Servo motor moves only backward

[jebril]

Hello all,

We have an older Gabbiani CNC cutting machine (1992) from Italy. Its servo drive and servo motor are from Siemens. Now we have the problem, that the servo motor of the x-axis moves only backward and can't move forward !!

All sensors and actors are OK. I checked all inputs and outputs of the PLC, there is nothing that blocks the motor to move forward.

Also, when the motor was not assembled on the gear, we tried to run the motor forward, but it did not work. Otherwise as we run the motor backward
it works !!


So any one can help me or have an idea about this problem? especially, why the servo motor moves only in one way , backward ?!?!!?!


thank you very much

[Al_The_Man]

In many systems the overtravel limits are set up to inhibit motion in the direction of the overtravel switch, check the forward switch for stuck in condition.
Al.

[mujid]

Check if the forward annd reverse command are provided to the servo driver, if both ok try to replace the servo motor, when the situation persist then the problem is come from the servo driver. hoped will help.

[jebril]

Hello,

how could i test the forward and backward signals, if they are provided to the servo drive or not??

siemens technical support advised me to put 1.5 V to the input of the servodrive (simens simodrive 611A) (pins 56-14) and checked. the motor also moved backward and didn't move forward when I changed + and -.

[mujid]

Using your dc volt meter , apply forward command check the voltage polarity, then apply reverse command then voltage polarity should be reversed.

Or you can try the siemens guy suggest, but if it will not moving forward then you have problem on your servo driver. hoped will help.

[jebril]

hi mujid,

I already checked the voltage of both commands. backward movement gives voltage (1.5v to 10v) but foraward movement is 0 V !! I tried to give the servo drive 1.5 V from external battery, but nothing happend !

could somthing break the motor to move forward? because there is input signal (forward command) for servodrive "external battery" but the PLC doesn't release the motorbreak and didn't turn the motor on (unlike backward movement) !!

[mujid]

1. If you read 1.5v to10V for backward then you should read -1.5V to -10V for forward , if you only read 0V for forward the forward command was not provided.

2.While doing test using battere, Have you exchange the batere polarity ? it will give forward and revers command. Take care for over travel , more save when you disconnect the motor belt !!!
good luck