Talk Composites - The Forum for Advanced Composites

Issues with what i think is shrinkage!

http://www.talkcomposites.com/Topic20817.aspx

By Undercover - 3/18/2016 11:06:01 AM

ive been attempting to make a mould. I got the part and cleaned it up, gave it 3 or 4 coats of #8 release wax. I also gave a few coats got the surface that the plug was sitting on. 

I gave it a good coat of tooling gelcoat, bit thick in places but a good coverage all over. I taped up any holes where i didnt want gelcoat or resin going.

I let that pretty much go off, so there was still a little bit of tackiness left. And starting laying. About 2 layers thick but up to 4 maybe 5 and intricate areas. 

I let it all dry and attempt to demould. 
As you can see from the picture, didnt go too well. Once i did get it removed i attempted to put the part back in but it wouldnt fit

Mould seemed smaller than part.  Any ideas?
By Hanaldo - 3/19/2016 12:11:11 AM

Then do 7-8 layers of the 300g. Your mould is no where near strong enough to demould a part like that, especially on the flanges. 

You need to change the angle of those mounting points. Just a small change would do (think 1 degree), if you use filleting wax to taper them then this would help immensely. 

Alternatively what I have done recently on a part with no draft angle is build a nut into the mould, so that you can thread a bolt in behind the problem area and push it out from behind. Of course you need to take care to seal the nut to prevent resin binding the threads etc.