neilc said:
If you started sanding plastic at 80, I can imagine you'd never get the scratches out of it. And you're probably heating it up causing even more challenges.
It can be tough to guess the highest effective grit to take out scratches, so I usually go one step higher than I think I should and work back if necessary.
Some on the FOG in the past, have said RO90 and 125 are more of a learning curve than 150. I wouldn't know. Do not have them. What I can further suggest is be gentle but let them know you are in charge. You may also find a hard pad easier at first.
I've never used the 90, but having spent many hours with both the 125 and 150, I would say that it is easier to get the 125 to submit to your will. The 150 isn't really harder to control (balance), but when it gets traction in rotary mode, it will pull much harder and travel farther than the 125.
Most of my plastic polishing experience is with acrylic solid surface material. However, I have done a few projects where I polished polycarbonate (laptop shells). This summer, after I bought my own RO125, I had to try it out on the fogged-over headlights on my truck. When your favorite tool is a hammer, every problem looks like a nail...
I didn't use anything but the discs packaged in the systainer, and I didn't have much to lose if things went south, so I started out with 220 and didn't make much progress. Usually, I would step down to a lower grit, but instead I just switched over to rotary and used the Rotex more like a grinder to take out the heavy scratches, then back to RO to clean it up. After that it was RO the rest of the way out with 400 and 2000.
Those seemed like huge steps to me, but I was just using what was available, and it was acceptable for the project. I wet sanded the 400, but the 2000 was dry. I cleaned the surface with denatured alcohol between grits (habit). I didn't have a bonnet or anything, so I improvised with a microfiber cloth stuck to the hook pad and buffed it with some really light compound. Definitely not the method I would use if the project was vital or for pay, I would go get the proper grits of discs, as well as the proper density of pad. Polishing compound curves without a soft pad (or even a hooksaver pad on the stock pad) is sort of a losing proposition. Oh, yeah, I'd probably hook everything up to dust collection as well.
I have used 3M discs, Abranet/Abralon discs, and Festool discs for a variety of sheens when polishing acrylic. I'm of the opinion that the Festool and 3M Tri-Zact abrasives last much longer than other options in the 80-320 grit range, and for flat surfaces the paper-backed discs definitely outperform the Abranet discs. I never came across a 3M product that works like the Abralon or Festool Platin discs, which really work great at high grits, dry.
