Bài giảng Lean production systems - Chapter 5: Lean scheduling - Nguyễn Như Phong
8/13/2018
LEAN SCHEDULING
GVC. ThS. Nguyễn Như Phong
Kỹ thuật Hệ thống Công nghiệp
ĐH BÁCH KHOA – ĐHQG TPHCM
(Tài liệu giảng dạy cho ISE)
2018
LEAN SCHEDULING
Lean scheduling
Scheduling concepts
The pacemaker
Supermarkets
RRS
Mixed model scheduling
Lean batch sizing & EPE
Kanban & Pull
Material handling route
Heijunka & capacity management
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LEAN SCHEDULING
Scheduling
Push scheduling
Pull scheduling
Pull sys construction
Building blocks
Workstation
Buffer / supermarket
Scheduling concepts
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Scheduling concepts
Scheduling concepts
enable
most repetitive-production
many less-regular-flow plants
implement successful lean scheduling sys
in a value stream
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Scheduling concepts
Demand smoothing the starting point
The smoother the demand,
the more stable the production,
the easier 2 implement
Enable supermarket inventory reduced
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Scheduling concepts
Takt time - the drumbeat
Pitch time –
the repeating increment
Container moved & material handler circulates
Pacemaker
Production scheduled at one single point
Other stages pulled / flowing
in a FIFO sequence 2 the final stage
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Scheduling concepts
Kanban
Pull sys
Enable the coordination & synchronization of flow
governed by the pacemaker
Avoid overproduction & high light problems
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Scheduling concepts
Pacemaker schedule
aided by 2 concepts
RRS
Mixed model scheduling
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Scheduling concepts
RRS
Runner product – dedicated facilities
Repeaters scheduled at regular intervals
Strangers fitted around repeaters
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Scheduling concepts
Mixed model scheduling
Running the smallest pos. repeating batch size down a line
One piece flow – ideal
Inventory reduced, cell balanced
Regularity of flow –
Making & moving in one repeating sequence all day
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Scheduling concepts
Lean batch sizing
Stages involving longer CO operations
Governed by the pacemaker
Synchronization maintained
Inventories kept low
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Scheduling concepts
Material handler
Hold the whole process together
Regular route , circulating around the plant
every pitch increment / round multiple of PI
Collect up kanbans,
pick needed parts, deliver the requirement
Look out 4 any deviation
Separate function
Move parts & prod
Make & assemble
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Scheduling concepts
Heijunka sys
Leveling at the pacemaker
Planning & execution sys
Establish work 4 each pitch increment
Authorize the work 2 begin on time
Also a problem detection tool
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THE PACEMAKER
Single PM
The stage around which whole VS scheduled
The heart
Avoid amplification problems
Create synchronization
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The pacemaker
Often but need not be a constraint / bottleneck
Well down stream
Upstream – pulled
Downstream
Flow 2 be FIFO or
Go into FG supermarket
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The pacemaker
Rely on as smooth a demand as pos
Operate at / near the pitch increment as the drumbeat
Under-capacity scheduling
95% of the pitch time 2 allow 4 little variation
Heijunka box –
scheduling mechanism
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SUPERMARKETS & FIFO LANES
Lean aims at one piece flow
Flow takes place bw. supermarket
Traditionally
Large amount of inv. before & after w/s
Waiting to move,
waiting for the next operation, buffer
SM areas grouped together
enable MH to visit regular routes,
go shopping for parts
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Supermarkets & FIFO lanes
SM often established at/where
the boundary bw. loops of pull
2 VS converge / diverge
2 CONWIP loops meet
WIP permission bw. w/s
Under visible Kanban control or
CONWIP or
DBR
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Supermarkets
WIP in SM
Types
Ordinary
SS needed 2 carter 4 uncertainty demand
BS needed 2 carter 4 process uncertainties.
A little more helps highlight the causes of problems
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Supermarkets
FG SM
Wall of shame
demand management & schedule stability
Need 2 regard the inventory dynamically
Clear marker sys shows excess inventory
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Supermarkets
Not use ASRS as a SM
more inv,
visibility prevention,
slow response
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The Ten Rules for Supermarkets
1. Lot size differences
2. In front of the customer
3. Material flow splits up into different directions
4. Between very different cycle times
5. Between different shift patterns
6. When creating different variants
7. For merging of material flows
8. For large distance between processes
9. High demands on flexibility and reaction time
10. For change of responsibility
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FIFO lanes
FIFO lanes
Inv brought in at one end, removed from the other
Good lean SM practice even though a bit more space
Avoid date sensitive inv problems
Good for visibility & housekeeping
Monitoring easy via dates / color coding
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What FIFO
FiFo lanes
an important part of any lean material flow.
a very simple way to define
both the material & information flows
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Why FIFO
Decoupling of Processes
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The Rules for FiFo
No part can overtake another part
A clearly defined maximum capacity
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Advantages of FiFo Lanes
A clearly defined material flow.
A lean material flow
A clearly defined information flow.
Helps visual management.
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When to Use a FIFO
Whenever no reason for a supermarket.
The Ten Rules for Supermarkets
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When to Break FiFo between Two Processes
Batch Processing
Priority Orders
Parallel FiFo Lanes due to Space Constraints
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When to Break FiFo between Two Processes
Variation in Storage Cost
Changeover Optimization
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When to Break FiFo between Two Processes
The part flow not identical for all parts
FiFo almost always gets broken in job shops.
Batching, optimizing, and prioritizing open jobs.
If a supermarket is the better option.
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RRS
Powerful idea 4 lean scheduling
Prod/prod family
Runner
Repeater
Stranger
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RRS
Runner
Sufficient volume
to justify dedicated facilities / cells
Not all the time, at-and-when basis, not 2 share
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RRS
Repeater
Intermediate vol
Dedicated facilities not justifiable
Scheduled at regular slots
Quantity varies, slot time remains constant
Every day/other day/week
Advantages of order & discipline
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RRS
Stranger
Low/intermittent vol
Fitted into schedule around the regular repeater slots
Lowest priority
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RRS
Production plan / scheduling construction
Pareto analysis RRS categories
Runners –
Repeaters
Strangers
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RRS
Runners –
little concern so long as adequate capacity.
enjoy own resources
Heartbeat goes all the time
Repeaters
Schedule backbone
Slotted in at regular intervals as often as cap allow
Max flow & min inventories
Transfer batches smaller than production batches
Breakfast every day
Strangers
fit around the repeaters
Shopping sometimes
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RRS & ABC classification
Useful way 2 think of lean scheduling & pull options
Tight kanban – TK: Small SS
Loose kanban – LK: More SS
MRP: Lack of repetition make kanban less feasible
Forecast based sys - FBS
2 bin - TB
Reorder Point - ROP
Go see – GS
Vendor managed inventory - VMI
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RRS & ABC classification
ABC inventory classification
A – expensive items
B – intermediate
C – low cost commodity items
Efforts 2 convert S R R
Reducing & eventually eliminating MRP
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RRS & ABC classification
Rn
Rp
TK
LK
2B
S
A
B
C
TK
LK
MRP / FBS
MRP
2B/ROP
2B/GS
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