Press Fit Plastic parts
Press Fit Plastic parts
(OP)
Presently press fit a thin walled PTFE .1000 inside diameter part onto a PEEK part to create an air tight seal. In time I noted the PTFE to cold flow enough that I suspect low pressure air may get by. I'm looking to replace the PTFE with another material. These are screw machined parts that need to withstand mild acidic vapors The PEEK material is $$, we use 100 parts per assembly, so cost is a factor. Delran is OK but may become stiff after much exposure to the acidic vapor. So low cost, mild chemical resistance to acidic vapors, resistance to cold flow to maintain a slight PF & ability to easily screw machine thousands of parts are key. Any suggestions are most welcome, thank you.





RE: Press Fit Plastic parts
It's also a plastic, so by definition will move so as to relieve any applied stress.
It is therefore not the perfect material for this application, aside from its chemical resistance.
It might be possible to improve its effective lifetime by increasing the wall thickness a bit, and more so by providing something that will continue to apply stress even when the PTFE moves, e.g. a tight fitting rubber sleeve or even a heavy o-ring.
Most/all successful tube joint systems for PTFE store strain energy in some material other than the PTFE, typically an o-ring somewhere outside the fluid boundary.
The first alternate material that comes to mind is polypropylene, which is cheap, but very difficult to machine accurately. It can, however, be injection molded, so it may be worth exploring in that form.
Mike Halloran
Pembroke Pines, FL, USA
RE: Press Fit Plastic parts
RE: Press Fit Plastic parts
We use KEL-F http://en.wikipedia.org/wiki/Polychlorotrifluoroet... some solvent & acid vapor applications.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Press Fit Plastic parts
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Press Fit Plastic parts
Dgallup - injection molding cannot hold PF tolerances of +/-.0005", also the screw machined parts a about a dollar, a tool would be around $20K
RE: Press Fit Plastic parts
You have left out so much about your application. All that is clear are inflexible barriers for cost, size/shape, shape, and fabrication method. No information on pressure to be resisted, engagement length, install/remove cycles, tolerances on mating part interface geometry (smooth, barbed, ridged,) options for liquid adhesives.