The focus of JIT is to improve the system of production by eliminating

all forms of WASTE.

Just-In-Time Philosophy

JIT is a long-term approach to process improvement. It uses timeliness as a lever to lower costs, improve quality and improve responsiveness. However, JIT requires enormous commitment. It took Toyota more than 25 years to get right!

Just-in-Time

• Downstream processes take parts from upstream as they need.– Get what you want– when you want it– in the quantity you want.

4. Just In Time-- What is It?

• Just-in-Time: produce the right parts, at the right time, in the right quantity – Requires repetitive, not big volume– Batch size of one– Short transit times, e.g. keep 0.1 days of supply

Characteristics of Just-in-Time Pull method of materials flow Consistently high quality Small lot sizes Uniform workstation loads Close supplier ties Flexible workforce Automated production Preventive maintenance

Push versus Pull

• Push system: material is pushed into downstream workstations regardless to the demand or whether resources are available

• Pull system: material is pulled to a workstation just as it is needed–

From a « push » to a « pull » System

Work is pushed to the next station as it is completed

SUPPLIERS

CUSTOMERS

A workstation pulls output as needed

SUPPLIERS

CUSTOMERS

From a « push » to a « pull » System

JIT Demand-Pull Logic

Customers

Sub

Sub

Fab

Fab

Fab

Fab

Vendor

Vendor

Vendor

Vendor

Final Assembly

Here the customer starts the process, pulling an inventory item from Final Assembly…

Then sub-assembly work is pulled forward by that demand…

The process continues throughout the entire production process and supply chain

Pull Versus Push SystemsPull Versus Push Systems

A pull system uses signals to request A pull system uses signals to request production and delivery from upstream production and delivery from upstream stationsstations

Upstream stations only produce when Upstream stations only produce when signaledsignaled

System is used within the immediate System is used within the immediate production process and with suppliersproduction process and with suppliers

Pull Versus Push SystemsPull Versus Push Systems

By pulling material in small lots, inventory By pulling material in small lots, inventory cushions are removed, exposing problems cushions are removed, exposing problems and emphasizing continual improvementand emphasizing continual improvement

Manufacturing cycle time is reducedManufacturing cycle time is reduced Push systems dump orders on the Push systems dump orders on the

downstream stations regardless of the downstream stations regardless of the needneed

Basic Elements of JIT

Consistently high quality• Consistently meeting customer’s expectations. • Just-in-time systems seek to eliminate scrap and rework

in order to achieve a uniform flow of materials

• Use quality at the source which is having employees act as their quality inspectors such that never passing on defective units to the next process.

• Poka-yoke (mistake proofing method) designing fail-safe systems to minimize human errors. Ex: design parts to be assembled in only one way- the correct way.

Small lot sizes

• JIT systems maintain inventory with lot sizes that are as small as possible.

• Small lot sizes have three benefits:1)small lot sizes reduce cycle inventory which

reduces the time and space involved in manufacturing and holding inventory.

2)small lot sizes help cut lead times then cutting pipeline and (WIP) inventory. (longer processing, longer inspection, defects delays)

Small lot sizes

• Benefits of small lot sizes:3) small lots help achieve a uniform operating

system workload.setup times must be reduced to realize the

benefits of small-lot production.

Uniform Workstation Loads• Uniform loads can be achieved by assembling

the same type and number of units each day, thus creating a uniform daily demand at all workstations

• Two models of production1) Line production: all daily requirements of a model

are produced in one batch before another model is started

2) Mixed model assembly: mix of models in smaller lots in a sequence (set up times should be low)

Standardized Components and Work Methods

• The standardization of components, called part commonality or modularity, increases repeatability.

• each worker performs a standardized task , Productivity tends to increase.

Close Supplier Ties

• JIT systems operate with very low levels of inventory, close relationships with suppliers are necessary.

• Stock shipments must be frequent, have short lead times, arrive on schedule, and be of high quality

• Purchasing managers focus on three areas: reducing the number of suppliers, using local suppliers, and improving supplier relations

Flexible Work Force

• Workers in flexible work forces can be trained to perform more than one job.

• Workers can be shifted among workstations to help relieve bottlenecks as they arise without resorting to inventory buffers--an important aspect of the uniform flow of JIT systems.

• they can step in and do the job for those on vacation or out sick.

Preventive Maintenance

• Because JIT emphasizes low inventory between workstations, unplanned machine downtime can be disruptive.

• Preventive maintenance can reduce the frequency and duration of machine downtime.

• One tactic is to make workers responsible for routinely maintaining their own equipment and develop employee pride in keeping their machines in top condition

Streamlined Production

Flow with JIT

Traditional Flow

CustomersSuppliers

Customers

Suppliers

Production Process (stream of water)

Inventory (stagnant ponds) Material

(water in stream)

Waste in Operations1. Waste from overproduction (manufacturing an item

before it is needed and with more quantities) this increase both inventory and lead time

2. Waste of waiting time (product is not moved and processed, poor materials flow, poor processes linkages this waiting may be 90 percent of LT)

3. Transportation waste (excessive movement and materials handling, risk of being damaged, lost, delayed, a cost for no added value

4. Inventory waste (a capital outlay that has not yet produced an income, excessive Inv hides shop floor problems, Increased inv is a result of overproduction and waiting)

5. Processing waste (more work is done on a piece than what is required by the customer, high precision equipment when simple machine is sufficient, overutilization of expensive assets)

6. Waste of motion (unnecessary efforts related to ergonomics like bending, stretching, reaching, lifting and walking) jobs with excessive motion should be redesigned

7. Waste from product defects (quality defect results in scrap and rework and wasteful costs lost capacity, scheduling efforts, increased inspection, and loss of customer good will)

8. Underutilization of people

Waste in Operations

Lowering Inventory Reduces Waste

WIP hides problems

Lowering Inventory Reduces Waste

WIP hides problems

Lowering Inventory Reduces Waste

Reducing WIP makesproblem very visible

STOP

Lowering Inventory Reduces Waste

Reduce WIP again to findnew problems

Reduce VariabilityReduce Variability

Inventory levelInventory level

Process downtimeScrap

Setup time

Late deliveries

Quality problems

Inventory Inventory levellevel

Reduce VariabilityReduce Variability

Scrap

Setup time

Late deliveries

Quality problems

Process downtime

Causes of VariabilityCauses of Variability

1.1. Employees, machines, and suppliers produce Employees, machines, and suppliers produce units that do not conform to standards, are units that do not conform to standards, are late, or are not the proper quantitylate, or are not the proper quantity

2.2. Engineering drawings or specifications are Engineering drawings or specifications are inaccurateinaccurate

3.3. Production personnel try to produce before Production personnel try to produce before drawings or specifications are completedrawings or specifications are complete

4.4. Customer demands are unknownCustomer demands are unknown

Variability ReductionVariability Reduction JIT systems require managers to reduce JIT systems require managers to reduce

variability caused by both internal and variability caused by both internal and external factorsexternal factors

Variability is any deviation from the Variability is any deviation from the optimum processoptimum process

Inventory hides variabilityInventory hides variability Less variability results in less wasteLess variability results in less waste

Performance and WIP Level

• Less WIP means products go through system faster• reducing the WIP makes you more sensitive to

problems, helps you find problems faster• Stream and Rocks analogy:

– Inventory (WIP) is like water in a stream– It hides the rocks– Rocks force you to keep a lot of water (WIP) in the stream

JIT Production system

Step1: Awareness Revolution

• it is important that everyone, including the production workers and the outside vendors, undergo the awareness revolution.

• But the best place to start is at the top

Step2: 5S’s factory improvement

• 5s factory improvement: proper arrangement• (seiri), orderliness (seiton), cleanliness (seiso),

cleanup (seiketsu), and discipline (shitsuke).

• Arrangement and ordinariness is a first stepvisual red tag strategy (kanban)

Step 3. Flow Manufacturing

1. Continuous flow production line (U-shape or line arrangement)

2. Compact specialized and general-purpose equipment

3. One-piece flow (Shish Kabob production)4. Minimum Cycle time5. Multi-process handling6. Multi-skilled workers7. Standing (chair-free) operations

Flow Mfg: Scheduling Small LotsFlow Mfg: Scheduling Small Lots

AA BB CCAA AAAABB BB BB BB BB CC

JIT Level Material-Use ApproachJIT Level Material-Use Approach

AA CCAA AAAA BB BB BB BB BB CC CCBB BB BB BBAA AA

Large-Lot ApproachLarge-Lot Approach

TimeTime

Step4: leveling

Matching capacities with loads (with customer needs)

Step 5. Standard Operations

• Reveal and discover the net time for current operating conditions

• Figure out the problems regarding work balance, ergonomic factors, and variation

• Find out the real causes and plan improvement• Implement the improvement.• Standard operations, (use instruction manual).

Reduce Setup TimesReduce Setup Times

Use one-touch system to eliminate Use one-touch system to eliminate adjustments (save 10 minutes)adjustments (save 10 minutes)Step 4Step 4

Step 5Step 5Training operators and standardizing work Training operators and standardizing work procedures (save 2 minutes)procedures (save 2 minutes)

Repeat cycle until subminute Repeat cycle until subminute setup is achievedsetup is achieved

Initial Setup Time

Step 2Step 2Move material closer and

improve material handling (save 20 minutes)

Step 1Step 1

Separate setup into preparation and actual setup, doing as much as possible while the machine/process is

operating (save 30 minutes)

Step 3Step 3Standardize and

improve tooling (save 15 minutes)

90 min —90 min —

60 min —60 min —

45 min —45 min —

25 min —25 min —

15 min —15 min —13 min —13 min —

——

Quick Setups

• SMED Principles: (Single Minute Exchange of Dies) • Separate internal setup from External setup• Convert internal setup to external setup• Streamline all aspects of setup• Perform setup activities in parallel or eliminate

them entirely

SMEDSome examples included:• Bringing the dies to the press ahead of time • Assuring that the dies were complete

including all fasteners • Modifying all dies to the same physical size,

eliminating setup adjustments

• Specialized handling equipment • Quick acting fasteners

Common Techniques for Reducing Setup Time

1. Maintenance, Organization and Housekeeping It often happens that setup problems are related to poor

maintenance such as worn parts, worn tooling, dirt, or damaged threads. Disorganization and poor housekeeping are also contributors to setup problems. These are easy to fix and should be a first step.

2. Internal Elements to External Internal elements occur when the machine is down.

Examine each internal element and see if it cannot be done externally. For example, the pre-heating of an injection molding die could be done before it goes into the machine.

Common Techniques for Reducing Setup Time

3. Improve Elements Here we examine every element to see how we can

eliminate it, simplify it, reduce the time required or improve it in some other way.

4. Eliminate Adjustments Adjustments are often the most time consuming,

frustrating and error prone parts of a setup. There are many ways to eliminate them entirely and this is the ultimate goal.

Kanban

• Japanese for ‘signboard’• Method for implementing JIT• In order to produce, you need both material

to work on, and an available kanban.• Each work station has a fixed # kanbans.

KanbanKanban

Kanban is the Japanese word for cardKanban is the Japanese word for card The card is an authorization for the next The card is an authorization for the next

container of material to be producedcontainer of material to be produced A sequence of kanbans A sequence of kanbans

pulls material through pulls material through the processthe process

Many different sorts of Many different sorts of signals are used, but signals are used, but the system is still called the system is still called a kanbana kanban

KanbanKanban

1.1. User removes a User removes a standard sized standard sized containercontainer

2.2. Signal is seen by Signal is seen by the producing the producing department as department as authorization to authorization to replenishreplenish

Part numbers Part numbers mark locationmark location

Signal marker Signal marker on boxeson boxes

Figure 16.8Figure 16.8

KanbanKanban

Figure 16.9Figure 16.9

Work Work cellcell

Raw Raw Material Material SupplierSupplier

KanbanKanban

Purchased Purchased Parts Parts

SupplierSupplier

Sub-Sub-assemblyassembly

ShipShip

KanbanKanban

KanbanKanban

KanbanKanban

KanbanKanban

Finished Finished goodsgoods

Customer Customer orderorder

Final Final assemblyassembly

KanbanKanban

More KanbanMore Kanban When the producer and user are not in When the producer and user are not in

visual contact, a card can be usedvisual contact, a card can be used When the producer and user are in visual When the producer and user are in visual

contact, a light or flag or empty spot on contact, a light or flag or empty spot on the floor may be adequatethe floor may be adequate

Since several Since several components may components may be required, be required, several different several different kanban techniques kanban techniques may be employedmay be employed

More KanbanMore Kanban

Usually each card controls a specific Usually each card controls a specific quantity or partsquantity or parts

Multiple card systems may be used if Multiple card systems may be used if there are several components or there are several components or different lot sizesdifferent lot sizes

Kanban

• Workstation 2 finishes a part, outbound moves over• WS2 has a blue tag available, so it gets another part

to work on:– 2 takes off 1’s green tag giving it back to 1, and – puts on it blue tag and moves it into position.

Flow of work

32

Kanban

• When 3 finishes a part, – Finished parts move over one spot– It has to have a red tag available to put on,– It gets a part from 2’s outbound pile, – And gives the blue back to 2

Flow of work

32

Kanban

• When 3 finishes a part, – Finished parts move over one spot– He has to have a red tag available to put on,– He gets a part from 2’s outbound pile, – And gives the blue back to 2

• 3’s production will be taken by 4, offstage right.– Tag goes back into 3’s bin

Flow of work

32

Kanban

• Red finishes his part next.

• But 4 hasn’t freed up any of the red kanbans, so there is nothing for 3 to work on now.

• 3 could maintain his machine, or see if 4 needs help

32

32

The Number of Kanban CardsThe Number of Kanban Cardsor Containersor Containers

Need to know the lead time needed to produce a container of parts

Need to know the amount of safety stock needed

Number of kanbansNumber of kanbans(containers)(containers)

Demand during Demand during SafetySafetylead timelead time ++ stockstockSize of containerSize of container==

Number of Kanbans ExampleNumber of Kanbans Example

Daily demandDaily demand == 500500 cakes cakesProduction lead timeProduction lead time == 22 days days(Wait time + (Wait time + Material handling time + Material handling time + Processing time)Processing time)Safety stockSafety stock == 1/21/2 day dayContainer sizeContainer size == 250250 cakes cakes

Demand during lead time Demand during lead time = 2= 2 days days x 500x 500 cakes cakes = 1,000= 1,000

Number of kanbans Number of kanbans = = 5= = 51,000 + 2501,000 + 250250250

Advantages of KanbanAdvantages of Kanban

Allow only limited amount of faulty or Allow only limited amount of faulty or delayed materialdelayed material

Problems are immediately evidentProblems are immediately evident Puts downward pressure on bad Puts downward pressure on bad

aspects of inventoryaspects of inventory Standardized containers reduce Standardized containers reduce

weight, disposal costs, wasted space, weight, disposal costs, wasted space, and laborand labor

Example

• A switch is assembled in batches of 4 units at an “upstream” work area.

• delivered in a bin to a “downstream” control-panel assembly area that requires 5 switch assemblies/hour.

• The switch assembly area can produce a bin of switch assemblies in 2 hours.

• Safety stock = 10% of needed inventory.

2.75 or 3 4

5(2)(1.1) C

dL (1SS)

k size of container Expected demand during lead time + safety stock

Characteristics of JIT Partnershps

• Few, nearby suppliers• Supplier just like in-house upstream process• Long-term contract agreements• Steady supply rate• Frequent deliveries in small lots• Buyer helps suppliers meet quality• Suppliers use process control charts• Buyer schedules inbound freight

Typical Benefits of JIT• Cost savings: inventory reductions, reduced scrap, fewer

defects, fewer changes due to both customers and engineering, less space, decreased labor hours, less rework.

• Revenue increases: better service and quality to the customer.

• Investment savings: less space, reduced inventory, increased the volume of work produced in the same facility.

• Workforce improvements: more satisfied, better trained employees.

• Uncovering problems: greater visibility to problems that JIT allows, if management is willing to capitalize on the opportunity to fix these problems.