Michael Moore
Titanium
- Joined
- Jun 4, 2004
- Location
- San Francisco, CA
Even the small ones seem to sell for the price of a modest manual lathe that has a lot more parts and material in it. I'm talking about just the table/servo/brake combo, not the ones that add electronics by having a dedicated controller on them.
Is it because of high precision worm gears to avoid backlash?
If timing belts are fine for driving the ball screws on my Tree CNC mill, why aren't there (or are there?) rotary tables with a timing belt drive from the servo? It seems like there could be a big pulley on the spindle of the rotary table and a small one on the servo to gear things down to get small increments of rotation at the spindle and magnify the torque of the servo.
The one photo of a cutaway CNC RT I could find
http://www.workholding.com/RT160%20Section.jpg
shows a couple of big ball bearings behind the platen, a worm gear in the middle of the spindle, and more big bearings at the far end.
You could almost just get a sturdy spindle/headstock assy off of a lathe with junk ways and power it via a belt and have a vertical (horizontal spindle) rotary chuck/table. Of course that might end up pretty heavy and bulky if you used the headstock from a big lathe. Or just get a spindle (like this one from a Mori Seiki)
http://www.eurospares.com/graphics/metalwork/morispindle.jpg
and shorten it and make a housing.
I presume there are lots of details to the design of a CNC RT that I'm not aware of, but I'm definitely curious.
cheers,
Michael
Is it because of high precision worm gears to avoid backlash?
If timing belts are fine for driving the ball screws on my Tree CNC mill, why aren't there (or are there?) rotary tables with a timing belt drive from the servo? It seems like there could be a big pulley on the spindle of the rotary table and a small one on the servo to gear things down to get small increments of rotation at the spindle and magnify the torque of the servo.
The one photo of a cutaway CNC RT I could find
http://www.workholding.com/RT160%20Section.jpg
shows a couple of big ball bearings behind the platen, a worm gear in the middle of the spindle, and more big bearings at the far end.
You could almost just get a sturdy spindle/headstock assy off of a lathe with junk ways and power it via a belt and have a vertical (horizontal spindle) rotary chuck/table. Of course that might end up pretty heavy and bulky if you used the headstock from a big lathe. Or just get a spindle (like this one from a Mori Seiki)
http://www.eurospares.com/graphics/metalwork/morispindle.jpg
and shorten it and make a housing.
I presume there are lots of details to the design of a CNC RT that I'm not aware of, but I'm definitely curious.
cheers,
Michael