Post curing mould (and the part)

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Post curing mould (and the part)

Author	Message
Warren (Staff)	Warren (Staff) posted 5 Years Ago HOT Post Details
Group: Administrators Posts: 2.5K, Visits: 8.5K	It looks quite tight on some of the curved wing edges - but hard to see properly so may just be the photo's. Also you can get vacuum that is hard to break sometimes. Also consider possibly the resin hadn't fully cured at first attempt as epoxies in particular, grip the mould surface if a little bit green. Warren Penalver Easy Composites / Carbon Mods - Technical Support Assistant
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okkim	o okkim posted 5 Years Ago HOT Post Details
o Group: Forum Members Posts: 14, Visits: 102	Yes, but I don't understand why. The fenders go in and out in the mould easily now. Edited 5 Years Ago by okkim
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Hanaldo	Hanaldo posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	So it released ok but was mechanically tight?
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okkim	o okkim posted 5 Years Ago HOT Post Details
o Group: Forum Members Posts: 14, Visits: 102	I got the fenders off! They were super tight!! The paint wasn’t stuck as I thought. I used wooden long wedges to pry those off. First I heated the fenders but it didn’t help.
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okkim	o okkim posted 5 Years Ago HOT Post Details
o Group: Forum Members Posts: 14, Visits: 102	Gelcoat was cured in a room temperature (about 20C). I didn't heat it. So then it must be the paint I used. I'm so pissed right now I will try to heat it and then maybe add some thinner to break the paint.
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Hanaldo	Hanaldo posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	Oh dear... This is heartache. The heat won't be the issue if the gelcoat cured at room temperature. If you accelerated the cure of the gelcoat by applying heat before it cured, then this could mess with the release. But once already cured, the gelcoat can't then bond to the substrate if it is later heated. So I daresay the coating on the pattern was not compatible with the gelcoat and it has reacted and stuck. Either that, or an application issue. None of that really helps you now, but unfortunately there isn't much you can do now. Heat may help, as polyesters break down quite quickly with heat and you may be able to damage the gelcoat enough to break the bond. Realistically I think brute force is really the only thing that is going to get the part out, so chances are it is going to get pretty damaged in the process.
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okkim	o okkim posted 5 Years Ago HOT Post Details
o Group: Forum Members Posts: 14, Visits: 102	Yes, I can see that now. But how can I remove the fender without bending or breaking the mould?
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oekmont	oekmont posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 550, Visits: 27K	Wax release agents are usually known for their problem with elevated temperatures. The one in your link explicitly says that it's for room temperature use only. And the sun heats things up very unevenly. It could be that some spots got even higher than 55°C.
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okkim	o okkim posted 5 Years Ago HOT Post Details
o Group: Forum Members Posts: 14, Visits: 102	Maybe this does not belong to this thread, but my fender is now stuck in the mould badly I got the flanges out, but the paint is sticking to the mould. I'm SO annoyed. I used plastic wedges to pry it out, but the fender just starts to bend. I also tried air pressure, and high water pressure washer without luck. Could I heat the fender? Ot could I apply thinner in between the mould and the part? I used this release wax: https://composite24.co.uk/mold-wax I had the mould some hours in the sun about 55 degrees C, could that affect to the release wax not to release? I'm afraid to use it again!! Edited 5 Years Ago by okkim
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Steve Broad	Steve Broad posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 408, Visits: 4.1K	+x Hanaldo - 6/24/2020 12:57:21 AM +x Steve Broad - 6/23/2020 8:15:57 PM +x Warren (Staff) - 6/23/2020 4:13:47 PM Although Steve is technically correct, sometimes it is nice to be able to post cure carbon car panels to help avoid any softening when first exposed to a hot sunny day. Although in most climates, at worst you might get a little bit of fibre print from such sun exposure, it can be beneficial to post cure it anyway. If you choose to do so, you would want to post cure the mould as well before use. Generally for parts where there is likely a lag in time between making and fitting of a few weeks, its unlikely to be a major issue. However very hot/sunny climates and brand new fresh parts can cause a few issues with print when the part softens slightly on first exposure to the suns heat. The OP was asking about post curing the moulds, not the items :-) Post curing the carbon parts is a good idea if there is any chance of them being exposed to the sun for long periods, as you say. If using standard epoxy resin, I am guessing that the max temp you can post cure to is around 80 deg C ? Post curing carbon needs to be done in accordance to the manufacturers instructions. This tends to be an increase of around 0.3 deg C per minute, which is pretty slow. Whether this is important I have no idea, but I am sure Warren does. I'm sure Warren understood the OP's question, but it is always better to post-cure the carbon part BEFORE demoulding; in which case the mould also needs post curing prior to making the part. When post-curing prior to demoulding for both the mould and the final component, ramp rate is less critical and you can go straight to 50C. Of course, keep forgetting that we aren't talking prepreg here.
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