MACHINE AMD ATTACHMENT MODIFICATIONS

Setup reduction often requires machine modification which in' some cases could be fairly extensive if the full benefits of setup reduition are to be achieved. In some companies there may exiSv a misconception that one should not tamper with machine tools designed by experts. furthermore, some believe that the resale value of such general-purpose equipment could be reduced If it is modified for special jobs. (9)

Much oi Western industry relies too much on independent equipment suppliers. Very often they cannot design and produce their own production equipment, or even carry out major repairs

or modifications on the equipment they purchase. Subsequently

they do not have the ability to compete on the basis of unique process technology, something which is-not available "off-the- shelf" . (4)

In Japanese Industry we find there Is a large amount of equipment and machinery which has been designed and built "In- house" for specific production purposes. (3) Their machine shops are well-staffed and active, a place where many of the new process technologies are developed, and therefore unavailable to competitors. (4) By modifying, or even better, manufacturing, equipment can be designed so that fast setup hardware techniques are incorporated. Furthermore problems arising during actual production can be eliminated; something an external supplier could not foresee. (2) The Japanese in some cases cut their setup times essentially to zero since the machine is designed for just one job; all attachments and fixtures may be built so that no settings or adjustments are necessary. (3)

Modifications involve changes to machines where part of a machine may be redesigned or modified for quick changeovers. Also additional attachments may be added for slmplar setups. This Includes tooling changes where drills, dies, blades, jigs, etc, are standardised for easy attachment during a setup.

Applications of setup time reduction have been extensively documented (1,2). Therefore this section will merely summarise various examples for common setup problems. For more detailed explanations refer to the prescribed literature.

(a) DIB CHANGEOVERS

time and may cause bottlenecks. Whether the equipment Involved Is a metal press or a plastic forming machine, general setup reduction principles are similar with respect to related hardware. The following examples show general changes for machines, tooling, attachments and materials handling equipment.

(1) STANDARDISED DIE HEIGHT AMD CLAMPING POINTS

Shut height adjustment wastes time and requires considerable skill. These shut height adjustments are only necessary because die and clamping heights differ. This problem can be solved by attaching shims or blocks of appropriate thickness to standardise these heights (figure 4.5).

FIGURE 4.5 : Dio and Clamping Height standardisation

(11) DIB CENTERING

Precise die centering is necessary and must be carxled out with caution since the die could be destroyed 1£ the ram is not correctly alllgned. Therefore this operation Is time-consuming

and difficult. The setup can be Improved by making use of a centering jig made up of two plates as shown In figure 4.6; one side is attached to the machine and the other side to tlie die. The V-shaped projection between the plates allows for automatic centering In both X and Y planes.

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FIGURE 4.6 : centering Jigs (1)

( H i ) SIMPLIFIED PIE EXCHANGE

The conventional method often Involves an overhead crane which lifts the old die out of the machine, places it alongside, picks up the new die and places It in the machine. The first alternative Is to use roller conveyors on medium-sized dies. Figure 4.7 shows a progression of steps for simplification by means of the roller conveyor method. For this method the conveyor height is standardised to conform to the die height position In the machine (figure 4.8). This method Is preferred when human effort Is required since any lifting operations are eliminated.

FIGURE 4.7 : simplifying Die Exchange (1)

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An alternative method can be used when the machine does not allow £or the roller conveyor method. Figure 4.9 shows the correct method for hoisting dies. The new die is prepared in advance just before the changeover (stage 1), by suspending it just high enough to allow for lateral movement, using the first hoist. The other hoist is then used to lift the old die out of the machine (stage 2). The hoists are then moved along a rail and the new die is lowered into the machine (stage 3>.

FIGURE 4.9 : The Hoist Method (1)

(iv) COOLANT LIMB CONNECTIONS

Most injection moulding machines have a series of supply and drainage U n e a attached to the die for coolant purposes. In the conventional method each of these lines is attached separately. Figure 4,10 shows how connections can be simplified by means of using manifolds.

FIGURE 4.10 i Improved Coolant Line connections (1)

(V) DIE PBBHEATIMO

In the conventional setup a number of scrap parts are made until the die has heated up. (1) Therefore the new die must be preheated to eliminate this scrap. Methods Include steam generators and electrical heaters.

(VI) ELECTRICAL CONNECTIONS

A considerable amount of time can be saved by grouping Individual vires and sockets to form one plug and socket.

<b) INTERMBDIAR? JIOS

intermediary jlgo are used In order to eliminate adjustments during a setup. When blades are changed for example, holders, referred to as intermediary jigs, should be used instead o£ mounting blades directly onto the head. Dimensions can then be

set during external setup and holders merely have to be switched during Internal setup. Intermediary jigs may be designed in such a way so as to eliminate all adjustment (Internal and external), (1) This Is illustrated In figure 4.6 where the die Is automatically centred in the machlnm by means of a sub-plate or intermediary jig. This can also be applied to changing of lathe tips. Conventially tips are changed inside the machine, after which fine adjustments are required. For quick changeover the entire tool holder Mi l c h servos as the Intermediary jig) Is removed from the lathe and tips are changed outside the machine on a gauge during external setup (figure 4.11).

(c) FUNCTION STANDARDISATION

This Involves leaving the mechanism alone and modifying only the function. In effect, one multi-purpose mechanism Is designed In ordex to eliminate physically changing attachments. Therefore only a minor adjustment is required £ol- a setup. The following examples serve to Illustrate this point.

(i) ROTATING TOOL POST

The setup here merely requires rotating the tool post. Then tooling for the next setup can be Inserted behind the machine as external setup (figure 4.12).

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( U ) EXCHANGING PROFILE TEMPLATES

By sinking lineae templates Into a shaft one can obtain the required copying function by merely rotating the shaft (figure 4-13).

FIGURE 4.13 8 Rotating Profile T .mplate II)

(d) FUNCTIONAL CLAMPS

A functional clamp is an attachment device serving to hold objects in place. This involves fixing attachments to the machine and usually takes the form of nuts and bolts. A bolt is passed through a hole in the attachment and fixed into a nut on fche machine. The bolt must be turned a large number of times into the nut before the attachment Is tightly secured onto the machine. However, it la only the last turn that tightens the bolt and the first turn that loosens it, The time required for the remaining turns are wasted. Figure 4,14 illustrates some of the one-turn or quick release attachments.

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FIGURE 4.14 : Examplea of Seraw Improvement (1)

(e) MECHANISATION

Mechanisation should preferably be the last stage of the setup reduction programme. Mechanising un inefficient setup operation will only achieve limited time reductions, and will do little to remedy the basic faults of a poorly designed setup process. (2) It is much more effective to mechanise setups that have already been streamlined. It should also be noted that mechanisation can involve a large capital layout, therefore It is ad "’sable to Investigate If this small improvement is cost effect..