Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: marc erasmus on June 09, 2009, 03:50:57 AM

Title: slave axis suddenly reverses while jogging
Post by: marc erasmus on June 09, 2009, 03:50:57 AM: we have notices on one of our machines that the 1 axis on the gantry will suddenly reverse , with hectic results, like it tries to twist our gantry in half, during a jogging move!!! has anybody else ever found this or know how to solve it!!! it is not consistant but seems to only happen during a jog...can any body help?
regards marc
Title: Re: slave axis suddenly reverses while jogging
Post by: Hood on June 09, 2009, 04:15:35 AM: Check the Dir connections, could be a loose connection on that axis making it change direction, could also be noise. Might be worth changing out the keyboard just in case but that is unlikely as I would have thought both motors on that axis would reverse..
Hood
Title: Re: slave axis suddenly reverses while jogging
Post by: marc erasmus on June 09, 2009, 04:41:58 AM: thanks hood, i know what you mean, we have changed the keyboard out, problem still occurs. it is extremely random, any ideas how to shield the step and dir wires from noise, must the box be rewired?

do you know if servo systems are less susceptible to noise?
Title: Re: slave axis suddenly reverses while jogging
Post by: Hood on June 09, 2009, 04:47:46 AM: You can either rewire between the breakout and drive with shielded wire or you can buy braided sleeve that you can slip ove the original wire. Only ground the shield at one end and have all of your shield wires grounded to one point rather than the nearest convenient ground.
If its noise on a Dir wire then dont think it would matter whether it was servo or stepper except if you were getting into the types of drives I use as they are differential Step/Dir and all other I/O is 24v so noise is much less of a problem.
Hood
Title: Re: slave axis suddenly reverses while jogging
Post by: marc erasmus on June 09, 2009, 05:56:29 AM: thanks hood, i will do as you recommend,i think the braided sleeve will be the best bet. tell me , would those be delta servo drives by any chance?
Title: Re: slave axis suddenly reverses while jogging
Post by: Hood on June 09, 2009, 09:01:52 AM: No they are Allen Bradley DSD but there are lots of different makes out there, Yaskawa, Omron etc etc Just need to make sure they support Step/Dir inputs.

Hood
Title: Re: slave axis suddenly reverses while jogging
Post by: keithmech on June 09, 2009, 01:23:02 PM: what brand of servo drives are you using?
Title: Re: slave axis suddenly reverses while jogging
Post by: marc erasmus on June 10, 2009, 02:18:28 AM: we are using stepper drives on this machine, why do you ask?
Title: Re: slave axis suddenly reverses while jogging
Post by: Sashko on June 15, 2009, 01:52:04 PM: Marc,

I have the same problems with my steppers in all axes and just in one direction.
Can you tell me did you solve your problem?
Title: Re: slave axis suddenly reverses while jogging
Post by: marc erasmus on June 17, 2009, 03:59:49 AM: i havent solved it yet sashco, but am going to get a lot of screening "sock" today so we can screen from interference. we think that interference and possible bad earthing could be the problem. check back with me in a couple of days
Title: Re: slave axis suddenly reverses while jogging
Post by: Wombat on June 18, 2009, 12:53:32 PM: Quote from: marc erasmus on June 17, 2009, 03:59:49 AM
i havent solved it yet sashco, but am going to get a lot of screening "sock" today so we can screen from interference. we think that interference and possible bad earthing could be the problem. check back with me in a couple of days

I'm also signing on to hear of a possible remedy. I have this problem with my new plasma table, but only in the Y++ direction - everything else seems to perform fine. I can get rid of it by increasing the step pulse setting to 5 under config->motor tuning, but that's not the way it was tested and setup by my manufacturer, so something is amiss.
Title: Re: slave axis suddenly reverses while jogging
Post by: marc erasmus on June 19, 2009, 03:54:24 AM: ok, i will post mu findings once we sort it out...glad to know we are not the only ones with this problem. something we have noticed though, is that our step and direction signals run past a mqain power line...check that out!