Learning Objectives After reading this lesson you will be able to understand Designing of product layout Line balancing Cycle time and theoretical minimum Designing of process layout
This lesson introduces you to the concept of design of product as well as process layout. Youlearn to appreciate the meaning and significance of line balancing, cycle time and the allied concepts. The behavioral dimension is also stressed upon. Dear students, by now all of us are familiar with the process of layout planning, which we discussed in the previous lesson. Design of product as well as process layout is an intricate as well as fascinating process, as you shall soon realize. Let’sstart now. Design of product layouts In product layout, equipment or departments are dedicated to a particular product line, duplicate equipment is employed to avoid backtracking, and a straight-line flow of material movement is achievable. Adopting a product layout makes sense when the batch size of a given product or part is large relative to the number of different products or parts producedAssembly lines are a special case of product layout. In a general sense, the term assembly line refers to progressive assembly linked by some material handling device. The usual assumption is that some form of pacing is present and the allowable processing time is equivalent for all workstations. Within this broad definition, there are important differences among line types. A few of these arematerial handling devices (belt or roller conveyor, overhead crane); line configuration (U-shape, straight, branching); pacing (mechanical, human); product mix (one product or multiple products); workstation characteristics (workers may sit, stand, walk with the line, or ride the line); and length of the line (few or many workers). The range of products partially or completely assembled on linesincludes toys, appliances, autos, clothing and a wide variety of electronic components. In fact, virtually any product that has multiple parts and is produced in large volume uses assembly lines to some degree. A more-challenging problem is the determination of the optimum configuration of operators and buffers in a production flow process. A major design consideration in production lines is theassignment of operation so that all stages are more or less equally loaded. Consider the case of traditional assembly lines illustrated in Figure 7.3. In this example, parts move along a conveyor at a rate of one part per minute to three groups of workstations. The first operation requires 3 minutes per unit; the second operation
Figure 7.3 Traditional assembly line
Requires 1 minute per unit;and the third requires 2 minutes per unit. The first workstation consists of three operators; the second, one operator; and the third, two operators. An operator removes a part from the conveyor and performs some assembly task at his or her workstation. The completed part is returned to the conveyor and transported to the next operation. The number of operators at each workstation was chosen sothat the line is balanced. Since three operators work simultaneously at the first workstation, on the average one part will be completed each minute. This is also true for other two stations. Since the parts arrive at a rate of one pr minute, parts are also completed at this rate. Assembly-line systems work well when there is a low variance in the times required to perform the individualsubassemblies. If the tasks are somewhat complex, thus resulting in a higher assembly-time variance, operators down the line may not be able to keep up with the flow of parts from the preceding work station or may experience excessive idle time. An alternative to a conveyor-paced assembly line is a sequence of workstations linked by gravity conveyors, which act as buffers between successive operations. An...