Need help with sanding/buffing PLASTIC.. which compound etc?

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smokedlights

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Well I am pretty good at buffing out fresh black paint etc.. I am running into a new problem. Often times I sell tail lights or used lenses and am pretty anal so I like to clean them up nicely. I am finding it extremely difficult (compared to paint) to sand out defects of plastics and then buff..

Im thinking I need a different compound and/or pad/technique? If I even go 1000-1500-2000 3m compound on 3'' 3m purple pad I am have a tough time removing scratches. It becomes next to impossible to get any major scratches out of them because I can never get the sanding scratches out.. The only thing that remotely works is wetsand with 2000 ONLY, and buff. But again I cant get any kind of defect out with only 2000.

Im thinking of trying 3m superduty compound or This> Says its for tail lights/plastic? Buff Compound Plastic 13 oz Tube

Suggestions?
 
start a little lower on your grit. even the 3M kits start you out at 400 then 800 then 3000.

I go 400, 800, 1500, 2000, 3000, then use a orange Buff and shine with a heavy cut compound. (btw i do not like 3m finesse it) I use Megs UC or something along that line. then Ill use UP and then the megs uv protect.

even doing that, I uncovered some deep blemishes someone else put in the lights. the best you can do is reducing them to a less noticeable condition. or buy a new light. if you take it down too much you will make the lens to thin or warp.
 
ya thats my problem im afraid of, even if I go below 1000 im having a HARD time getting the scratches out even after working up to 2000 afterwards. If I go any lower my problem will only get worse..
 
The issue is likely that you are not completely removing the 1000 grit scratches with the 1500

Removing 2000 grit scratches should be accomplished with most compounds
 
That is Correct Allen. That is kind of my question, Im use to working with clear coat/paint etc. Straight polycarbonate is different apparently in how the sanding works and how each one takes out the next. It seems as if 800 doesnt take out 600 as easily, on plastic like it does clear coat etc.. same with 1500 doesnt take out 1000, and so on..
 
Lots of variables when sanding

- Over Lubrication
- Clogged Paper
- Quality of Papers
- Uneven Pressure

Mike Stoops has some good information on basic sanding that might fill in some of the blanks

I change direction when I change grit. It makes it easier to see when the previous scratches have been refined and are uniform with the new grit
 
Im quite familiar with sanding etc, like I said I can make black clear coat shine without any issues. Paper is new and not cheap, pressure is even Thats why im not understanding the straight plastic. Only thing I can think of is the plastic is softer then paint so even 2000 is making deeper gouges then it would on paint in which case I think a more coarse compound would work...?
Perhaps I need to change to some kind of product just for plastic? Or 3m superduty compound? Just dont want to be tossing money on random stuff. Tail lights are softer then headlights too it seems because I can refinish a headlight starting at 6-800 and work my way up and buff without issues..
 
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