Expanding foam for mould, solid enough ?

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Expanding foam for mould, solid enough ?

Expanding foam for mould, solid enough ?

Author	Message
TURK	TURK posted 10 Years Ago HOT Topic Details
Group: Forum Members Posts: 101, Visits: 662	Hi all, Anybody used the expanding foam you can buy from the diy stores, in aerosol form. I'd like to know what the difference is between that, and the 2 part stuff available. I understand that the 2 part stuff may be 'closed cell', probably making it harder. But can I get away with using the normal aerosol stuff usually used for insulation purposes ? I'd like to spray it into a form ( female mould ) about the size of a shoe box, then demould the expanded spray foam, and then brush on layers of Pattern-Coat Primer to make it harder to use as a main male mould. TURK Tags expanding foam Insulation Foam mould
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Hanaldo	Hanaldo posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	Actual PU foam (not the aerosol stuff) is closed cell, so the pattern coat primer won't harden it at all as it won't get absorbed. It will give you a hard shell, but once you sand through it then the foam underneath is still soft and will dig out very quickly. And you will definitely sand through, it can't be avoided. In a way I agree with Fasta, adding a layer of fibreglass will give you that solid base. However having done both methods, I prefer not to use fibreglass, simply because the nature of wet laying fibreglass naturally leads to high and low spots where you get resin rich areas. On parts where the dimensions are critical, this can be annoying because you sand through your coating to the fibreglass, and you aren't truly flat. So you have to build up the rest of the structure to make it flat, and before you know it you're a few mm off in places. I prefer to use profiles to give you the parts dimensions, then skim the foam with body filler before sanding down to the profiles. Yes you will sand through and chew into the foam in places, but this isn't such a big deal as you just fill them again. It's a bit of a tedious rinse and repeat procedure, but it allows you to follow your profiles very accurately and know that you are true to your shape.
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TURK	TURK posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 101, Visits: 662	Thanks Hanaldo for your time and expertise, very much appreciated. It makes great sense what you're saying, but because of the shape that's needed, contoured face, angled sides and two cone like apertures in the centre, I really have no option than to pour some sort of solid ( or near as solid as possible ) material into my mould that I'm creating. I've bought some Vac-Cast Epoxy casting resin, but can't find any how-to's on the web, so not really sure how to use it. I was hoping somehow that I could simply pour it into the mould to get a very durable male mould for vacuum forming. As it contains Aluminium, it's ideal for vacuum forming as the 'plug' will be subjected to high temperatures. I had considered using the profiles approach as in Paul's video on how to 'Pattern Making', when he demonstrates the Carbon Airbox. But with my project having two cone like apertures, I could never sand down the two 'holes' to the degree of accuracy needed unfortunately. We need a How-to video on how to cast resin I think ! Thanks mate. TURK
	Reply Like 5