2- Production planning models and systems Flashcards
What are the three classical production planning model?
1) Single-item uncapacited lot-sizing model (LS-U)
2) Master Production Schedule (MPS)
3) Material Requirement Planning (MRP)
General properties of Uncapacitated Lot-Sizing Model (LS-U)
Single-item, single-level, uncapacitated
Minimize total cost
Production cost (fixed + variable)
Inventory cost per unit in inventory at the end of each period
Satisfy all demand
Backlogging not allowed
No production capacity (infinite)
State the LS-U
Sets:
T = {0, . . . ,t, . . . , n}: discrete time periods
Parameters:
pt
: unit production cost in period t
qt
: fixed production cost in period t
ht
: unit inventory cost in period t
dt
: demand in period t
Decision variables:
xt
: production lot size in period t
yt
: binary variable for period t (yt = 1 if xt > 0)
st
: inventory at the end of the period t
(LS-U) min sum (pt xt + qt yt + ht st) for t∈T :t≥1
st−1 + xt = dt + st t ∈ T : t ≥ 1 (2)
s0 = sn = 0 (3)
xt ≤ Mt yt t ∈ T : t ≥ 1 (4)
xt ≥ 0 t ∈ T : t ≥ 1 (5)
st ≥ 0 t ∈ T (6)
yt ∈ {0, 1} t ∈ T : t ≥ 1 (7)
General properties of Master production scheduling Model (MPS)
Multi-item, single level, capacitated lot-sizing model
Production of a set of items (finished products)
Short-term horizon (at least total production cycle)
For each item, the model is the same as the LS-U
The items production plans are linked: capacity restrictions and common resources
State the Master production schedule (MPS)
General properties of the material requirement planning (MRP)
State the material requirement planning (MRP)
Make-to-stock (MTS)
Make-to-stock (MTS): independent demand must be already in stock
All procurement and production activities in anticipation of the demand (demand
forecasts)
Ideal for standard products, little variety or diversity (fast-moving consumer goods)
Make-to-order (MTO) or Assemble-to-order (ATO):
Some activities are performed after the external ordering
Delivery lead-time: time promised to customers for delivery
At the time of ordering: enough raw materials or semi-finished products in inventory
Remaining production lead-time ≤ commercial lead-time
Push phase (upstream)
Push phase (upstream) plans the procurement and production from raw materials up to
semi-finished products (demand forecast of semi-finished products)
Pull phase (downstream)
Pull phase (downstream) plans the production from semi-finished products (in
inventory) up to finished products (effective customer orders)
For which production policy is MRP used?
Customer-service leve
Customer-service level =% customer demand delivered on time
(minimal planning horizon length)
Total lead-time represents the required anticipation time in the planning process
(minimal planning horizon length)
Rolling-horizon approach:
the solution proposed for the early time periods is
implemented, the model parameters are updated, the model is solved again,…
Bill of materials (BOM) to compute dependent demand
Link BOM and MRP
Routing of components and link to MRP
Planning rules and link to MRP
Grafik: Single item decomposition planning models for a MTS policy
MPS scheme in Single item decomposition
Rough Cut Capacity Planning (RCCP)
- Final Assembly Scheduling (FAS)
Grafik: Planning models (item decomposition) for an ATO policy
Steps of MRP in single item decomposition
Capacity Requirement Planning (CRP)
Limitations of MRP decomposition scheme
Architecture of Advanced Planning Systems
Strategic network design problems
Supply chain master planning problems
