Eco friendly moulding material?


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pedro_chops
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Thanks Lester.
I wasnt thinking about using plaster for a mould to pour ali into.
But make a plaster mould in my workshop, and then take this to the ali castors for them to make a wet sand mould around this, pull the plaster mould out, then pour the ali into the wet sand mould.

I havnt done much research into investment plaster which I will definitely do, that sounds useful.


Lester Populaire
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pedro_chops - 6/26/2019 8:31:07 AM

I like the ali / steel idea, will definitely look into this.
If I make a mould out of plaster (dont post cure to avoid warping) then take this to the ali guys to sand cast it, that could work.

Plaster does not work as mould for aluminum casting as it is not temperature stable enough, especially without post cure. It will just explode with all the moisture in there. You need a proper investment plaster for this.
On top of that plaster is really porous and therefore has pretty poor release properties i would imagine...

flax on the other hand has a near identical cte to carbon so is well suited as mould for carbon prepreg parts.

pedro_chops
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I like the ali / steel idea, will definitely look into this.
If I make a mould out of plaster (dont post cure to avoid warping) then take this to the ali guys to sand cast it, that could work.
oekmont
oekmont
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The greenest materials I can think of, wich are 100% tested and save are aluminium and steel. Because they can be molten down and cast again over and over again.

pedro_chops
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Hi,

I am researching and testing to find the greenest way to mould patterns. I have already tested a few materials and now asking people on this website if they have any ideas for sustainable moulding processes.

I have access to offcuts of prepeg carbon from the automotive industry and looking into using this material instead of just throwing it away. If I can make moulds out of a green material then the product made from this reused carbon is a green product. As well as this reason my conscious will be clear : )  However, I am slowly coming to the conclusion that it is impossible to make an eco friendly mould that can withstand the conditions in the autoclave for the prepeg carbon (125 celsius and pressurized).

The first material I looked into was plaster of paris. I found plaster that also had polymer in the mix (I think this would be something similar to white wood glue) which proved to be strong under both compression and torsion, but every attempt always had problems when it came to post curing up to 125•c, such as warping or cracking. I tried different mould releases, also tried adding materials to the inside of the plaster such as chicken wire, but no success. The brands tested were Hurculite and Cassini's which I think are top of the range so cant blame the material. I've never used plaster before and really wanted this to work. If anyone has any likely ideas why this material warped/cracked after post cure I'm all ears. 

After this I looked into materials that can be used for wet lay mould making. There is an epoxy resin that has come out of the surfboard industry that has green credentials. It's called SuperSap, it uses waste material from the timber world to make some of its resin. Buuuuuuut..... this epoxy can't go over 70•c so not suitable for going in the autoclave.
Flax weave is also a material I have tested. This is a plant based material that can be used instead of glass. Although it can withstand the 125•c it did warp. The test piece for this was a plate shape, so if it was more boxed shape it may not have warped. It costs more than glass so for the larger moulds I cant use it, but might do for smaller moulds.


So I am coming to the conclusion that I will have to use the traditional materials (glass and epoxy) for a wet lay mould. 
But if I use this mould many times, then the amount of prepreg carbon used inside of the mould and not thrown away into landfill will outweigh the amount of material used for the mould. So it is still a 'green' product, but it would be much better if I did find a green moulding process.
 
If anyone knows of a material / method that I should look at please let me know.  Thanks


GO

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