Thursday, 22 August 2013
More Aluminium melting and casting.
I got a nice weather day off work with no commitments a few days back and decided it was time to fire up my second homemade furnace. You may remember I made a really small furnace a while back (HERE) and did melt a small amount of aluminium in it. I realised from that day that the furnace I'd made by insulating a paint can with fire cement was too small as I couldn't keep enough fuel burning in it to last through an entire melt. So a bigger furnace was needed.
I shelved the idea for a while as I realised to make a bigger furnace in the same way as the previous one would be quite pricey (remember I'm a miser!!) as I had made the walls of the small furnace out of pure ready mixed fire cement. I then stumbled across the answer in a youtube video by the user myfordboy who has an enormous number of informative videos about his home sandcasting processes. He had made a furnace mix by using 4 parts perlite ( a common moisture retaining insulating soil additive sold in all garden centres) and 1 part fire cement by volume..this meant that the amount of fire cement I had to buy was massively reduced...I reckon all in this second larger furnace has cost less than 20 quid and I blew 4 quid of that on a brand new bucket...decadent I know!! The other nice thing about using a perlite cement mix is that the resulting furnace is very light...in fact this one is probably lighter than the original one about 1/4 of its size.
Anyway this second melt and pour went well...I have also made some casting sand using bentonite clay (sourced from cat litter...don't worry I bought fresh I'm not that tight!)..but my casting sand was to wet to do a proper cope and drag type casting. So I just made indentations in the sand and poured some different shaped ingots. I did 2 melts and pours and burnt probably 2 quids worth of charcoal and used a few units of electricity but I have produced some good useable pieces of aluminium which I am slowly facing off in the lathe.
So next stop with this is to make some patterns for something and try a proper sand casting..may be a while pattern making is an art unto itself with a lot to learn...draft angles...shrinkage..fillets..all good fun though!