PRODUCTION PLANNING / CONTROL Flashcards
Define planning and control?
Planning: formalised forecast of future events. Affected by changes in production variables like late deliveries / machine breakages.
Control: process of coping with changes in these production variables.
What are sequencing techniques and their goals?
- Determining the order and time in which jobs should be carried out
- Aim to meet performance objectives of dependability, speed and cost.
What are some examples of sequencing techniques?
Physical constraint: jobs that physically go together are scheduled together (fabric example)
Customer priority: important/aggrieved customers/items can be processed before others irrespective of order of arrival of customer/item (hospital example).
Due date (DD): Prioritising based on when the work is due for delivery, irrespective of the size of the job / importance
Last in first out (LIFO): usually done for practical reasons, eg elevator.
First in first out (FIFO): serve customers in the sequence that they arrive
Longest operation time (LOT): sequence the longest jobs first. Has the advantage of occupying job centres for a long time.
Shortest operation time (SOT): due to cash-flow constraints, schedule shortest jobs first. payments can then be quickly received and cash-flow issues can be resolved
Describe Johnson’s method for sequencing?
- Sequences n jobs through 2 workstations
- Look for shortest processing time in job list
- If associated with WS1, schedule for first (or near to). If associated with WS2, schedule for last (or near last)
- Delete from job list and return to 1 until no jobs remain.
What is production management strategy and how is it divided?
- Deciding the manner in which signals are given to production system for starting and stopping work. Divided into push and pull.
Push: production signals are generated from the top down based on demand forecasts. Proactive
Pull: production signals are generated downstream, responding to immediate customer demand (bottom up)
Define / describe materials requirement planning (MRP)
Push system of production management that uses a bill of materials (BOM) (list of all raw materials, parts, sub-assemblies etc) and master production schedule (MPS) to make timing and volume calculations to meet forecasted demand.
What are the steps of MRP?
BOM is traversed from top->bottom and for each sub assembly the following is calculated for a time period:
- gross requirements: total quantity needed from the item in the time period
- scheduled receipts: quantity that will be received due to orders placed BEFORE the planning period
- projected on hand inventory: amount of on hand inventory expected to exist in the time period
- planned receipts: quantity of items received in the time period as a result of orders made IN the planning period
- planned order releases: quantity that is ordered in the time period
What is lean production / JIT (just-in-time)?
A pull approach that tries to meet demand instantaneously with perfect quality and zero waste. Originiated in Japan.
Describe lean production?
Takes out the traditional buffer inventory system (or massively decreases buffer inventory) so that problems with production system are felt much more quickly. This therefore means the problem becomes the responsibility of the entire production line to fix. This philosophy is about getting the entire enterprise to take action in eliminating problems in the production system.
Advantages / Disadvantages of lean production?
Advantages: problems become apparent faster and are dealt with by entire enterprise
Disadvantage: when stoppages occur, lack of buffer inventory (or smaller buffer inventory) means that enterprise cannot continue to function and so they cannot utilise their capacity.
What are some basic working principles of lean production?
Discipline: following work standards, essential for consistent quality
Equality: one person’s problem is everyone’s problem. eg everyone wearing the same uniform irrespective of rank
Development: a capable workforce will increase productivity.
Quality of working life: involve people in decision making, increase enjoyment of facilities.
Define waste?
Any activity that isn’t adding value
What are muda, mura and muri?
-Causes of waste
Muda: activities where no value is added to the production or customer. Often due to poorly communicated objectives.
Mura: lack of consistency. if tasks are not properly documented, when performed by different people there will be different results
Muri: unreasonable demands from resources. Often the result of poor planning.
What are some of the 7 types of waste identified by Toyota?
Over production: producing more than is immediately needed
Transport: moving items does not add value and should be minimised
Defectives: cannot be sold to customers and are therefore waste.
Ways to eliminate waste?
- Match supply and demand
- Flexibile processes
