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Sem 5 Prep
← OperationsProcess layout and CRAFT

Formulas for this chapter

Process-layout cost

Minimise SUM(i) SUM(j) Xij x Cij

Scoring any process layout. Cij is normally the handling rate times the centroid-to-centroid distance.

Xij
Number of loads moved from department i to department j
Cij
Cost to move one load between departments i and j
n
Total number of work centres or departments

Rectilinear centroid distance

d(i,j) = |xi - xj| + |yi - yj|

Building the distance matrix in a layout problem, exactly as the class CRAFT spreadsheet does with ABS formulas.

(xi, yi)
Centroid of department i in the layout
(xj, yj)
Centroid of department j

Adjacency cost rule

Cost of a flow = loads x rate, rate = 1 unit if departments are adjacent, 2 units if they are more than one apart

The simplified rule the class uses for the six-department factory, when only adjacency is given rather than distances.

loads
Number of moves between the two departments per period
rate
1 for adjacent, 2 for non-adjacent, in the units the question gives
Step 2 of 20
The real wordsTheory

The objective function

A major objective in designing process layouts is to minimise transportation cost, distance or time.

Minimise cost = SUM over i SUM over j of Xij x Cij where n = total number of work centres or departments i,j = individual departments Xij = number of loads moved from department i to department j Cij = cost to move a load between department i and department j

Two basic cost elements: the number of loads (or people) moving between centres, and the distance those loads move.

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