ISEN 315Spring 2011

Dr. Gary Gaukler

Push and Pull Production Control

“Push” system: Determines when and how much to produce based on forecasts of future demands

“Pull” system: Initiates production of an item only when the item is requested

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

Upstream stations only produce when signaled

System is used within the immediate production process and with suppliers

Enabling JIT: Pull System

Experiment

JIT Approach – Toyota Production System

• Philosophy:– 0 defects – 0 setup time– 0 inventory– 0 breakdowns– 0 leadtime– Lot size of 1

Toyota production video

Techniques for JIT Implementations

• Five areas of concern:– Quality– Resources– Design– Production Mix– Manufacturing

Quality-related Techniques

• Total Quality Management

• Autonomation

• Poka Yoke

JIT cuts the cost of obtaining good quality because JIT exposes poor quality

Better quality means fewer buffers and allows simpler JIT systems to be used

Quality

Resource-related Techniques

• Flexible labor

• Flexible equipment

Design-related Techniques

• Design for automation

• Design for simplification

• Modularity

Production Mix -related Techniques

• Mixed model production

• Small lot sizes

Manufacturing-related Techniques

• Kanbans

• Setup time reduction

• U-shaped layouts

High setup costs encourage large lot sizes Reducing setup costs reduces lot size and

reduces average inventory Setup time can be reduced through preparation

prior to shutdown and changeover

Reduce Setup Costs

200 –

100 –

Inve

ntor

y

Time

Q2 When average order size = 100

average inventory is 50

Q1 When average order size = 200

average inventory is 100

Reduce Lot Sizes

Reduced space and inventory With reduced space, inventory must be in

very small lots Units are always moving because there is

no storage

Implications for Manufacturing

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

Manufacturing cycle time is reduced Push systems dump orders on the

downstream stations regardless of the need

Pull vs Push Systems