Since the handwheel requires 2 setups to machine the top and bottom sides, some means of fixturing the part for the second round of machining was needed. I started by hot gluing a piece of MDF to the machine's bed to serve as a sacraficial top. I zeroed the machine then jogged it to the center of the 4"x4" cutting area and plunged the dremel, drilling a hole in the MDF. Then I moved it 1 1/2" in the +Y direction and drilled another hole. These were used to set up the part for the bottom machining.
I put a chunk of foam on the MDF and started the program. The machine worked great, first making roughing passes and then 2 finish passes. At the end of the program, I had manually added G-code to drill holes in the part at the same locations as I had drilled the MDF. When the top half was done, it was flipped over. 1/8" dowels aligned the holes in the foam with the holes in the MDF to recenter the part. For both setups, double sided tape held the foam down. The machine was loaded with the second program and run. The first attempt ran fine, except for some obvious mismatch on the X direction, until the second finish pass, when the Y axis hesitated and the cutter cut into the part! I stopped the program and removed the part from the machine. It had promise, but needed work...
I replaced the lead screw for the Y axis that seemed to be binding in places and set up a second block of foam for hacking. Again, the top side ran well. I flipped it over and the backside started taking shape. About 12 passes away from the end of the second finishing pass, the Y axis again hesitated and let the cutter slice into the part! The part can be salvaged and will be cast on the next calm day, but the problem was electronic, not mecanical. After some cussing and investigation, I tracked it down to a cracked solder joint on the board that managed to take out 2 of the controller IC's, the original and one replacement! It's back together now and seems to be running OK...
