quick spindle question

[xclr82xtc]

would it be ok to just buy a great big honkin servo motor that runs at like 6500rpm and uses gears to spin the tool 18000 plus??

and on the spindle note, can anyone give me some information on air bearings, im gonna machine/design this spindle myself to use standard tooling off of a hass, but i dont want to be tearing it down to rebuild bearings (remember 18000 rpm )

[RICHARD ZASTROW]

Insufficient information.

Precision sealed angular contact bearings can easily run at 18,000 rpm IF spindle shafts and housings can support them. Also, the torque, axial and radial forces match up with the bearings capacity (including adequate safety margin).

In order to make an intelligent decision, you need a lot of missing info.

Dick Z

[xclr82xtc]

ok...basically what im asking is, can i use a servo to power a spindle and gear box that im gonna machine myself. what else do you need to know?

[RICHARD ZASTROW]

Yes you can use a servo to drive a spindle, I do it on nearly all the spindles I design. How much power (torque) do you need?

Most servos don't do 18,000 rpm. So you will probably have to gear (belt & sprocket) up to the speed you want. (your original question). Remember to consider heat build up with 18,000 rpm.

Also, when using servos you have to look at the power charts. The torque drops off like a rock when you go faster than the rated speed.

If the application is milling/routing you might be able to use a less expensive type of motor with a variable speed control.

If you aren't threading or requiring a C axis interpolation??????????

Maybe we can entice the electronics/electrical guru's into this question. Al?

Dick Z

[xclr82xtc]

Originally Posted by RICHARD ZASTROW Yes you can use a servo to drive a spindle, I do it on nearly all the spindles I design. How much power (torque) do you need? this is yet to be determined...as i need to figure in the power drop with gear ratio. i will be doing mainly MMC metals...witch REQUIRE pcd high speed tooling/machining. but also some light steel work ( but rarely) i will probably put titanium on more than i do steel lol. (unless i start making my own connecting rods) Most servos don't do 18,000 rpm. So you will probably have to gear (belt & sprocket) up to the speed you want. (your original question). Remember to consider heat build up with 18,000 rpm. i thought of the belt at first and then i thought it might be better/safe/more "professional" to use a gear box mounted to the front of the servo. i was thinking of using the coolant system to cool/lube the gears, but i dont know if that would work. I'm completely prepared to mount an electric oil pumping system/cooler to the gear drive. i was thinking of a simple 2 speed design. 1:1 and 3(or 4):1. Also, when using servos you have to look at the power charts. The torque drops off like a rock when you go faster than the rated speed. so i have read, and seen on the charts but i have seen spindles rated at 6500 rpm. i could run that at 6000 with my 3:1 and get my 18000 If the application is milling/routing you might be able to use a less expensive type of motor with a variable speed control. If you aren't threading or requiring a C axis interpolation?????????? well origianally the idea was to use the 5th axiz and the spindle as a lathe...but now im thinking of have a seperate lathe tool and just using the spindle as live tooling, which would, as you said allow me to use a variable speed motor. this would also allow me at some point to mount a bar feeder and use my 5 axis as a vmc AND a live tooling lathe Maybe we can entice the electronics/electrical guru's into this question. Al? yes please! Dick Z

thanks for the response! they are limited on this site! lol

[RICHARD ZASTROW]

OK, I'll open up to criticism.LOL Does an induction motor with VFD sound applicable?

Dick Z