Screwing Around

I have the basic mechanical components made for my new screw based machine. The motor is a massive NEMA 34 servo motor with something like 900 ounce inches of torque. Being a servo this torque is available throughout more of the speed and acceleration range than with s similarly rated stepper.

The goal is to make a sleek self contained (expensive to build) unit but at the same time make it easy to disassemble for modifications during testing. The one thing I am least sure of is the ability of the motor’s built in bearings to serve as the only thrust bearings. Will probably have to add a thrust bearing but I planned for that eventuality. 

The ball screw shown in the pictures is hugely oversized. It is intended for use in my CNC router when i convert it to a much smaller size. This will make the screw from the router available and i will use that one in the fucking machine.

A couple of details worth mentioning. There is a magnet in the slider (orange thing the ball nut is mounted to) which can activate limit switches mounted in one of the tee slots. The slider and the bushing/endcap are made of Rulon J which is a very good bearing material but is insanely expensive. I just happen to have a lot of it bought surplus. Delrin or Molydel would be more affordable choices for these parts. I have some molydel that i will probably use for the next end cap i make because it will look better. I had a scrap of Rulon J of the right size so i figured i would mess that up before getting into my limited stock of molydel. The screw fits inside the ram tube and because it is so large it barely fits. There will be much more room for the smaller screw. There is a teflon bushing on the end of the screw to allow the rod to slide and hopefully be fairly quiet. I did not want to take the nut/slider assembly apart just for a picture. Will take a pic the next time i disassemble it.


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