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DFM | Standard tooling However, where you have different categories of

components that can be assigned with confi dence to a specifi c tool type from your tool standard, it is possible to go ahead with confi dence during the DFM phase to order the required standard mould parts from sub suppliers. When doing this, of course, it is important to recognize that some important characteristics of the injection moulded component will then be fi xed, such as the number, position and type of gate points and undercuts. This is essential to ensure that the complete tool system will function with the already ordered standard tool components. Using a tool system such as this can also provide evi-

Figure 1: Exploded view of a tool standard used by a European mobile phone OEM. Only the marked areas are customised at the tool maker Source: AST

dence for reusability of specifi c mould components when an injection moulded component reaches the end of its life cycle, such as hotrunners or complete mouldbase.

Also, these system tools can be used as prototype

moulds to test new component designs by simply producing new cavity and core sets and reusing the mouldbase from previous projects. This can be very cost effective and can also help reduce the lead time for prototype mould tools. Reusable mould bases are generally known as

Figure 2: Cavities for two different phone covers sharing the same tool type. Only the magenta areas are part specifi c Source: AST

tool type within the new tool standard. A fully specifi ed tool standard, for instance, will not make sense where the range of components to be moulded covers a huge variety of sizes or demoulding features (the tool features needed to demould undercuts on a plastic component design). It is also important to be sure that the catego- ries selected within the tool standard are suitable for both current and likely future part requirements. During the DFM phase of a product development

project, the engineering team needs to review whether the specifi c tool type selected is appropriate for the specifi c injection moulded component. The DFM engineer will know the tool standard and must be sure it can accommodate the size of the part and can handle the gating, cooling, functions and demoulding required. During the early stage of a product development it is possible to play with the component design in such a way that it suits a specifi c tool design, which is very often less costly than changing the tool to fi t the component design.

68 INJECTION WORLD | September 2013

mould frames. Some manufacturers do not remove these mould frames from the injection moulding machine when they have a product change during production - they just change the cavity and core stacks. This can not only reduce the downtime of a moulding machine during a product changeover but can also reduce the cost of capital equipment. Owning a tool standard can also have a benefi cial impact on product quality where production of the parts has been outsourced. Where, for instance, a manufac- turer is going to produce a specifi c product in Europe, Asia and in the US and plans to have the mould tools produced local to the manufacturing sites, the use of a single tool standard and design guide can reduce scope for quality variation. There is also a benefi t in the event that a tool is moved from one region to another as all the machine interfaces are to a defi ned standard.

About the author: André Eichhorn is general manager of Germany-based AST Technology. This is the latest instalment in a series of articles in which he discusses how part and moulding problems can be overcome at the start of any project by the application of Design for Manufacturing techniques. You can read the most recent articles in this series here, here and here. You can also visit AST Technology at the K-Fair in

October. Find the company in Hall 1, Stand E36. 

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