acrylic polishing

[900steve]

i've got a part machined from acrylic that i would like to polish. has anyone ever used a chemical polishing method, rather than an abrasive method to polish acrylic to a water-clear state?

thanks.

-steve

[JavaDog]

I've always done my polishing with compund and a cloth/wheel, or flame-polish for edges if tolerance isn't an issue. Of course, complex designs are a bit tricky that way (small inside corners, etc).

What type of chemicals are you looking at?

[Geof]

I have worked a lot with acrylic and I think it will be difficult to find a chemical (which will have to be a solvent of acrylic) that can give you a polishing effect without causing the acrylic to craze. The crazing may not happen quickly so if you find anything that seems to work I suggest you do a test piece and wait for several weeks before trying it on something valuable. Also any machined components should be annealed first. It is possible to get away with leaving out the annealing step when abrasive polishing is used but the finished surface is very prone to crazing even when it is only exposed to the vapors of numerous solvents.

[900steve]

i dont have any chemical in mind, but just from hearsay, i was told that there is a known chemical polishing method, rather than abrasive. i'll see what i can find out, but so far it looks like it's going the abrasive way.

[InspirationTool]

I've used flame polishing with a mapp or propane blowtorch. I have NO idea what this does to the mechanical strength however. You have to be careful not to cause bubbling, but it does work well.

Probably should be done outside as well.

-Jeff

[automizer]

I have been looking in to this too and have found some things that could work but as Geof said crazing is a problem. Trying to avoid buying a lot of products to try this out I have just played with flam polishing and buffer wheels as I have all the parts already in my shop. So far my biggest problem trying to polish a large surface is having the cut marks as fine as possible. You almost have to Polish befor you polish. What exactly have you cut? is it just a flat piece or do you have a fine 3D relief?

[InspirationTool]

I flame polished a part that was turned on a wood lathe.

-Jeff

[CNC Pro]

I noticed a new tool in the Onsrud catalog; it appears to be the body of a 2-flute style router bit without the brazed-on carbide. It’s coated in a diamond dust and is for polishing routed edges of plastic. Anyone here ever try one?

[automizer]

CNC Pro do you have the bit number? I would like to look this one up. You say its polishing the plastic is it for just a finnish cut do you think?

[ImanCarrot]

I use single point diamond tools on my ultra- precision air bearing lathe to cut Acrylic and other materials giving an OPTICAL finish straight of the lathe.

Single point mono crystalline diamond tools are the way to go- don't use poly crystalline- that gives a bad finish.

I've been polishing glass, germanium and plastic for over 15 years and only ever heard of ionic chemical polishing as an alternative to mechanical polishing or single point diamond turning, but as I recall it was a laborious and costly process.

There's an excellent product for Acrylic polishing called "Magic Polishing Compound" which beats CR39 polishing compound, Cerox and Rouge due to it being in a suspension (less caking and hence less scratches).

I've no connection with the company or biased interest, but would recommend their product unreservedly.

http://www.ceriumoptical.com/Magic.htm

[CNC Pro]

Hey automizer,
The Onsrud diamond tool I mentioned was the 75-000 series. They seem to offer them in straight (Part # 75-002) as well as different “profiles” such as (Part # 75-006) which appears to be for 45 degree chamfers as well as one with a .020” corner radius (Part # 75-012).
They are designed for finishing Acrylic and polycarbonates.

[automizer]

ImanCarrot with your experience in polishing you see people on the board here with there Lithofanes I'm wondering if you cut something like that out of clear is there a way to get it back to clear. Say with that product you talked about what type of machine could you use to polish it