q&a_reducing setup times

8/2/2019 Q&A_Reducing Setup Times

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LEAN MANUFACTURING SYSTEM

REDUCTION OF SETUP TIMES & PRACTICAL PROCEDURES FOR

REDUCING SETUP TIME

Questions from Previous question papers

1. Discuss four major concepts in reducing setup times. Discuss four practical steps for setupimprovements.

2. List and explain major concepts used to shorten set-up time.3. Explain clearly procedure followed in reducing set up time in manufacturing plant.4. Explain Reduction of set-up times.

Answers SETUP CONCEPTSTo shorten the setup time, four major concepts must first be recognized. Six techniques for applyingthese concepts are described herein. Most of these techniques were devised for applying concepts 2 and

3. To examine each concept and technique, the setup actions for the punch press operation will be used

as a main example, but the same approach can be applied to all kinds of machines.

Concept 1: Separate the internal setup from the external setup.Internal setup refers to those setup actions that inevitably require that the machine be stopped.External setup refers to actions that can be taken while the machine is operating.

In the case of a punch press, these actions can be taken before or after changing the die. These two kinds

of actions must be rigorously separated. That is, once the machine is stopped, the worker should neverdepart from it to handle any part of the external setup.In the external setup, the dies, tools, and materials must be perfectly prepared beside the machine, and

any needed repairs to the dies should have been made in advance. In the internal setup, only the removal

and setting of dies must be done.

Concept 2: Convert as much as possible of the internal setup to the external setup.

This is the most important concept regarding the single setup. Examples include: The die heights of apunch press or a molding machine can be standardized by using the liner (spacer) so that stroke

adjustment will be unnecessary (Figure1).

The die-casting machine can be preheated using the waste heat of the furnace that belongs to this

machine. This means the trial shot to warm up the metal mold in the die casting machine can beeliminated.


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Figure 1: Using a liner to standardize die height.

Concept 3: Eliminate the adjustment process. The process of adjustment in the setup actions usually

takes about 50 percent to 70 percent of the total internal setup time. Reducing this adjustment time isvery important to shortening the total setup time.Adjustment is usually considered to be essential and to require highly developed skills, but these are

mistaken notions. Setting operations such as moving the limit switch from the 100 mm position to the

150 mm position might be necessary. But once the limit switch has been moved to a certain position,further repetitive revision of the setting positions should be eliminated. Setting is a concept that should

be considered independently of adjustment. Examples include:

The maker of punch press may produce a machine that is adjustable to various buyers die heightrequirements. But each particular company (each user) could standardize its die height at a certain

size so that the stroking adjustment could be omitted (Figure 1).

Suppose the molding machine requires a different stroke of the knockout depending on the dieused, so the position of the limit switch needs changing to adjust to stroke. In order to find the rightposition, adjustment is always necessary. In such a situation, instead of only the one limit switch

five limit switches can be installed at the five required positions. Furthermore, in the new device,

electric current can be made to flow only to the necessary limit switch at a certain point in timewith one touch handling. As a result, the necessary to adjust the position is completely eliminated

(Figure 2).

To exchange the dies on the stamping machine, a revolving table car can be prepared. The ideabehind this revolving table car is the same as the principle of a revolver (gun). The procedures

follow (Figure 3):a. Detach the no. 1 die from the die holder of the press (production by this die is finished).

b. Push the table car to approach the press and then fix the stopper.c. Put the no. 1 die on the table car.d. Prepare only the upper part of the table car to set the no. 2 die on to the bolster.

e. Detach the table car stopper, pull the table car from the press and at the same time set the no. 2

die on the press.


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Figure 2: Installing limit switches at all required positions speeds knockout stroke adjustment.

Figure 3: Revolving table car.

It should again be emphasized that although the machine might be capable of changing positions

continuously. Only a few finite, stepwise positions are needed. The example of the five discrete limitswitches (Figure 2) is based on this idea. The number of setting positions needed in actual operations is

quite limited. Such a system can be described as the finite-settings built-in system. This system will

enable one-touch setup.

Concept 4: Abolish the setup step itself.


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To completely do away with the setup, two approaches can be taken: one, use uniform product design

and use the same part for various products; two, produce the various parts at the same time. The latter

can be achieved by two methods. The first method is the set system. For example, on the single die ofthe punch press, two different shapes of parts A and B were carved as a set. These two parts are

separated after continuously punching both shapes at the same time.The second method is to press the multiple parts in parallel using less expensive multiple machines. Forexample, one department uses a normal jack for a pressing function instead of the punch press. In this

department, each worker handles this small jack while he is engaged in other jobs as a multi-functional

worker. This jack is attached to a small motor for use and can perform the same function as a heavypunch press. If several jacks of this kind are available, they could be used in parallel for producing

various types of parts.


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PROCEDURE FOR SETUP IMPROVEMENTSThere are four procedures for attaining setup improvements. The first step is to separate the internal

setup from the external setup. The second step is to shorten the internal setup time by improvingoperations. The third step is to promote further reduction in internal setup time through equipment

improvement, and the fourth step is the challenge to reduce the setup time to zero. Each of these steps isdetailed in sequence in Figure 4.

Figure 4: Steps to improving setup time.

Step One: Differentiation of external and internal setup

Internal setup refers to actions that require the machine to be stopped external setup refers to actionsthat can be performed while the machine is operating. The main objective in this step is to separate the

internal setup from the external setup, and to convert as much internal setup as possible to external setup.

For conversion of internal setups to external setups and to decrease external setup time, the followingfour points are essential:

1 Pre-arrange jigs, tools, dies, and materials.

2. Maintain good operating condition for dies.

3. Create operating tables for the external setup.4. Maintain tidiness in storage area for detached jigs and dies.

The most important of these four points is the last one: maintaining a tidy storage area for tools, jigs, and

dies. Tools stored in a disorderly manner in a toolbox will cause workers to waste time searching forneeded tools-a typical wasteful operation creating no additional value.

Figure 5: Sketch of automatic stamping machine.


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For example, Figure 5 is a sketch of an automatic stamping machine. As shown, feeder and turnover

attachments must be exchanged as the configuration of the material to be fed into the machine is rotated.

Several changes have been made to convert internal setup actions to external ones. Figure 6 shows theinternal setup action prior to the improvement. The unloader attachments were kept at a tool storage area

away from the stamping machine causing the operator to go to the storage area to retrieve the tools. Thesetup was improved by locating unloader attachments just outside the safety fence near the stampingmachine with the intention of converting the test from an internal setup to an external one. However, it

still required time to retrieve the tools from outside the fence. Thus, to shorten the travel time, a

doorway was made in the safety fence enabling advance preparation of tools (an external setup).

Figure 6: Example of conversion from internal setup to external setup.

Step Two: Operations improvement

For the internal setup which cannot be converted to external setup, emphasis is placed on shortening

internal setup by continuously improving and monitoring operations. The following are key areas for

continuous improvement:

Keep tool and die storage areas tidy and organized Monitor effects of changing operations routine Monitor work force needs for each operation Monitor the necessity of each operation

Continuous examination of these areas will make improvement opportunities apparent. For instance,

Figure 7 illustrates an example of operations improvement. The top portion of the figure shows thetransfer of materials on a cranesaver in front of a feeder prior to revising the route. As shown, the

materials were usually transferred after the exchange of die was completed. By revising (improving) the

route (as shown in the lower portion of the figure), the materials can be transferred from point I to point2 while waiting for the unloader to unload the last stamped sheet. Then the die is exchanged. The result

is a decrease in footsteps and a reduced setup time.


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Figure 7: Operations Improvement.

Step Three: Equipment improvement

Suppose that all the methods to shorten the setup time have been performed within the limits of

operational improvements. The next strategy would be to improve the equipment. Following are severalways to do so.

Organize external setups and modify equipment so that a variety of setups can be selected withthe touch of a button. Also, recycle heat from machining operations and use for preheating ovens,

etc. Modify equipment structure or invent tools enabling a setup and setoff reduction. Also, examine

the devices for transporting the die or jig in and out of the machine area.

Eliminate adjustments needed to set the height or position of dies or jigs by using a limit switchand converting from manual to automatic adjustments.

Revise the standard operations routine sheet and provide training as equipment is improved.It is important to note that setup actions usually take about 50 to 70 percent of the total internal setup

time. Reducing this time is critical to shortening overall setup time.

Equipment improvement also includes the mechanization of manual operations, such as fastening a boltby oil pressure instead of by hand. Moreover, since many stamping machine setup attachments are fairly

heavy and are usually lifted by workers, lightweight attachments should be developed as part of theequipment improvement program.


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The following is an example of an equipment improvement at Daihatsu which has made it possible to

reduce the adjustment time of feeder centering. As seen in Figure 8, position setting of the side guides is

adjusted by turning a handle. Because the width of both side guides differs depending on each die, thehandle usually had to be turned numerous times to make the correct adjustment. As an improvement,

this position-setting action was converted to an external setup by using an automated motor.

Figure 8: Shortening of adjustment time for feeder centering.

Step Four: Zero setup

The ideal time required for setup is zero. To realize zero setup, a common part should be used for

various products. This could be achieved in the development and design stage of new models. For otherideas and methods, see Concept Four of the SETUP CONCEPTS.

Source: Toyota production system: An integrated approach to just-in-time

- By Yasuhiro Monden. - 3rd edition.

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