An Exact Formulation for MultiWorkshop Facility Layout Problem with Clearance Bounds An innovative multiworkshop facility layout problem is developed and investigated in this paper, which involves the placement of a series of departments into several workshop floors, meanwhile the clearance bounds among departments are also considered. In addition, the internal and external logistics costs are taken into account, both constitute total material handling cost. In order to solve the problem, a mixed integer linear programming model is formulated with minimizing objective of material handling cost. The model proposed in this paper is also able to present the unequalarea facility layout problem and special multifloor facility layout problem. Finally, several benchmark instances that match our problems are selected and solved using CPLEX software, and the best layouts of them are obtained.

Optimal Scheduling of the Reentrant MultiDegree Cyclic MultiHoist Scheduing Problem The current paper deals with the cyclic multihoist scheduling problem in electroplating lines considering rentrance. Identical parts are produced with processing time windows. Moreover, reentrance is also considered. These together make it more challenged to obtain better schedules improving the productivity. To achieve this, multidegree cycles are considered. To our best knowledge, this is the first research in this generally complicated scenario. In order to maximize the productivity of the production line, i.e. minimize the cycle time for a given degree, operations of hoists are first analyzed in detail to avoid their collision. Then, operations related the reentrance are modeled. Based on these work, a mixed integer linear programming model is proposed. An industrial instances is used to test the proposed model. It is solved using the commercial software ILOG CPLEX. Results illustrate the efficiency of the proposed approach.