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Author Topic: HELP: Mach 3 losing its reference position on Y axis...  (Read 2908 times)

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Offline RICH

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Re: HELP: Mach 3 losing its reference position on Y axis...
« Reply #10 on: September 20, 2016, 05:32:34 PM »
 
Quote
I BELIEVE I HAVE A SOLUTION

I assume you did some playing with tuning of the axes.
What was the max velocity before it skipped and same for accel? or said differently...
What is the vel and accel value that would not be reliable?

Back plotted the code and the pathing and looked ok. I'll post some pic's on what I was talking about.

Then as I looked at the gcode.....someting was bugging me ???........"light bulb" finaly went off in my head :D

G0 is a rapid command and any movement will be at the max velocity.
AND
All your movements are G0 so all the moves will be at max velocity even though you have an F20 in the
beginning of the code file.
SO
Watch the feedrate dro as you are running the program and you will see the actual feedrate values.

You can only limit the feedrate of a G0 via  the motor tuning velocity value.( Believe that is correctly stated)
I am  thinking  the setting of "Lock Rapid FRO to Feed Rate" in the config will not reduce it.

THUS
If your at the edge of a reliable velocity and accel tuning values you can end up skipping
when least expected. Only experience with what your doing will tell over time.

BTW,
Not sure what your doing to change tools, so the following may just be info from your program used.
You had a tool change, no  tools  listed in the tool table, no M6 or M0,  thus " T01 G49 G43 H01" or  H02
is of not much value.

Good For you so far, ;)

RICH


Offline Chet

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Re: HELP: Mach 3 losing its reference position on Y axis...
« Reply #11 on: September 20, 2016, 08:03:14 PM »
Hi Rich!  I only tweaked the velocity/acceleration a bit downwards with the hope the glitches were right on the margin.  And you are right that I do not specify the exact tool changes....  I just need the program to stop after the rough cut and I exchange cutting bits.  I'll check the rate of cut on next job....

Offline RICH

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Re: HELP: Mach 3 losing its reference position on Y axis...
« Reply #12 on: September 20, 2016, 08:07:46 PM »
I would still suggest you go thru  playing with the tuning. Dosen't take long to do and you will have some good info
on how conservative or aggressive your tuning is.


RICH
« Last Edit: September 20, 2016, 08:10:33 PM by RICH »

Offline Chet

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Re: HELP: Mach 3 losing its reference position on Y axis...
« Reply #13 on: September 20, 2016, 08:44:48 PM »
The challenge with playing with the tuning is that testing on Mach 3 can give false results....  It is a guide rather than a proof of performance.
When I was initially setting up the motors I spent considerable time tweaking the motors.  I'd do the testing with the up and down arrow keys and motors would happily hum (chirp & whistle?) along.  I'd do short runs and long runs without a hitch, BUT during a cut I'd catch the motor stall or skip.  And then I'd have to go back and tweak things down a bit.  Now I did get a great cut today, but if I have a problem with the next run I'll focus on the acceleration.  You'll notice that I'm at 37 Vel and 7.0 Acc  (using the practical setups you've seen, my acceleration could slow down to 3.7 and still be "reasonable"...)