David W. He

Design of assembly systems for modular products

To respond to the challenge of agile manufacturing, companies are striving to provide a large variety of products at a low cost. Product modularity allows production of different products by combining standard components. One of the characteristics of modular products is that they share the same assembly operations for a part of their structure. The special structure of modular products provides challenges and opportunities for the design of assembly systems. Given a family of modular products, designing low cost assembly systems is an important problem. In this paper, an approach for the design of assembly systems for modular products is proposed. The assembly system is decomposed into two subsystems based on the structure of modular products. The configuration problem of the assembly system is formulated and solved by a tabu search based algorithm.

Delayed product differentiation : a design and manufacturing perspective

Delayed product differentiation (DPD) is a design concept for improving customer satisfaction and manufacturing performance. In this paper, a methodology for implementing the delayed product differentiation strategy in manufacturing is presented. Three design rules are suggested. The impact of delayed product differentiation strategy on the performance of a manufacturing system is quantified and incorporated in the product design. The problem of selecting designs to minimize the total differentiation and manufacturing cost is formulated and solved. The methodology presented in the paper is illustrated with examples.

A structured approach for analysis of design processes

The purpose of this paper is to present a methodology for analyzing and improving design processes. The methodology presented uses a directed graph and the corresponding incidence matrix to represent a design process or the relationship between constraints and variables in a design problem. A qualitative analysis approach (critical analysis and concurrency analysis) Is used to analyze the process structure and improve it without considering the time aspect. The analysis explores a process structure as well as enhances concurrency of the design process. The critical analysis determines potential activities that may delay a design project and provides suggestions for improvement of the design process. A process with higher degree of concurrency is obtained and therefore the product development time should be reduced. Two examples from electronics illustrate the approach proposed. >

Performance analysis of modular products

In this paper, the impact of modular product designs on the performance of manufacturing systems is studied. The performance of product designs is measured by the makespan of the corresponding aggregate schedule of the manufacturing system. Design rules for the improvement of performance of a manufacturing system are developed. Based on the design rules developed, the selection problem of modular designs is formulated as an integer programming problem. The problem can be solved by an existing heuristic algorithm. Examples are provided to illustrate the issues discussed in this paper.

Decomposition in automatic generation of Petri nets for manufacturing system control and scheduling

Despite the efforts in developing Petri net models for manufacturing control and scheduling, the generation of Petri net models cannot be automated for agile manufacturing control and scheduling without difficulties. The problems lie in the complexity of Petri net models. First of all, it is difficult to visualize the basic manufacturing process flow in a complex Petri net model even for a Petri net modelling expert. The second problem is related to the complexity of using Petri net models for manufacturing system scheduling. In this paper, a decomposition methodology in automatic generation of Petri nets for manufacturing system control and scheduling is developed. The decomposition methodology includes representing a manufacturing process with the Integrated Definition 3 (IDEF3) methodology, decomposing the manufacturing process based on the similarity of resources, transforming the IDEF3 model into a Petri net control model, and aggregating sub Petri net models. Specifically, a sequential cluster identification algorithm is developed to decompose a manufacturing system represented as an IDEF3 model. The methodology is illustrated with a flexible disassembly cell example. The computational experience shows that the methodology developed in this paper reduces the computational time complexity of the scheduling problem without significantly affecting the solution quality obtained by a simulated annealing scheduling algorithm. The advantages of the methodology developed in this paper include the combined benefits of simplicity of the IDEF3 representation of manufacturing processes and analytical and control properties of Petri net models. The IDEF3 representation of a manufacturing process enhances the manmachine interface.

Designing an assembly line for modular products

To respond to the challenge of agile manufacturing, companies are striving to provide a large variety of products at low cost. Product modularity has become an important issue. It allows to produce different products through combination of standard components. One of the characteristics of modular products is that they share the same assembly structure for many assembly operations. The special structure of modular products provides challenges and opportunities for operational design of assembly lines. In this paper, an approach for design of assembly lines for modular products is proposed. This approach divides the assembly line into two subassembly lines: a subassembly line for basic assembly operations and a subassembly line for variant assembly operations. The design of the subassembly line for basic operations can be viewed as a single product assembly line balancing problem and be solved by existing line balancing methods. The subassembly line for the variant operations is designed as a two-station flowshop line and is balanced by a two-machine flowshop scheduling method. A three-station flowshop line for a special structure of modular products is proposed and illustrated with an example.

A scheduling problem in glass manufacturing

Abstract In this paper, a production scheduling problem in glass manufacturing is studied. The production facility consists of multiple identical production lines and each production line includes a number of serially arranged machines. The production is characterized by semi-ordered processing times in each product family, and the last machine in each production line is a bottleneck machine. Significant changeover times are required when products of different families are produced on a production line. The scheduling problem was modeled as a parallel no-delay flowshop scheduling problem (PNDFSP). The PNDFSP combines the parallel machine scheduling problem (PMSP) with the no-delay flowshop scheduling problem (NDFSP). While PMSP and NDFSP have received considerable attention in the literature, PNDFSP has not been well studied. A mixed-integer programming formulation is developed and an efficient heuristic algorithm is proposed. The sequential heuristic algorithm considers simultaneously the line changeover...

Design for agility: A scheduling perspective

Abstract Agility is the ability of a company to produce a variety of products in a short time and at a low cost. This demands that products and manufacturing systems be simple, robust, and flexible to allow for quick response to the changing market. Scheduling of manufacturing systems in a changing environment is complex. This paper attempts to simplify scheduling of manufacturing systems through appropriate design of products and manufacturing systems. An attempt has been made to generate rules that allow to design products and systems for easy scheduling. Four design for agility rules are proposed in the paper. The first rule deals with decomposition of a manufacturing system. The rule simplifies the scheduling problem and reduces the total changeover cost. The second rule is concerned with design of products with robust scheduling characteristics. Product designs with robust scheduling characteristics can improve the response of a manufacturing system to the changes in the product demand and mix and reconfigurability of the system. The third rule results in a streamlined assembly line which has the type of product flow that simplifies scheduling. The fourth rule emphasizes the reduction of the number of stations in an assembly line. Examples are provided to demonstrate the benefits from using these rules. The implemention of the four rules is also discussed.

Design for an Enterprise

Agility is the ability of a manufacturing system to produce a variety of products of high quality at low cost. This paper presents some insights into the benefits of concurrent design of products and assembly systems and offers a methodology for design for an agile assembly environment. Several rules for design for agile assembly are proposed and illustrated with examples.

Reengineering Manufacturing Processes for Agility

Agility can be achieved through the partnership of different companies sharing resources, information, and manufacturing capabilities. In a virtual enterprise, products are manufactured by a network of geographically distributed manufacturing partners. In order to achieve the necessary degree of agility, the distributed manufacturing processes have to be efficiently coordinated to timely react to the changing environment. In this paper, an approach to reengineering manufacturing processes is presented. The approach involves the Integrated Definition 3 (IDEF3) methodology, decomposing the manufacturing process based on similarity of resources, and scheduling the resultant Petri nets. Specifically, a sequential cluster identification algorithm is developed to decompose a manufacturing system represented as an IDEF3 model. A scheduling approach is presented to generate an aggregated schedule from sub Petri net models. The computational experience shows that the methodology developed in this paper reduces the computational time of solving the scheduling problem without significantly affecting its solution quality.