Balancing Workload and Workforce Capacity in Lean Management: Application to Multi-Model Assembly Lines

Abstract

While multi-model assembly lines are used by advanced lean companies because of their flexibility (different models of a product are produced in small lots and reach the customers in a short lead time), most of the extant literature on how to staff assembly lines focuses either on single-model lines or on mixed-model lines. The literature on multi-model lines is scarce and results given by current methods may be of limited applicability. In consequence, we develop a procedure to staff multi-model assembly lines while taking into account the principles of lean manufacturing. As a first approach, we replace the concepts of operation time and desired cycle time by their reciprocal magnitudes workload and capacity, and we define the dimensionless term of unit workload (load/capacity ratio) in order to avoid magnitudes related to time such as cycle time because, in practice, they might not be known. Next, we develop the necessary equations to apply this framework to a multi-model line. Finally, a piece of software in Python is developed, taking advantage of Google’s OR-Tools solver, to achieve an optimal multi-model line with a constant workforce and with each workstation performing the same tasks across all models. Several instances are tested to ensure the performance of this method.

A Comprehensive Review: Analysing the Pros and Cons of Assembly Line Balancing Methods

“…Most of the researchers that dealing with single-model line balancing were acknowledged the advantages and disadvantages of this type of line balancing in their research. The advantages and disadvantages of single-model line balancing are represented as below [7][8][9][10][11].…”

“…Many researchers working on multi-model line balancing acknowledged the benefits and drawbacks of this method in their studies. Below shows the advantages and disadvantages of multi-model line balancing [7,8,[12][13][14].…”

“…The vast majority of researchers that dealt with mixed-model line balancing recognised the advantages as well as disadvantages of this particular type of line balancing in their findings. The following are the benefits and drawbacks of mixed-model line balancing [7,8,12,15,16].…”

“…Advantages and disadvantages of single, multi and mixed-model line balancing[2,[5][6][7][8][9][10][11][12][13][14][15][16] …”

Improving Flexibility by Implementing Multi Product Assembly Line in Screw Air Compressor Assembly Line

“…It is necessary to single out the problems while doing ALB (Assembly Line Balancing) since there is a huge capital investment in the process of achieving efficiency (Boysen, 2008). It is necessary to implement all necessary kaizen and manual improvement technique to achieve highest efficiency with regards to facilities (Gruber and Todd, 2002, Gustavo et al, 2016, Fortuny-Santos 2020, Romero and Arce, 2017. It is important to rank the priority at which the bottle neck is eliminated which is a proven lean principal technique that has enhanced the overall efficiency (Kumar et al, 2016).…”