week 10: production planning and control

Question 1

sequencing

Answer 1

due date (DD)
- work sequenced according to when it is due for

last in first out (LIFO)
- usually selected for practical reasons

first in first out (FIFO)
- serve customers in order the y arrive

longest operation time (LOT)
- longest jobs first

shortest operation time (SOT)
- most operations become cash constrained

Question 2

Johnson’s method

Answer 2

applies to sequencing of n jobs through two workstations

algorithm
1. smallest processing time in the remaining jobs
2. if time associated with first station then schedule that job first or as near as possible. if that time is associated with the second workstation sequence job last or as near as possible
3. delete scheduled job from task list
4. if task remain repeat

Question 3

push vs pull systems

Answer 3

push:
- production signals generate din top down manner based on demand forecasts. signals given to work stations which push processed parts to subsequent workstation

pull:
- production signals generated downstream at point of delivery to customer and are transferred upstream to workstation
- darting with final workstation, each station pulls parts from previous
- just in time and lean manufacturing associated with pull

Question 4

Material requirements planning (MRP) definition

Answer 4

push system which uses BOM and master production schedule to make time and volume calculations to meet forecast demand

Question 5

5 items calculated for each time period in MRP

Answer 5

1. gross req- total quantity
2. scheduled receipts - quantity received due to orders placed before planning
3. projected on hand inventory - amount of inventory projected to exist at a time
4. planned receipts - quantity of items to be received in the time period from orders placed in planning period
5. planned order releases - quantity order in time period

Question 6

lead production / just in time

Answer 6

aims to meet demand instantaneously with perfect quality and zero waste
- means supplying products with perfect synchronisation with demand

Question 7

lean production working principles

Answer 7

• Discipline - following work standings for safety and quality
• Flexibility - to increase peoples responsibility
• Equality - one person’s problem is everyone’s
• Autonomy - delegating responsibility for direct decision making
• Development - more capable workforce increases productivity
• Quality of working life - involve people in decision making, increasing job security and enjoyment
• Creativity - indispensable element of motivation
• Total people involvement - staff take on more responsibility

Question 8

what are the three main causes of waste

Answer 8

• muda - no value is added. poorly communicated objectives. not understanding customer reqs
• mura - lack of consistency, e.g. tasks not properly documented

muri - unreasonable demands from rescorces

Question 9

7 types of waste

Answer 9

1. over productio
2. waiting time
3. transport
4. process
5. inventory
6. motion
7. defectives

Question 10

elimination of waste

Answer 10

• streamlined flow
• matching supply and demand
• flexible process
• minimising variability through levelling schedule and delivery
• mixed modelling