its driving motor mounted on a base.

§ It slides along its own ways and i actuated by another motor and trip dogs to

control the motion. Son work heads may contain tools and drive several tools in a

small area, f example, drills.

§ A separate device called a machine control unit is also provided i a Transfer

Machine. This unit is a panel containing replacement tool and tool motor which

automatically stops the machine when the tools need changing. It also indicates the

worn out tools. Fixtures and gauges are used so that the tools can be preset.

Advantages

1. Transfer machine can handle components of awkward size ai shape.

2. Operator fatigue is eliminated.

3. No manual handling (except loading and unloading).

4. Increased output. Fewer operations are required. Considerable saving in floor space

due to elimination of p” inventory and close grouping of machines.

5. Fewer operations are required.

6.Considerable saving in floor space due to elimination of p” inventory and close grouping

of machines.

7. Less scrap by avoiding manual error.

8. Greater overall accuracy.

9. Control of work movement through the shop is simplified.

10. Greater tool life due to optimum cutting condition.

11. Alignment of work is simplified and atomized in each station.

12. Cost of process inventory is reduced.

Disadvantages:

1. Initial cost is high.

2. Electrically very complex.

3. A breakdown of one machine forces the stoppage of machines.

4. Limited to high production industries only.

5. There is limit to frequent change of product design.

6. High skill servicing is required.

CLASSIFICATION OF TRANSFER MACHINES

Transfer machines are of three basic types,

(i) Rotary indexing table transfer machine.

(ii) Inline transfer machine.

(iii) Drum type transfer machine.

1. Rotary indexing table Transfer Machine:

When a component can be machined at eight stations or the components mounted on a

circular table or drum which can be indexed Opposite to each machining station.

2. In-line Transfer Machine:

§ The In-line Transfer Machine consists of a straight central bed. On both sides, the

machining heads or units are located and bolted at a suitable fixed pitch. simple

sketch of this machine is shown.

§ The central bed can be built up to a length of several hundred meters if necessary.

But if floor space is not available it need not be in a Straight line and it could be an

L shaped, square or rectangular type. The Component is transferred along guide

rails on the central bed either with or without the use of a pallet. But this depends

on the component size and shape. If pallets are used they must be returned back to

the starting Point.

§ This is done by a conveyor. The work may be a loaded manually Or automatically

onto the machine.

§ It is transferred by equal distances from station to station where it is automatically

located through dowels and clamped. The work can be

Machining operations at each station may be drilling, reaming, boring, counter

boring, spot facing, countersinking, milling and grooving.

§ The cutting tools have a fast approach and return. They may h arranged to the

work at any desired position or angle. Provision is i for removing the large

quantities of sward. Coolant is supplied filtered in large quantities.

§ An automatic lubricating system is required which automatica lubricates the moving

parts at specific time intervals. Automatic devices are provided to control jamming

of components, or a b down of some apart. This means that the controls at every

station linked that none will operate, if any one is not functioning correctly.

3. Drum type Transfer Machines:

§ Drum type transfer machine is similar in principle to the rotaly table. But the

arrangement is quite different. Here the components are being transferred around a

circular path to work stations.

§ They are radially positioned around the path at equal distances. The table is

replaced by a drum which is mounted on trunions so that the drum rotates about a

horizontal axis.

§ The work fixtures are fastened to the outside surface or periphety of the drum.

Wherever possible they are arranged to hold more than one component, since the

working capacity of the machine is limited.

Limitations:

1. In the drum type machine, the lower stations must be idle as it is impossible to

arrange a machining head to operate in the limited space under the drum.

2. Automats

3. 2. In rotary machines, there is a limit to the size of drum which, can conveniently

be mounted and indexed upon trunions.

4. 3 Therefore these machines compared to in-line transfer machines will always be

small

The methods of loading and transferring the work into position -- each station will

depend on the type of transfer machine, the shape a size of the work piece. Large

work pieces are placed into position at first station by an operator using electric hoists

and conveyors. L small work pieces are fed in large quantities into a hopper.

Hydraulic transfrr machine

§ Here a hydraulic cylinder is used to move, the transfer bar throu one station

pitch. In addition the cylinders are used to clamp the wot piece into position in

the fixture ready for machining.

§ The transfer 1 reverses and the spring loaded pusher dogs retract to spring back

operating position again at the end of the stroke. as the transfer’ moves forward

again, the dogs push the work pieces along the gui rails to the next station.

§ The advantage of hydraulic system is that it can be used to operate only transfer

devices, but also loading devices and clamping devices.

PART-A

1. Define automatic lathes.

2. State any four advantages of automatic lathes.

3. How does the cam draw power main spindle?

4. Mention the other names of single spindle automatic lathes.

5. What are the types of single spindle automatic lathes?

6. State the purpose of providing lead cam in single Spindle automatic screw culling

machine?

7. Mention the applications of single spindle automatic screw cutting machine.

8. What are the advantages of a sliding head automatic lathes?

9. What are the four major parts of Swiss type automatic lathes?

10. State the advantages of Swiss type screw culling machine.

11. State the principle of multi spindle automats.

12. Classify multi spindle automats.

13. Compare the parallel action spindle automatic lathes.

14. Define cam controlled automats

15. What are the purposes of using cam?

16. State any four factors to be considered

17. State the principle of transfer machines

18. What are the functions of transfer machines?

19.How the transfer machines works?

20. What are three types of rotary systems in rotary indexing table transfer machines?

20. State the advantages of rotary transfer machines

21. What are the different machining operations that can be performed on in-line transfer

machines?

22. What are the advantages of in-line transfer machines?

23. How drum type transfer machine c4ffers from rotary table transfer machine?

24. What are the limitations of drum type transfer machines?

25. What are the two types of transfer devices?

PART-B

l. Classify automats and describe any two in detail with neat fl sketches.

2 The working principle of automatic cutting off machine.

3 the working principle of single spindle automatic screw culling machine

4. Describe the working principle of Swiss type automatic

5. Classify multi spindle automatic lathes and explain bar type and magazine loading type

machine.

6. Write short notes on progressive action multi spindle automatic and transfer machines.

7. Classify transfer machines.

8. Explain the working principle of in-line transfer machine and how it differs from drum

type transfer machines.

9.Write short notes on automatic loading and transfer device.