Posts: 4
From:Arden, NC USA
Registered: Feb 2005

posted February 09, 2005 04:02 PM               

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I have a problem with some parts that are molded from thermoplastic material. I had 8 parts molded with a hole on the side of the part. I can't seem to get any answers from my process engineer who inputs the parameters into the mold. THe parameters have been viewed today and all is ok. Somehow, perhaps the injection speed or venting was not input correctly. Does anyone have any suggestions as to why this was occurring? Please advise ASAP.

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Posts: 630
From:Brodheadsville, PA USA
Registered: Jun 2001

posted February 09, 2005 04:32 PM               

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Sounds like a lack of fill which could be caused by:

Cold mold
Lack of cushion
Too low of a fill rate
Higher viscosity resin than the mold was designed to use.
Cold melt

Just some ideas.

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Posts: 385
From:McHenry, IL USA
Registered: Nov 2002

posted February 17, 2005 06:11 AM               

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Idea's is all that can be offered - but resolvment occurs faster when you disclose the specific polymer involved.

If it's really an atom bomb "top secret" in your Company, you could justify disclosure by just telling us the generic class of polymer involved (e.g. HDPE, PVC, etc.).

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Posts: 4
From:Arden, NC USA
Registered: Feb 2005

posted February 18, 2005 07:57 AM               

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quote:

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Originally posted by zabielski:
Idea's is all that can be offered - but resolvment occurs faster when you disclose the specific polymer involved.

If it's really an atom bomb "top secret" in your Company, you could justify disclosure by just telling us the generic class of polymer involved (e.g. HDPE, PVC, etc.).

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The material is an acetal polymer that is used for this part.

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Posts: 385
From:McHenry, IL USA
Registered: Nov 2002

posted February 20, 2005 03:51 PM               

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Thank you. I'd look at the venting design, as well as the molds, cooling pattern. Also look for correct hook-ups of the cooling hoses. It's a common overlooked problem.

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Posts: 1
From:Science Hill
Registered: Nov 2005

posted November 14, 2005 07:34 PM               

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I would have to agree with zabielski,
sounds like you have some trapped gas inside the mold.vents may not be cut deep enough for the vents to work as they should.

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