To cope with the intense global competition that is characterized by high product variety and short life cycles, manufacturers need to share manufacturing systems across products and product generations. Co-evolution of product families and assembly systems is proposed as a novel methodology for the joint design and reconfiguration of product families and assembly systems over several product generations. The co-evolution methodology capitalizes on the opportunities for design and assembly system reuse that are offered by modular product architectures and reconfigurable assembly systems. As a result, co-evolution can lead to reduced product development costs and increased responsiveness to market changes.
To cope with the challenges of market competition and the greater purchasing power of consumers, manufacturers have increased the variety of products they offer. Product families and reconfigurable manufacturing systems (RMS) are used to produce product variety cost-effectively. However, there is a lack of concurrent engineering methods for the joint design of a product family and an RMS, since existing concurrent engineering methods were developed for a single product and its associated manufacturing system. The presence of product variety brings challenges to the concurrent engineering of a product family and its reconfigurable assembly system (RAS), as the decision space is broader. This paper introduces a mathematical model for the concurrent design of a product family and a RAS. In addition, a mathematical model for the sequential approach to product family and RAS design is introduced to compare with the results of the concurrent methodology. A genetic algorithm has been developed to solve the models introduced for both the concurrent and sequential approaches. Examples are used to demonstrate the implementation of the concurrent approach to product family and RAS design and the benefits that could be achieved by using this approach. The solutions indicate that the concurrent design of product families and RASs leads to profits that are the same as or higher than the profits obtained with the sequential design approach. Therefore, the concurrent design of product families and RAS methodology is a more cost-effective approach to designing families of products and their associated manufacturing systems.
In order to gain competitive advantage, manufacturers require cost effective methods for developing a variety of products within short time periods. Product families, reconfigurable assembly systems and concurrent engineering are frequently used to achieve this desired cost effective and rapid supply of product variety. The independent development of methodologies for product family design and assembly system design has led to a sequential approach to the design of product families and assembly systems. However, the designs of product families and assembly systems are interdependent and efficiencies can be gained through their concurrent design. There are no quantitative concurrent engineering techniques that address the problem of the concurrent design of product families and assembly systems. In this paper, a non-linear integer programming formulation for the concurrent design of a product family and assembly system is introduced. The problem is solved with a genetic algorithm. An example is used to demonstrate the advantage of the concurrent approach to product family and assembly system design over the existing sequential methodology.
Machining wear models are useful for the prediction of tool life and the estimation of machining productivity. Existing wear models relate the cutting parameters of feed, speed, and depth of cut to tool wear. The tool wear is often reported as changes in flank width or crater depth. However, these one-dimensional wear measurements do not fully characterize the tool condition when tools wear by other types of wear such as notching, chipping, and adhesion. This is especially true when machining difficult-to-machine materials such as titanium. This paper proposes another approach for characterizing tool wear. It is based on taking measurements of the retained volume of the cutting tool. The new wear characterization approach is used to demonstrate the progression of volumetric wear in titanium milling.
This research introduces a new approach to analytically derive the differential equations of motion of a thin spherical shell. The approach presented is used to obtain an expression for the relationship between the transverse and surface displacements of the shell. This relationship, which is more explicit than the one that can be obtained through use of the Airy stress function, is used to uncouple the surface and normal displacements in the spatial differential equation for transverse motion. The associated Legendre polynomials are utilized to obtain analytical solutions for the resulting spatial differential equation. The spatial solutions are found to exactly satisfy the boundary conditions for the simply supported and the clamped hemispherical shell. The results to the equations of motion indicate that the eigenfrequencies of the thin spherical shell are independent of the azimuthal coordinate. As a result, there are several mode shapes for each eigenfrequency. The results also indicate that the effects of midsurface tensions are more significant than bending at low mode numbers but become negligible as the mode number increases.
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