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Technical Report: DCC-2007-09
A hybrid solution strategy for production planning
João P. Pedroso
DCC-FC, Universidade do Porto
R. do Campo Alegre 1021/1055 , 4169-007 Porto, Portugal
Phone: +351 220402919 , Fax: 351 22 402 950
E-mail: jpp@fc.up.pt
May 2007
Abstract
Production planning with lot-sizing and scheduling in industries where the cleaning times
depend on the sequence of the products can be modelled as a mixed integer problem. However,
this problem is very hard, and even small instances cannot be solved exactly in a reasonable
time. We propose a division of the whole production planning problem into its two subproblems,
and to solve each them independently: first the lot-sizing, then schedule the operations that
were determined for each machine, for each period. In this strategy, the lot-sizing part does not
take into consideration the changeover times. After scheduling the operations, if the cleaning
times make a solution infeasible, a constraint cutting this solution must be added. The lot-sizing
problem must be resolved, and its solution rescheduled, until obtaining feasibility. We propose
an algorithm for integrating lot-sizing and scheduling, and analyse the results obtained.
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