Hi all,

I have just purchased my first kits from easy composites. Thanks guys for the training videos, they are very simple to understand.

In making my first part I have experienced a couple of issue and would like to understand where I went wrong.

1.  I used MDF to make my mould, I apply several coats of wax and PVA release agent but could not release the MDF part from the mould, what did I do wrong, did I need to spray the MDF part first?

2.  I had some issues with moulding my carbon part due to the tight spaces and complexity of the part, would I be better off using the vacum method for this part?

Many thanks,




Matt

Hi Matt,

Thanks for the post and I'm glad you like what we do.

First off, your mould not releasing from the MDF pattern; sadly, that's no suprise at all. MDF is a very porous surface and needs to be completely sealed before you can use wax, pva or any other type of release agent. The two ways I would suggest for sealing MDF would be either Shellac (sometimes called sanding sealer) or 2 pack filler primer. You'll hear us talk about 2 pack filler primer a lot on this forum because it's our favoured method for sealing patterns. Don't ever be tempted to use a one pack (rattle can) filler primer, paint, primer, lacquer or varnish because they're very likely to cause release problems. You can get Shellac from B&Q or most DIY places; it's pretty old-school and you need to build up lots of coats with a rub down between each one but it's easy to use (no special equipment) and it works. 2 pack filler primer would be available from any paint suppliers (body shops, auto-paint suppliers) but needs a spraygun/compressor. Painting epoxy resin would be a third option and would also work well however it's a harder material than paint or shellac and so would take a bit more flatting and polishing.

Once you've used any of these processes to seal your pattern you'll find that you can put a much higher quality finish on the pattern before then applying your release agent and pulling the mould.

As for the part itself and the 'voids' that you've encountered; under the circumstances (a very difficult shape) I actually think you've done pretty well. A shape like this with lots of angles and returns will be very difficult to make without either a matched mould, vacuum or some other positive pressure because the carbon will always want to 'spring' itself straight in those corners and cause the voiding that you can see. Any vacuum assisted process (vacuum bagging, resin infusion, pre-preg) would make this much more possible. A possible suggestion that doesn't need all that extra equipment would be to just get some pressure on the inside of the laminate; the simplest way I know to achieve this is to put release film on the inside of the laminate after you've wet-laid the part and then to put one or two car sponges on the back and then press them down as much as you can before clamping them in place. This will keep some pressure on the back of the mould, holding the carbon fibre against the mould surface and hopefully preventing it from lifting off, leaving the voids that you see.

I hope this helps and look forward to seeing your next attempt!

All the best, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Hi Matt,

Thanks for the quick response.

I did add serveral layers of watered down PVA to try and seal the part.... I now know this is not the way forward.

OK I will use 2 pack filler primer, I have the required equipment in my garage for this so no extra expense for this. 

I think I will go the vacum route as I have a few other parts that I want to make, they to will be complex shapes.

Thanks again.

Matt

PS I will post the results once I have finsihed the part

For sealing MDF i have used Bondaseal G4 primer, its a moisture cured polyurethane primer that is often used to seal concrete.
It doesnt give a great finish but for a one shot mould for a repair or to produce a mould that can be worked on its fine, you will need to wax it & pva it for a decent release.

I usually seal MDF patterns with a 2 pack high build primer.  I flat this with something like a 320 DA disc.  I thrn lacquer that to get a nice glossy finish before using easylease.  This approach does require you to have a reasonable finish on the MDF.  You can get polyester based primers / topcoats designed specifically for this job.  I think its called crystix or something similar and you can use that for some final filling of gaps etc but it will then need sanding / polishing if you want it to be a glossy finish.

Thanks for the tips guys.

Hmm, thats rather irritating.  Does your MDF plug have parralel sides in its centre recess?  You really need a slight angle to get a good release?  The other Q I have is how many coats of easylease / wax did you use?  Whilst its a difficult part to make I'd have thought you'd have got it out OK.

Yes the part does have parallel sides on the center recess, I don't have enough room to add any signifigant angle to the internal walls.

From memory, 3 coats of easylease and 3 coats of wax.

I will try again and see what happens, the fun of making your own parts...

It will be the parrallel sides that are causing you issues.  You need at least a degree to stand a chance of release.  I've just made a plug from MDF.  I primed it, flatted it back with 320 grit discs, 7 coats of easy lease followed by 4 of wax and I just checked a drip of gel and it comes off OK.  Make sure you buff it up well after each coat of release agent / wax.  Fingers crossed for you.