Hybrid Push vs Pull
Push and Pull Production Systems
Make-to-Order: You say yes. I say no. You say stop. and I say go, go, go! – The Beatles
What Pull is Not!
• MRP with firm orders on MPS is make-to-order. • But it does not limit WIP and is therefore a push system.
Make-to-Stock:
• Pull systems do replenish inventory voids. • But jobs can be associated with customer orders.
Forecast Free:
• Toyota’s classic system made cars to forecasts. • Use of takt times or production smoothing often involves production without firm orders (and hence forecasts).
1 4
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000
http://www.factory -physics.com
http://www.factory -physics.com
The Key Difference Between Push and Pull
Push Systems: schedule work releases based on demand. • inherently due-date driven • control release rate, observe WIP level
Push and Pull Examples
Are the following systems essentially push or essentially pull?
• Kinko’s copy shop: • Soda vending machine: • “Pure” MRP system: • Doctor’s office: • Supermarket (goods on shelves): • Tandem line with finite interstation buffers: • Runway at O’Hare during peak periods: • Order entry server at Amazon.com:
Pull Systems: authorize work releases based on system status. • inherently rate driven • control WIP level, observe throughput
2
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000
5
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000
http://www.factory -physics.com
http://www.factory -physics.com
Push vs. Pull Mechanics
PUSH
(Exogenous) Schedule
Push and Pull Line Schematics
Pure Push (MRP)
PULL
Stock Point
...
Pure Pull (Kanban)
Stock Point
(Endogenous) Stock Void
Stock Point
...
…
Stock Point
Production Process
Production Process
Job
Job
CONWIP
Stock Point
...
Stock Point
Push systems do not limit WIP in the system.
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000
Pull systems
Make-to-Order: You say yes. I say no. You say stop. and I say go, go, go! – The Beatles
What Pull is Not!
• MRP with firm orders on MPS is make-to-order. • But it does not limit WIP and is therefore a push system.
Make-to-Stock:
• Pull systems do replenish inventory voids. • But jobs can be associated with customer orders.
Forecast Free:
• Toyota’s classic system made cars to forecasts. • Use of takt times or production smoothing often involves production without firm orders (and hence forecasts).
1 4
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000
http://www.factory -physics.com
http://www.factory -physics.com
The Key Difference Between Push and Pull
Push Systems: schedule work releases based on demand. • inherently due-date driven • control release rate, observe WIP level
Push and Pull Examples
Are the following systems essentially push or essentially pull?
• Kinko’s copy shop: • Soda vending machine: • “Pure” MRP system: • Doctor’s office: • Supermarket (goods on shelves): • Tandem line with finite interstation buffers: • Runway at O’Hare during peak periods: • Order entry server at Amazon.com:
Pull Systems: authorize work releases based on system status. • inherently rate driven • control WIP level, observe throughput
2
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000
5
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000
http://www.factory -physics.com
http://www.factory -physics.com
Push vs. Pull Mechanics
PUSH
(Exogenous) Schedule
Push and Pull Line Schematics
Pure Push (MRP)
PULL
Stock Point
...
Pure Pull (Kanban)
Stock Point
(Endogenous) Stock Void
Stock Point
...
…
Stock Point
Production Process
Production Process
Job
Job
CONWIP
Stock Point
...
Stock Point
Push systems do not limit WIP in the system.
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000
Pull systems