Planning and Scheduling in Manufacturing and Services
This document was created during APS's lessons in the Operational Management in Industry minor at Windesheim. This is in English and will be tested this way.
Difference ERP and APS:
- ERP = transactional system
- Based on MRP-II (Material Requirement Planning)
Work loading:
- Infinite loading = ignores capacity constraints, only helps to
identify bottlenecks
- Finite loading = allows only as much work to be assigned as
can be done with available capacity
APS is:
- Decision making Computer based
- Allocation Activities to be done on limited resources
- Business Processes Manufacturing & service industries
o Procurement, production, transportation, distribution
- Complex Mathematical techniques & heuristics
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,Decision making Hierarchy:
Why is planning done hierarchically:
- Certain decisions must be made earlier
o It takes a few years to build a new plant
o It takes several months to hire new people or build new silos
Exactly what SKU, color, machine, person, sequence on a machine
can be decided later
- Decisions made a higher level determine constraints at lower level
o More constraints on shorter horizon that are the result of earlier decisions
- Uncertainty increases over time
o Range of possible outcomes is larger on longer term
- Aggregated forecasts are usually better
o Longer term forecasts over at family level are more accurate than at SKU
level
- Complexity
o Aggregation is needed at higher level to reduce complexity
S&OP process Different, level different structure &logic
Volume planning = a planning level that does not ‘know’ about orders and which plans
volumes of demand in periods, based on an aggregate resource mode
Order planning = this is the level “where the order comes,” and here the order is
accepted and planned, based on the S&OP plan, more detailed capacity limitations,
and available material on an aggregate level.
Scheduling = this is the level where individual resources or employees are
selected and assigned. In other words, it is where the “what” of the levels above
is translated in a “how” to produce as efficiently as possible
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, Difference planning & scheduling:
Planning Scheduling
Buckets Bucketless (continuous time)
No sequence Sequencing
No complex constraints, setup times Complex constraints and setup times
Aggregated (families, resource groups) Detailed (SKU, machine/person)
Overview of manufacturing models
Project scheduling Job shop scheduling Lost scheduling
-Precedence constraints -Multiple operations, -Continuous productions
-Typical ojective, minimize different routes -Switching between
makespan -Minimize makespan, products incurs setup cot
-Critical jobs number of late jobs -Minimize total inventory &
-Construction/building -Single machine, parallel setup costs
industry, ERP machines, flow shop -Process industry
implementation - Customized industrial
hardware, hospitals
Statistic data:
Processing time (pij) = represents the time job j has to spend on machine i
Release date (rj) = the time the job arrives at the system i.e. the earliest time at
which job j can start its processing
Due date (dj) = represents the committed shipping or completion date
Weight (wj) = priority factor, reflecting the importance of job j in the system for one
time unit
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