what do i do with cracks in my mould

I think its because i had to be a bit aggressive getting the mould of the roof

There are also some very fine cracks which the camera wouldnt pick up

How do i fix them as it was an expensive mould and i dont want to scrap it

Wouldn´t it be possible to go over it with a thin layer of high viscosity epoxy and then sanding it down?

Hi,

I had decent results with this method:

01). Lightly working the crack and direct surrounding with a dremel tool, literally digging the mold. Your mold is made of mat, so its not like you were gonna break cloth fibers, which are supposed to be structural. Deepness would depend on ur mold thickness and / or how extended is the crack.

02). Fill the "hole" with resin or gelcoat. When i used this method, it was on the gelcoat side, so I filled it with gelcoat. if you have to work on reinforcment side, i would suggest using filler powder added to your resin or even finely cut glass mat.

03). Put a non stick film over it, taking great care not to push thru, so you would have an "indent". As the "non stick film", I used aluminium tape that I waxed, turn it upside down so the alu would touch the gelcoat and not stick to the mold. The tacky side of the aluminium tape would stick to another aluminium tape that this time would be applied on the mold. Dunno if it make sense, english is not my main language.... Maybe there's an easier way to explain it

04). When cured, release the aluminium tape. You should see a recess of gelcoat / resin. Goal is to have it above mold surface, but as low as possible to minimize sanding work.

05). Sand and buff if necessary.


I put a wonderful and artistic Paint drawing to this post. One day it might be worth $ 10 Millions.... Or not.


i used this method on a mold to produce parts that would use sandable gelcoat (parts produced are supposed to be painted), and I could achieve decent results for that specific application. i bet a very good result can be achieved by just spending more time on finishing.

one thing i did try too is to bond steel extrusion structure to a larger mold to rigifify it. It never disappointed me so far. Dunno if it helps get rid of cracks but I never saw one appearing once structure was bonded to mold.

Did u try to use compressed air to give a little demolding persuasion? Sometimes it helps. Also, if you use pva, it can be dissolved with resonably hot water, which could help release the part or mold-from-the-plug a little bit easier.

All this is given regarding my humble experience, so a good idea would be to wait for more inputs, but i hope it helped.

 



 


    A $1000 electronic device will always protect a 10 cents fuse

THANKS LADS,

WILL GIVE THAT AGO THIS WEEKEND UNLESS SOMEONE COMES UP WITH ANOTHER

BETTER SOLUTION,

Hi Daz,

Joe has got it about spot-on... the method we have used in the past, normally due to a dropped mould, is to dig out the length of the crack with a dremel bleed in some gel-coat and cover it with release film, (Joes foil method sounds great though) after curing it's a case of sanding it flat and polishing it, there's no quicker way than this, that I am aware of. 

The only thing worth pointing out is that you should not ever have to force something from the mould, with properly prepared moulds/patterns the release should never take any real effort, if you are hearing bangs creaks and cracks when you are releasing, or it takes longer than a minute then you need to address your surface preparation, from painted patterns we use easylease followed by release wax, for the moulds we just apply easylease, using this system we have produced hundreds of moulds and thousands of components and never had a 'sticker' getting your release right is something that will make everything a bit less stressful!

Paul Statham
Easy Composites / Carbon Mods - Technical

Cheers ,

I have been having a go today joes method hope it turns out ok.

I will have a go with commpressed air next time,

I may have to paint the part now if it comes out the mould dodgey

Ohh well everydays a school day  LOL

Thanks for the replies,

PS What can i do to the mould to make it 100% release my carbon part

i have no8 release wax and easylease is there anything  better than what i have ???

As Paul says, its all in the preparation of the mould and as he says using easylease on the mould to make the carbon part has not caused problems with releasing the part.

Perhaps a picture of the full mould may help.

I found on one project i did, I was trying to release from vertical edges which was difficult as it only takes it to be a fraction of a milimeter out on the mould for you to get mechanical lock.

i think what joe said was exactly what i always do but before adding the gel coat to the crack u diged i put a normal paint paper tape around the crack so i wouldnt mess arround so i wouldnt need to sand more than i should , if u want something more strong and faster, i put normal epoxy the two that u mix together ,it works and can be sanded and polished too.

also you can add a layer of pva (2 layers) which will result in fast release.

hope this will add an idea. also as joe said this is a way i used not an exact expert how it should be done.

best regards mhd alghoul mhdghoul@hotmail.com youtube channel :atmospherejo link is http://www.youtube.com/user/atmospherejo?ob=0&feature=results_main

Hey daz,

Any good news ?

 



 


    A $1000 electronic device will always protect a 10 cents fuse

Thanks for the replys ,

Yes good news Joe

I think its going to be a goer

Have filled the cracks with the new black gel coat ,,