Post by webgeek on Sept 8, 2011 22:33:09 GMT -5
Hi all; my father and I stopped by a rock shop in central Utah where we saw a series of beautiful stone spheres and learned that they can be made pretty easily. To that end, we've done some research and looked at every machine we can find on the web, read a book about it, looked at a machine in person, and talked to a few old hands at sphere making. With all that info, we went ahead and tried to come up with a design we think will work reasonably well without breaking the bank. I own a CNC milling machine so my plan was to make the frame for the gizmo out of plate aluminum to keep it simple and cheap. Ultimately this is overkill but it's fun and makes for a bullet-proof and attractive system when done.
The design is a 3-head machine using 6061 T-6 aluminum (aircraft grade) for the parts. The base plate is 3/8" thick and the motor mounts are 1/4". We've heard that accuracy of the machine is useful and indexing is a nice feature to have and so dowel pins are used to quickly index the machine with 1/32" steps. Tensioning of the motors is handled via a pair of springs on each motor mount that attach to the motor slide. I like this a lot more than using rubber bands or bungee cord at the top. With that said though, I recognize that more force might be needed and so each motor mount has a pair of tapped holes that can be used to secure springs between each mount if needed as well.
To keep things safe, all of the wiring for the motors and illuminated power switch will go via channels milled in the bottom of the base plate. The idea is that the motors will have a small waterproof connector and the wires will be potted in place with glue to keep them secure and totally waterproof. This means the machine can be washed down easily if needed by just removing the motors. The motors themselves are not waterproof but the intent is for the motors to angle down when cutting to ensure nothing drips back into them via the shaft. We are thinking of using these 110 AC motors specifically:
www.mcmaster.com/#6142K63
We believe the machine should work up to somewhere around 3-4" diameter spheres - depending on the size of the initial grinding cups. We are still researching this right now. The plan is to use part number VBP001 from this site www.sphereheaven.com/equipment.htm to hold diamond sanding pads. We'd modify the cups on the lathe as the third picture on the bottom of that page shows. We'd use various grits of the 4" pads on the page for the actual polishing. Initial grinding of the rough pre-form would use these cups: www.hplapidary.com/products/438-course-grit-1-316-2-14-inch-sintered-diamond-grinding-cups-9-cups.aspx
I've attached a handful of annotated pictures to this post. I'd love any feedback I can get as I really don't want to make a machine that has clear flaws. Right now it's all just in CAD and so is easy to fix. Any feedback would be greatly appreciated. Please let me know if you have any questions/comments, etc. Thanks!
-Mike
The design is a 3-head machine using 6061 T-6 aluminum (aircraft grade) for the parts. The base plate is 3/8" thick and the motor mounts are 1/4". We've heard that accuracy of the machine is useful and indexing is a nice feature to have and so dowel pins are used to quickly index the machine with 1/32" steps. Tensioning of the motors is handled via a pair of springs on each motor mount that attach to the motor slide. I like this a lot more than using rubber bands or bungee cord at the top. With that said though, I recognize that more force might be needed and so each motor mount has a pair of tapped holes that can be used to secure springs between each mount if needed as well.
To keep things safe, all of the wiring for the motors and illuminated power switch will go via channels milled in the bottom of the base plate. The idea is that the motors will have a small waterproof connector and the wires will be potted in place with glue to keep them secure and totally waterproof. This means the machine can be washed down easily if needed by just removing the motors. The motors themselves are not waterproof but the intent is for the motors to angle down when cutting to ensure nothing drips back into them via the shaft. We are thinking of using these 110 AC motors specifically:
www.mcmaster.com/#6142K63
We believe the machine should work up to somewhere around 3-4" diameter spheres - depending on the size of the initial grinding cups. We are still researching this right now. The plan is to use part number VBP001 from this site www.sphereheaven.com/equipment.htm to hold diamond sanding pads. We'd modify the cups on the lathe as the third picture on the bottom of that page shows. We'd use various grits of the 4" pads on the page for the actual polishing. Initial grinding of the rough pre-form would use these cups: www.hplapidary.com/products/438-course-grit-1-316-2-14-inch-sintered-diamond-grinding-cups-9-cups.aspx
I've attached a handful of annotated pictures to this post. I'd love any feedback I can get as I really don't want to make a machine that has clear flaws. Right now it's all just in CAD and so is easy to fix. Any feedback would be greatly appreciated. Please let me know if you have any questions/comments, etc. Thanks!
-Mike