Session 6 - Important Slides Flashcards
What are the objectives of Layout Planning?
Decisions regarding the physical allocation of the economic activity centres (occupying space) in a facility.
Objective: more effective workflow at the facility, allowing workers and equipment to bemore productive.
Different projects have different layout objectives:
• Efficient use of space
• Flexibility regarding volume, product, technology
• Process optimisation
• Physical proximity
• Human factors (heat, noise, …)
What is the QAP?
The Quadratic Assignment Problem is the mathematical formulation for intra-company location problems
How is the cost of an Assignment determined in the QAP?
The cost of an assignment is determined by the distances and material flows between all given entities = Organisational Entities OE.
What is the objective of the QAP in Layout Planning?
To minimise the total transportation costs occurring due to the chosen layout
What are the variables of the QAP?
1) n :Organisational Entities h&i
2) n :Locations j&k
3) thi :Material Flow Intensity from OE h to i
4) djk :Distance between locations j and k
5) xhj :Binary Decision Variable: =1 if OE h is assigned to location j, 0 otherwise
What are the Transportation costs per unit from OE h to OE i?
=sumj=1sumk=1 djk * xhj * xik
What is the objective function in QAP?
Min sumh=1sumi=1sumj=1sumk=1 thi * djk * xhj * xik
What are the 3 constraints of QAP?
1) sumj=1 xhj = 1 for h = 1,…,n : each OE h on exactly 1 location j
2) sumh=1 xhj = 1 for j = 1,…,n : each location j gets exactly 1 OE h
3) xhj = {0,1} : Binary Decision Variable
What is the SFLP?
Static Facility Layout Problem is a problem of finding positions of departments on the plan floor, such that departments do not overlap while (desired) objective is optimised.
What is the most commonly used objective in SFLP?
Minimising Material Handling Costs
=minimising the sum of the flow of materials over distance and transportation costs per unit per distance for each pair of departments
What is the DFLP?
When material flows between departments change during the planning horizon, the SFLP problem becomes Dynamic Facility Layout Problem
What is the objective function and its decision variable of the MILP formulation of DFLP?
Objective is to minimise the total costs. 2 parts:
1) Material handling costs +
2) Rearrangement costs
The ideas is that if the sum of this is smaller when there is a rearrangement, then that rearrangement would be minimising the total costs.
Decision variable is rti. It is 1, if department i is rearranged at the beginning of period t, and 0 otherwise.
What do the constraints of DFLP mean?
1) Departments do not overlap
2) Departments are within boundaries of plant floor
3) Rectilinear distance between centres of departments obtained
4) Orientation of departments controlled
5) Ensure department holds same position in any consecutive period if the it is not rearranged
6) Restriction of variables
