Jitsystem2

JUST - IN - TIMEJUST - IN - TIMESYSTEMSYSTEMCONCEPTS - AN OVERVIEW

N Ravichandran

By

N RavichandranExecutive Vice-President (Operations)Lucas-TVS Ltd, Padi, Chennai 600 050

Just-In-Time is…….

A Manufacturing system which produces :

• What the customer wants

• In the quantity the customer wants

• When the customer wants

While using the minimum of

Raw Materials

Equipment

Labour

Space

There is a focus on Waste Elimination and Lead time reductionthis would be the criteria for measuring the results of JIT efforts

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APPROACH

JUST-IN-TIME

STEP 5STANDARDISED OPERATIONS

STEP 4LEVELLING

STEP 3FLOW MANUFACTURING

STEP 2

THE 5S’s FOR FACTORY IMPROVEMENT

STEP 1AWARENESS REVOLUTION : PREREQUISITE FOR FACTORY IMPROVEMENT

HUMAN

AUTOMATION

CHANGEOVER

MULTI PROCESS

OPERATIONS

MAINTENANCE AND SAFETY

QUALITY ASSURANCE

KANBAN

VIS

UA

L C

ON

TR

OL

FL

EX

IBL

E M

AN

PO

WE

R

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JIT PRINCIPLES

• Create flow production

• Pace to ‘takt’ time

• Incorporate ‘pull’ production

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Flow production Benefits

One piece flow is the best method of exposing waste and abnormalities - making them intolerable to the production system

• Minimises waste• Minimises WIP

• forcing the recognition of all waste and abnormalities in the process• improving quality by

• creating instant feedback• facilitating a ‘corrective action’ culture

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TAKT TIME

• In German - refers to tempo set by the conductor of an orchestra

with his baton

• Uses JIT to set the production rate - which is equal to customer

demand rate

• In realty, the customer determines

the takt time

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Pull production• Stop producing by pushing parts through the assembly line• uses a demand signal at the last operation

• Implications• establishes a standard WIP• process is based on takt time• production is authorised based on customer request

• resulting in• consistent,• minimised lead time

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Pull Production -Characteristics

• Synchronised flow of raw materials

• Everything arrives just when its needed for production

• whether from outside supplier or a ‘feeder’ line

• No over production at any stage of the manufacturing process

• Nothing is produced which hasn’t been demanded by the

next production process

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Overlap areas

Timing marks

Batch ModeBatch Mode

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Batch ModeBatch Mode

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Batch ModeBatch Mode

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Batch ModeBatch Mode

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Batch ModeBatch Mode

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Batch ModeBatch Mode

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Batch ModeBatch Mode

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Batch ModeBatch Mode

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Batch ModeBatch Mode

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Batch ModeBatch Mode

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Batch ModeBatch Mode

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Batch ModeBatch Mode

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SUPPLIERSUPPLIER

Production, assembly and service lines

Production, assembly and service lines

departments ...Manufacturing units and service

CUSTOMERSCUSTOMERS

JIT SYSTEMJIT SYSTEM

Pull Pull

Kanban Control System

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What is Kanban• The literal translation is ‘sign’

• It is a system of material and production control

• It ensures work is ‘pulled’ by the customer

• Delivery right time / right amount

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SUPPLIER

CUSTOMER

Just in time Congrats !

The PULL system is controlled by the customer

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SUPPLIER

CUSTOMER

Too late!

The customer pulls,the supplier meets the demand

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SUPPLIER

CUSTOMER

Too much, too early !

The opposite of the PUSH,flow pushed by the supplier

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Simple signs used

to trigger

Material & Parts Replinishing

Parts Production

According to Usage rhythm

vs planning

Kanban is the tool

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Kanban examples

• Card

• Light signal

• Exchange of containers

• Empty space/floor markings

• Shelves

• Bar coded label

• Computer

• Etc.

User

Supplier

Computer

Suppliersignal

Userinput

Supplier User

4

Quantity:12

Part No:6789

From:MouldingTo:

Polishing

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Light signal

The card

KANBAN

To request a new delivery

Kanban examples (1)

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Container Exchange

The empty one signals a need for replenishing Kanban space

Kanban examples (2)

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The customer consumes

The Supplier replaces

The Supermarket

2731 8540122

Computer and bar codes

Kanban examples (3)

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KANBAN

JUST IN

TIME

Kanban rules

• The next process (customer) goes to get material (Pull) in the previous process (supplier).

• The previous process (supplier) produces or delivers according to the instructions of the next process (customer).

• In the absence of a signal no production, no delivery!

• There is a signal (card) for each container.

• Production/delivery: 100% quality and quantity.

• Minimum inventory and maximum turnover.

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PULL in Industry

LINE

LINE

INTERNAL

PRODUCER

SUPPLIER

ASSEMBLY LINE

SUPERMARKET

The inventory level depends on:The interval between PULLS

Production delay

Delivery delay

= signal

= material

A supermarket

The inventory levels depend on:

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• Machines in order of processes

• Small and inexpensive equipment

• One-piece flow production

• “U” shaped workflow - counterclockwise

• Multi-process handling workers

• Standing operations - moving while working

• Ergonomically correct operations

• Production paced to takt time

• “Standard operations” defined and implemented

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JIT - Characteristics

JIT Production Characteristics

• Machines in order of processes

• Minimises transportation, handling damages and excess motion

• Facilitates one-piece flow

•Small and inexpensive equipment

• Minimises capital expense for equipment

and space

• Reduces tendency towards large-batch production

• Increases production flexibility

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• One-piece flow production

• Eliminates excess WIP

• Eliminates defective batches

• Reduces lead time

• Facilitates quality control by making the full process easily

observable

•“U” shaped workflow - counterclockwise

• Reduces excess motion

• Facilitates multi-process handling

• Counter-clockwise due to “right-handedness” of people and machinery

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•Multi-process handling workers

• Gives workers responsibility for more than one production step

• Increases worker productivity

• Increases production flexibility

• Decreases WIP

• Creates an opportunity to re-deploy workers - expand capacity/new product

•Standing operations - moving while working

• Enables better part and tool presentation

• Supports multi-process handling

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•Ergonomically correct operations

• Work surfaces of equal height, minimise

lifting

• Reduces worker downtime due to work related injuries

•Production paced to takt time

• Relates to customer demand rate

• Reduces excess inventory

• Eliminates missed deliveries

• Increases productivity by matching operator cycle time to takt time

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• “Standard operations” defined and implemented

• Establishes a prescribed method for executing a manufacturing

process

• Reduces scrap/rework resulting from variations

• Ensures production process quality

• Implemented - means posted at the work station and adhered to

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Standard Operations are…A prescribed sequence of production steps

Assigned to operator

Which are balanced to the takt time

Goals are…

1. Output2. Quality3. WIP4. CostStandard ops cycle is

Identify

Defin

e

Implement

Sust

ain

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Standard Operations Cycle

focuses on…

1. Identifying the takt time

2. Existing layout and material flow

3. Existing work sequence

4. Cycle times

5. Quality, Safety, Waste, ergonomics

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Basics of Cycle time

Operator Cycle Time (OCT): The manual work content time required for an operator to complete one cycle of work process, exclusive ofwaiting timeMachine Automatic Time (MAT): The time it takes for the machine tocomplete its automatic cycleMachine Cycle Time (MCT): The sum of MAT and loading and unloading time

Operator cycle time does not include waiting for a machine auto cycle tpfinish

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Information begins to flow when a customer buys a car—let's say a Red convertible—from a car dealer.

The dealer tells the carmaker that he has solda red convertible andneeds another one forhis showroom.

THE FLOWTHE FLOW

Then, the car maker tells the parts makers that it needs parts to make another red convertible.

Things begin to flow toward the marketplace when the orders from the car maker reach the parts makers. They make the parts needed for the next red convertible and deliver them to the car maker. The car maker assembles the parts and delivers the newly assembled red convertible to the dealer.

Factory

Parts Factory Car Factory Dealer

Car makers don't just sit and wait for information to reach them from their dealers.They venture out into the marketplace to see what kinds of cars people like. Market research helps them anticipate what kinds of orders they are likely to receive from the dealers.

So, information flows. It flows from customers through dealers to the vehicle makers and parts makers. And things flow from the parts Makers and vehicle makers through the dealers to customers.

• Information Customer Dealer Car factory Parts factory

• Things Parts factory Car factory Dealer Customer

SMOOTHING THE FLOWSMOOTHING THE FLOW

Continuous flow

Levelling

Pull [Don’t Push]

Built-in Problem Solving

People

Leaner Manufacturing=Greener Manufacturing

A good way to make work flow smoothly is to arrange people and equipment in a continuous flow. That eliminates lots of waste, including the waste of accumulating unnecessary inventory. Manufacturers hate to have extra inventory.

Here's a workplace where work does not move in a continuous flow. People spend a lot of time carrying semifinished items to the next process. Lots of inventory piles up between processes.

Inventory takes up space and ties up money.

It accumulates dust and even gets rusty while sitting around for a long

time.

Things can get damaged when people carry them back and forth to and from the

warehouse

Here's a workplace where work does not move in a continuous flow. People spend a lot of time carrying semifinished items to the next process. Lots of inventory piles up between processes.

Arranging processes in a continuous flow reduces inventory and smooths the flow of work. But inventory still can accumulate between processes

Toyota solves that problem by making things one at a time

wherever possible. The idea is for each item to proceed to the

next process as soon as work is done in the preceding

process.

Of course, making things one at a time is impractical sometimes. Big stamping machines, for example, use different-shaped dies to make different kinds of parts.Manufacturers need to make a batch of parts each time they change the dies. But even in batch processing, they can use the principle of one-at-a-time processing. One way to make batch processing more like one-at-a-time processing is to use smaller batches.Instead of making 1,000 parts with each die change, the manufacturer can make 100 parts. That reduces the amount of inventory 90%. Using smaller batches means changing dies more frequently. That means stopping the machines a lot, which could be inefficient. But people can think of ways to change dies more efficiently.

Replace big lotsReplace big lots

LEVELLINGLEVELLING

Here is another way that Toyota smooths the flow of manufacturing. It mixes the production of different kinds of products smoothly through each day, week, and month.

Think of a car model that Toyota makes as a convertible, hardtop, and station wagon. And assume that customers are buying nine convertibles, nine hardtops, and nine station wagons each day. What would be the most-efficient way to make those cars?

The people who make parts for the convertibles would be busy in the morning. But they and their equipment would be idle in the afternoon and evening. In the same way, the people and equipment that make the parts for the hardtop and station wagon would be busy sometimes and idle sometimes.

You might think that Toyota should make all nine convertibles in the morning, all nine hardtops in the afternoon, and all nine station wagons in the evening. That would allow people to concentrate on one kind of work at a time. But let's see what effect that would have on the processes before and after the assembly processes.

On the other side of the assembly plant, cars would pile up between the plant and the dealers. Customers don't buy nine convertibles in the morning, nine hardtops in the afternoon, and nine station wagons in the evening. They buy different kinds of cars through the day and week.

Automakers need to make the different kinds of cars at more or less the same pace that customers buy the cars. Otherwise, they will end up with a lot of extra inventory in the form of unsold cars.

Toyota solves the problem by leveling production. If customers are buying nine convertibles, nine hardtops, and nine station wagons each day, Toyota assembles three of each in the morning, three of each in the afternoon, and three of each in the evening. It even distributes the production of convertibles, hard tops, and station wagons as evenly as possible through each shift: convertible, hard top, station wagon, convertible, hard top, station wagon, and so on.

That way, everyone who participates in the production flow works at a constant rate all the time. Toyota and its parts makers can deploy personnel and equipment to accommodate an average work load. They can avoid big fluctuations in needs of people and machinery. That saves money. And it helps maintain stable employment

Leveling production also helps avoid the problem of excess inventory of finished vehicles. The vehicle plants make the different kinds of cars at about the same pace that customers buy those cars. And they can adjust the pace as buying patterns change. So, dealers only need to maintain minimal inventory of cars to show and sell.

The Toyota Production System is a "pull" system. A vehicle

plant produces a car only after it receives an order from the

dealer. And the parts plants produce parts only after they

receive orders from the vehicle plant. In other words, the

plants make additional cars and parts only to replace cars

that customers actually have purchased. Customers pull

work through the production sequence by purchasing

vehicles.

PULL [Don’t Push]PULL [Don’t Push]

Toyota uses a tool called the kanban to "pull" work from one process to the next."Kanban" means signboard in Japanese. Usually, a kanban is a printed card that carries the name of the part or assembly and other relevant information, such as the name of the supplier. Every part and assembly that moves through the production sequence has an accompanying kanban. "Production instruction" kanban circulate inside each process. "Withdrawal" kanban circulate between processes.

Each process in the production flow is like a

customer for the preceding process. And each

process is like a supermarket for the following

process in the flow. Processes use withdrawal

kanban to "buy" parts from the preceding process

to replace the parts they have used. And the

processes each array the parts they have made for

the following process to withdraw when necessary

The parts on the loading dock

at a parts plant still carry their

production instruction

kanban. To pick up parts, a

driver from the vehicle

assembly plant brings a

withdrawal kanban. The

withdrawal kanban goes onto

a new box of parts in place of

the production instruction

kanban to "buy" the box of

parts. The production

instruction kanban goes back

into the parts plant as an

order for a new box of parts.

The supplier delivers the new box of parts to the vehicle plant indicated on its kanban

An operator at the vehicle plant removes the withdrawal kanban from a new box of parts when he or she uses the first item from that box.

The operator deposits the kanban that he or she removes from boxes of parts in a kanban mailbox nearby

Team leaders gather the contents of the kanban mailboxes at prescribed times—several times a day—and place them in collection boxes. The kanban postman picks the kanban up from the collection boxes..

...and takes them to a sorting room. There, an automatic sorter places the kanban in separate boxes for the different suppliers.

The drivers that bring parts from the suppliers stop in at the sorting room after unloading their trucks and pick up kanban to take back to their plants

No process can withdraw parts from a preceding process without a withdrawal kanban. And the only source of withdrawal kanban is parts that the following process actually has used. Likewise, no process can begin work on new parts without a production instruction kanban. And the only source of a production instruction kanban is parts that the following process actually has withdrawn.

Back at the suppliers' plants, the drivers deposit the kanban in collection boxes for subsequent sorting.

The entire production flow is like a long chain. Kanban

cycles are links in the chain that connect each

process to the following process. The final stage in

the production flow is the customer in the

marketplace. When the customer chooses and buys a

product, he or she pulls work through the whole flow.

Built-in Problem SolvingBuilt-in Problem Solving

Making work flow smoothly depends on preventing big

problems. To do that, Toyota designs its production

system to detect and solve small problems

immediately--before they become big problems.

Toyota trains people to identify possible problems.

And it lets them stop the flow of work whenever

necessary to solve any problems they detect. In

addition, the company designs equipment to stop

automatically whenever problems occur.

Here is how an employee can call attention to a problem and stop the production line, if necessary, to solve the problem. This employee has found a part that doesn't fit right.

The employee pulls on the line-stop cord overhead.

Pulling on the line-stop cord lights a

numbered lamp above the work

place. The employee's team leader

sees the lamp and comes to help.

Meanwhile, the cars on the

production line's belt conveyor will

continue moving until they reach

the next "fixed position." That is the

position where each process on the

production line has completed one

work cycle.

When the team leader arrives, the

employee explains the problem.

The team leader discovers a ring

that has slipped out of place. That

is why the part didn't fit right. The

team leader solves the problem

before the production line reaches

the next fixed position. So, the

line continues moving. If the team

leader had required more time to

solve the problem, the line would

have stopped at the fixed

position.

Here is an example of ways that Toyota improves

equipment to prevent problems from occurring and

to detect problems that do occur. The idea of

making these kinds of improvements continually is

what manufacturers call "kaizen." Kaizen is the

Japanese word for improvement. The idea is to

keep making one improvement after another.

Gradually, a lot of little improvements add up to

huge gains in productivity and quality and working

conditions.

This automatic welding machine welds a ring onto an assembly. Sometimes, an assembly comes along that is missing a ring. Toyota equips the welding machine with a simple mechanism to detect missing rings. If an assembly is missing a ring, the welding arm comes down further than usual. It comes down far enough to depress the stop button. That lights a warning lamp and sounds a buzzer to call attention to the problem, as well as stopping the machine.

Making things more efficiently means consuming less material and less energy. It means outputting less factory waste that must be burned or buried. So, the Toyota Production System reduces the environmental impact of manufacturing. But Toyota also works in other ways to harmonize manufacturing with the environment