Talk Composites - The Forum for Advanced Composites

Pattern-Coat Primer over Vac-Cast Epoxy Resin ?

http://www.talkcomposites.com/Topic22803.aspx

By TURK - 2/27/2017 8:31:19 PM





Hi guys,



With reference to my 'Quad Headlight Project'.


I'm trying to remedy an issue I have .........  Basically,  I made two tooling plugs out of Vac-Cast Epoxy resin,  and because of the amount of shrinkage I got from the material,  my tooling plugs are 2mm too small.  What I'm hoping to do is to 'build-up' the tooling plugs by applying a few coats of Pattern-Coat Primer.  
Is This possible  ?

As a picture speaks a thousand words ( or in this case, a few pictures )  here's the process I used .......  I used CS25 Silicone rubber to make the moulds after I had made the original plugs.  I got shrinkage from the Silicone,  I then cast my 'Vac-Cast' Epoxy resin into my silicone moulds  ( got more shrinkage from the vac-cast resin ),  then I vacuum formed the parts I needed  ( headlight mounting brackets )  got more shrinkage from the 3mm ABS I'm using ........  the result is,  my ABS plastic headlight mounting brackets are 2mm too small all around their circumference !   Sad   >>

 





The vac-cast resin tooling plugs came out absolutely superb,  well chuffed with that  BigGrin   and my very first vacuum formed parts  >>

 



After I cut and profiled the parts things were looking very good indeed  >>

 



And with the headlight units installed  >>

 



Then comes the assembly ........  the parts I make will fit the OE headlight retainers,  as you can see from the red arrow there's a 4mm gap  Angry
As I only need the 'footing' or base of the part to fit inside the headlight retainer,  I'm thinking I could simply apply a few coats of Pattern-Coat Primer around the base of my tooling plugs to close that gap  .......  do you think this would work ?  >>

 







This fix is only a temporary measure guys,  until I get the dimensions correct,  once the bracket fits in there correctly I'll simply make some more silicone moulds with these 'fixed' tooling plugs.

The entire process is here >  T4 Quad Headlight Project









Thanks all.





TURK
By TURK - 2/28/2017 12:46:03 PM





Excellent .......  that's good to know Warren  Smile

It's only 2mm all the way round the footing,  so not much,  will take a while to build it up though.
I can just use those 'modified' tooling plugs to make some more silicone moulds afterwards ........  once I've confirmed the fit.

Think I'll use the AS40  'addition cure' (platinum cure) silicone rubber for the next moulds as we discussed on the phone,  should be more stable with less shrinkage.


Thanks for your help mate, very much appreciated.




TURK