Safe Z Spindle off Restart error

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MadTooler
Posts: 20
Joined: Thu Nov 08, 2018 11:57 pm

Safe Z Spindle off Restart error

Post by MadTooler » Mon Nov 12, 2018 6:24 am

I am sort of convinced this may be a bug. My code was working with v4.33, but now it has a problem with 4.34. Upon halting a runing gcode within KMotionCNC on a 3 axis gantry router, it should stop the spindle and go to machine zero, which is does. Where it has trouble is with continuing the job.

With running the attached c program as the "Halt" command from KMotionCNC in mid gcode, the problem is seen after pressing the start again. It will drop the Z back to the appropriate height per the job, but then it will start running to the next XY per job but to the Z machine zero or whatever value I use in my Safe Z program.

My guess is Kmotion is confusing the last gcode commanded value, that was in this case from my Safe Z via MDI, with the next value when I am in mid gcode without any Z's further called until the end of program. The odd part is it does correctly recognize the last running gcode Z value, and does go to it first, but then overlays the Safe Z value to the next XY.

FYI, I am using the MDI function instead of Move in the initial KMotion example C due to a continued servo tuning problem that results in overshooting rapids that are not run as feeds, and a desire to command the specific machine zero location. Again, this was not a problem with 4.33.

Thanks
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TomKerekes
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Re: Safe Z Spindle off Restart error

Post by TomKerekes » Mon Nov 12, 2018 5:25 pm

Hi MadTooler,

You can’t use MDI commands to run GCode if you wish to resume running GCode.

Can you explain more clearly what overshooting problem you are having moving Z from KFLOP? Are you also moving it to zero?
Regards,

Tom Kerekes
Dynomotion, Inc.

MadTooler
Posts: 20
Joined: Thu Nov 08, 2018 11:57 pm

Re: Safe Z Spindle off Restart error

Post by MadTooler » Mon Nov 12, 2018 5:43 pm

Interesting. I have been using the MDI for a couple of years within this script and some other mcodes. There have not been any clear issues with v433. In any case, I will plan to adjust now that I know that it never should have worked the way I had managed.

The overshooting is a violent full throttle Move with very little if any ramping up to and down from commanded velocity. Or at least it seems. This is surely related to a tuning issue that I need to get back to where my step moves for my brushed dc servos looks good in the bode plots, but somewhere is getting way to much speed. I keep looking at "I" clamping variables and max pwm and others while missing what is wrong.

I will set this issue aside until I get back to my threads on cnczone with the tuning issues I never solved many moons ago.

Thanks

MadTooler
Posts: 20
Joined: Thu Nov 08, 2018 11:57 pm

Re: Safe Z Spindle off Restart error

Post by MadTooler » Tue Nov 13, 2018 6:32 am

Other than a gcode/MDI command to go to z0 g53, what would be a proper command in this script to go to z machine 0?

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TomKerekes
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Re: Safe Z Spindle off Restart error

Post by TomKerekes » Tue Nov 13, 2018 5:22 pm

Hi MadTooler,

Move(ZAXIS,0.0);

Would move Z to machine 0 without altering the GCode Interpreter State.
Regards,

Tom Kerekes
Dynomotion, Inc.

MadTooler
Posts: 20
Joined: Thu Nov 08, 2018 11:57 pm

Re: Safe Z Spindle off Restart error

Post by MadTooler » Wed Nov 14, 2018 3:05 am

Thanks, Tom. I get following errors when I use the Move command over longer distances. I tried it over a shorter distance and everything does perform correctly. When I figure out what I have set wrong and get my tune better, I am sure this will work perfectly well.

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TomKerekes
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Re: Safe Z Spindle off Restart error

Post by TomKerekes » Wed Nov 14, 2018 4:35 am

Hi MadTooler,

A common mistake is to have the max velocity set too high and not realize this until you make a move large enough to get up to a speed your system can't do. Similarly the acceleration might be set too high and not realize it until you make a move large enough to allow acceleration to ramp up to a level your ststem can't do. See also here.
Regards,

Tom Kerekes
Dynomotion, Inc.

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