Mixed-model Assembly Line Problem Research Articles

A dynamic material distribution scheduling of automotive assembly line considering material-handling errors

PurposeIn a kitting supply system, the occurrence of material-handling errors is unavoidable and will cause serious production losses to an assembly line. To minimize production losses, this paper aims to present a dynamic scheduling problem of automotive assembly line considering material-handling mistakes by integrating abnormal disturbance into the material distribution problem of mixed-model assembly lines (MMALs).Design/methodology/approachA multi-phase dynamic scheduling (MPDS) algorithm is proposed based on the characteristics and properties of the dynamic scheduling problem. In the first phase, the static material distribution scheduling problem is decomposed into three optimization sub-problems, and the dynamic programming algorithm is used to jointly optimize the sub-problems to obtain the optimal initial scheduling plan. In the second phase, a two-stage rescheduling algorithm incorporating removing rules and adding rules was designed according to the status update mechanism of material demand and multi-load AGVs.FindingsThrough comparative experiments with the periodic distribution strategy (PD) and the direct insertion method (DI), the superiority of the proposed dynamic scheduling strategy and algorithm is verified.Originality/valueTo the best of the authors’ knowledge, this study is the first to consider the impact of material-handling errors on the material distribution scheduling problem when using a kitting strategy. By designing an MPDS algorithm, this paper aims to maximize the absorption of the disturbance caused by material-handling errors and reduce the production losses of the assembly line as well as the total cost of the material transportation.

Mixed-model Assembly Line Problem with Consideration of Sequence and Conveyer Speed Simultaneously

Mixed-model Assembly Line Problem with Consideration of Sequence and Conveyer Speed Simultaneously

Solving Mixed-Model Assembly Lines Using a Hybrid of Ant Colony Optimization and Greedy Algorithm

The assembly line balancing problem deals with the assignment of tasks to work stations. Mixed-model assembly line problem is a type of assembly line balancing problem at which two or more models of the same product are assembled sequentially at the same line. To achieve optimality and efficiency of solving this problem, tasks at each work station have to be well balanced satisfying all constraints. This paper deals with the mixed-model assembly line balancing problem (MALBP) in which the objective is to minimize the cycle time for a given number of work stations. The problem is solved by using a hybrid of an ant colony optimization and a greedy algorithm (Ant-Greedy). MATLAB Software is used to perform the proposed method. Then, the proposed method is applied to a real case problem found in the literature for the assembly line of automatic changeover in the Electronic Industries Company in Iraq. The results of the proposed method are compared with the performance of the Merging Shortest and Longest Operation (MMSLO) method. The comparison shows that the Ant-Greedy optimization method is more efficient, where the efficiency increased from 93.53% for MMSLO method to 97.26% for the Ant-Greedy method.

Sequencing mixed-model assembly lines with demand management: problem development and efficient multi-objective algorithms

As a kind of production line, the mixed-model assembly line (MMAL) has been progressively adopted by industries to satisfy the diversification of customer demands. This study applied an MMAL sequencing problem for a make-to-order (MTO) strategy. Using the fuzzy technique for order preference by similarity to ideal solution (TOPSIS) approach, this study sorted customer orders, satisfying these by a desired due date being the main feature in MTO systems. This MMAL problem was investigated to achieve three minimization objectives: total set-up cost, number of work overload situations, and total earliness and tardiness costs, according to the specified priority of orders. Accordingly, a multi-objective particle swarm optimization (MOPSO) algorithm was developed for the proposed NP-hard model and the algorithm parameters were tuned by applying the Taguchi technique to the experimental design. The computational results of a comparison between the proposed MOPSO model and four multi-objective algorithms confirmed its advantages.

A Multi-Objective Cuckoo Search Algorithm Based on the Record Matrix for a Mixed-Model Assembly Line Car-Sequencing Problem

In the car-sequencing problem of mixed-model assembly lines, a series of cars with different model types will be put into the assembly line in a certain order considering a variety of goals and constraints. In this paper, a multi-objective cuckoo search algorithm based on the record matrix is proposed to solve this problem. In this algorithm, the factors, including the variation of parts usage rates, variation of workstation workload, idle time, overload time, and model switching cost are considered. The record matrix proposed in this paper is utilized to record the characteristic information of the optimal solutions and historical solutions. Meanwhile, two search strategies based on the record matrix are proposed to enhance the ability of local search and global search in the algorithm. The proposed algorithm is verified by a real case. The results show that the proposed model and algorithm have good results, and they have the potential to address other similar problems.

Integer programming models versus advanced planning business software for a multi-level mixed-model assembly line problem

Many manufactures are shifting from classical production environments with large batch sizes towards mixed-model assembly lines due to increasing product variations and highly individual customer requests. However, an assembly line should still be run with constant speed and cycle time. Clearly, the consecutive production of different models will cause a highly unbalanced temporal distribution of workload. This can be avoided by moving some assembly steps to pre-levels thus smoothing out the utilization of the main line. In the resulting multi-level assembly line the sequencing decision on the main line has to take into account the balancing of workload for all pre-levels. Otherwise, the modules or parts delivered from the pre-levels would cause congestion of the main line. One planning strategy aims at mixing the models on the main line to avoid blocks of identical units. In this contribution we compare two different realizations for this approach. On one hand we present a mixed-integer programming model (MIP), strengthen it by adding valid inequalities and enrich it with a number of relevant practical extensions. Also the actual objective of explicitly balancing pre-level workloads is considered. On the other hand, we illustrate how this strategy could be realized in an advanced planning system linked to an enterprise resource planning system, namely SAP APO. Finally, we perform a computational study to investigate the possibilities and limitations of MIP models and the realization in SAP APO. The experiments rely on a real-world production planning problem of a company producing engines and gearboxes.

Comparative analysis and optimization of Mixed Model assembly line using Genetic Algorithm

Line balancing aims at arrangement of different facilities like workstation, machines, tool, and operator in an adequate manner in order to obtain most efficient balancing of assembly line, its capabilities, flow of product and services. Various methods are proposed in the literature to optimize these parameters hence this research effort starts with the review of the various methods developed and to compare main features of few of them for their relative assets and limitation to allow choose the most suitable method for optimization of line balancing. The researchers used the average times of the tasks of the models as the timings of the tasks of the combined assembly line model while designing the assembly line which is an approximate method of dealing with the data. Hence, in this paper, the design of the assembly line of the models is done simultaneously for all the models using their original task times. Such an attempt gives a realistic design of the mixed-model assembly line using genetic algorithm for the balancing of this mixed model assembly line problem. A new methodology of balancing the assembly line has been adopted and the output is compared with conventional methods of line balancing. The optimization of assembly line using cyclic multipoint crossover method of genetic algorithm has been performed to obtained real offspring and the best chromosome is selected to find out the efficiency of assembly line. The superiority of this approach is demonstrated using a numerical example. The multi-objective genetic algorithm with cyclic crossover and with individual task times of the models is a unique contribution. Although the RPW method also gives better results other than any conventional methods of line balancing however when the population size (assembly lines) of the system increase and number of workstation are more than genetic algorithm method is suitable and gives better result and this research paper presents the comparative analysis of mixed model assembly line balancing methods and tries to find out the best possible solution in order to minimize no. of workstation, ideal time, bottleneck and increase the efficiency of plant

A new multi-objective approach in order to balancing and sequencing U-shaped mixed model assembly line problem: a proposed heuristic algorithm

Mixed model production is the practice of assembling different and distinct models in a line without changeovers responding to sudden demand changes for a variety of models. In this paper, to achieve a combination of balancing of the tasks and sequencing of models, both the balancing and sequencing problems are considered simultaneously. Three objective functions including: minimizing the cycle times, minimizing the wastages in each station, and minimizing the work overload by considering a multiple objective in both sequencing and balancing problem are investigated. One of the characteristics of this study is minimizing the wastages. The combination of those objectives in such problems has not been studied yet. Also, we propose a new heuristic algorithm and indicate that our results can be improved in the algorithm from the initial solution. Finally, the straight lines and U-lines in our problem are investigated; therefore, a decision maker can decide about the shape of assembly lines and compare the results in these cases.

Application of Metaheuristics to a Mixed-model Assembly Line Problem for Minimizing Makespan

Application of Metaheuristics to a Mixed-model Assembly Line Problem for Minimizing Makespan

Integrated Approach for Flexible Mixed Model Assembly Lines Balancing and Model Sequencing Problem

The manufacturers nowadays are forced to respond very quickly to changes in the market conditions. To adopt flexible mixed model assembly lines (MMAL) is a preferred way for manufacturers to improve competitiveness. Managing a mixed model assembly line involves two problems: assigning assembly tasks to stations (balancing problem) and determining the sequence of products at each station (sequencing problem). In order to solve both balancing and sequencing problem in MMAL simultaneously, an integrated mathematical model based on mixed integer programming (MIP) is developed to describe the problem. In the model, general type precedence relations and task duplications are considered. Due to the NP-hardness of the balancing and sequencing problem of MMAL, GA is designed to search the optimal solution. The efficiency of the GA is demonstrated by a case study.

Advanced scatter search approach and its application in a sequencing problem of mixed-model assembly lines in a case company

Mixed-model assembly line sequencing is significant in reducing the production time and overall cost of production. To improve production efficiency, a mathematical model aiming simultaneously to minimize overtime, idle time and total set-up costs is developed. To obtain high-quality and stable solutions, an advanced scatter search approach is proposed. In the proposed algorithm, a new diversification generation method based on a genetic algorithm is presented to generate a set of potentially diverse and high-quality initial solutions. Many methods, including reference set update, subset generation, solution combination and improvement methods, are designed to maintain the diversification of populations and to obtain high-quality ideal solutions. The proposed model and algorithm are applied and validated in a case company. The results indicate that the proposed advanced scatter search approach is significant for mixed-model assembly line sequencing in this company.

A Weighted Multiobjective Optimization Method for Mixed-Model Assembly Line Problem

Mixed-model assembly line (MMAL) is a type of assembly line where several distinct models of a product are assembled. MMAL is applied in many industrial environments today because of its greater variety in demand. This paper considers the objective of minimizing the work overload (i.e., the line balancing problem) and station-to-station product flows. Generally, transportation time between stations are ignored in the literature. In this paper, Multiobjective Mixed-Integer Programming (MOMIP) model is presented to optimize these two criteria simultaneously. Also, this MOMIP model incorporates a practical constraint that allows to add parallel stations to assembly line to decrease higher station time. In the last section, MOMIP is applied to optimize the cycle time and transportation time simultaneously in mixed-model assembly line of a real consumer electronics firm in Turkey, and computational results are presented.

Mixed-model assembly line balancing in the make-to-order and stochastic environment using multi-objective evolutionary algorithms

The present study introduces a multi-objective genetic algorithm (MOGA) to solve a mixed-model assembly line problem (MMALBP), considering cycle time (CT) and the number of stations simultaneously. A mixed-model assembly line is one capable of producing different types of products to respond to different market demands, while minimizing on capital costs of designing multiple assembly lines. In this research, according to the stochastic environment of production systems, a mixed-model assembly line has been put forth in a make-to-order (MTO) environment. Furthermore, a MOGA approach is presented to solve the corresponding balancing problem and the decision maker is provided with the subsequent answers to pick one based on the specific situation. Finally, a comparison is carried out between six multi-objective evolutionary algorithms (MOEA) so as to determine the best method to solve this specific problem.

Sequencing Mixed-Model Assembly Line under a JIT-Approach‌

Mixed-model assembly line is known to be a special case of production lines where various and different models of the same products are inter-mixed to be assembled on the same line. Using mixed model assembly line involves not only the traditional problems of assembly line design (i.e., determining the line cycle time, the number and sequence of stations of the line, and balancing the line) but also determining the sequence in which products will be scheduled for assembly. In each station, some components are assembled in the final products. Under just in time (JIT) approach; an objective is to have a fairly constant usage rate for each component going into final assembly to facilitate the use of Kanban or other JIT shop-floor systems. In this paper, a mixed approach, the sequencing mixed-model assembly line problem with a JIT-supply of required materials, ‌is studied and a mathematical model is proposed for solving it. The results are compared with a traditional approach. Some experiments are used to evaluate the performance of the proposed model.

Sequencing the mixed-model assembly line to minimize the total utility and idle costs with variable launching interval

A mixed-model assembly line (MMAL) is a type of a production line where a variety of products is assembled on it. A mixed-model assembly line problem involves not only solving the traditional problems of the assembly line design (i.e., determining the cycle time, the number and sequence of stations, and the balancing problem) but also determining the sequence of products in assembly line. The product sequencing has a high effect on the mixed-model assembly line efficiency. In this paper, we consider sequencing problem with a variable launching interval between products on the assembly line. A mathematical model is presented, which is capable to solve the small-sized ones of these problems. The considered problem involves two optimization problems (the sequencing problem and launching interval problem). Since this problem is strongly NP-hard, a hybrid metaheuristic algorithm based on the simulated annealing approach and a heuristic approach is developed. The heuristic approach (launching interval between products algorithm) is presented to solve the launching interval problem for each sequence. Numerical experiments are used to evaluate the performance and effectiveness of the proposed algorithm. Variable launching interval consideration in MMAL problem causes the higher complexity of this problem. However, this assumption improves the considered goals for this problem. Not only a power algorithm for MMAL is presented in this paper but also the effect of this assumption is discussed. Numerical experiments are used to evaluate the performance and effectiveness of the proposed algorithm.

A two-phase linear programming methodology for fuzzy multi-objective mixed-model assembly line problem

We develop a fuzzy multi-objective linear programming (FMOLP) model for solving multi-objective mixed-model assembly line problem. In practice, vagueness and imprecision of the goals in this problem make the fuzzy decision-making complicated. The proposed model considers minimizing total utility work, total production rate variation, and total setup cost, using a two-phase linear programming approach. In the first phase, the problem is solved using a max–min approach. The max–min solution not being efficient, in general, we propose a new model in the second phase to maximize a composite satisfaction degree at least as good as the degrees obtained by phase one. To show the effectiveness of the proposed approach, a numerical example is solved and the results are compared with the ones obtained by the fuzzy mixed integer goal programming and weighted additive methods. The computational results show that the proposed FMOLP model achieves lower objective functions as well as higher satisfaction degrees.

Mixed-model assembly line sequencing using beam search

In today's manufacturing environments, companies have to produce a large variety of products in small quantities on a single assembly line. In this paper, we use a beam search (BS) approach to solve the model-sequencing problem of mixed-model assembly lines (MMALs). Specifically, we develop six BS algorithms for part-usage variation and load-leveling performance measures. The results of computational experiments indicate that the proposed BS methods are competitive with the well-known heuristics in the literature. A comprehensive bibliography is also provided.

Time-based goal chasing method for mixed-model assembly line problem with multiple work stations

In sequencing problems for mixed-model assembly line in JIT production system, the Goal Chasing method (GC) is widely used for parts used leveling goal. The difference in assembly time of each product is not taken into consideration in the Goal Chasing method. Assembly time usually varies with product types. In recent years, the Time-Based Goal Chasing method (TBGC) has been proposed. The advantage of TBGC is to consider the influence of different assembly time of each product and idle time in production period. TBGC, however, has been only applied to single work station problems. In this paper, TBGC is applied to an assembly line problem with multiple work stations. Furthermore, the sequencing method and use of Simulated Annealing (SA) or Local Search (LS) for this problem are proposed.

Mixed-Model Assembly Line Scheduling in Consideration of Assembly Time.

In a mixed-model assembly line problem, two objectives has been proposed to decide the product scheduling. One is to minimize the work congestion and the other is keeping the consumption rate of each part. In JIT production system, the latter one is more important, so the goal chasing method (GC) has been prposed to achieve this goal. The difference of assembly time among each product was not cnsidered in any solution algorithms. Recently, the time based goal chasing method (TBGC) has been proposed in which the different assembly time among each product is considered. The good point of TBGC is able to consider the idle time contained in an assembly line. However, TBGC is only applied to a single work station problem. In this paper, TBGC is applied to an assembly line and numerical experiments are presented.