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Author Topic: Lost Steps with backlash compensation  (Read 1823 times)

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Lost Steps with backlash compensation
« on: February 22, 2015, 02:08:25 PM »
Do I have to use 'Exact Stop' rather than 'Constant Velocity' when backlash compensation is enabled (R3.043.066)?

After a long time chasing lost steps have now found that this is linked to backlash compensation. Lost steps has been as much as 9mm in one go - (between changes in direction?).  The feed rate speed was increased to 750mm/min for this test.
 When backlash compensation is turned off no steps are lost, even at this  feed rate.
Lost steps have been reduced by lowering the Backlash % max speed setting from the initial 20% to 10%. At 20% speed there ia a loud clonk on changing direction as compensation takes up the slack. (Steps lost) At 10% the movement is less violent.
Have also set 'Exact Stop' but would prefer to be in 'Constant Velocity' for better finish.

Any other experience/advice would be welcome.

Machine is Wabeco f1220E with upgraded 3.5Nm nema 34 stepper motors with G540 driver. 48v power supply.
The backlash Compensation is set to X 0.06, Y 0.04, Z 0.04
Feed rates have been reduced to 500mm/min acceleration set to 90. Step pulse set to 4 .Dir pulse at 3

Offline Hood

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Re: Lost Steps with backlash compensation
« Reply #1 on: February 22, 2015, 07:18:40 PM »
There are a few settings that affect backlash comp, one is the shuttle accel on General Config page.
I never use comp so don't really know what is best but Rich usually states a rule so hopefully he will come in with the info. Failing that do an advanced search for Backlash comp rul and the user name of Rich and you should find info.

Hood

Offline RICH

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Re: Lost Steps with backlash compensation
« Reply #2 on: February 22, 2015, 09:01:15 PM »
Could never find the file on backlash setting so put info in Members Doc's. Here is the link:

http://www.machsupport.com/forum/index.php/topic,29149.0.html

RICH
Re: Lost Steps with backlash compensation
« Reply #3 on: February 23, 2015, 02:17:22 PM »
Many thanks to Hood and Rich for their input. I will have to play around with my settings.

I thought I had it about right set at 10%. I was unaware of the shuttle wheel setting.  Strangely Hoss recommends setting the % BL speed to 100% and the shuttle speed at 0.005.
I have checked my setting and is currently 0.004. Increasng the % speed in my case would make it more likley to lose steps. but will look deeper into this after trying different shuttle wheel speeds.
Will report back if any improvement is gained.

Regards John.
Lost Steps with backlash compensation
« Reply #4 on: February 23, 2015, 06:17:44 PM »
Just a point.  You have got the backlash settings matching the actual backlash?  If it doesn't it will cause symptoms which can be like lost steps.


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Re: Lost Steps with backlash compensation
« Reply #5 on: February 24, 2015, 01:26:52 PM »
Thank you . Yes I have.

Regards John.