helibrdr
Posts: 4
Joined: Thu Feb 06, 2014 6:55 pm

Backlash Compensation

Thu Feb 06, 2014 7:14 pm

I can't find any settings for Backlash Compensation in the Process Window. Is there a way to add it in the Scripts tab?

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jimc
Posts: 1124
Joined: Wed Aug 28, 2013 11:02 pm
Location: mullica, nj
Contact: Website

Re: Backlash Compensation

Fri Feb 07, 2014 8:28 am

please explain backlash compensation. backlash on what exactly?

helibrdr
Posts: 4
Joined: Thu Feb 06, 2014 6:55 pm

Re: Backlash Compensation

Fri Feb 07, 2014 10:15 am

Backlash is the play or lash due to any gap in between two moving parts.. For example in between two gears if they do not mesh tightly you can move one gear slightly before it starts moving the other gear. This is commonly used in machine tools or anything else driven by gears/belts. For my Makerbot 2X I end up with about 0.15mm in the X and 0.19mm in the Y direction due to gears/belts. I would like to compensate for that to make parts more accurate. This is most important for smaller parts/thin walls compared to long dimensions. There is not backlash compensation in the Process menus but I was hoping I could possibly add it into the init g code file if possible.

helibrdr
Posts: 4
Joined: Thu Feb 06, 2014 6:55 pm

Re: Backlash Compensation

Fri Feb 07, 2014 10:17 am

If you want to calculate the backlash in your system you can use this part/calculations.... http://www.thingiverse.com/thing:5745 . Run the part with no scaling, calculate backlash and rerun the part. From that you can calculate any scaling factor due to material shrinkage/stepper issues.

lamina
Posts: 11
Joined: Tue Oct 15, 2013 2:54 am

Re: Backlash Compensation

Fri Feb 07, 2014 1:34 pm

Backlash compensation on all CNC machines is to allow for the slight (hopefully) difference in head movement when a direction change occurs. On gear drives this is due to the load being transferred to different sides of the threaded components (this is vastly simplified) - on belt drives this is due to stretching or slight misalignment between the toothed belt and the teeth of the driver gear. Backlash compensation essentially 'tightens' up the system slowly prior to movement. I haven't measured th backlash on my M2 but I will now do so :-)
Richard

lamina
Posts: 11
Joined: Tue Oct 15, 2013 2:54 am

Re: Backlash Compensation

Fri Feb 07, 2014 2:36 pm

Hi, on our M2 which has been set up with pretty tight belts on the X and Y axis and a threaded Z axis the backlash is 0.005 mm on the belts and 0.004 on the thread. I don't think backlash compensation would work too well on a 3D printing system which has many thousands of head direction reversals all of which would take up time to take up the 'slack'. Based on my experience of complex CNC milling backlash compensation doubles the machining time - at least - so not a preferable option for a 16 hour print :-)

Tshulthise
Posts: 12
Joined: Wed Oct 16, 2013 5:44 pm

Re: Backlash Compensation

Fri Feb 07, 2014 8:58 pm

You don't need backlash compensation on 3D printers. The belts are designed to have nearly zero backlash and the forces are very low compared to milling operations.

The main sources for error in 3D printers are flexing of components, linear bearing slop (some printers), temperature effects, setup inaccuracy (axes not perpendicular), loose belts or pulleys, wobble in the z-axis due to forces transferred from the z axis lead screw to the bearing system, and inaccuracies in the lead screws themselves depending on what quality your machine uses.

If you use the z axis retract option then a backlash compensation would be helpful. I don't think they've included it in the software though. I never use it so it doesn't matter to me.

Hope that helps,
Tony

dtwrv6
Posts: 15
Joined: Tue Jan 28, 2014 8:34 pm

Re: Backlash Compensation

Sun Feb 16, 2014 8:52 am

I've always thought that the z-axis retract should be in whole number revolutions, not inches or mm. This would minimize round off errors and go a long way to eliminate z-wobble.

hscharke
Posts: 5
Joined: Wed Nov 04, 2015 10:07 am

Re: Backlash Compensation

Mon Nov 09, 2015 4:37 am

Hallo,

I would like to bring this topic to life again...

I'm using a M3D Micro where backlash seems to be a common problem.
I made some test prints and yes, my circles are oval and not round.
M3D team published some manual in order to calibrate the printer but thats completely crap (https://printm3d.com/solutions/article.php?id=80)
I have done according to manual but its not working.
I have used trial and error method which took me entire weekend and some 20 test prints to determin correct backlash compensation values.
The trial and error values are completely different to the results from M3D manual.
My circles are more round now ... but still not perfect.

However, can Simplify3D help here with some setting or better some automated algorithms or test prints to find out backlash values?

Many thanks in advance

Kathy
Posts: 3
Joined: Sat Dec 26, 2015 8:28 pm

Re: Backlash Compensation

Thu Dec 31, 2015 10:18 am

Hi hscharke, I have been using that M3D backlash guide to adjust mine. I still don't have it right. I am getting gaps and splits in my cookie cutters on the top where dough can get caught. Could you please let me know backlash settings you used and maybe that will help me? Thanks.

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