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Re: Mach4 positioning error
« Reply #40 on: December 15, 2019, 07:50:12 PM »
Hi,
I use Delta B2 series servos which have a 160,000cpr encoder (40,000 line) and the electronic gearing applies to that native encoder pulse stream.

It is possible for the drive to produce an encoder signal (A,B,Z) which is synthesized from the native encoder pulse stream. These encoder output
channels could be used to drive stand-alone DROs for instance, and they are programmable from 4 lines to 40000 lines per rev.

This is an example of "encoder output scaling factor" but has no relevance to your electronic gearing (which applies to the native built in encoder)
or your steps/unit values.

Craig
My wife left with my best friend...
     and I miss him!
Re: Mach4 positioning error
« Reply #41 on: December 16, 2019, 10:45:15 AM »
Hi Guys,

I adjusted p11 to 4 and p12 to 20 but the servo gave an alarm with that settings so i increased the p12 to 4000 with that setting it works without giving any alarm.

But these values has nothing to do with the error i am reading, today i checked X and Y axis, X axis works more noisy, there is noticeable backlash and it is almost 100micron short in 10mm movement. So i guess increasing the ball number within the ballscrew nut was not a good idea. I am gonna reverse it to its original ball number(105) tomorrow.

In Y axis before measured error still there but it is also increased by 10micron and its not a reading error. I didnt touch anything related with that axis but its error increased.

I am where i was at the beginning of this post, this does not look like a mechanical or servo/step motor based error to me, because nothing changes when i tweak the parameters or realign the ballscrews. Tweaking the step per unit value or electronic gear ratio value does not make it any better, it makes it worse and the error readings changes with days.
 
Today while taking the measurements i noticed something within the controller which i think should not be happening, there is "step" led on PMDX bob which flashes when u send pulse signal to the servo/step drives. While the machine was at rest and i wasnt touching anything that "step" led was flashing in high frequency intervals like it does when u send a pulse signal.

I believe that led should flash only when u move an axis. Anyone has an idea about this?

another thing; Delta spindle drive shows on its display 0.1-0.2 changing frequency input in idle state.

There is a 3phase EMC filter in main line input, but no EMC filter before the control cabinet.

I didnt have time to test one axis with a shorter cable directly connected to the pmdx bob, tomorrow i am gonna try it and if it does not work, i am gonna completely bypass the controller, hook up another motherboard and a parallel port bob from outside, connect it to the Y axis for example and send signal to it then we will see if this is related with the noise within the controller.

There is no HF source within the controller, its just the motherboard, PMDX+ESS+spindle board attached to pmdx and input boards, there is only a small PSU(with metal cover) which supply power to the motherboard. There is no noise source that i know of but that led should not be flashing in idle state.

Regards,

Hakan


 
Re: Mach4 positioning error
« Reply #42 on: December 16, 2019, 12:09:19 PM »
Hi,

Quote
I adjusted p11 to 4 and p12 to 20 but the servo gave an alarm with that settings so i increased the p12 to 4000 with that setting it works without giving any alarm.

When it gives repeated alarms with the following error (P12) set to 20 means that the servo cannot accurately follow the
toolpath. You need to work out why. With the setting at 4000 what you are saying is that you'll tolerate:

4000/10000 x 25=10mm of deviation before the machine faults.

The most likely problem is that you have too high acceleration set in Mach4 so the toolpath will zoom off in a new direction
but the servo can't keep up because it has to lunk a huge piece of iron around.

Set all the acceleration parameters in the servo drive as high as you possibly can then reduce Machs acceleration in that axis until
the machine no longer alarms. That then is the true measure of the acceleration the servo is capable of producing with
that axis mass.

Craig
My wife left with my best friend...
     and I miss him!
Re: Mach4 positioning error
« Reply #43 on: December 16, 2019, 12:16:23 PM »
Hi,

Quote
There is no HF source within the controller, its just the motherboard, PMDX+ESS+spindle board attached to pmdx and input boards, there is only a small PSU(with metal cover) which supply power to the motherboard. There is no noise source that i know of but that led should not be flashing in idle state.

You are correct, the step signal should not be flashing unless the axis is moving.

Do you have an oscilloscope? I would probe the step output of the ESS and the step output of the BoB.

Craig
My wife left with my best friend...
     and I miss him!
Re: Mach4 positioning error
« Reply #44 on: December 16, 2019, 02:28:43 PM »
Hi Craig,

I will adjust p12 later as u describe when i solve this huge problem.

I forgot to mention that i saw that flashing led 2 times in machine idle state and it didnt go away until i move an axis back and forth for some time.

I dont have an oscilloscope but if tomorrow Y axis moves as it should be with parallel port commands from another computer, i will take apart all the controller cabinet and build it from scratch electric/electronic wise, thanks.

Regards,

Hakan
Re: Mach4 positioning error
« Reply #45 on: December 16, 2019, 06:39:16 PM »
Hi,

Quote
I forgot to mention that i saw that flashing led 2 times in machine idle state and it didnt go away until i move an axis back and forth for some time.

I believe you have found the root cause of the problem which inspired this thread.

Quote
with parallel port commands from another computer, i will take apart all the controller cabinet and build it from scratch electric/electronic wise, thanks.

You are in danger here of identifying the problem area WITHOUT finding out why. You may succeed in fixing the problem with a rebuild but still be none the
wiser as to what is happening.

Clearly you have invested a lot of time and money into this project, find a technician with an oscilloscope and pay him/her to indentify the problem properly
or risk having the same thing occur later.

Quote
I will adjust p12 later as u describe when i solve this huge problem.

With regards this problem there may be a software oscilloscope in the tuning software, if any. If you monitor the position error you will learn a huge amount about
your machine and controller. I have attached a screenshot of part of the Delta software scope. Note how you can identify and monitor certain variables, like
commanded position and feedback position etc. Very useful for identifying problems.

Craig
My wife left with my best friend...
     and I miss him!

Offline RICH

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Re: Mach4 positioning error
« Reply #46 on: December 17, 2019, 08:54:33 AM »
I believe that led should flash only when u move an axis. Anyone has an idea about this?

The PMDX manual has detailed info about the LED's.

RICH
« Last Edit: December 17, 2019, 08:56:30 AM by RICH »
Re: Mach4 positioning error
« Reply #47 on: December 17, 2019, 11:17:19 AM »
Nice catch RICH.  :)

From that manual:

"Steps LED Flickers when activity is detected on pins that may
be used for step signals. The PMDX-126 does not know which
pins are being used as “step” signals, which are used as “direction” signals or which are used
for some other function.  The PMDX-126 assumes that all of the signals listed in Table 14
could possibly be step signals and monitors them for activity. 
The PMDX-126 also does not know the polarity of the step signals, so it looks for a rising edge on
any of the signals listed in the table and calls that “step activity”. 
This has the side effect that changing a direction signal may cause the “Steps” LED to flicker. 
Likewise, any activity on parallel port #1 pin 1 or parallel port #2 pins 1 or 16 will cause the “Steps” LED to flicker."

"When using outputs “1”, “14”, ‘16”, 17”, “A”, “B”, “C” or “D” for step and direction
signals, connect the “step” signal to pins “1”, “16”, “A” or “C” in order for the
activity monitor to function correctly."
Re: Mach4 positioning error
« Reply #48 on: February 19, 2020, 12:11:42 PM »
Hi Guys,

I wanted to close this thread by writing the real cause of the errors i was reading.

I was not the electronics, noise or Mach4, i changed the controller from mainboard to bob completely and it was repeating the same errors.

The error was there because of the mechanical problems, half of it was because of the angle errors in the support units i ordered from a manufacturer in China(they should be 0.01 accurate but manufacturer did them 0.1 accurate because of the misunderstanding) which i connected the ballscrew bearing units and motors. And the other half was because of the backlash and error in the real pitch values, when backlash compensation done and step per unit pulses tuned after scraping the support pieces and paralleling/squaring them to the each axis by hand within 5 microns, now, every axis has good positional repeatability with max 15microns error.

I think the best thing can be done in here is to replace the longest axis's ballscrew/support units with 40mm diameter, double nut, C3 precision, mid preloaded ballscrew and C3 heavy duty support units because the one i have in hand in the Y axis has the best backlash value of 5microns.

And for measuring the positioning error and tuning the every axis of this type of machines i think the best way is to get a precision linear scale from a good brand like mitutoyo and use it to take the measurements via Mach4.

The one i attached below should be more than enough for my purpose it has 5-6microns accuracy within 1000mm, any of u connected this kind of linear scale to Mach4 before? or know how to connect it to Mach4 via pmdx-124 and ess? any other breakout board needed?

My aim is just reading the encoder values with Mach4 and tune the axis manually.

Thanks to all of u for your help.
 
Regards,

Hakan
Re: Mach4 positioning error
« Reply #49 on: February 20, 2020, 09:40:45 AM »
Hakan,

Thanks for getting back to us with the root cause of your issue!

You should be able to read encoders into Mach 4 given you have enough pins and your BOB supports it.

The ESS is able to use all inputs for encoder input as far as I know. The one limitation is that you must use single ended quadrature encoders. The ones you linked look to be FANUC output which wouldn't work directly. There are some companies which sell converters for converting SIN/COS, LVDT, resolver, or other types of feedback to quadrature, but they are not super cheap.

I'd recommend finding encoder that directly output quadrature (5V TTL), however here are some links for converter boards if you prefer to go that route.

http://www.pico-systems.com/resolver.html

http://pico-systems.com/osc2.5/catalog/product_info.php?products_id=33&osCsid=qgn1d3kdkqc3v8b254gs00sj51

http://pico-systems.com/osc2.5/catalog/product_info.php?products_id=27

https://www.vegacnc.com/hardware/resolver-to-encoder-w-hall-din-panel-mount/vega-2790502/

Mike