engleski

An Approach towards Identification of Common Components in Product Family

Objectives Product family is a set of products, which beneficially are created from a common set of components for obtaining a range of product variants, which are able to cover certain market segments (Andreasen et. al. 2001, p. 20). An important matter during the development of the product family is the higher producibility, meaning fewer parts to manufacture ; smaller number of items ; easier data management ; stock reduction and simpler material handling in the manufacturing. One of the first tasks in development of product family is to define the common components, which are re-used in the product variants. Analyzing only the technical documentation it is not enough to get answer on question which components are common and which components should be redesigned in product family. Therefore the key factor of product family development is the process of identification of common components which are more reused in the product variants than in the group of products. In this research a product family from industry was used as a case product family. Some improvements had been made earlier to the product family, but the improvements were made based on assumptions and experience. There was not any actual analysis carried out for basis of the improvement. The objective of this research is to identify the guidelines for analysing the group of existing individual products and to increase the commonality in product family. Methods Methodology begins with the analysis of internal and external variety between the products. External variety should be defined from the existing group of products and it represents the necessary variety seen from the customers’ viewpoints. The internal variety should be defined based on the external variety. Internal variety represents the necessary variety seen from the company’ s viewpoint. The final internal variety is defined at the latest phase of product family development. After the external and internal variety is defined the commonality index (CI) is measured. For comparison of existing products the assembly-function decomposition diagram was established. The analyses of the products based on to the assembly-function decomposition diagram and the results of the analyses were collected into a table. The initial values on CIs were calculated using the methods from Martin & Ishii [2], Macker & Trelevan [3], and Kota et al. [4]. The initial commonality indexes are compared to the values of the CIs after the modifications to the product family. Based on the collected data the new commonality index was calculated toward the method proposed by Jiao & Tseng [5]. The new commonality index was used to indicate the trend of the components on the value of commonality index. Some components increase, and some decrease, the value of the commonality index. The aim is to identify components which decrease the value of commonality index. Those components should be then redesign with the aim of increasing the commonality index after the redesign. The redesign process is directed by geometrical differences between the components. The process of identification, analysis and redesign of components is repeated until the level of re-usage is high enough in the product family. Those components are now candidates for modules in product variants. After the product family is defined the final commonality index is calculated using the first three methods. The process is repeated until the value of final commonality index is higher then the value of initial commonality indexes. Results The study made to the case product during this research bred two different kind of new architecture. The first one was structurally similar to the existing one but it had major enhancement in the part level. The commonality in the product family was better, meaning there were fewer parts to produce. The second one was essentially a new concept of the product family. It actually increased the number of parts per product variant but when considering the whole product family the new architecture reduced the total number of components. Conclusions Without the detailed analyses it would not have been possible to come up with the mentioned results. It is now obvious that the detailed analyses are a mandatory when genuinely developing the product family. And an efficient method for analysing the product family is the usage of the commonality indexes. They reveal, when correctly used, the weak points of the product family in a sense of producibility. Some indexes showed the overall commonality whereas other indexes took the features (masses, costs, etc.) also to consideration. Hence usage of just one index might lead the development into wrong direction. References 1. Andreasen, M.M., McAloone, T., Mortensen, N.M., 2001. Multi-Product Development – platforms and modularization. Lyngby, ISBN 87-90130-34-0 2. Martin, M. and Ishii, K., 1996. Design for Variety: a Methodology for Understanding the Costs of Product Proliferation. In: K. Wood, ed. Design Theory and Methodology – DTM ’ 96, Irvine, CA, ASME, Paper No. 96-DETC/DTM-1619 3. Wacker, J.G. and Trelevan, M., 1986. Component Part Standardization: An Analysis of Commonality Sources and Indices. Journal of Operations Management, 6 (2), pp. 219 - 244 4. Kota, S., Sethuraman, K. and Miller, R., 2000. A Metric for Evaluating Design Commonality in Product Families. ASME Journal of Mechanical Design, 122 (4), pp. 403-410 5. Jiao, J. and Tseng, M.M. 2000. Understanding Product Family for Mass Customization by Developing Commonality Indices. Journal of Engineering Design, 11 (3), pp. 225-243

Commonality index; product family; product variant; functions

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