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Appropriate metal coating for sealing LDPE bags

 

I am working on a project sealing LDPE bags. We are looking to seal the bags with 303 SS rollers and 6061 Aluminum sealing bars. I know that we need some form of coating on the tools to prevent the poly from sticking. I am currently looking at two options: a PTFE coating or a TiN coating. In addition to preventing the poly from sticking, I also need a low coefficient of friction on the parts. Overall tolerancing is not a major issue execpt for a bearing surface and threads on the rollers. However, from what I have read, neither of the coatings would present a major issue. I would appreciate any insight or direction that could be provided to me on this topic. Thank you very much to anyone who takes any time to answer my question.

Craig Armacost
- College Park, Maryland

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Hi, Craig. Do you have reason to believe that chrome plating is not the right coating? It is less expensive, more corrosion resistant, and offers a much lower coefficient of friction than TiN.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
 

This is for a food application. I have always been under the impression that such a coating shouldn't be used in this situation?!?!

Craig Armacost
- College Park, Maryland

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You may be right, Craig, but I've never heard that. I've seen packaging machinery, which the food is directly contained in, hard chrome plated for wear protection; toasters chrome plated; specialty bar spoons chrome plated. If there is a rule against it then it's high time I learned about it, so I hope someone will let us know :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey