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December 13, 2018, 14:32:48 pm


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Author Topic: Mach3 help, please!  (Read 210 times)
lloydsp
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« on: December 06, 2018, 00:51:38 am »

I've configured Mach3 with a PMDX-126 breakout board, and a PMDX-107 PWM spindle control, both driven by an ESS (ethernet smooth-stepper) board.

I've got all axes moving, and the spindle VFD voltage responding properly to the requested speed -- BUT...


I cannot seem to get the stepper axes correct for what "seems normal".  The drivers are 10-microstep-per-full step Gecko 503, the stepper motors are 200steps/rev, and the lead screws are 5tpi.

But unless I set the stepper microsteps to 10x or more than shojuld be necessayr,

Thanks, Lloyd
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« Reply #1 on: December 06, 2018, 01:03:09 am »

10x5x200 = steps per inch nominal.  

Start with modestly low acceleration.

Some Gecko Drives require tuning.  I seem to recall it consisted of running the axis at a low speed continuously and adjusting a pot until the motor had a sweet smooth sound.  

The Gecko handles the transition from microstepping to stepping when running fast, if that drive has that capability.  You still feed it like its microstepping.   

Did I not understand the question?  

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Bubba
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« Reply #2 on: December 06, 2018, 01:09:06 am »

I cannot seem to get the stepper axes correct for what "seems normal".
********************
Not sure I understand what you mean by this.. Is the commanded travel distance the same as what you are measuring?
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lloydsp
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« Reply #3 on: December 06, 2018, 02:29:25 am »

Boy!  I don't know what happened to my post, but what it says isn't what I typed!  Darn!

Anyway... Thanks, I know what the steps/inch should be, in fact, I built one of the two machines I use weekly -- but not with Mach3 as the control.

Yes... 10K steps per inch.  It's true the G203V will switch to full-step activity at certain rpms, but it doesn't do a full step for each 'input step'... that remains at 10 steps per full step.  The motor just runs as if it were being full-stepped to get better torque.  And this model is 'self-tuning' for smooth operation.

No, the problem is that when I tell Mach3 10K steps per inch, it goes at about 10x too fast, misses steps, and only 'sees' about 1/10th of the steps it should (but not exactly 1/10th).  When I set it to 100K per inch, it works approximately as expected... but that just bothers me, and I want to know why.

It's GOT to be something I did wrong.  I've never had this sort of problem with any other soft before.

Lloyd



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Garyhlucas
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« Reply #4 on: December 06, 2018, 03:06:19 am »

My money is on your drives not actually microstepping, but doing full steps.
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Dragonfly
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« Reply #5 on: December 06, 2018, 08:04:06 am »

Yep, seems to be something related to driver micro step settings. And perhaps its 'intelligent' behavior. Maybe there is a step rate threshold?
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lloydsp
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« Reply #6 on: December 06, 2018, 15:24:04 pm »

The Gecko 203V doesn't have any USER-settable parameters except for max winding current, which is set via a chosen resistor.

It is possible that the drive is entering its 'full step mode', but when a G203V does that, it divides incoming pulses by 10, and only issues one step per 10 issued by the controller.  At some step rates, full steps work more-smoothly and with better reliability than do micro-steps.

It's a pretty fool-proof drive.  I have them on several pieces of equipment I built from scratch, including designing and building the controllers.  This is just my first foray into Mach3.  I didn't build the PMDX-126, the PMDX-107 daughter-board, or the ESS smooth-stepper.  So, beyond setting things "the way I'm told", there isn't much I can do the affect their behaviors.

So... I won't rule it out, but I don't think it's the G203V mishandling the job.

Lloyd
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Bob La Londe
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« Reply #7 on: December 06, 2018, 15:26:29 pm »

My next step would be to ask one of the 3 Ms over at GeckoDrive.  I never could keep them straight, but one of them was usually helpful.  Atleast until you mentioned a failing in their drive or design, and then they would stop responding or refer you to the manuals you already memorized from reading through them so many times.  LOL.  

I'm no longer a fan of GeckoDrive.  I feel they are overly optimistic with many of their specs. One of the 3 Ms told me they design everything with a 20% safety margin.  Well 20% is a bit light of course, but that safety margin in my opinion is marginal at best.  In fact I feel that the spec itself is often marginal.  Yes, I push things a bit.  

Anyway, ask them.  At first atleast they will gladly help you with any obvious solutions you may have missed.  
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« Reply #8 on: December 06, 2018, 15:34:00 pm »

It does sound like either the drives are full stepping or there is a step multiplier set somewhere in the other hardware.  



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lloydsp
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« Reply #9 on: December 06, 2018, 17:03:56 pm »

Yeah, well, I solved it.  As usual, it was MY fault, not the hardware!

Two things: 

1) The Mach3 setup instructions with a PMDX-126 controller don't mention this, and I didn't think of it:
   A) Many (perhaps most) stepper drives accommodate low-active signals on step and direction.  Some are fixed, and some have pin selections you can make to get there.  The instructions ASSUMED low-active signals, but...
   B) The Gecko 203V is positive-going-only.  So I had to reverse the active states in the software to accommodate it.  The bad thing is, I've built stuff with these drives before, so I knew that... I just forgot.

2) I used some 'canned' demo g-code from the Mach3 web site.  I should have written my own.  The code had a fairly well-hidden G21 (use metric units).  I needed a G20 to go in inches.  Duh!

I fixed both, and the motors are now moving as expected, and the correct distances.

It wasn't any hardware misbehaving except the hardware between my ears!

Lloyd
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Dragonfly
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« Reply #10 on: December 06, 2018, 17:45:03 pm »

Quote
It wasn't any hardware misbehaving except the hardware between my ears!
Well, hardly anyone here would  deny he hadn't had problems with that hardware Smiley
Good you solved the issues quite fast.
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Bob La Londe
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« Reply #11 on: December 06, 2018, 22:59:32 pm »

Hardware?  You mean wetware. 
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lloydsp
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« Reply #12 on: December 06, 2018, 23:46:55 pm »

Well...  Linda has always accused me of being a "hard-head", so I just figured...

<smile>
Lloyd
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