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Multi-component | DFM


Multi-component moulding is an increasingly popular option today but still presents special considerations for the product development team, writes André Eichhorn


Taking the risk out of multi-shot


Multi-shot or multi-component moulding techniques have been used in the plastics industry since the early 1970s but the technology has grown in importance in recent years as designers have exploited the ability it provides to enhance the appearance or tactile response of a product, integrate new functionality, or reduce assembly costs. One factor behind the growing popularity of multi-


component moulding is the improvement that has been made in hot runner and injection moulding machine technology. Mould tool design and manufacturing know-how has also developed to a level that makes it possible today to effectively realise even the most ambitious projects. Multi-shot applications have been used in the


automotive industry for many years, often to eliminate complex and costly assembly procedures. For example, car lens and multi-colour automotive stop lights are almost always now moulded this way. And replacing assembly with a single automated production process – even one which requires a substantial capital investment in complex tooling – means an improvement in product quality. Multi-component moulding is also useful where several surface textures are required in one part, either


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for functional or aesthetic purposes. Multi-shot injection of a combination of hard and soft polymers – such as polypropylene with thermoplastic elastomer – is perhaps the most common application of the technology today and is applied across a very wide range of industries, with the production of tooth brushes and razors prime examples. In many situations, multi-component design considerations are driven by two key desires:


 To improve the visual appearance and/or tactile fi nish of the product;


 To reduce total manufacturing cost by eliminating expensive post processing operations such as painting, plating or assembly.


Consider the example of a casing for a mobile phone (shown in Figure 1). The phone manufacturer wanted to achieve a soft warm surface feel and a very good grip. But cost was also very important at the


expected annual production volume of two million units.


January/February 2013 | INJECTION WORLD 47


Figure 1 below: A multi-


component mobile phone


cover moulded from PC/ABS blend and TPU.





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