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MMZG 538 Toyota Production

System

Rajiv Gupta

BITS PilaniFebruary 2014

Session 7

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Module 1 Recap of Session 6

Module 2 Error Proofing (Poka Yoke)

Module 3 Standard Work Module 4

Introduction to 5S

Module 5

Summary and wrap up

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Session 7

Begin Module 1

Recap of Session 6

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Recap

One of the main reasons for batch manufacturing is long

set-up time. Batch manufacturing goes against the

principle of smooth flow in production. In addition, set-up

time is non-productive time and, therefore, a form of

waste. Therefore the focus in TPS is to reduce set-uptimes

Reduction of set up time requires that we analyze all the

activities that go into a setup.

Some of the changes require little or no investments.Others may require changes to the equipment or to the

fixtures, methods of clamping, etc.

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Recap

The result orientation of western manufacturing

companies focuses on keeping machines running.

However, the TPS approach of Jidoka, or autonomation,

focuses on shutting down a process if there is a problem,

and taking corrective and preventive measures.

Andons are chords that workers can pull to stop a line in

case there is a problem.

Poka-yoke means error proofing. The TPS approach is

to prevent the occurrence of errors. However, if an erroroccurs, a warning should alert the worker so that the

error may be corrected.

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Recap

If the line stops once and the focus is on

countermeasures preventing the problem, then

the loss of production is more than offset by the

elimination of future stoppages.

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Session 7

End of module 1

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Session 7

Begin Module 2

Error Proofing (PokaYoke)

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Poka-yoke Poka-yoke involves the use of implementing simple

low-cost devices that either detect abnormalsituations before they occur, or once they occur, stopthe line to prevent defects.

Poka-yokes reduce a worker's physical and mentalburden by eliminating the need to constantly check

for the common errors that lead to defects. Common errors: Missing process steps (e.g., flux not applied prior to

welding)

Process errors (e.g., weld applied does not meet standard)

Mis-set work pieces (e.g., piece set backwards and weldapplied to wrong place)

Missing parts

Wrong parts

Wrong work piece processed.

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Poka-yoke

Poka-yoke should have the followingcharacteristics:

It should be simple, and easy to use

It should not need significant upkeep It should be reliable

Generally it should not be expensive

Inspect 100 percent of the items.

Provide immediate feedback so as to compel

countermeasures

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Using Poka-yokes Two Types of Action

When a poka-yoke detects an error, it should eithershut down the machine or deliver a warning.

Shutdown A light sensor stops a drilling operation when it fails to

detect the requisite number of holes in the work piece.

A machine will not start if a work piece is incorrectlypositioned. The on switch sends a weak electric currentto reference pins, and only when the part makescontact with each pin will the machine start.

A tapping machine stops because the metal sensor

fails to detect a washer at each drilling point. A supplier process stops feeding the downstream

process when it is full (i.e., when the desired number ofparts have been provided).

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Using Poka-yokes Warning

Warning poka-yokes alert us to abnormalities byactivating a buzzer or light

The most famous is perhaps the Toyota andonboard, which alerts the group leader to problems

by lighting the process number, playing a piece ofmusic, or both

The Toyota andon is engaged when a teammember pulls the cord that runs along the line

The line continues to move until it reaches a fixedposition. Because each process has a fixedposition, team members are able to complete atleast one operating cycle.

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Three Types of Poka-Yoke

Detections Detection of deviations in the work piece

Detection of deviations in the work method

Detection of deviations from some fixedvalue.

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Deviations in the Work Piece

Weight. Establish a weight standard and weigh

each product using a balance.

Dimensions.Make standards for thickness, inner

and outer diameter, and so on, and identifydeviations using limit switches, stoppers, jigs,

photoelectric eyes, and the like.

Shape. Make standards for angles, number and

positions of holes, curvature, and so on, anddetect deviations with limit switches, locator pins,

interference in chutes, and similar detectors.

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Deviations in the Work Methods

This type of poka-yoke uses sensors to detect

errors in standard motions, for example:

A photoelectric sensor counts the number of times a

worker's hand breaks the beam in reaching for a part.If the requisite number of counts is not met, parts

must be missing.

A counter counts the number of spot welds made on

a work piece. The clamps will not release unless the

correct number has been made.

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Deviations in the Work Methods

Downstream process cannot proceed unless the

upstream process has been completed. For

example:

In drilling and welding, a welding jig should be madethat will only hold work pieces that have been drilled.

When assembling multiple models, photoelectric

sensors should be used to detect characteristic model

shapes. The sensor can then be linked to partscontainers, such that only containers required for the

given model will open.

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Deviations From a Fixed Value

A limit switch can be used to count the number

of holes drilled in a work piece.

Weld tips can be changed when a certain count

is reached. A counter stops the weldingmachines when the requisite count is reached

and will not restart until a new tip is installed.

If the number of parts in an assembly kit is

standardized, leftover parts will indicate

omission errors.

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Deviations From a Fixed Value

Work cannot proceed unless the value of

a critical parameter is in the predetermined

range. For example:

Pressure gauges shut down processes when

overpressures or leaks are detected.

Thermocouples shut down motors when

excessive temperatures are detected inbearings.

Torque wrenches provide torque in a target

range and shut down outside the range.19

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Session 7

End of module 2

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Session 7

Begin Module 3

Standard Work

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Standard Work

Standards form a very fundamental basis for

TPS. Without standards, TPS would not be

possible.

Standard sets a desired or ideal way for

performing a task or a job. A clear standard provides a basis for

comparison. If there is a deviation from the

standard it should be easily visible. Standards are not meant for bookshelves.

They should be on the shop floor.

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Without Standard Work

Processes tend to be unstable andunpredictable

There is extensive fire-fighting. Poor use

of management time to put out fires. Shortterm orientation

Improvements are not sustained. Sporadic

performance Difficult to have a flexible workforce as

new people may adopt different methods

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Without Standard Work

Measurement of performance becomes difficult

as goals are not clear

The wheel tends to get reinvented all the time.

Repetitive elements are not captured. Capacities are not clearly stated. Customer

promises are difficult to keep.

Very difficult to determine staffing levels and howmany machines to buy

Product costing is less accurate. Profits suffer.

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Work Sequence

The work sequence is the order of actions that

each worker must perform within the given takt

time

This helps give the worker a clear set of instructionsregarding how the task needs to be performed. It takes

guesswork out of the process

It ensures that the job, especially if done at multiple

machines, can be completed within the takt time

The instructions are provided in a pictorial form and should

take into account ergonomic considerations

Details on the tools, jigs and fixtures should also be clearly

stated

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In Process Stock

The standard quantity of work-in-process is the

minimum necessary quantity of WIP within the

production line and between each pair of

processes Inventory at the end of the line or in a store is

not included in the standard in-process stock

Without the standard WIP, the predetermined

rhythmic operation cannot be achieved

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In Process Stock

In process stock may be carried due to the

following reasons

Quality checks may require one or more pieces for

inspection at a machine Parts may be kept in inventory to permit temperatures

to drop from one operation to the next, when such a

drop is necessary

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Charts Used to Define

Standardized Work Production Capacity Chart

Standardized Work Combination Chart

Standardized Work Analysis Chart

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Production Capacity Chart

Contains information about machine and

manual times required for processing a

part Production capacity is given by

Capacity = Operational time per shift

------------------------------------

(Process time+setup time/unit)

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Session 7

End of module 3

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Session 7

Begin Module 4

Introduction to 5S

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5S As Hygiene

If we think of 5S only as a way of cleaning up for

a visit, then it is like wiping ones face although

we may not have taken a bath for days.

Eventually lack of hygiene will result in infection.

Similarly lack of 5S will result in inefficiency, high

cost and poor customer service.

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Housekeeping and 5S in Plants

Why is housekeeping important in the plants?

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Housekeeping and 5S in Plants

Why is housekeeping important in the plants?

Poor housekeeping makes it difficult to find what

we need when we need it

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Example

Would it be easy to find the part you need in the above pictur

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Now compare how easy it is to find a part in the above picture

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Example

First In First Out and inventory control would be very difficult

in the above picture

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Housekeeping and 5S in Plants

Why is housekeeping important in the plants?

Poor housekeeping makes it difficult to find what we

need when we need it

Poor housekeeping leads to lack of FIFO and excessinventory

Poor housekeeping can lead to accidents and

product damage.

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Also the material on the

floor can cause a person to

slip and hurt himself

There is a good chance that

cartons and tins piled up like

this can fall and damage the

product

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Would this not be a much safer place to work?

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Housekeeping and 5S in Plants

Why is housekeeping important in the plants?

Poor housekeeping makes it difficult to find what we

need when we need it

Poor housekeeping leads to lack of FIFO and excessinventory

Poor housekeeping can lead to accidents and product

damage

Poor housekeeping leads to errors

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Housekeeping and 5S in Plants

Why is housekeeping important in the plants?

Poor housekeeping makes it difficult to find what we

need when we need it

Poor housekeeping leads to lack of FIFO and excessinventory

Poor housekeeping can lead to accidents and product

damage

Poor housekeeping leads to errors Good housekeeping leads to better space

utilization

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See the amount of space wasted

by having empty cartons andother unnecessary material on th

floor

Also, the cartons are stacked so

high that retrieving them isvery difficult

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Not only does the above picture show clear and narrower aisles

but the cartons are also stacked at a height that makes it easy

to store and retrieve. Better space utilization and easier handling.

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Housekeeping and 5S in Plants

Why is housekeeping important in the plants? Poor housekeeping makes it difficult to find what we

need when we need it

Poor housekeeping leads to lack of FIFO and excess

inventory Poor housekeeping can lead to accidents and product

damage

Poor housekeeping leads to errors

Good housekeeping leads to better space utilization Poor housekeeping presents a poor image to

customers

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Example

Would a customer walk into an area whose entrance is like this?

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Doesnt this look much better?

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Housekeeping and 5S in Plants

Why is housekeeping important in the plants? Poor housekeeping makes it difficult to find what we

need when we need it

Poor housekeeping leads to lack of FIFO and excess

inventory Poor housekeeping can lead to accidents and product

damage

Poor housekeeping leads to errors

Good housekeeping leads to better space utilization Poor housekeeping presents a poor image to

customers

Good housekeeping improves employee moraleand productivity

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How would you like to work

in a place that looks like this?

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Would such an environment not make you want to work?

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Session 7

End of module 4

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Session 7

Begin Module 5

Summary and wrap up

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Summary

Error proofing is necessary to ensure that human

error is minimized

Standards are extremely important for TPS to be

successful

Standards help surface problems, provide a basis

for continuous improvement, and can be used for

training and measuring performance.

Standard work involves the best method for doing aparticular job. It involves the standard time (takt

time), the work sequence, standard work in process

and63

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Summary

5S is an organized approach to housekeeping

and is a prerequisite for standard work

5S is not to be mistaken for general cleaning up,

especially that done prior to the visit by seniormanagement

5S has a great impact on productivity, FIFO,

safety, and employee morale

There are 5 pillars of 5S which need to be

implemented in the correct sequence

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Session 7

End Module 5

Summary and wrap up