Pre Pregs cutting and making templates question

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Pre Pregs cutting and making templates question

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morepower	morepower posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 242, Visits: 1.2K	Any wet lay glass mould will have some shrinkage when you make a pre-preg part. It will warm up and expand then as it cools contract back again. If you de-mould cold then the mould will not last too long if the mould is a multiple section mould. It can crack the mould after only 3 or 4 pulls. I have had that happen once. If it is an open mould and the part will come out easily then it should last for as long as you need if you look after it.. But a mould like my Fuel tank shell has to be de-moulded hot or I have to have a pre-preg carbon mould if I want to allow it to go down to room temp. Cutting pre-preg is easy and I use a scalpel as I get 100 blades at a time and it cuts a very clean edge too.
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Hanaldo	Hanaldo posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	Yeh that's true, the expansion can be a problem. To be honest I haven't had any real issues yet, my moulds are still ok, but I do notice how tight the parts are in the mould. Rich, when you demould hot do you get very bad print-through?
	Reply Like 3
TomDesign	TomDesign posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 454, Visits: 2.5K	ok guys i do infusion molds how to get nice overlaping join i mean then? my mirrors mold if from 4 pieces if i connect them i gonna see not nice dark line joined how to avoid that?
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morepower	morepower posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 242, Visits: 1.2K	Hanaldo (19/10/2016) Yeh that's true, the expansion can be a problem. To be honest I haven't had any real issues yet, my moulds are still ok, but I do notice how tight the parts are in the mould. Rich, when you demould hot do you get very bad print-through? No issues with print through. Once the moulds have been post cured and ready to use, they should be nice and hard. Luckily I only have to cure at 72 degrees C so the moulds are more warm than really hot. I think if there is going to be a print through issue it would happen regardless of de-moulding hot or cold. The worst mould section for me is the fuel tank top, It has a good compound curve shape so is best removed hot to help stop it shrinking onto the top of the tank. BUT it also has a thick square edged filler cap neck that is prone to being chipped on the edge so I have to use the extraction bolt to lift it a little then let it go completely cold to let the neck shrink back. That it the only problem I really get with wet laid glass moulds. The carbon tooling I can leave to go stone cold and not have any issue with expansion or shrinkage as it heats up or cools.
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morepower	morepower posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 242, Visits: 1.2K	TomDesign (19/10/2016) ok guys i do infusion molds how to get nice overlaping join i mean then? my mirrors mold if from 4 pieces if i connect them i gonna see not nice dark line joined how to avoid that? You will get some line on any join to be honest. Its a fact of life. It is best to either accept it or try and do something to use the line to your advantage. Like making a V or an obvious change in direction. This is out of the mould and not trimmed yet. I have a large join for the whole side of the tank. I cannot match the weave of the top along its whole length so it looks odd at some point. So I change the direction of the weave to make it more attractive to look at. But I also have to V the top which is a one piece mould section too so it adds work but makes the whole think look more visually attractive. Hanaldo you can now see what I mean about the filler cap neck too.. The mould is very thick there so it takes a long time to cool so I have to lift the mould a little to clear the main body then just let it cool to allow it to come up with out damaging that neck area of the mould. With a carbon mould it just slides up nicely hot or cold.
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TomDesign	TomDesign posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 454, Visits: 2.5K	so how i can join in infusion connect nicely mirrors if they from 4 pieces?
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MarkMK	MarkMK posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 338, Visits: 2K	With infusion, unless you're using 'Profinish' fabric that has the resin binder to help hold it together, then apply a light mist of spray-tack before cutting. Something like Cytec's 'Aerofix 3' will work well. I use an Olfa roller cutter, which does give nice clean cut lines when jointing pieces together and if you try and put your overlaps into corners, you can do a really good job of minimising the appearance of any joins
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TomDesign	TomDesign posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 454, Visits: 2.5K	any images how overlaping results getting?
	Reply Like 2