[strangetanks]

I've built a cnc router a couple years ago and am about to retrofit a bridgeport. CNC router uses stepper motors and I'm a little unfamiliar with servo motors.

My question is if I retrofit the milling machine with servo motors, using gecko drivers, will mach3 show the position if you turn the handles manually? Sort of a poor mans DRO. I'm sure this has been asked and answered somewhere but I'll be damned if I can figure out where.

Also, my steppers have a lot of "drag" when they are off and you move them manually. Do servo motors do the same thing?

I'm not too concerned about backlash compensation in the DRO as I figure its basically like using a manual machine except your looking at a screen instead of the dials.

Thanks everyone.

[Al_The_Man]

Mach closes the servo loop to the drive, not to the controller/HMI so it cannot show actual position, only anticipated posn.
Servo's do not have the inherent Indent that steppers have, so when not energized they should rotate freely.
Al.

[strangetanks]

Mach closes the servo loop to the drive, not to the controller/HMI so it cannot show actual position, only anticipated posn.
Al.

So in other words the readout on mach3 will not increment if the servos are turned manually. Did I read that correctly?

[Al_The_Man]

Yes.
Al.

[wizard]

I've built a cnc router a couple years ago and am about to retrofit a bridgeport. CNC router uses stepper motors and I'm a little unfamiliar with servo motors.

My question is if I retrofit the milling machine with servo motors, using gecko drivers, will mach3 show the position if you turn the handles manually? Sort of a poor mans DRO. I'm sure this has been asked and answered somewhere but I'll be damned if I can figure out where.

I don't know of any adaptations that allow Mach 3 to do that. In the case of the Gecko drive the encoder feedback goes to the motor amp. You would need a system that allows encoder feedback to the CNC software, EMC can do this from what I understand. It might be worth checking out Mach 4 when it comes out. The Mach guys are giving Mach 3 a massive overhaul for the Mach 4 version, I don't know if it will allow position feedback closer through Mach though.

Also, my steppers have a lot of "drag" when they are off and you move them manually. Do servo motors do the same thing?

Servos won't have the same issues as steppers as the technology is completely different. However servos won't allow you to move an axis if powered up and enabled. Some systems allow you to move things around if the servo is disabled. Others may cause problems due to voltage feedback to the amp when the motor is rotated.

I'm not too concerned about backlash compensation in the DRO as I figure its basically like using a manual machine except your looking at a screen instead of the dials.

Thanks everyone.

I wouldn't say that, using a DRO, especially a good one with lots of helpful features, is a different experience. A DRO that doesn't have mechanical lash in its installation frees you from the mental gymnastics required to be sure that all backlash is taken out before starting a cut.

[wizard]

So in other words the readout on mach3 will not increment if the servos are turned manually. Did I read that correctly?

Mach 3 Puts out step and direction signals and thus doesn't support such feedback in its basic form. The KFlop guys have a Mach front end for their hardware. I'm not sure what that afford you though. So best to talk to them or get on a forum oriented to their hardware The KFlop site is: Dynomotion | Motion Control Boards. I don't have any of dynomotions hardware or software so you will have to get info from them.

[Hood]

There are controllers available for Mach that will feed encoders back to Mach to update the DROs.
I use the CSMIO/IP-A controller, from CS-Lab, on my Chiron FZ12S and it updates Mach from the encoders. If I rotate the motors manually when disabled Mach is updated, if I E-Stop then Mach knows where it is etc etc. It however is for use with analogue control servo drive/amps and not Step/Dir.
I am not certain but I think the Hicon from Vital Systems may feed the encoders back to Mach but you would have to check up on that, it is for use with Step/Dir drives.
Here is my Chiron just in case you are wondering what one is
Hood
https://www.youtube.com/watch?v=JS9mh_iMing

[strangetanks]

Thanks for the info everyone, I'm sure I'll have more questions when I start really digging into this project. The DRO function while nice isn't all that important to me and the relatively small amount of machining I do.