Sheltered Work Centers Research Articles

The multi-objective assembly line worker integration and balancing problem of type-2

The consideration of worker heterogeneity in assembly lines has received a fair amount of attention in the literature in the past decade. Most of this exploration uses as motivation the example of assembly lines in sheltered work centers for the disabled. Only recently has the community started looking at the situation faced in assembly lines in the general industrial park, when in the presence of worker heterogeneity. This step raises a number of questions around the best way to incorporate heterogeneous workers in the line, maximizing their integration while maintaining productivity levels. In this paper we propose the use of Miltenburg’s regularity criterion and cycle time as metrics for integration of workers and productivity, respectively. We then define, model and develop heuristics for a line balancing problem with these two goals. Results obtained through an extensive set of computational experiments indicate that a good planning can obtain trade-off solutions that perform well in both objectives.

A multiple-rule based constructive randomized search algorithm for solving assembly line worker assignment and balancing problem

This paper proposes a constructive heuristic approach for the assembly line worker assignment and balancing problem (ALWABP). ALWABP arises when the operation time for every task differs according to the worker who executes the task. Since the operation times of tasks vary due to the workers, the problem requires a simultaneous solution to the double assignment problem. Tasks must be assigned to workers and workers to stations, concurrently. This problem is especially proposed in sheltered work centers for the disabled. However, it is not only important for the assembly lines with the disabled, but also for manually operated assembly lines with high labor turnover. In this paper, a multiple-rule based constructive randomized search (MRBCRS) algorithm is proposed in order to solve the ALWABP. Thirty nine task priority rules and four worker priority rules are defined. Performance of the proposed MRBCRS is compared with the relevant literature on benchmark data. Experimental results show that the proposed MRBCRS is very effective for benchmark problems. The results show that the algorithm improves upon the best-performing methods from the literature in terms of solution quality and time.

Flow shop scheduling with heterogeneous workers

We propose an extension to the flow shop scheduling problem named Heterogeneous Flow Shop Scheduling Problem (Het-FSSP), where two simultaneous issues have to be resolved: finding the best worker assignment to the workstations, and solving the corresponding scheduling problem. This problem is motivated by Sheltered Work centers for Disabled, whose main objective is the labor integration of persons with disabilities, an important aim not only for these centers but for any company desiring to overcome the traditional standardized vision of the workforce. In such a scenario the goal is to maintain high productivity levels by minimizing the maximum completion time, while respecting the diverse capabilities and paces of the heterogeneous workers, which increases the complexity of finding an optimal schedule. We present a mathematical model that extends a flow shop model to admit a heterogeneous worker assignment, and propose a heuristic based on scatter search and path relinking to solve the problem. Computational results show that this approach finds good solutions within a short time, providing the production managers with practical approaches for this combined assignment and scheduling problem.

Hybrid heuristics for planning job rotation schedules in assembly lines with heterogeneous workers

Abstract We investigate the problem of balancing assembly lines with heterogeneous workers while considering job rotation schedules. This problem typically occurs in assembly lines in sheltered work centers for disabled. We propose a hybrid algorithm that uses a Mixed Integer Programming (MIP) to select appropriate schedules from a pool of heuristically constructed solutions. A local search based on MIP neighborhoods is used as a post-optimization method. Our results show that this approach is fast, flexible and accurate when compared with current available methods.

Alternative tools to mass production and human performance indicators in sheltered work centers of Valencian community (Spain)

Purpose: The most popular alternative systems to mass production at an academic level (lean manufacturing, agile manufacturing, flexible customization, mass customization...) share many characteristics. Our article identifies an extensive set of alternative practices to mass production; analyzes the classification of practices in categories (Flow, TQM, TPM, Customer Relations, Supplier Relations and Human Resources Practices) and analyzes the impact on several human performance indicators such as satisfaction, absenteeism, voluntary turnover, permanent contracts, knowledge, personal & social adjustment activities and integration of workers into ordinary companies.

Simple heuristics for the assembly line worker assignment and balancing problem

We propose simple heuristics for the assembly line worker assignment and balancing problem. This problem typically occurs in assembly lines in sheltered work centers for the disabled. Different from the well-known simple assembly line balancing problem, the task execution times vary according to the assigned worker. We develop a constructive heuristic framework based on task and worker priority rules defining the order in which the tasks and workers should be assigned to the workstations. We present a number of such rules and compare their performance across three possible uses: as a stand-alone method, as an initial solution generator for meta-heuristics, and as a decoder for a hybrid genetic algorithm. Our results show that the heuristics are fast, they obtain good results as a stand-alone method and are efficient when used as a initial solution generator or as a solution decoder within more elaborate approaches.

Alternative tools to mass production and human performance indicators in sheltered work centers of Valencian community (Spain)

Alternative tools to mass production and human performance indicators in sheltered work centers of Valencian community (Spain)

On solving the assembly line worker assignment and balancing problem via beam search

Certain types of manufacturing processes can be modelled by assembly line balancing problems. In this work we deal with a specific assembly line balancing problem that is known as the assembly line worker assignment and balancing problem (ALWABP). This problem appears in settings where tasks must be assigned to workers, and workers to work stations. Task processing times are worker specific, and workers might even be incompatible with certain tasks. The ALWABP was introduced to model assembly lines typical for sheltered work centers for the Disabled. In this paper we introduce an algorithm based on beam search for solving the ALWABP with the objective of minimizing the cycle time when given a fixed number of work stations, respectively, workers. This problem version is denoted as ALWABP-2. The experimental results show that our algorithm is currently a state-of-the-art method for the ALWABP-2. In comparison to results from the literature, our algorithm obtains better or equal results in all cases. Moreover, the algorithm is very robust for what concerns the application to problem instances of different characteristics.

Job rotation in assembly lines employing disabled workers

In this paper we consider the programming of job rotation in the assembly line worker assignment and balancing problem. The motivation for this study comes from the designing of assembly lines in sheltered work centers for the disabled, where workers have different task execution times. In this context, the well-known training aspects associated with job rotation are particularly desired. We propose a metric along with a mixed integer linear model and a heuristic decomposition method to solve this new job rotation problem. Computational results show the efficacy of the proposed heuristics.