Filler for use with ABS plastic?

[Akshay]

Hi can someone recommend a good filler to use on automotive ABS plastic? I have cut a section out of ABS plastic which is to house a light but I need to fill in the rough edges. I've done a trial run with Isopon P38 filler but found it can leave a fine pitted surface which shows up after painting (spray can).

Is there a more suitable product to use on plastics, because most of these fillers refer to metals in their application.

 

[Diyisfun]

In my previous life I used to use tons of P38 & equivalents, you can get this so fine its like glass. You fill, rub down using wet & dry, then fill again using a piece of plastic to wipe over as you fill, then rub again.
THey use it for car repairs & paint over it without the air holes showing.

 

[Akshay]

Thanks. It seems that all I need then is to use some good old wet and dry paper and a little patience to get the finish I need. Can I assume that this will also help mask the division between the filler and plastic?

 

[Diyisfun]

You will not see the join, but the problem you have will be with cracking, caused by flexing & expansion rates.

info
I had a builder start fitting doors & door furniture for me, unfortunatly he fitted the handles where he wanted them, not where I did. I got him to fit where I wanted & I filled the holes, he was amazed at the result, it was a painted paneled door I even scratched the wood pattern back on.

 

[Akshay]

Ok thanks, there is another product which is used on plastic bumpers and allows for flexing but can still be sanded. Should I consider this sort of filler over the P38? I was thinking of doing some temperature testing (in freezer, then microwave), to test for thermal effects on my prototype. What do you think?

 

[Diyisfun]

Forget the microwave idea, m/waves work by moving water molecules.
Whatever you use will crack. I used to patch polystyrene sheet for protype domestic appliances, if people know its a sample or development its accepted.

 

[Symptoms]

Ak - I bet you didn't use a primer/filler spray before your finish coats. As the name suggests this is the coat that gets rubbed down with wet and dry, and with repeated applications (sometimes one is enough but usually more) done until you are left with a flat 'unpitted' surface. It is this surface that gets the finish.