Cutting UHMW?

[Joe Pelonio]

I have a customer asking for a quote to cut a few hundred items from UHMW (Ultra high molecular weight polyethylene). I never ran into this material before, has anyone tried to cut it on a laser?

[Larry Bratton]

Extremely tough stuff. I doubt the laser will cut it. CNC maybe. Just a guess after reading the info about it.

[Jim Beachler]

It will cut best with woodworking tools. Such as cnc or saws.

[Mike Milli]

I have actually been wondering the same thing. I have some scrap pieces of 1/8" UHMW coming for a trial run. I will let you know how it goes.

[Joe Pelonio]

I have actually been wondering the same thing. I have some scrap pieces of 1/8" UHMW coming for a trial run. I will let you know how it goes.
Please do. The parts he needs are pretty small for a CNC.

[Dan Hintz]

Joe,

Due to the density, you'll get a lot of melting...make sure you cover everything with tape to keep the edges clean. If the parts are really small, you may not get the degree of accuracy you need due to the melting.

[Jim Beachler]

How small of pieces are you talking about??

I cut pieces on my machine down to less than a 1" by 1" square with no problems.

Jim

[Joe Pelonio]

How small of pieces are you talking about??

I cut pieces on my machine down to less than a 1" by 1" square with no problems.

Jim
I think they are more like 1/2", but I'm waiting for him to send the artwork. One of those Monday-Friday places. It sounds like it may be similar to High Density Polystyrene which I have managed to cut, but leaves a rather rolled edge due to melting, and that may not be acceptable for this application.

[Michael Hunter]

How thick is it?

I have done lots of 1mm thick stuff : it does have its problems ...

You need a hot cut (high power/slow speed/high ppi) in order that the molten plastic can be blown away by the air-assist before it sets. (See Andrea's recent posts about that problem).

The molten plastic tends to flow over the bottom of the work, so as Dan says, use tape *** if it will stick *** to protect the bottom. Protecting the top results in a narrower kurf if you need very accurate sizes.

Masking or laser protection tape will stick reasonably well to clean sheets with a smooth surface. If the surface is rough it won't stick (the last sheet I processed looked as though it had been extruded between hacksaw blades).

Beware of flare-ups, particularly if you have tape protection that isn't sticking well. The loose tape acts like a wick and makes flareups much worse.

If you are cutting small details close together, you may find it helps to split the job into sections so that you don't cut adjacent parts one after another. (i.e. the material has a chance to cool down a bit before the next cut in that area).

Hope this helps.

[Joe Pelonio]

Thanks for the tips. When I did the Polystyrene I found that transfer tape misted with water helped a lot. He hasn't yet told me the thickness, but I'd guess about 1/16". The e-mail came late Friday before I got back from my day job, so I expect to hear more details tomorrow when I'm home for the holiday (I doubt his company takes the day off).

[James Rambo]

Joe, I know this is an old thread, but how thick was the UHMW and how did it cut. I have a similar job (small parts). Thanks. Jaime

[Joe Pelonio]

Wow, this is an old one. His thickness was 1/16", and while it cut fine, he eventually decided that he liked the look of sandblasted ABS better, and switched to it. I have done probably 8-10 jobs since for them with as many as 1.500 parts made of the stuff and they have been very happy with it. A little stinky but cuts cleanly if I apply transfer tape first, otherwise it leaves some residue on the surface which is not acceptable as it show on their finished product. It also tends to be warpy so I have to stick down the center to the vector grid to keep it flat.

[James Rambo]

Thanks Joe, I will also be cutting 1/16" the parts are to be 1" and larger. I will probably use blue masking tape top and bottom to keep the part clean. I have a good exhaust fan and neighbors about 1/4 mile away. I have some 1" and 2" square pieces of 1/4" thick lead that I use to keep stuff flat.
Thanks for the answers.