just-in-time prof. jiang zhibin dept. of ie, sjtu
TRANSCRIPT
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