[brunolundh]

I am almost 3 years into build my Avid CNC pro 4" x 8" with DMM servos.
Rack and pinion system so servos need to rotate the opposite way to move it one way.

Almost got it running but í have the problem that the slave servo goes the wrong (right) way when I put it in Slave to Y mode.

I cant invert the rotation because slave servo settings just follow the settings of the master servo.

Feel pretty stupied because I can´t find anyone with the same with the same problem and this style of CNC routers is popular.

Eding software

Regards
Christer

[brunolundh]

I found it out.
Very logical. Just switch DIR+ and DIR-

[brunolundh]

. Just switch DIR+ and DIR-

That was wrong, now they ONLY go way way :withstupi

[arie kabaalstra]

erhm... in that case.. Flip the wiring of one of the servo's?

[brunolundh]

The servos dosent work like that. The encoder flip out.

In this case with DMM I needed to put all reference voltage in a pin on the driver

[arie kabaalstra]

Ok.. i admit.. i don't know anything about servo's.. but.. maybe... inverting the encoder signal in some way?..

[joeavaerage]

Hi,
most modern AC servos have serial connected encoders, and it's not possible to invert it....and even if you do you have made a real cockup.
With an inverted encoder the drive detects an error between the commanded position and the actual position (as reported by the encoder), and the drive will
excite the servo to reduce the error.....but because the encoder is inverted the servo will go the wrong way, so the error increases, so the drive increases the excitation.....
and the error gets even bigger.......until it crashes.

If you invert the encoder you have to reverse the direction of the servo also otherwise you will cause the servo to 'run away' and crash. With an AC servo that requires that you swap
two phases to the servo.

Modern AC servos are very plainly labeled with respect to phasing and encoder polarity such that this 'run away' does not occur, you are advised to stick to it. There are better ways to do this.

Craig