CHAPTER 3 PROBLEM STATEMENT AND OBJECTIVES

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1 64 CHAPTER 3 PROBLEM STATEMENT AND OBJECTIVES 3.1 INTRODUCTION The reality experiences single model assembly line balancing problem as well as mixed-model assembly line balancing problem. If the products assembled in a company have unlimited demand values, then the company assembling the products can setup a dedicated assembly line for each of the products. If the products have seasonal demand values (production volumes), then the company can use a mixed-model assembly line to assembly a select set of products which have some similarity in terms of tasks of the products for short duration and the mixed-model assembly line can be redesigned based on the changing composition of production volumes of the products from time to time. Hence, in this research, both the problems are considered. 3.2 SINGLE MODEL (SM_D_S) ASSEMBLY LINE BALANCING PROBLEM The single model assembly line balancing problem consists of a set of tasks with precedence relationships among them and with associated tasks times. The type 1(SALB-1) single model (SM_D_S) assembly line balancing problem is considered at the first stage of this research. The objective of this problem is to group the tasks into a minimum number of workstations, which in turn maximizes the balancing efficiency for a given cycle time.

2 Inputs of Single Model (SM_D_S) Assembly Line Balancing Problem The inputs of the single model assembly line balancing problem considered in this research are as follows. 1. Number of tasks. 2. Deterministic task times. 3. Precedence relationships among the tasks represented in the form of a precedence network. 4. Cycle time, which is computed based on the production volume per shift of the product which is to be assembled Objectives of Single Model (SM_D_S) Assembly Line Balancing Problem are as follows. The objectives of the single model assembly line balancing problem 1. Development of four different GA based algorithms to maximize the balancing efficiency of the single model assembly line balancing problem by minimizing the number of workstations. 3. Comparison of the results of the best GA based algorithm with the results of a mathematical model.

3 MIXED-MODEL (MM_D_S) ASSEMBLY LINE BALANCING PROBLEM The mixed-model assembly line balancing problem comprises of a set of models in which each model represents a product. The difference between the models in terms of presence of tasks in them will be less. So, there will be a single assembly line consisting of a minimum number of workstations, which can be used to assemble all the models. In this problem, a combined precedence network is obtained by merging the precedence networks of the models and then an assembly line to assemble all the models is designed using that combined network. If a set of tasks is assigned to a workstation in the mixed-model assembly line, all the tasks of that workstation may not be performed for all the models when they visit that workstation Inputs to Mixed-Model (MM_D_S) Assembly Line Balancing Problem as follows. The inputs of the mixed-model assembly line balancing problem are 1. Number of models. 2. Set of tasks of each model. 3. Deterministic task times of each model. 4. Precedence relationships among the tasks of each model represented in the form of a precedence network. 5. Combined network of the models. 6. Production volumes of all the models (A common cycle time is computed based on the sum of the shift-production volumes of the models). 7. Ratio of shift-production volumes of the models

4 Objectives of the Mixed-Model (MM_D_S) Assembly Line Balancing Problem without Sequencing of Models The objectives of the mixed-model assembly line balancing problem without sequencing of the models are as follows. 1. Development of four different GA based algorithms to maximize the average balancing efficiency of the models for a common cycle time of the mixed-model assembly line balancing problem without sequencing of the models. 3. Comparison of the results of the best GA based algorithm with the results of a mathematical model Objectives of Mixed-Model (MM_D_S) Assembly Line Balancing Problem with Sequencing of Models The design of the mixed-model assembly line balancing problem with sequencing of the models consists of two stages as listed below. Grouping the tasks of the combined network of the models into a minimum number of workstations for a common cycle time of the models which in turn maximizes the average balancing efficiency of the models. Sequencing the models in the assembly line such that the makespan of assembling the models is minimized. The objectives of this research on the mixed-model assembly line balancing problem with sequencing of the models are as follows.

5 68 1. Development of four different GA based algorithms to maximize the average balancing efficiency of the models for a common cycle time and minimize the makespan of sequencing the models in the assembly line.