| More advice on plastic molding design & stereolithography - page 2 of 2 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Below:
more advice on plastic molding design & stereolithography
for parts with specific needs & features. 1. If you need moldings to have tight tolerances, don't specify too many, as this will be very difficult to achieve consistently. Due to the vast range of material types & grades available, it is not practical to suggest a single tolerance level for all types of moldings & materials. However, BS7010:1988 provides help on tolerances achievable for each material type & is available to view or buy from BSI's web site (we mostly exceed these tolerances with correct tool design &/or optimisation). 2. As a guide, if stereolithography cannot produce features which are on your CAD model, they are probably too small or delicate & it is extremely unlikely that the plastic injection molding process will be able to either. Thus, before having the tool made, ensure you increase the size or thickness of these features. 3. Unless absolutely necessary, avoid undercuts and holes in the side of parts, as this will mean that the mould tool will need expensive side action parts in order to produce them in the molding. 4. Should you need to have a textured surface on your moldings, allow 3 - 5° draft angle to enable the mould tool to be made so that the moldings can be easily extracted from the tool cores or cavities. 5. If you want text or logos on your parts, consider how important this is & allow enough room on your part. An inexpensive way, is to get the text/logo engraved on the tool, as this only needs to be paid for once for it to appear recessed or stood up on your molding. For a more professional, eye catching design, the text or logo can be hot foil or pad printed onto your parts after molding in a range of different colours. 6. If possible, design parts like Shaver Plugs so the 2 Case Halves can be moulded & then screwed or snap fitted to the Connector afterwards. This is quicker & more cost effective than designing the Shaver Plug so the Connector needs to be loaded into the tool by an Operator to make the finished Plug.
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