Investment Casting Costs - The Home Machinist!

Post by Dick_Morris » Wed Feb 01, 10:10 pm

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Especially when you consider what people are doing with a $300 resin printer to make their waxes I don't understand why the service is not more affordable?

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The opportunities of a resin printer and investment casting in model building are truly amazing. I can't speak on the cost of contracting for castings but I do have a good feeling for what it costs in a home shop. maybe this will put the costs in perspective. The simple truth is that there can be considerable expense in time and money beyond the printer.

Although free 3D software (like Freecad) is available and has awesome capabilities, it takes a significant time investment to go beyond the basic functions. Unless one is very skilled, it can also take considerable time to design a complex part for 3D printing.

The actual 3D printing involves another skill set with its own learning curve that takes an investment in time. When staring out, it's common to experience repeated failures as part of the learning curve. Castable resins tend to be a bit more difficult to cast successfully than utility resin.

An example, here are some variable costs for a a 1/8 scale laird crosshead. The resin suitable for casting cost 3-4 times the cost of a utility resin. Not a massive expense, but crosshead used about $2.00 in resin. It also took about 2.3 pounds of investment powder at a cost of just under $5. I'm guessing that electricity for running the burn out oven through a cycle and melting the metal may cost another $5 to $10, although it's typically split over several castings. Virgin silicon bronze would cost about $10. Crucibles are expendable and the wear and tear for one melt probably costs about $1 to $2.

A new, small burn out oven will start at $600. My first one had a 6" cube chamber which only allowed me to burn out and out a couple of flasks at a time. After a couple of years of watching the ads I found one used that would hold 6 to 8 flasks. It cost $200 plus about another $200 and 50 hours of time to repair it and do some modifications. New, it would have cost $2,100.

A casting station which includes the bell jar, pump, and place for doing the vacuum casting will cost about $650. By buying a vacuum pump and chamber and making the casting table you can get by for about $300. Depending on the style and size of flask, they will cost $15 to $35 each. They are reusable, but you will probably want several sizes and possibly several of the size you use most.

An electric furnace with crucible for melting the metal will cost $250 to $350 depending on size.

Adding sprues to a part and putting it into the flask will take at least ten minutes, more if there is a tree of a number of parts. Mixing the investment, vacuuming it, pouring it into the flask, vacuuming it again, getting it ready for burn out, and cleaning up the utensils before the investment sets up takes about 20 minutes.

It can take an hour for the metal to melt, but the actual time for casting and cooling the flask in a bucket of water only takes about five minutes. Cleaning the investment from the flask and casting takes me 10 to 20 minutes per flask in the summer when I can use a pressure washer and 30 minutes to an hour if I have to do it in a bucket water and using picks. It's nice to have the option of bead blasting to remove the remaining investment and oxidation on the surface of the castings and it doesn't take very long, but that's another several hundred dollar expense, not including the compressor.

Investment casting parts adds a lot of capabilities over sand casting, fabrication, or hogging parts out of a chunk of metal. It's not cheap, but I'm glad I made the investment. It's made me look differently at how I attack many of the parts that I model and allows me to do things that weren't practical with the other methods. I'm glad to have it as another tool in the tool box.

I started to post a response on the Nathan check valve thread, but the cost of making castings wasn't relevant to the original post.The opportunities of a resin printer and investment casting in model building are truly amazing. I can't speak on the cost of contracting for castings but I do have a good feeling for what it costs in a home shop. maybe this will put the costs in perspective. The simple truth is that there can be considerable expense in time and money beyond the printer.Although free 3D software (like Freecad) is available and has awesome capabilities, it takes a significant time investment to go beyond the basic functions. Unless one is very skilled, it can also take considerable time to design a complex part for 3D printing.The actual 3D printing involves another skill set with its own learning curve that takes an investment in time. When staring out, it's common to experience repeated failures as part of the learning curve. Castable resins tend to be a bit more difficult to cast successfully than utility resin.An example, here are some variable costs for a a 1/8 scale laird crosshead. The resin suitable for casting cost 3-4 times the cost of a utility resin. Not a massive expense, but crosshead used about $2.00 in resin. It also took about 2.3 pounds of investment powder at a cost of just under $5. I'm guessing that electricity for running the burn out oven through a cycle and melting the metal may cost another $5 to $10, although it's typically split over several castings. Virgin silicon bronze would cost about $10. Crucibles are expendable and the wear and tear for one melt probably costs about $1 to $2.A new, small burn out oven will start at $600. My first one had a 6" cube chamber which only allowed me to burn out and out a couple of flasks at a time. After a couple of years of watching the ads I found one used that would hold 6 to 8 flasks. It cost $200 plus about another $200 and 50 hours of time to repair it and do some modifications. New, it would have cost $2,100.A casting station which includes the bell jar, pump, and place for doing the vacuum casting will cost about $650. By buying a vacuum pump and chamber and making the casting table you can get by for about $300. Depending on the style and size of flask, they will cost $15 to $35 each. They are reusable, but you will probably want several sizes and possibly several of the size you use most.An electric furnace with crucible for melting the metal will cost $250 to $350 depending on size.Adding sprues to a part and putting it into the flask will take at least ten minutes, more if there is a tree of a number of parts. Mixing the investment, vacuuming it, pouring it into the flask, vacuuming it again, getting it ready for burn out, and cleaning up the utensils before the investment sets up takes about 20 minutes.It can take an hour for the metal to melt, but the actual time for casting and cooling the flask in a bucket of water only takes about five minutes. Cleaning the investment from the flask and casting takes me 10 to 20 minutes per flask in the summer when I can use a pressure washer and 30 minutes to an hour if I have to do it in a bucket water and using picks. It's nice to have the option of bead blasting to remove the remaining investment and oxidation on the surface of the castings and it doesn't take very long, but that's another several hundred dollar expense, not including the compressor.Investment casting parts adds a lot of capabilities over sand casting, fabrication, or hogging parts out of a chunk of metal. It's not cheap, but I'm glad I made the investment. It's made me look differently at how I attack many of the parts that I model and allows me to do things that weren't practical with the other methods. I'm glad to have it as another tool in the tool box.

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