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26th January 2022, 11:24 PM
#1
Re: Insert molding metal terminals
I believe you will need to tweak the terminal design to ensure the melt flow and cavity pressure doesn't damage them. But, if not properly supported in the mold; they can move and may get twisted or bent in the process. Does the terminal need to be flat or can it be round in shape? This helps with resin flow around it. Also you might should design some stepped rings into the insert so that the resin can fill these smaller areas and give you maximum sealing around the insert.
I over-molded inserts into a PP-GF bottle and a PE extrusion grade resin bottle in the past. They had these rings in the terminals plus O-rings that were over-molded into the part. Another job molded the bottle and a snap in insert with O-rings was pressed into the top of the bottle. So you may want to do a prototype tool and test all of these points before commiting to building a mold and ordering inserts!
Copper is NOT to be used with POM! I think that is your first problem to resolve! They will react in a NOT favorable way to one another! POM can be rough since it can/does out gas some of the formaldehyde from the melt. Now your choice may be the best one but you still should be careful.
Mold temp for the resin should be very hot which could reduce fill pressure. BUT, the injection gate must stay open long enough to pack the shrinkage out of the part as the resin shrinks while in the cavity. So you should end up with a long hold time/higher pressure and short cooling time. I don't think you want to mold the inserts into a part and then try to over-mold/bond it into a part.
Rick
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27th January 2022, 07:36 PM
#2
Re: Insert molding metal terminals
I greatly appreciate the response Rick.
Unfortunately, the terminal has to be flat to mate with the connector. I already had added some steps into the terminals to help with the sealing. The terminals are currently designed to have a tin plating, do you think this sufficient to minimize the reaction between the terminals and the POM?
Also, I had considered doing a snap in connector for the part. However, the connector isn't one that is available for purchase so that would mean I would have to custom produce it, leading to the same problems, or buy go with a standard one that snaps in, which would require multiple connector harnesses and significantly raise the price of each part.
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28th January 2022, 08:38 AM
#3
Re: Insert molding metal terminals
Wow! I learnt something from Rick. Those are some good suggestions. Did not know about POM - Copper. Thanks.
Just to answer one question about POM - POM bonding,: Yes, they will bond well. It is best to have them the same grade. Also make sure the premold is resin rich. This is in case you decide to take the premold - overmold route.
Suhas
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9th February 2022, 01:39 PM
#4
Re: Insert molding metal terminals
For sealing terminals did you considered silicone seals?
Something similar we using on connectors that we overmold with TPE.
If tool desined properly and you dont use some exsesive injection preassure melt wont damage terminals.
There is also possibility to do potting than overmold, but that will increase price of part for sure.
Do you plan to make insert molding manual by worker or automatic by robot?
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