Supporting > Casting
Casting bench upgrade
Dan Rowe:
I bought some production flasks several years ago and the price of a vacuum pot to go with them was over $1000 at the jewelry shop so I said NO thanks I would build my own.
Well, that I finally got around to making a vacuum pot for the flasks. I ordered a 7" long piece of 6" steel pipe and a couple of 8" x 8" x .5" steel plates for the ends. I bought the conversion flanges so the vacuum pot can be used with either 4" or 3.5" production flasks when I originally bought the flasks.
The first step was to cut the edges of the square plates closer to size for the lathe. I used my Butterfly die filler with the saw overarm for the work with a normal hacksaw blade.
Then I cut a V-notch in an old cutting board so it could be used as a guide to trim the 4 corners of each end plate.
I taped a 1/2" hole in the center of both plates and trimmed both plates round with a bevel for welding to the section of pipe. The end for the adapter plates needed a 5.5" hole in it. I went to set it up in the mill and I found out that I did not have enough Z space to chain drill to remove the center section. I just got a mini mill base for my Servo drill press and it had enough Z space for the job but, the chuck will only take a 1/8" drill so I had to drill a lot of holes. Drilling 144 holes in 1/2" plate was a real work out for the Servo drill press but, it got the job done.
The final step before welding was to finish bore the top plate.
It has been a while since I have done much arc welding, and some of my bead was in the wrong place. This made me have to mill the face of the vacuum pot. I used the 1/2" bolt to clamp the pot to the mill table and used a pull-down vise on either side for extra stability. The weld bead did not respond to a file so I used a carbide milling cutter to save wrecking a good HSS cutter.
I made up a tree of 30 Shay truck parts for the test pour in the smaller 3.5" production flask.
Here are the flask and vacuum pot just after I poured the bronze.
And finally here is the tree of bronze parts ready for clean up.
A successful casting bench upgrade.
Cheers Dan
RMO:
Dan,
Would you mind explaining a bit more about the vacuum pot, its uses and how this improves your castings? I am just starting on the concept of casting and am interested in learning more.
Thanks
Mike
Dan Rowe:
Mike, I learned how to do lost wax casting from a book, which I still use when I have to make the calculations necessary like water to investment ratio for flask size and how much metal to weigh out for the pour. It is a really good reference book for the subject Centrifugal or Lost Wax Jewelry Casting by Murray Bovin.
The reason I moved to production perforated flasks was not really to get a better casting it was so I could get more parts in a single flask. Here is a photo of my operation using solid flasks:
The electric graphite crucible is white hot in the photo, as I just poured the solid flask on the vacuum table. There is a red silicon gasket under the flask that can just be seen as it is mostly behind the splash guard. Several other flasks can be seen in front of the kiln. The solid flasks are 2.5" SS muffler pipe that I cut to length. It would have taken me about that many flasks to do the 30 parts I did in a single pour with the perforated flask. So I saved time and investment and had to heat less metal because there is a large sprue button on each solid flask. I only needed 200 grams of bronze for the 30 parts and most of that was for the premade sprue base that all the parts were attached to. I like all my parts to keep the wax injection sprue from the rubber mold, so all I have to do is use sticky wax to glue then to the base structure.
Here is a shot of the vacuum table with a bell jar and the flasks are vacuumed to remove the bubbles before setup.
The vacuum pot I made has a gasket below the pot and there is a red silicon gasket above and below the aluminum adaptor plate. The holes in the perforated flask allow the vacuum to be drawn from all directions, not just at the bottom with a solid flask. The perforated flask seals on the bottom of the rim so I do not have to trim the flask to get a good seal, and it has a much wider surface to seal with. The solid flask only has the wall thickness of the tube to seal. I have worn out two good files draw filling the base of the tubes to make a flat sealing surface. I now use a muffler tube expander as a chuck so I can true the tubes on the lathe safely.
The reason I chose vacuum lost wax casting over centrifugal casting is I can do a larger part than can be done with a centrifugal setup, and the number of parts I can do with the new vacuum pot is much greater that what can be done with a centrifugal setup.
If I missed anything just ask more questions and hopefully I will have a good answer. (Everything I explained and more is in the book.)
Cheers Dan
RMO:
Thanks Dan, that clears it up somewhat. I will have to take a look at the book.
Mike
Dan Rowe:
Mike, after you read up on this ask questions if you have any. I started casting with a handheld crucible and a rosebud tip on my OA torch. That works fine for small pours and getting started with solid flasks. I helped on a few centrifugal pours as I had a lot of experience with an OA torch when I took a class in jewelry.
Cheers Dan
Navigation
[0] Message Index
[#] Next page
Go to full version