I thought I 'd share a weirdness with you guys: my oldest printer refuses to do large prints. I suspect it’s Sanguinololu that is to blame but - can’t prove it. I can do cigarette-packet-sized prints all right, and many of them at the same time, but if I try to print something large - say 10 cm tall, about 6 hours worth of print at .2 layer height - the printer refused to move the Z axis. Just goes through the layer moves abd grinds a hole in the side of the filament, without moving a .2 in the upwards direction, until I give up.
Same model, reduced by 50% - prints without a hiccup. Am at loss. Did anyone ever hear anything like that? Is there a cure?
Firmware limit? G code says to go higher and the firmware says no-way?
Yeah this sounds like a limit you’ve programmed into your firmware, if you home your Z can you tell it to move higher than the print using your pc?
@Joe_Spanier I think I will film it to show what it looks like. In fact the head never lifts off the table. Homing happens all right, start of print happens as usual - but the Z lift never happens. Firmware limit? What is there in Marlin that limits Z movement this way? And in any case, a 10-centimetre skull is well within the 15-cm height that is defined in my firmware…
@Liam_Jackson homing Z works, everything works. If I pause the print I can manually perform moves in any direction, including up on Z. But - the printer, once released, continues to work without ever lifting over the table.
that sounds like it might be a slicer issue. Have you looked in your code to see if z moves are in there? Can you post the code thats giving you issues?
@Joe_Spanier nah, not Kisslicer - I have looked into the problem gcode and into a couple of other gcodes that print well, and the Z movement codes are identical. Plus, and what is most weird, the whole system behaves as is Z level changes with each layer change - Octoprint shows a layer has changed, even the LCD screen attached to the Sanguinololu shows the layer has changed. And only an acute-eyed printer operator can notice the head is too low when it’s at the table glass and the layer count shows 5 mm… 
Two weeks ago I had some weird behaviour with my #Graber i3 / #Sanguinololu. Then I updated #Cura to 14.07 and all the problems were gone.
@enhydra well, this bug has been with me for a year now. On Repetier, now on Marlin, through the latest iterations of Kisslicer and several hosts including the latest Octoprint - nothing changes.
Oh, hope you geht it solved soon.
That’s really odd, the fact you can jog the axis above that height means it probably isn’t the firmware limit and pretty much rules out hardware issues.
Is it always at the same height or after the same period of time?