Hello Guest it is March 28, 2024, 04:55:10 AM

Author Topic: Problems with losing position  (Read 27405 times)

0 Members and 2 Guests are viewing this topic.

Re: Problems with losing position
« Reply #30 on: February 13, 2014, 02:34:12 PM »

The no nonsense combo that WILL absolutely work is Windows XP32 with Start Term (version 7) drivers. 

Steve

Steve (Smurph),

Is there a version of Mach you prefer with this combination?

Thanks Darek

Offline smurph

*
  • *
  •  1,544 1,544
  • "That there... that's an RV."
    • View Profile
Re: Problems with losing position
« Reply #31 on: February 13, 2014, 07:21:33 PM »
I'm running Version R3.043.062.  But I'm sure the newest Mach3 Rev. would also work.

Steve

Offline bubba

*
  •  80 80
    • View Profile
Re: Problems with losing position
« Reply #32 on: March 01, 2014, 12:48:17 AM »
CNCToolDie,

Try out this plugin: http://www.smcomp.com/~smurph/galil/Galil-st.zip

See if it fixes the stop problem.

Hey Smurph has the Plugin in the Downlaods section been updated to this?

Steve


Offline smurph

*
  • *
  •  1,544 1,544
  • "That there... that's an RV."
    • View Profile
Re: Problems with losing position
« Reply #33 on: March 01, 2014, 12:29:24 PM »
No, it has not been updated.  I will have to build a full release and get the web gods to comply with a small sacrifice of some inanimate object.  :)

Offline bubba

*
  •  80 80
    • View Profile
Re: Problems with losing position
« Reply #34 on: March 01, 2014, 04:29:58 PM »
Ok got it!
So we should use this oneYes?
http://www.smcomp.com/~smurph/galil/Galil-st.zip

Thanks,
Joe
Re: Problems with losing position
« Reply #35 on: March 03, 2014, 10:51:22 AM »
Follow up, that may help somebody else following this thread.  With this new plugin I was cutting a small circle .400 with 1/4EM, then moving off 5" in Y to change the part then repeating many times (x100), I found I was losing location in Y.  Knowing Galil pretty well I carefully reviewed the Galil plugin log and saw no cause for the drift.  I then recreated the arc program in DMC language and ran it in DMC smart terminal (ST), it did drift in Y although a factor of 10 less over the same number of cycles, but still not right.  Neither Mach or ST ever drifted in X, even when I made the 5" move in X.  I think this proves what Steve originally suspected that I must have something mechanically wrong with my CNC.  Over the weekend I took Y completely apart and did find a point of slip, I am fixing that.  Thank you Steve! ;D  

Any thoughts why the mechanical would cause a greater position loss in Mach3 than it would in ST...  Hmmm as I write this I think the difference could be the motion profile dynamics are different in Mach3 than they are in ST, so it makes sense that the mechanical flaw would show it self differently.  To show a flaw in ST you need to push the motion profile harder with more complex moves, this is why I did not originally see the problem.  It is like a car with a mechanical flaw may not show when a Granny (ST) drives it, but will show when a race car (Mach) driver drives it.  You can push ST harder with greater AC SP and more moves, you just have to do that in testing like this.  I could have saved myself some time by pushing things harder in ST.  I learned something here.

Also while I am redoing things I am changing the gear ratio of Y to match X.  I advise somebody building a machine to do this because it makes it much easier to use ST to test (or use for production in a pinch) since you can not easily have a different pulses per inch in ST like you can in Mach3.

Matt

Offline bubba

*
  •  80 80
    • View Profile
Re: Problems with losing position
« Reply #36 on: March 03, 2014, 11:37:36 AM »
Thanks for that Matt.

If you would not mind could you try to explain the gear ratio part of Mach.
I keep reading that section, but I just do not really get it

Thanks,
Joe

Offline smurph

*
  • *
  •  1,544 1,544
  • "That there... that's an RV."
    • View Profile
Re: Problems with losing position
« Reply #37 on: March 03, 2014, 11:45:30 AM »
Matt,

I'm glad you found the issue!  Those things can be hard to diagnose for the very reasons you stated.  

And you also raised a really good point about drive ratios!  Galil does provide some relief for mismatched ratios or encoder counts with the ES command.  But it is limited to Vector Mode operation.  So it is best to have the ratios the same to reduce headaches.  Trying to code a circle in Galil code with different axis ratios can make one's head explode...

Steve

Offline smurph

*
  • *
  •  1,544 1,544
  • "That there... that's an RV."
    • View Profile
Re: Problems with losing position
« Reply #38 on: March 04, 2014, 02:38:49 AM »
If you would not mind could you try to explain the gear ratio part of Mach.
I keep reading that section, but I just do not really get it

In Mach, we need to know the amount of encoder counts that results in 1 unit of measure.  If you set your machine up for inches, then we want to know how many encoder counts/steps it takes to move the axis exactly 1 inch.  Hence the term Steps per Unit.  One of my machines is 12700 steps per inch.  This is inclusive of any gear reduction!  But in the end, we don't care about the gearing.  Only about how many steps it takes to get to one inch.  If you set Steps Per Unit in "Config -> Motor Tuning" to this value for each of your axes, you can't go wrong. 

Mach allows each axis to have a different steps per unit.  In a simple scenario like a 45 degree angle cut, X may move 2000 counts and Y may move only 1000 counts.  But if the steps per unit for X and Y are correct, they will both move the same distance and thus produce the 45 degree angle.  This works fine in Mach because we told the machine to move a certain distance that is based in the user units for X and Y.  This is a lot tougher to deal with on the Galil because you are not dealing with distances.  You are working in encoder counts!!  1000 counts on X would be exactly half of the distance of 1000 counts in Y in the 45 degree angle scenario. 

So in Galil code, you have to do a little math in your head to extrapolate a distance based on the number of counts it takes to get there for any particular axis.  In stead of saying "G01 G91 X1 Y1" in Mach, you would give the Galil a command of "PR 2000, 1000" to do the same move.  PR is "Position Relative" (incremental move) and is equivalent to G91 in G code.  So you can see here that having the same number of counts to move each axis a certain distance is VERY beneficial when working in the Galil environment.  It makes things a lot more simple.  Now, how about plotting a circle with X and Y counts per inch being different?  Boom!  Mushroom cloud!  At least in my head it is. 

This is not an issue in Mach because Mach does all of the math for you.  Isn't Mach wonderful?  Thank you Mach!

Steve

Offline bubba

*
  •  80 80
    • View Profile
Re: Problems with losing position
« Reply #39 on: March 04, 2014, 07:59:37 PM »
Thanks