Cnc machining uhmw

Cnc machining uhmw

Milling plastic is about as easy as it gets. I make my own recycled HDPE loafs of plastic to machine out of blow molded plastic bottles.

So you don’t have a deposit applied to plastic bottles to be refunded when you return them for recycling in your country? That had some very notable social impact on people without income in addition to the actual recycling over here.

@Marcus_Wolschon Years ago we had a deposit on glass beverage bottles. But that was just a pain for consumers so it was removed. Now we just have mandatory recycling containers. Which has a notable impact on people with income. If it is about money then it is best to target people that have it.

I’m in the process of squaring up my last run of plastic blocks that I made now.

I fly cut them on my milling machine to clean them up. They come out of my mold pretty rough.

Silicone mold?

@Marcus_Wolschon Sheet metal. HDPE shrinks a lot as it cools. It warps a lot too. I am not sure how commercial manufacturers deal with all of that. I know I have run into issues with internal stresses machining pieces I’ve made. Which is one limitation in all of this. I made these parts that ended up not working. Due to the depth of cut in the middle they just curled. That caused misalignment. I’ve tried annealing a block, but so far I have not machined that one to see if that relieved the stress, or not. Just what happened to that block when I reheated it I’d say was somewhat of a failure though. I let that part cool not clamped and it ended up with quite a muffin top. It is a problem I’ve no practical solution to yet. Overall for a lot of things homemade HDPE remains a useful prototype material in my shop though, despite its limitations. It is fun stuff.

I had that problem trying to recycle machinable wax. Anything thicket then 10mm would crack under internal stress when cooling. You could try to let it cool very slowly

@Marcus_Wolschon Yeah I’ve tried that, and others have tried it. A few say it works, most say it doesn’t. I’m in the doesn’t work camp myself. The stress comes from how the plastic is cooled, which is under clamp pressure. If you don’t clamp the plastic you get a lot of bubbles, and a piece shaped like a potato chip. Now I’ve taken a clamped piece and melted it again, then let it cool without clamping it. But then it warps. Well part of it is shrinkage as it cools too. Let’s just say you get a random shape when all is said and done. It doesn’t matter how slowly you cool HDPE either. It always screws up. well, the slower you cool it the slower it screws up. But in the end you always end up with a screwed up piece. At least that has been my experience. I find it easier to simply accept the limitations. As fixing them so far has proved to be rather impractical to me.