Backlash speed

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11 Dec 2015 14:13 #66814 by remartinez
Backlash speed was created by remartinez
Good morning to all,
I have Backlash setup in the ini file for my axis. Is there a way to decrease the speed on the backlash? My stepper motors jerk pretty hard when the backlash kicks in.

Thank you,
Raul

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11 Dec 2015 14:36 #66816 by cncbasher
Replied by cncbasher on topic Backlash speed
not that i am aware of ..
however , if your getting jerk , then it's proably you have the backlash set a little too far , try reducing by 2 or 4 steps ,
dont worry the stepper motors can handle it . it's more tweaking the values you have a little bit closer to ideal .

of course it's better to handle the backlash mechanicly and solve the mechanical issue long term .

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11 Dec 2015 15:30 #66824 by remartinez
Replied by remartinez on topic Backlash speed
Backlash is set to .01.
Will try to work on mechanical backlash but might have to purchase antibacklash ball nuts.

Thanks
Raul

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11 Dec 2015 17:11 #66836 by cncbasher
Replied by cncbasher on topic Backlash speed
what ballscrews & nuts do you have, or using at present

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11 Dec 2015 18:02 #66838 by Todd Zuercher
Replied by Todd Zuercher on topic Backlash speed
There are lots of places backlash can hide besides between your nut and screw. Be sure to check them all. Places like the end support bearings for the screw is a very common place for large amounts of slop. Worn and sloppy ways is another.

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11 Dec 2015 18:42 #66844 by remartinez
Replied by remartinez on topic Backlash speed
Cncbasher- I have Rotton ballscrews and nuts installed on my mill.


Todd- Thanks for the hints. Ill be shore to check everything to eliminate any slop.

Thanks,
Raul

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16 Mar 2016 13:31 - 16 Mar 2016 13:32 #71713 by GaryLa
Replied by GaryLa on topic Backlash speed
I tried setting the backlash parms and got an error from pathpilot. I called tech support and they stated they don't support the backlash feature.

I know you can set BACKLASH= but as I remember it, you need to also increase the velocity so that backlash can be removed quickly.

This is where pathpilot complained on boot. It didn't like that I had increased the max velocity setting (according to linuxcnc docs) and refused to run.
Last edit: 16 Mar 2016 13:32 by GaryLa.

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16 Mar 2016 14:11 #71716 by PCW
Replied by PCW on topic Backlash speed
You do not need to change your velocity settings to use backlash compensation

You _do_ need to change your STEPGEN_MAXACCEL settings to 1.5 to 2X
the machines axis acceleration value:

linuxcnc.org/docs/2.6/html/config/ini_co...tml#sub:AXIS-section

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18 Mar 2016 01:38 #71836 by GaryLa
Replied by GaryLa on topic Backlash speed
Yes, I know. But PathPilot will not boot with that value changed.

I said "velocity" because I didn't remember the particular value's name. The point really is, that Tormach doesn't support a lot of changes to their files. I've changed one line in an INI file and had the program insist that a re-install was required.

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18 Mar 2016 09:28 #71850 by cncbasher
Replied by cncbasher on topic Backlash speed
pathpilot shows a " re-install" popup on ANY error in the hal or ini files , this can point you in all sorts of directions other than the correct one.
take a look at the file in gcode/../../pathpilotlog.txt
this will show the actual error , once the error is fixed the re-install popup will go .

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