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Testing for Missed Steps
« on: October 31, 2016, 03:17:07 PM »
Greetings,
Just finished my Joes CNC Evo.  Happy with it so far, but his a few snags last night.  Noticed that I had to be losing steps big time.  My circles were looking like eggs!  Yes, I have a noisy 2.2kw chinese spindle, but I have nice shilded wire and have connected the ground pin to the casing.   I have several times had EStops thrown when the spindle's not running.  Not sure what's going on, but I went ahead and jacked the Debounce up to 2000.  Seems to have fixed it to some extent.  The EStops aren't happening any more, but i was still losing steps both on X and Y (dual drive).  So after some reading, I put the Y and X on Step Low Active (supposed to help?)  It did!  Now it appeared I was only getting lost steps on X, but not Y.  So I disabled Step Low Active on X and it seems good so far, but of course every time I go to run a job I'm nervous.

LOOOONG STORY to ask this one little question.....Does anyone know of any wizards to test for lost steps.  I have 2 home switches installed, X and Y, nothing on Z.  I'm thinking like a wizard that would home the machine, then move it some number of steps out, then return it, ideally it should be the same number of steps back to the switch, but if it's more/less, it could tell you so you would know you still have an issues somewhere?  Does it exist, and where?

Thanks!!

Offline Tweakie.CNC

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Re: Testing for Missed Steps
« Reply #1 on: November 01, 2016, 02:06:54 AM »
Just a suggestion…

You should regard increasing the Debounce as a sticky plaster rather than a cure and you really need to address the cause of the problem which, from what you say, could well be electrical noise.
As a first step, check that your limit/home switches (and Estop) use good quality shielded cable, with the shield connected to a ‘single point Earth’ at the controller end only.

Tweakie.
KEEP SAFE !
Re: Testing for Missed Steps
« Reply #2 on: November 01, 2016, 03:02:49 AM »
I agree.   I know it's a problem.   I don't have any limit switches setup, just 2 home switches.   But my estop wires aren't shielded.   To make sure I understand though, I would hook up the shielded wire to the estop button, the other end to my g540 and the drain line to ground on my g540?

Offline Tweakie.CNC

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Re: Testing for Missed Steps
« Reply #3 on: November 01, 2016, 05:30:15 AM »
I think you should fit a common (star) Earth tag at the controller end. This tag would then be securely connected to Earth. All shielded cables would have their shield connected to this tag (the shield at the other end of each cable insulated and left unconnected). Your home switches should use shielded cable and your estop should use shielded cable.
Treat Earth and GND as two separate circuits.

Some while back I did a short write-up (mainly for beginners) which may be of interest. http://openbuilds.com/threads/electronics-101.693/

Tweakie.
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Re: Testing for Missed Steps
« Reply #4 on: November 01, 2016, 11:27:40 AM »
While I haven't yet implemented all of your suggestions.  I did go back and rewire my EStop with a grounded cable like the one I connected from my VFD to the Spindle.  After doing so, I turned the Debounce down to 0 and ran a bunch of jobs as a test.  DEAD ON!  No missed steps as best I can tell!  Thanks so much for the help!

Offline Tweakie.CNC

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Re: Testing for Missed Steps
« Reply #5 on: November 01, 2016, 11:43:45 AM »
I am pleased to hear that you have it sorted.
Maybe good to set the debounce at around 200 for normal operation.

Tweakie.
KEEP SAFE !