Hi everybody, I know you all love pictures so here's some for your entertainment.
This is a minature (1/12 scale) steam turbo generator body as fitted to some German locomotives early last century.
cast in silicon bronze, it is about 2" long.
The pattern was rapid prototyped by the customer , don't know what process but the surface quality was not the best , as you can see , but he is happy and doesn't mind doing a little polishing!
here is the pattern (left) the casting and a wax pattern.
This is the silicone rubber mould for making the wax patterns.
It is held in a steel jacket to prevent distortion when filling under pressure from the injection machine.
The aluminium core makes the hollow shape inside!
And finally all my research looking for a wax glue was wasted , well perhaps I have learned what doesn't work.
I was getting good results with ordinary PVA wood glue but after a production run several castings had surface imperfections ....doh!
from the shape of the scars it is obvious that the glue is not burning away completely and the residue is carried into the casting surface.
I am trying a longer burn-out cycle and increased ventilation to see if this can be cured.
I can't see there being anything in PVA that won't burn , any ideas?
but for now its back to sticky wax and soldering iron.