My quest to produce a bronze tank for my 1:35 scale Girls und Panzer castings has begun.
I have started to assemble the Tamiya plastic model kit previously purchased, see below. I also started to make some moulds so that I could make wax versions of the tank parks for casting. However, when I created the wax version of the lower tank body I had difficulty creating accurate renditions of the track drive sprockets. I also had some logistic difficulty in creating a silicone rubber mould for the tank turret.
After doing all this work I came to the realization that the silicone rubber costs to produce this work will be excessive. Also, it looks like I won’t be able to make the wax model nearly as precise or accurate as the original plastic model.
A reset of plans is required.
I have now decided to abandon the wax model and instead burn out directly from the plastic model. This will, of course, destroy the original plastic model. But, if the casting succeeds then I will have a far better result. This will also be far less expensive as the cost to buy a plastic model kit is much less than the cost for silicone rubber.
My research into the burnout of polystyrene plastic suggests the following:
- I will need to set my kiln at a hotter temperature (815 C) to ensure that the plastic effectively vaporizes. I believe my Satin Cast silica investment material will handle this temperature without breaking down.
- Polystyrene melts at 250 C so my elimination stage will have to occur at a higher temperature.
- As the parts will have thin plastic walls I will also have to set my final flask temperature near 540 C to ensure that the metal flows when I pour. Due to the size of the model the metal may cool and solidify too soon.
- The density of polystyrene plastic is near 1.0, similar to wax. I will not need to adjust my calculations for the amount of metal I will require when I cast the parts.
That’s what is fun about this mad science experiment. Nothing is learned unless something different is done.
Some pictures of my (aborted) wax modelling are shown below.
My next post will show my setup for casting.