Robert J. Graves

Flexible assembly systems: The scheduling problem for multiple products

Abstract Flexible assembly systems (FAS) promise to be an efficient processing approach for producing small and medium-sized batches of products. One vitally important element which affects the achievement of high performance by the FAS is its scheduling/dispatching component operating within the production planning and control system (PPCS). A detailed definition of the FAS scheduling process is given and key differences between this process and the classical simple job shop scheduling process are discussed. A mathematical model is developed for the minimize makespan problem, and it is shown that the problem is NP-complete, that it is one the most difficult problems in the class of decision problems that can be solved by polynomial time nondeterministic algorithm (NP). The design of heuristic solution procedures is also discussed.

Design knowledge acquisition for DFM methodologies

Design for Manufacturability (DFM) is a philosophy that encourages the communication of manufacturing information at the earliest stages of design in order to design parts and products that can be produced with greater ease and economy. This paper discusses the extensive experience gathered during the development of several DFM models in order to draw some conclusions and express some concerns that should be of interest to all those who develop or use manufacturing models that rely on design knowledge acquisition of knowledge from domain experts and/or industrial sites.

Flexible assembly systems: an approach for near real-time scheduling and routeing of multiple products

An algorithm for the near real-time dispatching and routeing for multiple product assembly in a Flexible Assembly System (FAS) is described and initial test results are reported. The description of the FAS environment is drawn from an actual installation for which the algorithm design was intended.

Flexible assembly systems: test results for an approach for near real-time scheduling and routing of multiple products

SUMMARY An algorithm for the near real-time dispatching and routing of multiple products in a Flexible Assembly System (FAS) environment, called schedule, was described in an earlier paper. This paper presents extended test conditions and results associated with the use of schedule over the test conditions. The extended testing includes results on algorithm performance for larger and more complex assemblies, larger workloads, parametrization on the urgency factor setting in schedule randomization of job due-dates, and a distribution of the job release dates for the workloads assigned to the FAS.

An examination of routeing flexibility for small batch assembly of printed circuit boards

SUMMARY In this paper, we examine and quantify the effects of introducing new processing flexibility in the rapidly changing environment of printed circuit board (PCB) assembly. Specifically, we perform experiments designed to establish the benefits and determine the limitations associated with the introduction of routeing flexibility. We examine system behaviour as batch sizes are reduced in an environment characterized by moderate set-up requirements. We further demonstrate that the performance of flexible routeing policies in this environment is adversely affected by larger batch sizes and that the introduction of routeing flexibility leads to improved system performance in small batch assembly.

Hierarchical scheduling approach in flexible assembly systems

The scheduling and dispatching problem for flexible assembly systems operating in a MRP environment is described. These flexible assembly systems (FAS) can perform the required operations on multiple product types which are assembled simultaneously. A non-exact procedure is presented as the basis for SCHEDULER and DISPATCHER functionality in a hierarchical scheduling system design.

Design for Injection Molding: a Group-technology-based Approach

The design of parts for economical manufacture by injection molding is an important element in the broader design strategy known as design for manufacturing (DFM). This paper provides an insight into the process of developing a DFM model for injection molding and into the use of such a model in the context of part design. The costs due to the mold making, the costs due to processing and the costs due to material are determined by the features of the part design, and models are presented to demonstrate these dependent relationships. The knowledge for the model databases was gained through extensive interactions with mold makers and molders. An example of the use of the models is also presented and discussed in detail.

Managing new product time to market using time-cost trade-off methods

The timing of a new product introduction is critical to the success of the product. A late product will not have as great a return on investment if it enters a saturated market, contains outdated technology or incurs increased development costs. To maintain the planned market entry of a product network techniques such as time-cost trade-off may be used. The time-cost trade-off method, however, does not explicitly include the costs of late market entry. The method presented here incorporates the marketplace costs within the time-cost trade-off framework.

Integrated decision making in a flexible assembly system: a new approach for operational control

Abstract The degree to which flexibility in product mix, flexibility in product routeing, and flexibility in buffer sequencing can influence manufacturing system performance is the focus of this paper. Of special interest is the performance of material flow control architectures which integrate these flexible control concepts. The manufacturing context is that of diverse mixed technology circuit boards assembled using a cellular approach. The research methodology is that of simulation using the SIMAN and FORTRAN languages. Results indicate that the incorporation of flexibility concepts into material flow architectures can significantly affect system performance, especially when properly integrated with other operational control mechanisms.

Research in the 1990s

The Material Handling Research Colloquium convened June 19–21 in Hebron, Kentucky and brought together over 40 researchers from nearly 25 institutions. The objectives of these two and one-half days of intensive meetings were the exchange of viewpoints, the assessment of the state of material handling research, and the identification of key issues confronting the material handling research community. The goal was to anticipate the directions of material handling research in the 1990s through an examination of current activity and the identification of key barriers. The following sections of this chapter provide some insight into the kinds of problems being addressed, as well as the methodologies and approaches being used by researchers.