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Author Topic: Random Change of Z Axis Direction  (Read 5628 times)

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Random Change of Z Axis Direction
« on: May 05, 2014, 04:07:16 PM »
Hello - I'm just new on the forum - because till now, my machines worked fine with Mach3 and Smoothstepper Ethernet. But now I encounter a severe problem on a milling machine. I installed the following parts: Smoothstepper ESS - BOB - Modules to change dir/pulse signals to differential signals A and B (these are modules for SEW Servo drives). - I didn't yet finish the construction of the machine, so I can only move the axis by keyboard signals. I can't explain when the problem arrives, but sometimes it arrives that by pressing the PgUp or PgDn Key the axis moves in the wrong direction. Then I check the ports and pins settings Motor Output the Dir low active. Then the axis moves again in the correct direction. But suddenly the Z-axis turns in the incorrect direction. - The X and the Y axis move fine (finally I hope so - I'm not 100% sure!).
It is a real bad problem with maybe bad consequences. What can I do? The constructor of the SEW Modules tells me, that the modules work correct (he has made several tests). Shall I put the the Dir Puls in the motor configuration to a higher value or shall I use the sherline 1/2 pulse mode? Or shall I reduce the steps per mm (now on 1000). The SEW MDS Servo Drive accepts up to 200kHz.

Thanks a lot for every help
Re: Random Change of Z Axis Direction
« Reply #1 on: July 02, 2014, 11:39:00 PM »
Hi Daniel,

Have you resolved this problem?  What output port and pin are you using?  It probably isn't the motor driver, but the next time it happens you can confirm it has swapped polarity by using your multimeter to measure the voltage on the direction input of the motor driver.  First measure the voltage when it is working properly, and then measure it after it has unexpectedly changed direction.  Be sure to remember which multimeter lead you had on each terminal.  You should probably measure the voltage at the output of the ESS, the output of the BOB, the output of the differential drivers, and the input of the motor driver.  You might not need to use the conversion modules since the ESS can output quadrature (A and B) directly instead of Step & Direction.  The setting for each axis is on the ESS's config page.

You said "I check the ports and pins settings Motor Output the Dir low active".  I assume the Dir had been set to low active and you clicked it twice (once to Active High, and again to Active Low) to make sure it is set properly?  Or was it Active High when you opened up the dialog and it should have been Active Low?

What version of Mach are you using?  And what version of the plugin?


Re: Random Change of Z Axis Direction
« Reply #2 on: July 03, 2014, 02:36:41 PM »
Hi Greg

Thank you very much for your answer. - I resolved the problem by changing the SEW Servodrives and put in Lenze EVS 9300 ES Servodrives with modules to change pulse and dir to A and B signals. Since then - the machine works wonderful. - I think it was a problem of the modules that change the pulse and dir to A and B for the SEW Servodrives. The developper of the SEW modules didn't work fine, so I got some EMV problems.