The Shop > Metal Stuff
lost pla/pattern castings ?
vtsteam:
ps. picclock, if you want, I can move this thread to the "Metal Stuff" sub-forum -- it will more likely be seen there by people like Ironman, who has visited occasionally in the past. And others into casting here. Up to you...
vtsteam:
Just a little bit more of my experience -- the only lost wax type casting I've done is lost foam, with metal pour burn-out. I got some nice results with patterns I would not have been able to mold easily otherwise. But there were some drawbacks that I didn't like, and for the most part I have returned to making conventional wooden patterns, except for very special circumstances.
My main issue with lost foam is that it takes a lot of time to make a pattern and its mould casing. For me, that represents a couple days. And if the pour doesn't go well, you have to make a new pattern and mould again.
With a conventional pattern, (and I can make those in a matter of hours, usually), If I get a bad pour, I can pour again using the same pattern within an hour or less. Or make multiple parts with one pattern.
A wooden pattern also becomes part of a library of patterns I can use to make other things. I've re-used many of my patterns for different projects. Or replaced worn parts with a copy. So I like all of that.
Joules:
For casting the wheels you could try two part moulds, If it was me I would exaggerate the band for the treads and machine them afterwards. In fact you probably want to think quite bit about including extra material for machining and shrinkage. The oxide painted pattern above has domed ends on the bosses, these are 5 degree taper at the edges, same with the lugs for mounting. Yeah, don't forget draft and this will exacerbate the layer problem, hence my comment about wet sanding, filling and sanding again to get a smooth finish.
I still have a lot of sealing and sanding to do, this won't be ready for Friday :(
vtsteam:
You'll never cast diagonal treads on traction engine wheels with spokes or holed rims in a two part mold in plaster (or greensand for that matter) with a conventional pattern. Lost wax only.
Joules:
My bad, I should have said rims, not wheels and it would be three part mould to get the gap in the rims. Steel treads on ally rims makes far more sence.
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