need help selecting servos and amps

[Daniel Wilcox]

I have a shizuoka an-s running EMC2. It has steppers on it currently, which keep loosing step and they're slow (nema 43, yes, 43). I'd like to replace them with servos so i can have some feedback to my controler as far as position, and also so i can kick it up from 80-90ipm to at least 200. Any recomendations for motors, encoders, and amps? I'm running a Mesa 5i20 i/o board if it matters, and this is a heavy chunk of iron for anyone not familiar with the machine.
I was looking at the 3 axis kits, but i dont know about the gecko drives. it looks like there is no feedback to the controler itself as far as position and i dont like that. Am i wrong here? Also, i was considering just doing the x and y axis for now, since thez seems to be fine (quill feed).
Thanks in advance,
Dan

[vintageracer]

Hi Dan,

I know how you feel. I have a Dyna Mectronics DM4400 retro fitted with a Gecko G540 but still using the original 160oz steppers. I lose steps during heavy cuts on a regular basis and re homing the machine is an inconvenience with 50ipm rapids.
I'm planning on converting to DC servo's but the options are almost overwhelming.
I've done a fair bit of research on servo's and depending on your budget you have a few good choices.
If you have the cash, go with brushless servos and driver package from Glentek, they have NEMA framed servo's designed for stepper replacement.
But if you have a smaller budget, like myself, I would suggest the Keiling servo's with CNCdrive Dugong drivers.
I've used both the Gecko 203v's and the G540 stepper drivers and the Gecko stuff is top notch. However the 20amp limit on the G320 drivers will restrict your acceleration of the larger servo's that you and I both require.
Some people have mentioned not liking the Keiling servo's, but for the price they are hard to beat. Equivalent sized servo's from a brand name manufacturer will run 5 to 10 time the cost of Keiling motors.
As for position feedback, the encoder usually feeds back into the servo driver. I'd like to put glass scales on my machine for absolute postion but Mach 3 doesn't have the ability to handle the extra position input.

Hope this helps,
Timothy

[samco]

You don't want to buy step/dir drives for your application. That would be going backwards. You want emc to close the control loop so you know exactly where you are at all times.. You have the mesa hardware which will give you a very powerful setup. do you have any of the daughter boards for the mesa? the 4 axis servo interface? That would allow you to use any industrial standard +/-10 servo drives. (or you could do PWM+DIR without) If it was me - I would be keeping an eye on ebay for some inexpensive copley or a-m-c drives. (or buy new) I am sure there are others...


As far as the size of the servos.. I don't know. Maybe someone will be able to shed some light on this.