I like chemical polishing

[Evan]

I CNC'ed a part for a small project today from polycarbonate and to finish such parts I have been experimenting with chemical polishing. For acrylic and polycarbonate methylene chloride works the best. And boy does it work! It will make even a cruddy tool marked fuzzy part look good. The part turns crystal clear in just a few seconds. All you need is a shallow metal or glass container with a glass cover so you can see what is happening. For this part a cleaned tuna can is perfect. I put a small metal nut in the bottom to rest the part on. Pour in a teaspoon of methylene chloride, place the part on the spacer and cover the can with the sheet of glass. Then direct a hair dryer at the can for a few seconds until the MC begins to visibly evaporate.

In less than 60 seconds the part will suddenly become entirely transparent. Remove the lid immediately and wave some fresh air over the part. After a few seconds carefully pick it out of the container using some needle nose pliers or whatever will work best. Let it dry out for a couple of minutes and that is it.

Naturally, metheylene chloride is on the chemical bad actor list. It can be found at your local supplier of plastics or a shop that makes plastic products. It is no worse than the fumes from gasoline or other volatile solvents but because it has very little odor it is very easy to have enough in the air to be dangerous to health and also pose an explosion hazard. Do this out side or in the garage with all the doors open and you won't have a problem. Do not eat or drink etc... Store outside the house in a metal container.

It can also be used to wipe down the edge of acrylic or polycarbonate after machining and will turn it glass clear instantly. once the part is treated it should be allowed to dry for at least 10 or fifteen minutes. Parts that have been treated and will subsequently be fastened together should be allowed to dry for at least an hour to prevent gluing, unless you want them glued. It is the recommended solvent for gluing these plastics.

The part, which is intended as the rotor in a small centrifugal water pump.

[Liger Zero]

Ain't plastic nifty?

You can also flame-polish and flame-debur some materials. It's a knack. KEEP THE TORCH MOVING!

[Evan]

Flame polishing doesn't work on polycarbonate unless you first bake it in the oven for about 4 hours to remove the water adsorbed in the surface. If you don't, it forms lots of ugly little bubbles just as it begins to clear.

[Doc Nickel]

A magnetic water pump impeller, if I'm not mistaken.

Doc.

[Evan]

Yep, magnetic drive. It's nice not having moving seals to deal with.

[Bill in Ky]

Always nice to read your post's Evan, thanks!

[rockrat]

Enjoyed that post Evan, thanks.

I didn't know about that trick. Although, I have flame polished polycarb without the bubbles. Maybe just luck because I have also flamed it and found the bubbles appear. Now I know that I have a better alternative!

rock~

[Dawai]

They do the insides of some very expensive stainless instrument tubing the same way.. HOW??

I got a four foot piece made into a blow-dart gun. Found a mouthpiece that just fit the tubing. It's shiny too..

Seems it was over a grand per hundred feet. I ordered special roller benders to put it together. I forget why it was spec'ed. I had a piece of titanium stuck back behind the door to make me a large bore toy.. had to turn it in, had to account for every scrap of it.

[lazlo]

They do the insides of some very expensive stainless instrument tubing the same way.. HOW??

Stainless steel is electropolished -- very different process.

[Evan]

That is something else I intend to try. The thing that has held me back is dealing with boiling hot acids or alkali liquids. I'll have to build a "hot glove box" to do it in .