UHMW: When To Use It, When To Not

Posted: April 24, 2017 in UHMW
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UHMWPE (Ultra-High Molecular Weight Polyethylene) often abbreviated as “UHMW” is one of the most popular and well known industrial plastics. UHMW is seen as a “Jack of All Trades” in many applications while being more available and less expensive than other plastic options. While this is true to a degree, UHMW has limitations that means it will not solve all problems in all situations. In fact, it has some properties which make it deficient and the “DIY” community should keep this in mind.

When to use UHMW:

UHMW excels at taking impact and it is virtually unbreakable, it’s also very slick and the colder the operating temperature is, the better it performs. This is why UHMW is so popular in applications such as toboggans or as rails on sleds: impact + cold + slickness are all important to the application, and it does really well in this application. UHMW is also easy to work with as it drills, saws, and lathes well. It functions as wear pads, sliding blocks, fenders, and in other impact absorbing applications.

When NOT to use UHMW:

The main application we here at Redwood Plastics see UHMW incorrectly used in is bearing applications. UHMW is a poor choice as a bearing for two reasons:

1.) it is difficult to machine to tight tolerances (+-) 0.02″ are the best you can usually hope for and

2.) UHMW has low load bearing capabilities (500-800PSI). In a DIY bearing application nylon or Tuffkast will be superior.

The issue with tolerances is important to hit home: UHMW is not a dimensionally stable material. Not just compared to metals but even compared to many other plastics. We regularly receive drawings and requests for UHMW parts where we cannot quote based off the requested tolerances (or have to get a written waiver for acceptable tolerances). This lack of dimensional stability extends to thermal expansion and contraction which is why it is so hard to guarantee tolerances: if the part is manufactured in 30 degree weather but used in 90 degree heat the dimensions of the UHMW will drastically change!

We hope this points you in the right direction if UHMW is or isn’t right for your project. But if you have questions, or might be wondering what an alternative material could be, please contact us and we’d be glad to help!

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