Autoleveling is broken

Hi folks,

I need to get this sorted out. I've had my printer for over two years and every time I press print it's probably 50/50 if the print will work or not.

Autoleveling is broken. There is no other conclusion that I can draw. I autolevel before every print, printing identical parts, and sometimes the hotend is too high on the first layer.

I did the probe repeatability test, and I'm seeing 30 microns stdev.

I'm using the Marlin "release" branch from July 2015.

I'm considering trying a more recent version of the firmware, but I have two issues:

1. How do I migrate my existing settings to the more recent version of the firmware? Should I create a patch file? What's the procedure you use?
2. It looks like branches got renamed at some point or something, as I don't see a "Release" branch on github. So what's the branch I should use? 1.0.x ?

Would upgrading my firmware even help? Was this a known bug that was looked at or fixed?

Thanks!

Edited 1 time(s). Last edit at 03/04/2016 05:01AM by foul_owl.

I don't know an efficient way of migrate to newer version of marlin, what I simply does is to copy anything that's important on your current config.h and bring them slowly to the recent update.

I forgot the version 1.0.x release date, but the one almost stable would be the RC branch, there are also 'rcbugfix' branch that they use it to fix any known bugs reported. I'm currently going to test out the today's rcbugfix branch because of some critical bugs last time and need to reconfirms if it is still there

As for auto bed leveling problem, it might has something to do with the offset values, left and right position are not leveled correctly (for prusa based). This feature are quite hard to solve as I also having problem on the bed leveling being incorrect

I'd say if it's an i3 it might be the two z motors out of sync resulting in an angle between the bed and the x carriage. You can put an object on your bed and lower the x carriage on to it one side. Then move it to the other side and do the same, then the x carriage is level (the two z motors are in sync) with the bed.

It might be wear or bends in threaded rods, or other mechanical wear in slides, bearings etc... Two years of moderate use will wear some stuff out.

As for marlin yes print out your config files and just manually port them over rc3 has slightly different config to 1.0x but its logical (a little more logical really).

Edited 1 time(s). Last edit at 03/11/2016 12:18PM by DjDemonD.

I run auto bed leveling on my FT 2020 with a BLTOUCH and Marlin 1.1.0 RC3. Starting up, it works perfectly BUT if I go right on to a second print or a third print, there's a chance that it will do exactly as you say and start with the nozzle too high or probe for zero in the wrong place. My guess is there's a logic bug SOMEWHERE in there but, for me, since everything is dialed in and working great, if I'm going to do multiple prints, it's just as easy to hit the 'reset' button and select my next project. It always works that way. I'll just wait until someone figures out the bug.

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Folger Tech 2020 i3 and FT-5 as well as modified JGAurora A5 with direct drive E3D/Titan. All running the BLTOUCH.
Great kits. Having fun and running the heck out of them.
Running Marlin 1.1.0 RC8 on the i3 and FT5. Custom firmware on A5.
Folger Tech Wiki board >[folgertech.wikia.com]

I've recently read that it might be compression or stretching in your flexible couplers. Replace them with rigid ones and try it. I'd second this idea, as my i3 (dual z motors, tr8 leadscrews, flex couplers) has always had a slightly vague z=0 position, but my smartrapcore alu with a belt driven z axis does not suffer from this problem. If I get time I was going to do a single motor conversion with rigid pillow bearings at the base and the motor at the top driving a belt with pulleys between the two leadscrews.

One way to prevent the compression of flexible couplers is to place a small bearing inside and have the shafts make contact with it. The bearing still allows the coupler to bend.

Good idea, won't prevent stretching of the coupler but its halfway there.