8. Pull Production1. Production Control Systems

i. Objective: is to ensure production demands are met.ii. Make the required products in required quantities in required time.iii. Push Production- Schedule based systemiv. Pull production – Schedule is based on what is required at the end stage.

2. Pull and Push Production Systemsi. A Simple Pull System

ii. Pull production process

iii. Why Pull production cannot be stockless- Stockless production - JIT- Example of Multiple Products

Iv Push Production Process- items processed in batches- Made to schedule- Typical push system

Example-1: Pull Production for Multiple Products

Example -2: Push Production

Table 8.1

Component Part Material Quantity

A 400

B 240

C 440

D 600

M 840

N 400

O 440

S 240

V 600

R 1680

T 840

3. PULL AND PUSH CONTRAST

i. Some basics-Pull – Kanban based- Push- MRP based-Timing-Batch Size-Priorities- Interference

ii. Containers and Cards- Standard -Sized containers- Kanban cards

- Difference between Kanban and kanban

iii. Rules of Pull Productioni. Relates to material movementii. Relates to quantity and priorityiii. Relates to overproduction

iv. Relates to cooperation and defect prevention v. Relates to level productionvi. Relates to inventory reduction

4. PROCESS IMPROVEMENT

I. Continuous improvement – reduction of buffer stockII. Setup time reductionIII. Reduction in standard quantity

5. Necessary Conditions for Pull Production Systemsi. Planning and Control responsibilityii. Production to just meet demandiii. Reduce WIPiv. Implementation of preventive maintenancev. Introduction quality control effortsvi. Setup time reduction and small lotsvii. Plant layout linking all operationsviii. Uniform production levelsix. Encourage team work and cooperation

6. How to Achieve Pull Production

i. Pull system as a fixed- quantity/reorder-point system1. ROP = D(LT) + SS

Where D – demand rate LT – lead time SS – Safety stock

2. Containers in a BufferK = D(P+C)/Q Where K – Number of containers

P – Production time C – Conveyance time Q – Size of standard containers

ii. Fixed- Quantity Order Rule1. Container size2. outbound and inbound buffers

iii. Conveyance KanbansKC = D(C)/Q

iv. Production kanbans1. KP = D(P)/Q

2. Time element in computing P

3. Safety Factor, X- This is to account for minor fluctuation in demand- Formula

K = {D(LT) (1+X)/Q}- Example problem

v. Single -card System, No.2vi. Signal Kanban

1. Two types of Signal kanbanSP-Kanban or production signal kanbanSM-kanban or material signal kanban

7. CONWIP METHOD OF PULL PRODUCTIONi. CONWIP- Constant work in processii. Difference

Kanban authorization cards move from the last operation to the first operation.The # of cards , K = D(P)/Q

iii. CONWIP production processiv. This is much more tolerant of changes in product mix and production volumev. Floating bottlenecks.

8. WHAT, MORE CARDS?i. Pull production is not definitely immune to unanticipated events and therefore there must be

devices/safeguards in place to take care of them. The following are the methods typically used to deal with this situation.1. Express cards: Usually different in colors are used to expedite production or move “emergency” items.2. Temporary cards- issued whenever it becomes necessary to deviate from the normal pull pattern.3. Odd numbered cards: are issued to take care of replacing defective item that are not usable.

ii. Practical Matters

9. OTHER MECHANISMS FOR SIGNAL AND CONTROLi. Wheeled cartsii. Kanban squaresiii. Golf ballsiv. E-kanbanv. Clothespin clipsvi. Milk run- for items with intermittent demandvii. Kanban sequence board

10. PULL OR NOT TO PULLi. Confined to repetitive productionii. Useful for product familiesiii. When does not pull workiv. Back to MRPv. Both systems at oncevi. Getting started