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MMZG 538 Toyota Production

System

Rajiv Gupta

BITS PilaniJanuary 2014

Session 4

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Module 1 Recap of Session 4

Module 2 Value Stream Mapping Example (contd)

Lean Principles

Module 3 Value Stream Mapping Example (contd)

Future State Map

Module 4 Types of layouts and material flow

Module 5 Design of machine cells

Module 6 Summary and wrap up

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Session 4

Begin Module 1

Recap of Session 3

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Recap

Material flow is integral to TPS as it affects the lead

times and inventories on the shop floor

The principal reasons for intermittent movement of

materials is batch manufacturing, long set-up timesand an attempt to reduce per unit costs

Product type layouts were used in mass

manufacturing for high volume parts. Process

layouts were meant for low volume job shops.

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Recap

Group layouts were developed as a hybrid between

product and process layouts. They were efficient in

terms of flow and could be used for low to medium

volumes of families of products Typically, value is added to parts for less than one

percent of the time it spends in the plant. However,

the majority of improvement efforts are focused on

improving this one percent. There is a largerpotential for benefits by looking at the remaining

time the part spends in the system.

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Recap

Value Stream Mapping is a macro level charting

technique that highlights the discontinuities in flow in a

system. It can be used as a tool to significantly improve

material flow and system throughput

Value Stream Mapping is applicable to both

manufacturing, as well as non-manufacturing processes.

By analyzing the current state maps and applying lean

principles, we can greatly reduce discontinuities in

material and information flow.

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Session 4

End of module 1

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Session 4

Begin Module 2

Value Stream Mapping Example (contd)

Lean Principles

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Lean Principles

Takt time = Available time per shift/Customer demand rate per shift

= 27600 sec/460 pcs

= 60 sec/pc

i.e., we need to produce at the rate of one part every 60 secs.

In practice we may set the production rate a little higher to allow

for changeover time and equipment down time and delays

1. Avoid over-productionproduce to takt time

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Lean Principles

2. Develop Continuous Flow

One piece at a time

Little or no inventory between operations

Operations linked to each other

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Lean Principles

3. Where continuous flow is not possible, use supermarket

pull

- Used when operations are far apart

- Used when an operation is done at a supplier- Used when operations are not balanced

- Used when process is unreliable

Customer

ProcessSupplying

Process

Supermarket

KanbanKanban

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Lean Principles

Customer Process goes to supermarketand withdraws what it needs

This withdrawal triggers a kanban, which

is a signal to the supplier process toreplenish that product

The supermarket links the customer

process to the supplier process preventingindependent scheduling of the 2processes

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Lean Principles

4. Schedule only one process- It is called the pace maker

- Linked to the customer order

- Downstream processes have to be continuous flow

Process 1 Process 2Process 3 Process 4

Pace maker

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Lean Principles

5. Level Production Mix

O X

O X O X O X O X O

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Lean Principles

6. Create Initial Pull

- At the pacemaker

- Small consistent amount of work

- Could be a container or a bin

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Initial Pull

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Decide on a pitch which represents consistent incremental work.

Let us say that the takt time = 30 seconds and the pack size is 20

pieces, then the pitch will be 30 seconds x 20 pieces = 10 minutes

So your production schedule will give the pacemaker instruction to

produce one pack quantity every 10 minutes.

Also every 10 minutes, you will take away one finished pitch quantity

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7:00 am 7:10 am 7:20 am 7:30 am 7:40 am

O O

X

OO

X

Load Leveling Box

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Session 4

End of module 2

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Session 4

Begin Module 3

Value Stream Mapping Example (contd)

Future State Map

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Key Questions For The Future

State1. What is the takt time?

2. Will you build to a finished goods supermarket from

which the customer pulls, or directly to shipping?

3. Where can you use continuous flow processing?4. Where will you need to use supermarket pull systems?

5. Which will be the pacemaker process?

6. How will you level the production mix at the pacemaker

process?7. What increment of work will you consistently release to

the pacemaker process?

8. What process improvements will be necessary?

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Question 1: What will be the takt time?

Available time per shift = 28,800 secs

1200 secs (for 2 10-minute breaks) =

27,600 secs

Customer demand per shift = 460 pieces

Takt time = 27,600/460 = 60 secs

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Question 2: Should the company build to a

finished goods supermarket or directly to

shipping?

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Future State Map

Dispatch

L

R

Customer

Demand

Weld+Assy

First Step- Build to supermarket

FutureDirect to shipping

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Question 3: Where can the company

introduce continuous flow?

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Future State Map

Blank Weld Weld Assy Assy

60

1 s

39 s

46 s

62 s

40 s

Operators reqd = 187/60

= 3.12

3 or 4

Apply Kaizen to reduce

Total work content to 168 sec

Operators reqd = 168/60

= 2.8

Use 3 operators

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Future State Map

WeldWeld

Assy

Assy

Improve welder setup time

Improve welder uptime

Weldchangeover

Welderuptime

Work content

< 168 secs

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Future State Map

C/T = 56 sec

C/O = 0

Up =100%

Blanking

Dispatch

L

R

Customer

Demand

Weld+Assy

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Question 4: Where will supermarket pull

be used?

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60

L

R

Stamping

Batch

LH = 600

RH = 320

1.5 days Weld + Assembly

C/T = 56 sec

C/O = 0

Up =100%

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Question 5: Which single point should

receive the production schedule

(pacemaker)?

Question 6: How should production be

leveled at the pacemaker?

Every part every day

Every part every pitch

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Question 7: What consistent amount of workshould be released to the pacemaker

process?

Question 8: What process improvements arenecessary?

Elimination of changeover time in welding

Improvement of uptime of the second weldingprocess

Reduction of waste in assembly cell to bring total

work content to 168 seconds

Reduction of setup time at the stamping press 31

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Stage Coils Blanks Weld/

Assy

WIP

FG Prod

LT

Inv

Turns

Before 5d 7.6 d 6.5 d 4.5 d 23.6 d 10

After 2 d 1.5 d 0 4.5 d 8 d 30

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Session 4

End of module 3

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Session 4

Begin Module 4

Layout types and material flow

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Lathe

Lathe

Lathe

Drill

Drill

Drill

Milling

Milling

Milling

Process Layout

Lathe Drill Lathe

Drill Milling Grind

Lathe Grind

Product Layout 35

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Product Layouts

Product layouts were designed to maximize flow,

but for high volume products

The machines were special purpose and

automation was hard automation, i.e, the systemwas designed for a specific part and volume

The system was inflexible

It was easy to supervise

Scheduling was relatively easy

Lead times were generally short

WIP was low36

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Process Layouts

Process layouts were used for low volume

products

Machines were general purpose and parts

requiring processing could be produced on anymachine of a particular type, e.g., lathe, etc.

Supervision and scheduling were more difficult

Lead times were long

WIP was high

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Lathe Milling

Lathe Drill

Lathe Drill

Milling

Milling Milling Drill

Grind Grind

Group 1

Group 2

Group 3

Group Layouts

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Group Technology

Attributed to Mitofanov, a machinist, who was

looking for similarities in part shapes

Group technology was the forerunner to

machine cells Initial applications were in coding and

classification of parts for reducing redundant

effort in part design

John Burbidge devised Production Flow Analysis

to group parts that needed similar routings and

the machines into cells

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Machine Cells

Machine Cells A group of machines used to complete a sequence of

operations on a family of parts

The parts in a family does not have high volumes, but

the family has sufficient volume to justify thededication of the machine cell

By restricting the movement of each part to a smallarea, material handling and control is easier,inventories are low and therefore lead times short.This gives the machine cells the efficiency of productlayouts

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Machine Cells

Machine Cells Unlike product layouts, group layouts/machine cells

have the ability to accommodate a family of parts

Due to this, when product mix and volumes change,

the machine cell is able to absorb the fluctuation. Thismakes the group layout/machine cell flexible like theprocess layouts

Machine cells are easy to supervise and schedule

WIP and lead times tend to be low

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Session 3

End of module 4

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Session 3

Begin Module 5

Design of machine cells

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Machine Cells

Machine Cells

Machines are arranged typically in a U-shaped layout

Each operator is assigned multiple machines,not of the same type

Input and output stations tend to be near eachother next to a transportation aisle

Components are delivered either to the firststation and moved with the product, ordelivered by a water spider to each station

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Machine Cells

Machine Cells

Generally the machining capacity is morethan required.

As production volume changes, adjustment ismade to the staffing of the machine cell. Thismakes the machine cells flexible in terms ofproduct mix and volumes

By making a group of workers responsible forthe complete production of a part, there is agreater sense of satisfaction for the workers

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Machine Cells

Machine Cells

Due to better communication within the cell, ifthere is a quality problem, it is detected

quickly and adjustments made to preventfurther defectives from being produced

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Machine Cells

Input

Output

Mach 1Mach 2

Mach 3

Mach 4 Mach 5

Example of a machine cell with 2 operators

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Machine CellsMachine Cells

Input

Output

Mach 1Mach 2

Mach 3

Mach 4 Mach 5

Example of a machine cell with 1 operator

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Machine Cell Design

The number of operators and the assignment of

machines to the operators depends on the manual work

content, the walking times and the takt time

Takt time determines the pace at which the cell should

complete one piece

The sum of the manual times and the walking times

should be less than or equal to the takt time

When more than one operators are used, the largest

sum of the manual times plus the walk times should beless than or equal to the takt time

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Session 4

End of module 5

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Session 4

Begin Module 6

Summary and wrap up

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Summary

Lean principles are used to analyze Current State

VSMs

When creating Future State maps, the attempt is

reduce, or eliminate discontinuities in the flow

The VSM will indicate areas where Point Kaizen is

needed in order to achieve smoother flow

Machine cells are a hybrid between product and

process layouts Machine cells have the advantages of efficiency of

product layouts and flexibility of process layouts

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Summary

Machine cells require multi-skilling of operators

Due to the improved communication in of

machine cells, quality of products is improved

Due to the completion of all or most productionof a part within a cell, there is greater worker

satisfaction

In the design of machine cells, we need to

establish the number of workers based on takt

time and the manual time required

As the production volume changes, the number

of workers can be adjusted55

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End Module 6

Summary and wrap up

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