Simulation model for assembly lines with heterogeneous workers

This article investigates the impact of controlled imbalance levels on assembly lines, and its effects on two important performance indicators: throughput and work in process (WIP) level. Using a five workstations line simulation, with different degrees of imbalance and different configurations, we could conclude that there is a relationship between extra capacity added to non-constraints and average WIP level and line throughput. Simulation revealed that, using bowl shape configuration, the higher the imbalance, the higher the throughput, with less WIP. These results allow proposing new studies to create a framework for evaluating the feasibility of investments in extra capacity visa -vis those gains in resources efficiency.

A study of the effect of imbalance on the performance of un-paced production line is carried out in this project. An Un-paced production line is defined as a series or workstations where work is carried out to complete a process. There is no outside pacing agency forcing the stations to complete their respective operation in a fixed time. Instead the stations are free to carry out their work at their own pace and transfer the job to the next station only after the completing the operation. Previous research has largely been done to either determine the production rate of balanced lines or to find the unbalancing strategy to maximize the production rate. Real-world production lines however are seldom balanced and it is hardly ever possible to unbalanced them in a particular way. Generally the designers have to allocate workload on stations within the given constraints of unbalancing. In this study a 5-station line with exponentially distributed operation times with no buffer capacities is considered. A practical situation where 5 means operation times are to be assigned on 5 stations is considered. Assuming that precedence restrictions are minimal the operation can be permuted on stations. A number of data sets with different kinds of imbalances and with different degrees of imbalance have been used for arriving at important conclusions. In this phase, it is assumed that the optimal workload assignment strategy is known for exponentially distributed operation times on the 5-station line. An expression is then proposed that calculates a degree of closeness to optimal for any ordering. The degree of closeness can then be used to grade various orderings. The relationship of degree of closeness to production rate has been found to be imperfect but effective, especially, at lower degree of imbalance. The results and conclusions presented can be very useful for designer of un-paced lines as well as to researchers as they present useful insights in the behaviors of unbalanced lines.

A study of the effect of imbalance on the performance of un-paced production line is carried out in this research work. An Un-paced production line is defined as a series or workstations where work is carried out to complete a process and working time is not constant in work stations. There is no outside pacing agency forcing the stations to complete their respective operation in a fixed time(variation of time for every worker because the assembling or making any product the time is not constant for each work). Instead the stations are free to carry out their work at their own pace and transfer the job to the next station only after the completing the operation. Previous research has largely been done to either determine the production rate of balanced lines (fix the time for each work is same) or to find the unbalancing strategy to maximize the production rate. Real-world production lines however are seldom balanced and it is hardly ever possible to unbalanced them in a particular way. Generally the designers have to allocate workload on stations within the given constraints of unbalancing. In this study a 5-station line with exponentially distributed operation times with no buffer capacities is considered. A practical situation where 5 means operation times are to be assigned on 5 stations is considered. Assuming that precedence restrictions are minimal the operation can be permuted on stations. A number of data sets with different kinds of imbalances and with different degrees of imbalance have been used for arriving at important conclusions. In this research we assume optimal strategy 1 is not known. The complete set of 60 ordering was examined closely. We obtain guidelines for designers in arriving to a relatively better ordering. The result shows that we utilize this ordering according their work timing on the station and maximize the production rate of the unbalanced line.

MATEC Web of Conferences, 2018

One of the efforts company did continuously to compete was to reduce waste or anything that is not adding value to products such as waiting activity that cause unbalance of workload between workstations on a production path. This condition resulted in idle work station, accumulation of intermediate goods, and low work station utility. Companies finds an unbalance workload. This work station are apparently have to wait in a given time after workstations does behind it finished. For that reason, this study aims to balance the workload between workstations and increase the company production capacity. This research uses simulation approach by modelling the initial production with software promodel and evaluate performance the the initial production with an indicator current content, output, and average time in operation. The performance of the initial production line model was the smoothness index of 2007.5, the current content of 10 units, the output of 34 units, and the average time ...

The International Journal of Advanced Manufacturing Technology, 2010

A computer simulation model was used to evaluate a bowl versus inverted bowl assembly line arrangement for normal and exponential distributions and variances equal to 1 and 16. The model was developed on the basis of a realistic case problem and applied to a sixstation assembly line. The results show that the inverted bowl is superior to the bowl arrangement for a normal distribution in terms of the total elapsed time evaluation criterion; however, with an exponential distribution, the bowl was found better than the inverted bowl for the same criterion. On the basis of the average percentage of working time and the average time in the system evaluation criteria, the bowl was found superior to the inverted bowl for a normal distribution. Similar results were obtained for an exponential distribution with a variance equal to 1, but no definitive inference could be made with a variance equal to 16.

International Journal of Industrial Engineering

A fundamental characteristic of today´s competitive environment is the need for shorter product life cycles and increased demands for customization. These aspects are difficult to satisfy operating with traditional production lines. The development of JIT U-lines has been an emerging response to compete in this type of environment. The present work describes the utilization of simulation to guide the improvement efforts during the redesign of a traditional assembly line system in a Mexican manufacturing facility. The approach taken is a two-level one. A macro model that simulates operations at plant level and assesses the synchronization of material flows between warehouses and assembly lines and is used to determine materials handling resource requirements and overall layout options. The second level is detailed and at the line level. Here, Balancing, operator assignments and buffer sizes are defined for each line. The space required and detailed layout for each line are also determined.

European J. of Industrial Engineering, 2015

In this paper we study an assembly line balancing problem that occurs in sheltered worker centers for the disabled, where workers with very different characteristics are present. We are interested in the situation in which complete parallel assembly lines are allowed and name the resulting problem as parallel assembly line worker assignment and balancing problem. We present a linear mixed-integer formulation and two heuristic solution methods: one is based on tabu search and the other is a biased random-key genetic algorithm (BRKGA). Computational results with a large set of instances recently proposed in the literature show the advantages of allowing alternative line layouts.

To evaluate performances of U-shaped un-paced mixed model assembly line may be complicated. This complication is a result of blockage and starvation caused by the arrival of different models to the line, having different assembly time requirements at each station. Considering the throughput as the main operational design objective, the effects of these phenomena on line throughput are very difficult to evaluate. Unfortunately, its evaluation is fundamental in almost all procedures and algorithms developed to solve U-MALBP (U-shaped Mixed-model Assembly Line Balancing Problem), since the estimation of objective functions that includes performance indicators is often required. The only practical method to accurately evaluate throughput is a simulation study, which is very time consuming and hard to perform. For this reason, instead, various performance measures, not simulation based, have been presented in literature in order to evaluate and compare design alternatives. Unfortunately,...

To compete in an ever growing manufacturing environment, companies have to improve their productivity. This study describes the improvement activities of the ABC Company in Malaysia, using a line balancing technique. With these improvement activities, the company managed to reduce the total time required to complete 600 product units per week, from 256.49 hours down to 208.06 hours, and the lead time from 5 days 7.9 hours down to 4 days 6.8 hours. This study also proposes assembly line improvements, using simulation methods, by focusing on a Material Handling Operator (MHO) solution. A MHO is assigned to a transport box container, from one station in the assembly line to another, so that operators at each workstation can concentrate on their own tasks. Using a process simulation approach, this paper compares the performance of the production model using MHO with that of a production model without MHO. The feasibility of this solution is then discussed.

The concept of mass production essentially involves the assembly of identical or interchangeable parts of components into the final product at different stages and workstations. The relative advantages and disadvantages of mass or flow production are a matter of concern for any mass production industry. How to design an assembly line starting from the work breakdown structure to the final grouping of tasks at work stations has been discussed in this paper using two commonly used procedures namely the Kilbridge-Wester Heuristic approach and the Helgeson-Birnie Approach. Line Balancing (LB) is a classic, well-researched Operations Research (OR) optimization problem of significant industrial importance. The specific objectives of this paper is to optimize crew size, system utilization, the probability of jobs being completed within a certain time frame and system design costs. These objectives are addressed simultaneously, and the results obtained are compared with those of single-objective approaches.