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Backlash not applied during manual JOG?
« on: January 01, 2016, 10:12:24 PM »

I've just built a new G0704, using Mach 4.

Here is a link to my backlash test
https://drive.google.com/file/d/0B7IRZwlMOrbxVGVEaHJCZzQ5Ymc/view?usp=sharing

As you can see in the video I can cycle 1 inch off zero and back to zero with no drift.    When I approach zero with my indicator zero my X axis and back off zero, there is backlash present during my jog moves.   The DRO shows movement, and no table movement.  I expect backlash values to be applied to Jog moves as well as MDI commands.

Am I missing something?  am I crazy?  shouldn't manual Jog moves be backlash compensated as well?

Thank you
Pete 
Re: Backlash not applied during manual JOG?
« Reply #1 on: January 01, 2016, 11:13:15 PM »
I don't think any CNC applies backlash comp for manual moves. When you run a manual machine you always deal with the backlash by approaching a point always from the same direction or by cranking the other way by the backlash amount. In auto backlash comp occurs because the cnc knows to keep the tool on the path. There is no path when jogging, so know way to know what should be done.
Re: Backlash not applied during manual JOG?
« Reply #2 on: January 01, 2016, 11:17:34 PM »
well that makes me feel better that I'm not crazy or have missed a setting...   This explains it..

Just getting started with this mill, and the hobby..
Re: Backlash not applied during manual JOG?
« Reply #3 on: January 02, 2016, 08:54:12 PM »
What motion device are you using?

FYI - the Mach4 development team decided that backlash compensation would be handled by the plug-ins and devices, not by the Mach4 core (i.e. Mach4 motion planner).  So whether your device supports backlash compensation, and how and when it is "enabled" is up to the plug-in.

Bob
Re: Backlash not applied during manual JOG?
« Reply #4 on: January 03, 2016, 04:38:57 AM »
Warp9 Ethernet smooth stepper.

Offline DazTheGas

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Re: Backlash not applied during manual JOG?
« Reply #5 on: January 03, 2016, 05:01:45 AM »
Backlash is not yet implemented in the ESS plugin but will be in the new plugin that should be release shortly (please).

DazTheGas
Theres always time for a choccy biccy
Re: Backlash not applied during manual JOG?
« Reply #6 on: January 03, 2016, 08:39:59 PM »
DazTheGas,

so I'm a bit confused then.    I thought backlash was compensated in the Motor tuning variable in Mach?  or Does the motion controller do the compensation?  or do the two work together?

Finally any idea on when the new plug in will be available?

Thank you
pete
Re: Backlash not applied during manual JOG?
« Reply #7 on: January 03, 2016, 09:36:36 PM »
so I'm a bit confused then.    I thought backlash was compensated in the Motor tuning variable in Mach?  or Does the motion controller do the compensation?  or do the two work together?
There is indeed a field in the motor configuration tab for setting the backlash.  While the Mach4 core does nothing with that value, the plug-in is able to read that value** and use it for their backlash algorithms.

** note that plug-ins are also free to disregard that value and force you the enter a value somewhere in the plug-in specific configuration dialog.  It all depends on how the plug-in is written, and I have no idea how any plug-ins other than the PMDX plug-ins handle that.

Bob

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Re: Backlash not applied during manual JOG?
« Reply #8 on: January 04, 2016, 09:24:57 AM »
For the record:

    Darwin was written prior to Mach4, but to the specs of M4 at that time which didn't call for it.. So backlash was not added
to Darwin. There is a school of thought, which was prevalent during my time in Mach3, that backlash
shouldn't be corrected and that backlash should be mechanically fixed or accepted, personally I tend
be be in that camp on my own machines anyway. Minimizing backlash with springs or anti-backlash nuts etc
is probably the best way to deal with the issue, but when applied to a core application, there is no end to
the misery it can cause to the logical application of motion rules in the engines. 
    Its like asking your cars software to help with a loose steering wheel, could be done, but probably
shouldn't be..it would affect other safety issues right down to the tires. Just my 2 cents, and I
thought Id explain why Darwin doesn't have backlash..

Art
Re: Backlash not applied during manual JOG?
« Reply #9 on: January 04, 2016, 10:00:39 AM »
I agree backlash should be removed from all mechanical parts... unfortunately mechanical parts wear and your going to get backlash... after playing with Mach4 and Darwin and knowing what I know now I would have never purchased it.... I'm not knocking it but it doesn't have all the things that mach3 had and probably never will.... so I am now moving to Linuxcnc which has changed alot since I last looked at it and works very well with the parallel port. hopefully I can find another use for Mach4 and Darwin so it won't be a waste of money.  

Dave