Start of CNC Z-Axis

Z-Axis Motor Mount











I decided that the best way to deal with the Z-Axis was a ballscrew and that the best way to do that was to machine an end to attach to the ballscrew that would fit through the bearing block and connect to the motor. It has a 0.500 bearing surface with a 1/2x20 adjusting nut and a 0.375 connecting end. I also need to shorten the connecting end shaft by about 0.25".
I am using an existing Nema23 motor mounting plate, but I had to make new hexagonal standoffs because the ones I had were too short for the adjusting nut and the lovejoy connector. The new standoffs are 2.5" long and both ends are drilled and tapped 10x32.
The bearing support will fit in the same location as the stock bushing for the stock leadscrew.
Here is the motor mount, standoffs and bearing block, bearings and ballscrew end all assembled.
I cut off a section of ballscrew, annealled the end, and turned it to fit in the end of the fitting I made. I turned the end of the ballscrew about .002 larger than the pocket in the end piece and pressed it on to the end of the screw. I used the tailstock on my 12x36 lathe as a press and pressed the machined end onto the ballscrew. I had left it 0.250" long so that if I dinged up the end, I had room to clean it up. When I was done pressing it on, I turned of the extra length.
Here is the ballscrew assembled with the main bearing support, the double ballnut and the nut support for the carriage.
Then I decided to mount the other end into the hole where the original leadscrew connects to the standard gear box. I had cut the screw about 0.500" long so I parted that off and then I turned the end of the ballscrew to fit into the hole for the original leadscrew on the gear box.
I removed the existing carriage that attaches to the saddle. Then I did a test fit to the lathe. I stuck the end in the gearbox stub, mounted the motor end bearing support, and bolted on the carriage plate to which to mount the ballnut.

Next step is to layout the ballnut mount for the carriage.
I got the z-axis ballscrew mounted. I used a 3/4" piece of cast 6061 Mic-6 to replace the original carriage. I marked the top two holes with a transfer punch. The holes for the ballnut support I marked out using a small square to give me the top and bottom of the screw in relation to the carriage. I made the ballnut support from a piece of 1" x 2" 6061 aluminum bar. After I laid out the bolt holes and drilled them, I marked the center of the screw on the carriage plate and the support piece. Then I used a transfer punch again to mark the holes on the carriage plate. I drilled them and tapped them. Next I bolted the support piece to the carriage. Then I used a transfer punch through the end bearings for the screw to mark the center for the hole for the ballnut.
It had a 3/8 hole through it that was on the edge of where the threaded hole would go. So rather than have an interrupted cut, I turned a plug and super glued it in place. That worked out fine. I bored the hole out to 0.875 and then threaded it 15/16" x 16 in the lathe.
I used a thin 1/2"x20 locknut to adjust the play between the two end bearings. I installed a 3/8" to 1/4" lovejoy connector and mounted the motor. Now I need to wire everything up so I can give it a try.

Last Modified 12/1/07 11:41