New Machine Build- Problem with Linear motor/panasonic driver

[raghav2984]

Dear All,
I'm new to CNC machine building. My first assignment is to work on a high precision machine using Linear motor. It has 2 axes (X & Z) both identical in mechanical and electrical/electronic aspects. Z axis works fine all the time. But the X axis faces problem like Run-away, jerky motion, vibration and improper direction sense. The driver trips stating error like over-loading & over-speeding during the above mentioned conditions. But sometimes, if the stage is moved manually during servo-off and subsequent servo-on condition makes the stage to move continuously without any issues (though this is also not a repeatable solution, as the amplifier trips often). Also due to this erotic motion of the motor, there is fault/following error flag raised in the controller. Could there be any problem with motor???

Z axis is not at all affected by any of the above mentioned problems. following are the details of the driver, controller and motor.

Panasonic driver - Customized.
Umac controller from Delta tau
Sodick linear motor (50mm max. travel range) - 3 phase

Kindly help me in addressing this problem by providing some possible causes of the error. All your suggestions are appreciated. Thanks in advance.

[mike_Kilroy]

your description is consistent with bad phasing. this does not sound like a 'bad' motor but more likely a bad feedback device. You did not say what the feedback is but with delta tau and old panasonic drive I will assume halls and incremental encoder. sounds like a loose wire on a hall feedback (there are 3) - they are used on power up to phase the system then it switches over to encoder feedback. if enc problem the DT prob would complain. so i vote for bad hall thing.

btw, did it used to work? if so, what happened just before it stopped working? thats a clue. did it crash? is it new and never run yet?

[raghav2984]

Hi Mike,
Thanks for the reply and sorry for the late response. I had sorted out the phasing problem. As you mentioned, it was due to encoder connection. just swapped A+ and A- and it did the magic.

Now I face the problem of high noise level. I could segregate the noise due to three reasons:
1)Electrical
2)Environmental
3)Mechanical

with electrical creating the maximum of 300nm when the servo-on condition for the 2 motors. i want to eliminate this noise and make the movement of stage much smoother because I could see hunting of the motor at stationary position and a large following error. The encoder is having a resolution of 5nm, but couldn't achieve anything near to tens of nm also. I suspect whether it may be because of SMPS of the panasonic driver. Can a linear drive solve my problem? Can you suggest any linear driver company, if you know?

Thanks for your valuable reply.