Auto Bed Levelling Glitches

[Fri]

Attached is my current firmware.

[old man emu]

Just an aside having nothing to do coding.

Has anyone noticed that the probe servo hits the Z-axis Carrier when you try to move the extruder to the limit of travel in the X direction?

Crash (Medium).jpg

This is the plate that needs modification. It needs a slot cut in the right hand edge to allow to servo motor to move more to the left.

Plate to modify.jpg

Old Man Emu

[AbuMaia]

Here you go OME. http://www.thingiverse.com/thing:335632 This is the one I use on the i3v.

I used this one http://www.thingiverse.com/thing:167440 with the i3.

[Roxy]

Attached is my current firmware.

I don't see it attached???

[MiniMadRyan]

well I'm back to fiddling again after a short holiday and some more pressing projects.

Fiddled with the Z probe offset values quickly, and was just wondering, would I only see the effects of this change after starting a print? What I did was changed that variable, then ran a G28 followed by a G29 and then lastly a G1 Z0...all values were the same prior to modifying it. I understand that my G28 wouldn't be affected, but I always assumed the following commands above would simulate the start of a print.... oh well, will try some prints later this week when I get more time!

[MiniMadRyan]

Well this is weird. So as Roxy suggested, I modified my Z_PROBE_OFFSET_FROM_EXTRUDER and then ran some prints.

My real offset difference was -8.60, so what I did was change this to -10.60 thinking that, since I know the extruder is more than 4mm off of the surface when it prints, this would be fine.

Ran the print, and still too high. Killed the print, and manually measured the difference between the extruder and bed. -9.60mm. I then changed my Z_PROBE_OFFSET_FROM_EXTRUDER to 12.60, theoretically then, on my next print it should bring the head down to -7.60 difference....but to my surprise, the second print, still too high, when cancelled and measured is still almost exactly -9.60 difference.

Right, I haven't a clue where this is all going wrong now.... puzzled!

[MiniMadRyan]

Alright, I removed my Z_RAISE_BEFORE_HOMING thinking maybe that would help. No change in the outcome though.

Most interestingly though, with the Z_RAISE_BEFORE_HOMING set to 0, when the printer moves to the centre of the bed, the X &Y Motion is much much quicker, so much so that I believe I heard the y motor jump a bit, and confirmed it did, when after I killed the print, the bed return crashed slightly.....

[MiniMadRyan]

That's it, I give up. I've tried everything I can think of and everything that's been suggested here. I used AbuMaia's suggestion and have my Z Height half decent after running a G28, G1 Z0.

Everything else though, what the heck!??!!!! I modified my Z_PROBE_OFFSET_FROM_EXTRUDER a FULL 4MM from what it actually is (8.60 to 12.60) looking for any change, and yet my head is still 9mm too high....I don't ******* get it!!!

[AbuMaia]

MMR: in your marlin_main.cpp, find this code:

      #ifdef ENABLE_AUTO_BED_LEVELING
        if((home_all_axis) || (code_seen(axis_codes[Z_AXIS]))) {
          current_position[Z_AXIS] += zprobe_zoffset;  //Add Z_Probe offset (the distance is negative)
        }

Take the distance you found after doing a G28 then G1 Z0, then moving the nozzle to the print bed, and add it to the zprobe_zoffset, like so:

      #ifdef ENABLE_AUTO_BED_LEVELING
        if((home_all_axis) || (code_seen(axis_codes[Z_AXIS]))) {
          current_position[Z_AXIS] += zprobe_zoffset+4;  //Add Z_Probe offset (the distance is negative) *added +4 since my Z0 was too high*
        }

That should help keep the G28 Z0 where it is supposed to be. This should not affect the G29, however.

[MiniMadRyan]

Thanks AbuMaia, that's what I ended up doing earlier. My g28 z0 works beautifully but like you said, g29 is still out to lunch.

After a g29 my z height is reported as 4.52, and even after a z0, the head is a good 9mm too high...