Lecture 6: Requirements Planning

Question 1

How does PUSH scheduling work?

Answer 1

• In a PUSH system, the orders are planned and issued centrally
• Upon completion, the order is moved forward, until the next process is issued with the order to start processing it
• Hence, the longest lead time process sees the new order first
• This is BACKWARD scheduling

Question 2

What is MRP and why was it invented?

Answer 2

Material requirements planning

A set of techniques which uses BOMs, inventory data and the master production schedule to calculate future requirements for materials.

Invented in ’60s to cope with complexity of scheduling.

Computerised inventory control & production planning system

Schedules component items and processes when needed

Question 3

Net requirements is?

Answer 3

Gross requirements + Allocations

—

On hand balance + scheduled receipts

=

Net requirements

Question 4

MRP can be used to generate a wide range of outputs such as:

Answer 4

• Inventory order action: details of when orders for raw materials must be placed
• Factory schedule: broad timing information on what should be occurring throughout the factory over the planning time horizon
• Machine loading information: data on the quantity of work to be undertaken by each machine
• Rescheduling data: given some discrepancy between reality and the schedule, the MRP system can indicate precisely what will be affected by late completion of some component

Question 5

Limitations to MRP

Answer 5

• Assumes infinite capacity
• Works with fixed lead times and fixed batch sizes
• Has no feedback - having issued the plan assumes it will work
• Forecasting data may not be accurate
• Inventory levels may not be accurate
• Any delay prior to assembly will prevent completion
• MRP pushes production so can distort demand patterns in supply chain

Question 6

Explain Just in Time scheduling

Answer 6

Production orders are based on replenishment

Demand signal is conveyed via kanban cards

System is tightly controlled, as it is fragile, (unable to cope with large swings in volume/product mix)

Requires suppliers to deliver components using JIT

Need to keep schedule variability within 5-10%

Question 7

Explain the push pull system

Answer 7

Question 8

What is OPT

Answer 8

Optimised production technology

Further production planning/control/scheduling approach:

Main concept is importance of bottlenecks

• Protect throughput at bottleneck
• Bottleneck becomes pacemaker
• Every minute not used at constraint is a minute lose

Question 9

Explain the different aspects of MRP, JIT and OPT

Answer 9