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Pre-heating stainless steel inserts for overmoulding ABS

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henry234

Materials
Nov 4, 2016
1
I am currently involved in reviewing an overmoulding process, where a cast stainless steel (17-4 PH) custom insert is overmoulded with a flame retardant ABS. All aspects of the processing are going well from our perspective: The final products meet customer requirements from a dimensional, functional and aesthetics perspective. However, our customer has recently performed some thermal fatigue testing on the parts and has proven that there may be some risk due to residual stresses in the components. They believe residual stresses have appeared in the components during overmoulding of the stainless steel insert and they want us to investigate how the processing can be altered to improve the test results.

One suggestion from the customer has been for us to start to pre-heat these stainless steel inserts prior to overmoulding. Through discussion with the customer, we have agreed a target of heating the inserts up to as close to the mould temperature as possible. For this particular grade of ABS, the recommended mould temperature is 160oF-180oF.

This product is manufactured in moderately low volumes. We currently mould around 1000 pieces per month, but this figure will steadily rise over the next year or two, possibly to around 5000 per month. The tool itself has two cavities. The inserts are loaded manually by an operator. The inserts are not large, they are approximately 1 inch cubed in volume.

Does anyone have experience of taking this step before? Can anyone recommend suitable equipment to perform this pre-heating action? I have been thinking that a laboratory hot plate may be useful, but I am concerned about operator safety of handling the inserts and working with an additional heat source at the machine too. Thanks for your help or advice in advance.
 
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