05_Master Production Scheduling Flashcards
Task of Master Production Schedules
- development of plant specific production schedules considering potential capacity bottlenecks
- planning horizon: 3 - 12 months
- basis for MRP (material requirements planning)
- Result: Specific production quantities for final products and key sub-assemblies
Types of production systems categorized by customer order decoupling point
Non-order driven production
1. Make to Stock (Forecast Driven Production: Final Products) [e.g. Pharmaceuticals]
Order driven production
2. Assemble to Order (Forecast driven production until Sub-Assemblies) [e.g. Computer Dell with different performance features]
3. Make to Order (Forecast driven production until Components) [e.g. Cars, Machines]
4. Engineer to Order (Forecast driven Production until Raw Materials) [e.g. Satellites, Chips]
Raw Materials; Components; Sub-Assemblies; Final Products; Distribution
3 Process types of production
- product variety
- production process
Material transfers, Material flows, Products, Order size
1. One of a kind production
- product variety: i**ndividual **
- production process: few material transfer, unfrequent material flow, individual products, low order size
2. Batch production
- product variety: variable
- production process: batchwise material flow, medium material transfers, medium order size
3. Mass production
- product variety: homogenous
- production process: many material transfers, continuous material flow, high order size, homogenouse prooducts
Material transfers, Material flows, Products, Order size
Characteristics of Mass Production
Process type of production
- Typically several production sites and distribution centers
- Integration of suppliers, production and distribution (Supply chain management(
- Make-to-stock or assemble-to-order
Single Bottleneck analysis
for Mass Production
Procedure for solving linear optimization problem
- linear optimization model
- remove redundant constraints
- solve to determine optimal solution through prioritizing resource with highest marginal contriubtion of decision variable / constraint
- criterion for single bottleneck = **profit per unit of bottleneck consumption **
e.g. Max 8 x1 + 12 x2
s.t. 0.5 x1 + 1 x2 =< 8
x2 =< 0
x1 =< 8
P1 = 8 / 0.5 = 16
P2 = 12 / 1 = 12
-> **prioritize x1 **
x1 (opt) = 8 x2 (opt) = 4
Profit (opt) = (8 x 8) + (4 x 12) = 112
Single Period master Production Scheduling
mass production
- linear optimization model
- remove redundant constraints
- solve arithmetically or graphically
Multi Period master production scheduling
Assumptions
Mass production
Minimization of inventory holidng costs
Assumptions:
- Storable products
- Constant per unit costs
- Given requirement quantities to be satisfied without shortages
- no extra capacity e.g. overtime
Objective of linear optimization model for multi-period master productin scheduling
minimize inventory holding costs
Linear optimization model for Multi-period master productin scheduling
- Indices
- Decision variables
- Data
- Non-Negativity constraint
1. Indices
j ∈ J Products
i ∈ I Resources
t ∈ T Periods ( t=1,…,T)
2. Decision Variables
x(jt): Production quantity of product j in period t
y(jt): Inventory of product j at the end of period t (y0 = given)
3. Data
a(ij): Consumption of resource i per unit of j
B(it): Available capacity of resource t in period t
d(jt): Forecasted demand of product j in period t
h(j): Inventory holding costs per unit and period fo rproduct j
4. Non-negativity
- x(jt) >= 0 for j ∈ J, t ∈ T
- y(jt) >= 0 for j ∈ J, t ∈ T
Characteristics of Batch Production
- different variants of a basic product tpye are manufactured using same production equipment one after another
- changover times and costs e.g. major setup for a product family and minor setup for product variants
- e.g.: food production, detergents, cosmetics
- **Make to stock or assemble to order **
Methods for Master Production Scheduling
1. Mass production (flow shop)
2. Batch production (cellular)
3. One-of-a-kind productin (job shop)
-
Mass Production
- linear optimization model for single period
- linear optimization model for multi-period minimixing inventory holding costs [no setup costs considered] -
Batch Production
- linear optimization model for multi-period minimizing setup and inventory holding costs -
One-of-a-kind
- Critical Path Method (CPM) using EFS, EFE, LFS, LFE
Characteristics of One-of-a-kind Production
- individual products produced in very small order sizes
- often customer-specific adjustment of prodcut desing
- only limited number of production orders at the same time in the system
- large work volume, numerous production tasks, complex project structure
- long throughput times and tight due dates
Additional planning tasks for
One-of-a-kind production
- preparation of bids
- planning of costs and resource requirements
- project structuring
- determination of feasible due dates
- concurrent monitoring of times, resource utilization and costs
**Total Buffer Time
Critical Path Method [CPM]
One-of-a-kind
TB (j) = LFE(j) - EFE(j) = LFS(j) - EFS(j)
Critical Path
Critical path method (CPM)
in context of one-of-a-kind production
- connects all tasks which together determine the shortes possible duration of the project with
TB(j) = {0, when no due date is given or
TB(j) = {due date - EFE(j), when due date is given
