melting UHMW

[Hobbiest]

Outside on my smoke break from the kids, grabbed some UHMW shavings and fired up the propane torch. It smokes a little, probably because the flame was concentrated on it, not the vessel, but once it cools it still retains its lubricity! Don't do this on the stove! bad fumes! had to get the kids out of the kitchen...fast! exhaust is on now. Will try more when the wife gets home. Anybody ever done this?

[CraftWorx]

Sounds interesting!

Might have to play with that idea.

Are you looking at casting some parts? At least that is what pops in to my mind.

Ace

[Hobbiest]

yeah...slides...maybe injection mold later on

[chuckknigh]

What kind of temperature are we talking about? I still have quite a bit of my cutting board left, and slides might be a good use of what's left. I don't think it's truly UHMW, but it's hard, waxy, and slick.

Maybe just warming it to soft and forming it would be a better approach for me.

-- Chuck Knight

[Hobbiest]

I think that this stuff has a pretty low melting point. I melted it with a small propane torch in no time, so it can't be more than about 500deg...in fact that would be generous. Course I'm used to melting aluminium...1300 deg F, 3/4" propane burner, 20 psi of gas, blue flame about 18" long! Sounds like a small jet engine. I am starting a new job tommorrow, in a machine and fab shop! It'll be weird...haven't worked a job for 9 mo...took the wife up on her offer of "you think its so easy being at home with the kids!"...she had a harder time than I did! Anyway, if I get any time after work to fart around, I'll do some more tests. I think that cutting board is some kind of nylon. The main advantage that I see of actually melting it, is great surface quality once re-solidified, and close tolerence. I'll get some pics up as soon as I got some!

[strat]

i did a search and melting point is like 276 F pretty low i picked a a stick of this stuff not to long ago machines fine but i like the thought on the melt and mold ..............

[strat]

http://www.garlandmfg.com/plastics/h...mingparts.html
they talk a bit about it here

[CraftWorx]

Was just wandering. What kind of pressure levels (psi) are required for injection molding.

Would you use your CNC router to make the dies or molds?

Aaron

[ballendo]

Chuck,

Glad you brought this up...

Cutting boards are NOT generally UHMW. They are nearly always a related plastic called HDPE (High Density PolyEthylene). Milk jugs are "regular" PE.

The difference between using cutting board material and REAL UHMW (Ultra High Molecular Weight- the PE is assumed when the term UHMW is used) is great, especially when there is a constant force against the part in question. UHMW is FAR better at resisting "cold flow".

As far as injection moding is concerned, there is an inexpensive book by Vince Gingery--offered by lindsaybks.com -- on the topic, and there have been a couple articles over the years in the village press mags Home Shop Machinist, Machinist Workshop, and Projects In Metal...

Ballendo

P.S. For best results with plastic bearings, use a VERY THIN wall thickness, and back it up with something structural, like alum, steel, or perhaps wood. The plastic movement due to temp and humidity is far greater than you think, and the use of thin sections lets you get the benefit without some of the costs. Bottom line is that your machine(s) will work better, and be stiffer...


[QUOTE]Originally posted by chuckknigh
[B]What kind of temperature are we talking about? I still have quite a bit of my cutting board left, and slides might be a good use of what's left. I don't think it's truly UHMW, but it's hard, waxy, and slick.

[HuFlungDung]

Anybody seen This Hour has 22 minutes lately, where they have the guy interviewing the "scientific layman", Bob McDonald (or a charicature of him?)

I can imagine the dumb reporter asking,

"Then, you'd want to make sure you're in good physical condition before you try lifting a piece of this Ultra-High-Molecular-Weight polyethylene, then? Should a person get their doctor's okay first?"