Optimization of workcell layouts in a mixed-model assembly line environment

Abstract

Mixed-model assembly lines enable automotive manufacturers to build different vehicles using the same equipment and facility. They allow a more rapid response to changes in customer demand. However, the increased production flexibility creates new challenges regarding assembly line planning and balancing. Part of this problem is how to allocate stock within the workcells so that non-value added operations, such as walking and waiting, are minimized. This paper addresses the issue of workstation layout optimization. Different formulations can be used to minimize non-value added time depending on the level of sophistication desired. We present three different optimization formulations and give an example of an optimized workstation layout.

Part feeding at high-variant mixed-model assembly lines

“…However, the part feeding and the corresponding in-house transportation problem have been widely neglected. Specific material flow problems that have been addressed in literature are the determination of storage locations and part feeding policies (Deechongkit and Srinon 2009;Klampfl et al 2006;Battini et al 2009) and the choice of the unit load Part feeding at high-variant mixed-model 123 for individual parts from of a given set of container types (de Souza et al 2008). In their paper, Vaidyanathan et al (1999) deal with the in-house route planning problem, i.e.…”

Design of multi-product manufacturing lines with the consideration of product change dependent inter-task times, reduced changeover and machine flexibility

“…For example, the inter-task time spent on walking to part bins for the second task of two tasks could be large depending on the part bin location, as shown in Fig. 1. There are a few studies that considered walking time in a workstation with a given set of task orders [10].…”

“…A topic worth more attention is the sequence dependent intertask time [10][11][12][13] in manufacturing system design for product variety. The conventional studies of manufacturing lines often assumed that the total time to perform a set of manufacturing tasks in a station does not depend on the task sequence in that station.…”

“…However, some research has shown that, in many real situations, task sequences significantly affect the sizes of inter-task times. The examples include the walking time of a worker between part bins [10] and the movement time of a robot to perform welding on different locations of an automobile. These unaccounted inter-task times and task time variability often lead to using trial-and-error based tolerance and buffer time [14] rather than the exact cycle time in system design.…”

Design of single assembly line for the delayed differentiation of product variants

“…It is indicated that for such arrangement; the workload differences increase drastically among those identical stations when product variety increases in a mixed products assembly line in addition to the stock allocation problem. Consequently, continuous production rescheduling and process re-sequencing are needed (Boysen et al 2007), besides the need for an optimized assembly stations layout to eliminate non-value added process elements such as walking and waiting (Klampfl et al 2005). The serial line can be bent in a U-shaped line for more homogenous workloads of assembly stations, however, balancing these workloads requires production scheduling integration with tasks assignment to stations (Miltenburg 2002).…”