Rotary Table Servo Motor

[bigbigJimbo]

I am looking for a servo motor as a 4th axis for a 4" rotary table could anyone recomend a suitable motor for this purpose,
I am currently in the throws of retrofitting a seig X3 with Clifton servo motors and therefore I do not want to mix by using a stepper motor.

Jim

[JFettig]

Something around 100oz-in peak torque would be about what you need, I am not completely sure what the pittman motors put out, but they are smaller motors and I have seen one on a rotary table at one time:
http://cgi.ebay.com/2-48V-DC-Pittman...QQcmdZViewItem
There usually is more on ebay.

Jon

[Al_The_Man]

You need to consider a way of clamping the table when in position as it is not desirable to use the servo to hold position against the machining forces, if there is sufficiently low back lash you can use a brake on the motor, You will then have to disable the motor when braked, and only enable when moving, this also allows the use of a smaller size motor, mechanical clamping is the prefered way and usually is the method used on commercial tables.
Al.

[webbch]

Al, so the mechanical design of a 4-th axis rotary table is different than a manual rotary table? (i.e. do they use a some kind of ballscrew-type drive?)

The reason I ask is that I thought a 4-th axis rotary is capable of continuous contouring, not just being used as a positioner (although it appears this is what often (but not always) happens in actuality). Thus, if the mechanicals are similar (barring the clamp you speak of), I see no reason why a 4-th axis (from factory) rotary COULD be used for contouring, while the mechanical-converted-to-servo COULD NOT.

Naturally you would need to ensure your rotary table is nice and tight, and in the end clamping the table will likely be a better solution while taking a cut, although sometimes I expect you would like the flexibility of perhaps taking lighter cuts while contouring, which rules out the clamping-during-cutting proposition.

Chad

[RotorRouter]

I don't know if this is of any help but worm gears with ratios of higher than 10:1 are unable to transmit torque from the wheel to the worm.

Worm gears have a low efficiency due to sliding friction. Therfor the motor will have to be bigger but it is this friction that should eliminate the servo from having to hold position against the machining force.

Just a thought.

[webbch]

RotorRouter,

I may be mistaken, but I think the concern centers more around any level of slop between the wheel and the worm gear, as any level of slop will allow the table to oscillate back and forth during a cut causing chattering, unless table locks are applied. You make a good point about the 10:1 ratio though. It makes sense that a very small thread pitch on the worm gear would minimize any potential back-drive of the wheel.