Just-in-time

Prof. Jiang Zhibin

Dept. of IE, SJTU

Tools of Lean Manufacturing

Pull Systems / KanbanA Tool for Implementing Pull Systems

Lean ProductionThrough Waste Elimination

Operational Stability

JITQualityat the

SourcePeople

JIT Goals

Zero defects Zero excess lot size or lot size of one Zero setups Zero breakdowns Zero handling Zero lead time Zero Surging

Level production plan and uniform product mix

Need to Reduce Cost

Traditional Method(Push)

Seller Driven

Modern Method(Pull)

Customer Driven

SellingSellingPricePriceProfit =Profit =CostCost ++

(SELLER)

SellingSellingPricePrice -- CostCost

==

PROFITPROFIT (MARKET)

Just in Time

History - Japan 1980s conclusion

Japanese industry worked “smart” - JIT Think of JIT as minimum stock

production Type of relationship: close &

intimate? JIT internal JIT - in client-server stream external JIT

Japanese Experience

Waste in operations from

overproduction

waiting time

transportation

inventory waste

processing

motion/movement

product defects

concentrate effort on shop floor

CQI focus

staff ownership of problems

Minimizing Waste: Inventory Hides Problems

Work in

process

queues

(banks)

Change

orders

Engineering design

redundancies

Vendor

delinquencies

Scrap

Design

backlogs

Machine

downtime

Decision

backlogsInspection

backlogs

Paperwork

backlog

identify defects from a supplier early in the process saves the downstream work

identify defective work from upstream stations, saves the downstream work

Forecast randomordersMaster

productionschedule

(MPS)

MRP1

Designchanges

Bill ofmaterial

Stockmovements

Inventoryrecord

Reports

8

AggregatePlan (product groups)

Firmorders

From Aggregate to MPS to MRP1

Time-phased planhow many + when we will build each end item.

Time-phased planhow many + when we will build each end item.

MRP2MRP2

JITJIT

Just-In-Time (JIT)

a system for high-volume production with minimal inventory (raw materials, WIP, finished goods).

involves timed arrivals @ workstation JIT reduced ‘buffer’ stocks no waste in production system a “Pull” system thru the plant

a management philosophy expose problems & bottlenecks Take away ‘security blanket” streamlined production factory & warehouse networks

• participation• industrial engineering/basics• continuing improvement• TQM• reducing set up times• smaller lot/order sizes sizes• stable environment• supply partnership

Requires

JIT Requirements 1Kanban Pull Demand pull Back flush Reduce batch/lot sizes

Work with suppliers Reduce lead times Frequent deliveries Project usage requirements Quality expectations

Reduce inventory in Stores Transit Conveyors calculation from MRP & EOQs

JIT Requirements 2Quality Worker responsibility SQC Enforce compliance Error proffing Automatic inspection

Quality Worker responsibility SQC Enforce compliance Error proffing Automatic inspection

Stabilise Schedule Level schedule Under utilize capacity

Operations Design Link operations Balance workstation capacities Review layout for flow Stress preventive maintenance Reduce lot sizes Reduce setup/changeover time

Operations Design Link operations Balance workstation capacities Review layout for flow Stress preventive maintenance Reduce lot sizes Reduce setup/changeover time

People Focus pay harmonisation supportive unions subcontractor networks hands-on manager style quality commitment &

group involvement

JIT Requirements 3

Product Design Improvement

DFM & process design Modules & fewer parts Quality standards upgrade housekeeping clarify process flows revise equipment & process

technologies

Problem-solving Root problem Long-term solution Team contribution Line-specialist cooperation Learning Measure performance CQI Monitor & report

Problem-solving Root problem Long-term solution Team contribution Line-specialist cooperation Learning Measure performance CQI Monitor & report

JIT and Demand-Pull

Customer

Supplier

Supplier

Supplier

Supplier

Final Assembly

Fabric

Fabric

Fabric

Fabric Subass

Subass

Call (Kanban) & PullCall (Kanban) & Pull

Call (Kanban) & PullCall (Kanban) & Pull

Call (Kanban) & PullCall (Kanban) & Pull

Client Server StreamingAvoid too much material stocks & WIPIncrease materials coordination & movement

Bin

SawSaw Supplier'slocalwarehouse

Supplier'slocalwarehouse

Finished GoodsWarehouse

Finished GoodsWarehouse

GrinderGrinderLatheLathe

Bin

Call for moreCall for more

MaterialswarehouseMaterialswarehouse

Bin

Bin

Bin

Bin

CustomerCustomer

JITdeliveriesJITdeliveries

Call for more

Call for more

What is Kanban?

developed at Toyota 1950s to manage line material flows. Kanban ( Kan=card, Ban= signal ) simple movement system

“cards” to signal & communicate reorder information boxes/containers to take “lots” of parts from one work

station to another (client-server). Server only delivers components to client work station as &

when needed (called/pulled). minimise storage in the production area. Workstations only produce/deliver components when called

(they receive card + empty container). The work-station produces enough to fill the container Kanban = an authorization to produce more inventory We thus limit the amount of inventory in process.

Benefits of Kanban

An information network used to control production quantities

A communication process that controls the movement of material

A cost reduction (waste elimination) tool that prevents over production

A quality control enforcer because it limits lot quantities to small amounts, thereby allowing defects to be identified early in the manufacturing process

Benefits of Kanban (cont.) Manages just-in-time production Gives specific part number, quantity,

location, and time demands to lower work centers

Identify excess in plant inventory levels Identify potential inventory shortages (low

stock indicators) Limits quality rejects by

reducing lot size produced

Kanban Pre-conditions

There are four pre-conditions for

the successful implementation of

Kanban

Point of use Point of use inclusion (all parts inclusion (all parts on the assembly line)on the assembly line)

Level productionLevel production

Stabilized processesStabilized processesQuick Changeover Quick Changeover proceduresprocedures

Kanban

Market Address

<<Market_Address>>

Kanban Number

<<KAN>>

Line-Side Address

<<Line_Side_Address>>

Part Number

<<Part Number>>

Route

<<Route>>

Part Description

<<Part Number>>

Bar Code Area

Dock Code

<<Dock Code>>Supplier Code

<<Supplier Code >>

Quantity

<<Quantity>>

Serial Number

Comment:<<Comment>>

What Does a Kanban Card Look Like?

Kanban No.Kanban No. 5678990 5678990 part No: part No: 66789X66789Xdescription description 16ga. Copper 16ga. Copper

WireWireunits units Ft.Ft.reorder/lot qty reorder/lot qty 2020store location store location Row 12, Bin 6Row 12, Bin 6supplier supplier BICCBICCsupplier tel supplier tel 0208-891-01210208-891-0121supplier part supplier part RT45502RT45502routing processName/location of next procesName/location of preceding processcontainer type & capacitynumber of containers released

• accurate data: correct part nos, accurate data: correct part nos, quantities & measure'tsquantities & measure'ts

• visible - chart if material ordered visible - chart if material ordered & when& when

• fool proof for no stockoutsfool proof for no stockouts• minimum inventoryminimum inventory• clear & complete info. to clear & complete info. to

supplierssuppliers• link inventory directly to demandlink inventory directly to demand• Tie in with POP: issuing orders, Tie in with POP: issuing orders,

receiving & authorising accounts receiving & authorising accounts payablepayable

• accurate data: correct part nos, accurate data: correct part nos, quantities & measure'tsquantities & measure'ts

• visible - chart if material ordered visible - chart if material ordered & when& when

• fool proof for no stockoutsfool proof for no stockouts• minimum inventoryminimum inventory• clear & complete info. to clear & complete info. to

supplierssuppliers• link inventory directly to demandlink inventory directly to demand• Tie in with POP: issuing orders, Tie in with POP: issuing orders,

receiving & authorising accounts receiving & authorising accounts payablepayable

Function of Kanban Helps to reduce passage of defects from one area to another by

identifying preceding processes. Provides pick-up and/or transportation information, which includes “where

from” and “where to” locations. It can also, in some cases, indicate schedule times for pick-up.

Communicates production information. It tells what to produce and how many are required. Function No. 3 also states Kanban must be produced in the order received.

Prevents overproduction and excessive transportation by restricting in-bound raw material and the production quantity of a process to specific pre-determined lot quantity indicated on the Kanban. It allows ordering of multiple lot quantities only to the extent of Kanban available to be replenished

Serves as a work order indicating what has been produced and identifies the physical product

Reveals existing production problems and maintains inventory control

Rules of Kanban

Never send defective products to downstream processes The downstream process draws only what is required by

the Kanban from upstream processes. The upstream process produces items in the quantity and

the sequence indicated by the Kanban. Parts are never to be produced or conveyed without a

Kanban Kanban must be attached to the actual containers of parts Kanban is a tool to fine tune production

Inter-process Kanban FlowD F

B D FA B C D E FA B C D E FA B C D E F

Market Place

Post Office

Kanban Post Office

4

V1

V2

V3

V4

V5

V6

A

AA

CC

EE

AA

CC

EE

5

3

2

1

Assembly WithdrawKanban Mailbox

Inter-Process

BBB

C

E

DDDD

FF

ff

Y

X

Z

Minimizing Waste: Kanban Control System

Bin Part A

Bin Part AMachine

Center Assembly Line

Material Flow

Card (signal) Flow

withdrawal kanban

production kanban

CSdL )(1

k capacity of container

Expected demand during lead time + safety stock

k = No. of kanbans in card set d = Average No. of units demanded over the periodL = lead time to replenish order (same units of time as demand)S = Safety stock as % of demand during lead timeC = Container size

How many Kanbans? Each container = minimum replenishment lot

size.Calculate lead time required to produce a

"container"

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 (1S)

k size of container

Expected demand during lead time + safety stock

"Re-engineering" & Kanban

Modern production methods 1. Modular/cell production 9 group technology). 2. Reduce set up, lead and waiting times between procedures. 3. Flow-of-products-oriented layout of processes & machines layout.

Products flow smoothly from start to finish, parts do not sit waiting to be worked on, forklift trucks do not travel kilometres to move parts from one area of the plant to another.

4. Flexible manufacturing of mixed models 5. Theory of Constraints - drum-rope-buffer (Goldratt). Building in extra

redundancy. 6. Total Preventive Maintenance, prevent machines from breaking

down or malfunctioning during production time 7. Team-Work & Autonomation (decision by worker to stop line) 8. Kaizen: Continuous improvement 9. Housekeeping