Swing Shift LW Casting
The more I think about Lost Wax (LW) Casting and I review all the information I have gathered and learned, I see a direction I think I will be following. At this point I don’t see myself doing large scale duplicate casting of parts. I have seen the pictures of fifty rings on a central sprue all being cast at one time, also using rubber master molds and wax injection for duplicates. That’s what I call manufacturing.
If I were a professional making a full living in metal casting and jewelry, then that kind of LW casting would definitely be in my league. As a private individual just doing my thing, I may never get there. Ops, never say never, but I make my point. Perhaps I will want to do matching multiples one day.
It’s very early in my personal pursuit of LW casting so I am still very formative in understanding the process and developing my long term goals.
I have discovered one important “lesson learned” now that I have done about an equal number of centrifugal castings and vacuum assist castings. There is a basic law of thermodynamics that has to be considered in the mass of metal that is melted for the casting. A good casting has to do with the number of heating units (BTU’s) contained in the puddle of metal a whole lot more than the temperature of the metal. Try to force too many BTU’s into the liquid with high temperature it will boil and change the alloy content.
A small thin mass of metal cools a whole lot faster than a large mass of metal. That law has exposed itself twice in my gravity/vacuum assisted pouring of silver. In small quantities of metal, the pour has to be very quick and the torch continues heating the metal as it is being poured.
When doing Centrifugal casts, I was doing exactly the same. The torch heat is on the puddle as the arm is released. The full speed acceleration is almost instantaneous and the liquid metal is flung with force many times that of gravity into the mold in a very hot liquid state in a few hundred milliseconds. That can’t be duplicated in gravity/vacuum assist casting that may take a second or so to pour. So I haven’t been able to do small castings very well so far.
My conclusion: Larger pours with lots of mass and BTU’s in the puddle are far easier and likely to be successful than small thin Items with low metal volume that are cast by gravity/vacuum. Actually, I read that somewhere too. Now I know it’s true.
I struggled with this violation of thermodynamic law trying to gravity cast a small thin medallion in pewter. After months of trying in rubber and aluminum molds, I abandoned the project. Small pewter items are always successfully done on a centrifugal spin caster using a vulcanized rubber mold.
Some pewter items are created in wax, cast in silver and detailed, then the silver master used to create the vulcanized rubber mold for spin casting with pewter.
Centrifugal LW casting is the solution for small items. Since I want to do small items I see some handwriting on the wall. It’s not graffiti. It say, “Go with the flow, get into the swing.”
Follow up: Centrifugal Casting Machines