Lee Luong

Modelling and evaluation of product fitness for service life extension

Based on the concepts of the ‘3Rs’ (reduce, reuse, and recycle), service life extension (SLE) is regarded as an environmentally friendly way to relieve rampant waste problems by prolonging the use-life of retiring products and preventing them with their unexplored value from being discarded too early. However, challenged by fast-changing technology and physical deterioration over time, a major concern in planning product SLE is how fit a product would be to serve an extra life. This paper intends to present a mathematic model and evaluation approach to provide a systematic estimate for a products potential to serve an extended life. Using fuzzy logic, the model is formulated to represent a products fitness for SLE based on its functional, physical, as well as structural characteristics. A number of indicators are integrated into the model to facilitate the evaluation and to identify weaknesses for improvement or redesign.

Developing a multi-objective genetic optimisation approach for an operational design of a manual mixed-model assembly line with walking workers

A walking worker assembly line (WWAL), in which each cross-trained worker travels along the line to carry out all required tasks, is an example of lean system, specifically designed to respond quickly and economically to the fluctuating nature of market demands. Because of the complexity of WWAL design problems, classical heuristic approaches are not capable of solving problematic design characteristic of WWAL of very large design space. This paper presents a new genetic approach to address the mixed model walking worker manual assembly line optimisation design problem with multiple objectives. The aim is to select a set of operational variables to perform to the required demand for two product models. The goal is to produce the required models at the lowest cost possible, whilst keeping within an ergonomically balanced operation. Genetic algorithms are developed to tackle this problem. This paper describes the fundamental structure of this approach, as well as the influence of the crossover probability, the mutation probability and the size of the population on the performance of the genetic algorithm. The paper also presents an application of a developed algorithm to the operational design problem of plastic electrical box assembly line.

Prediction and analysis impact of operational design of a manual assembly system with walking workers on performance

Manual assembly lines, with workers travelling with the work along the line to perform all required tasks, are an example of assembly systems which have greater flexibility over traditional systems due to an improved response to product demand variability. Implementing assembly systems in this way is difficult, especially when operational design reflects an incomplete understanding of how workers can best perform within the system. Different operational designs for such systems have a profound impact on the performance of the system in terms of productivity and ergonomics. This paper analyses the performance of walking worker assembly line (WWAL) in different operational designs. A mathematical model was developed, which considers the effects of a number of operational design variables. An industrial case study is presented here to demonstrate the effectiveness of the proposed model. The results indicate that WWAL can be designed to improve performance, flexibility and labour costs by approaching productivity and ergonomics collaboratively. The results obtained by the model prediction were compared with computer simulation results. Comparison validated the accuracy of the proposed model. The model provides partial characterisations of the optimal design of WWAL and can be used to develop heuristics for local or global optimisation.

Mathematical modelling for process design of walking worker assembly line in productivity and ergonomics perspectives

High worker-hour productivity and improving ergonomics conditions are major concerns of industry, especially in human-centred production systems (e.g. manual assembly systems). From the view of some manufacturing managers, converting fixed worker assembly line to walking worker assembly line (WWAL) involves opportunities and pitfalls for both mentioned aspects. This view point is supported by the complaint, i.e. no modelling research that can help them to develop their own capacity in the design of WWAL considering both productivity and ergonomics. This paper proposes a mathematical model that can be used by designers, manufacturers and dealers for the effective design of WWAL that significantly affects the productivity and ergonomics performance measures. Different combinations of process design parameters are compared with several alternative scenarios of WWAL design using well-planned numerical experiments. Graphical analyses were carried out to examine the relationships between design parameters (factors) and performance measures. The model can support WWAL practices in two ways: firstly, it can improve the understanding of how such systems behave and what factors drive performance. Secondly, it can help to determine what types of policies for successful operation of this system can quickly and economically be selected in light of the different levels of production demand.

Using simulation in verification of a mathematical model for predicting the performance of manual assembly line occupied with flexible workforce

Designing a dynamic system with inherent randomness requires a predictable and dependable mathematical model accurately representing the essential aspects of real systems. So it is necessary to establish a confidence level in the mathematical model of this system by carrying out a verification process for this model to collect evidence. This paper deals with verification of the mathematical model designed for the prediction of performance of manual assembly lines occupied by a flexible workforce referred to as walking worker(s) assembly line (WWAL). To verify the mathematical model, it was applied to an illustrative industrial example. Also experiments carried out on this example were simulated using a software package. Then, the predicted results of the mathematical model were compared with simulation results. Comparison leads to the verification of both the accuracy and the serviceability of the mathematical model developed.

Biomechanical Assessment of Lower Limbs Using Support Moment Measure at Walking Worker Assembly Lines

Manual assembly line work is currently still necessary in the manufacturing industry. The human body despite its organic limitations is still more flexible than machines, and the human mind possesses creative and intuitive functions above that of robotic devices. Automation and robotic cells have limitations and manual assembly lines are considered a significant and justifiable solution (Hunter, 2002). In traditional assembly lines, such as Fixed Worker Assembly Lines (FWAL), each worker has a designated task, and is required to continuously repeat that task. Although FWALs are efficient and generally reliable, they have the following deficiencies (Wang et al., 2005): uf0b7 Low flexibility (in terms of workers and products), uf0b7 Need constant attention and management, and uf0b7 Difficult balancing.

A Framework for the Modelling and Optimisation of a Lean Assembly System Design with Multiple Objectives

The newest assembly system is lean assembly, which is specifically designed to respond quickly and economically to the fluctuating nature of the market demands. Successful designs for these systems must be capable of satisfying the strategic objectives of a management in manufacturing company. An example of such systems is the so-called walking worker assembly line WWAL, in which each crosstrained worker travels along the line to carry out all tasks required to complete a job. Design approaches for this system have not been investigated in depth both of significant role in manual assembly process design; productivity and ergonomics. Therefore these approaches have had a limited success in actual applications. This chapter presents an innovative and integrated framework which offers significant potential improvement for productivity and ergonomics requirements in WWAL design. It establishes a systematic approach clearly demonstrating the implementation of a developed framework based on the simultaneous application of mathematical and metaheuristic techniques. Atiya Al-Zuheri University of South Australia, Australia & Ministry of Science and Technology, Iraq Lee Luong University of South Australia, Australia Ke Xing University of South Australia, Australia DOI: 10.4018/978-1-4666-5836-3.ch005

Impact of Walking Worker Assembly Line Configuration on Ergonomics Performance

Abstract Manual assembly lines with walking workers may be designed in many configurations. Different configurations have profound impact on the performance of the system. This paper analyses and evaluates the ergonomics performance measures for different system configurations. Based on developed mathematical model, different combinations of structural factors are compared to evaluate effects of these factors on the mentioned performance. The work demonstrates that various design factors should be considered jointly when designing or redesigning walking worker assembly line because setting different levels for factors can considerably affect the ergonomics performance of the system.