The task of designing and planning an assembly system is complex and challenging. Today, planning results are often dependent on the experience and methodological skills of the planner as well as on ...the available planning tools available. Digital processes are used to accelerate the planning process and establish the best possible shared knowledge base. Currently, the planning is partly supported by digital tools such as digital models and simulations. A disadvantage of digital modelling and simulation studies is their complex and expensive development. This paper presents a digital and partially automated planning process for the concept planning of an assembly system for a customer-individual product, in which not only the assembly system with its number of workstations is planned, but also the positioning of the required materials at the individual workstations is carried out considering ergonomic aspects. This is demonstrated using the example of a customer-individual last-mile electric vehicle.
In several occupational sectors, workers are daily exposed to vibrations induced by automatic, pneumatic, or electric tools, with a consequent increase of musculoskeletal disorders. In this paper, a ...bi-objective manual assembly line design model is proposed, aiming to avoid excessive daily vibration exposures. The developed model allows to minimise both total equipment costs and vibration levels by respecting the threshold values defined in the ISO 5349-1. The ϵ-constraint approach is used to address both objectives and to find the Pareto frontier. The model is applied to several instances to evaluate the computational limit of the solving method, as well as to an industrial case to provide managerial guidelines. The results show that the method can solve small and medium size instances. Moreover, the case study points out that safe vibration exposure levels can be achieved also with a low additional investment and that solutions equal from an economic point of view can be different from a vibrations exposure one.
Manufacturing systems are socio-technical systems, with explicit interactions between humans and technologies in shared workspaces. These shared workspaces could also be called hybrid collaborative ...manufacturing systems, which involve workers as well as technological equipment and combine the benefits of human workers and new Industry 4.0 technologies, such systems are particularly useful in a context requiring flexibility and adaptability. Furthermore, the new Industry 5.0 approach has the objective to shift toward more human-centric and resilient manufacturing systems. The key problems to solve in the design of collaborative manufacturing systems are the combinatorial assembly line balancing problem and the equipment selection problem. An efficient and sustainable line requires a cost-effective choice of equipment while improving the ergonomics and the safety of workers. Both decisions of balancing workload and the assignment of equipment impact the ergonomics of a collaborative system and present conflicting criteria. To this end, we propose a multi-objective approach, the objectives are the optimisation of the investment costs and the ergonomics with a fatigue and recovery criterion. We propose to linearise the fatigue and recovery to formulate a new Mixed Integer Linear Programming formulation. We developed an exact multi-objective solving algorithm based on the ϵ-constraint to obtain the trade-off between these objectives. We conducted numerical experiments with different instances from the literature with promising results for instances with up to 45 operations. Finally, we discuss insightful managerial conclusions and future research perspectives.
This article presents a novel approach for the automated design of assembly lines that combines the assembly line balancing problem with resource selection and the positioning of the chosen resources ...into one single optimisation problem. Existing approaches for the automated planning of assembly plants either focus on one planning step or work through different planning steps sequentially. So far, no method exists that sufficiently takes into account the interdependency between the selection and positioning of resources. This article addresses this problem by presenting a bi-level optimisation approach for the automated design of assembly lines. A nested genetic algorithm is used to solve an assembly line balancing problem that includes the selection of production resources while simultaneously considering the layouting options for the chosen resources. Three examples for the evaluation and validation of the algorithm are presented. The presented approach is economically promising as the design of assembly lines requires a lot of expert knowledge and is still mostly done manually.
•Resource constrained multi-manned assembly line balancing problem is addressed.•Mathematical models of the problem firstly have been improved.•An effective hybrid algorithm based on particle swarm ...optimization is developed.•Computational study shows the effectiveness of the proposed solution methods.
Resource investment and balancing problem of an assembly line with parallel multi-manned workstations can be defined as the assignment of tasks to reduce the cost of the line, which includes the cost of opened workstations and required renewable resources. Although mentioned problem has been commonly occurred in industrial environment that produce large scale products in high volumes, there have been restricted number of studies in the literature about this field. This article proposes a new mixed-integer linear programming approach that can be used in solving small size instances of the problem. In addition, a new hybrid method has been developed to solve larger scale instances by combining particle swarm optimization algorithm with a special constructive heuristic. In the constructive heuristic, serial schedule generation scheme widely used in solving resource constrained project scheduling problems has been adapted to resource investment problem with some modifications. Proposed metaheuristic has been compared against a tabu search and cuckoo search algorithm taken from the assembly line balancing literature. Many precedence diagrams commonly used in solving various assembly line balancing problems in the literature, have been used to generate test instances for the considered problem type. After solving these test instances using each solution methods, it has been observed that the proposed hybrid metaheuristic yielded the solutions, which have acceptable deviations from the lower bounds.
This article presents a novel alternative subgraphs assembly line balancing problem with resource selection and parallel stations. The model considers both the choice between different process ...alternatives and the selection of production resources for the various tasks. It also allows parallelization of stations in the balanced line, thereby improving the flexibility of the algorithm. The objective of optimization is to minimize the total cost of the planned line. A genetic algorithm is used for solving the model. To evaluate its functionality, the approach was applied to 486 well-known reference problems. In addition, the reference problems were expanded to create a new set of reference problems that serve as a benchmark for the algorithm's new capabilities. The results show that the presented algorithm is feasible for solving the formulated assembly line balancing problem.
Purpose
Industry 4.0 emerged as the Fourth Industrial Revolution aiming at achieving higher levels of operational efficiency, productivity and automation. In this context, manual assembly systems are ...still characterized by high flexibility and low productivity, if compared to fully automated systems. Therefore, the purpose of this paper is to propose the design, engineering and testing of a prototypal adaptive automation assembly system, including greater levels of automation to complement the skills and capabilities of human workers.
Design/methodology/approach
A lab experimental field-test is presented comparing the assembly process of a full-scale industrial chiller with traditional and adaptive assembly system.
Findings
The analysis shows relevant benefits coming from the adoption of the adaptive automation assembly system. In particular, the main findings highlight improvements in the assembly cycle time and productivity, as well as reduction of the operator’s body movements.
Practical implications
The prototype is applied in an Italian mid-size industrial company, confirming its impact in terms of upgrades of the assembly system flexibility and productivity. Thus, the research study proposed in this paper provides valuable knowledge to support companies and industrial practitioners in the shift from traditional to advanced assembly systems matching current industrial and market features.
Originality/value
This paper expands the lacking research on adaptive automation assembly systems design proposing an innovative prototype able to real-time reconfigure its structure according to the product to work, e.g. work cycle, and the operator features.
This paper deals with the multi-model assembly line balancing problem (MuMALBP) in a reconfigurable environment. The considered line is composed of a fixed number of workstations and can produce ...different products in batches. Each product requires an appropriate line configuration. Thus, when the product changes, the line has to be reconfigured to satisfy new requirements related to task precedence and cycle time constraints. Reconfiguring the line consists in reassigning certain tasks between the existing workstations. The objective of this paper is to design a line configuration for each product while minimizing the maximum number of task reassignments whatever the sequence of product arrival. To solve this NP-hard problem, a mixed-integer linear program (MILP) is first formulated. Subsequently, a constructive heuristic and a MILP-based heuristic, named Halt-and-Fix, are developed to solve large-size problem instances. All the approaches are tested and approved on a dataset derived from the well-known instances of the assembly line balancing literature. The numerical results show that the Halt-and-Fix heuristic provides a better trade-off between solution quality and CPU time, compared to the constructive heuristic and the MILP formulation.
•A reconfigurable multi-model assembly line balancing problem is considered.•The aim is to design a best line configuration for each product.•The objective function minimizes the maximum number of task reassignments.•A MILP formulation is proposed with pre-processing techniques.•Constructive and MILP-based heuristics are developed.•A comparison between the approaches is given on the basis of a benchmark data set.
•A new Robotic Assembly Line Design Problem is proposed and studied.•An MILP formulation is develop in order to solve the new proposed problem.•Several practical extensions are combined in a single ...assembly line design model.•Instances based on real robotic welding assembly lines were solved.•A potential economy of approximately 5.9% was observed in real-world line design.
Spot welding assembly lines are widely present in the automotive manufacturing industry. The procedure of building the vehicle’s body employs several robots equipped with spot welding tools. These robots and tools are a quite costly initial investment, requiring an efficient and conscious line design that meets product demands and minimises implementation expense at the same time. In this paper, the Robotic Assembly Line Design (RALD) problem is proposed and studied based on practical characteristics from an automotive company located in Brazil. A Mixed-Integer Liner Programming (MILP) formulation is developed allowing: (i) station paralleling, (ii) equipment selection, and (iii) multiples robots per workstation. The mathematical model aims at minimising the total cost at the desired production rate, which involves robots, tools and facilities. The proposed model considers dead time during a cycle, space constraints, task assignment restrictions, and parallelism possibilities. Dead time is an unproductive and fixed work-piece handling time included in the capacitated transporter robots’ movement time. Computational experiments were performed in order to evidence the parameters’ influence over the optimal line design solution. In addition, practical case studies were conducted with parameters collected from a real-world robotic welding assembly line located on the outskirts of Curitiba-PR (Brazil), reaching optimality. Compared to the strictly serial lines, the model led to great advantages by allowing parallel stations in the production system, making it possible to evaluate an expected trade-off between the production rate and the total cost; reductions of several hundred thousand dollars on the production layout cost can be achieved by the company, as indicated by the studied cases.
This article presents a novel approach for the automated 3D-layout planning of multi-station assembly lines. The planning method is based on a comprehensive model of the used production resources, ...including their geometry, kinematic properties, and general characteristics. Different resource types can be included in the planning system. A genetic algorithm generates and optimizes possible layouts for a line. The optimization aims to minimize the line's area and the costs for assembling the line while simultaneously optimizing the resources' positioning to perform their tasks. The line's cycle time is considered as a boundary condition. For the evaluation of different layout alternatives, a multi-body simulation is performed. A parameter study is used to set the algorithm's parameters. Afterward, the algorithm is applied to three increasingly complex examples to validate and evaluate its functionality. The approach is promising for industrial applications as it allows the integration of various resource types and individualization of the optimization function.
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