Can't stop printing midair.

I've been having some weird issues with my printer lately, and I haven't been able to figure it out over the past week, even with the help of the IRC channel, so hopefully with some more eyes on the problem, we can figure out what's going on.

Whenever I try to start a print, the printer will go through the setup just fine, heating the bed and hotend, homing all axes, and then doing the probing for the bed auto-leveling. Just before it starts trying to print, it'll go to the correct height at the corner of the bed, and then raise up for no apparent reason and begin printing in midair.

Autoleveling and then moving the printhead around with pronterface will have no issues, and will compensate for the tilt of the bed, and hold the correct height based on my testing with a sheet of paper and whatnot, but whenever it starts actually printing, it'll do so 1-2mm above the glass for reasons known only to the printer itself.

This issue popped up apparently at random, I had a handful of good prints before the issue cropped up, even managing to get my first print onto bare glass. The only change between a good print, and this new air printing is that I changed the value for esteps/mm from 841 to 851.8

The printer is a Makerfarm i3v 10", running Marlin that I pulled from github on February 9, 2015 on a RAMPS 1.4 with the RepRapDiscount smart controller. The issue happens regardless of if I try to print from SD card, Pronterface, or Octoprint.

[www.youtube.com] is a link to a recording of the problem, along with the output from pronterface during the print.
[pastebin.com] is the first 50 lines of the file being printed in the video.
(As a side note, the output from the M114 commands that I was using to try to find the problem are not showing up in the console at all, despite the rest of everything being there.)

Things I've tried so far include:

• Removing a line from the starting Gcode that moved the carriage up 15mm while heating the hotend.
  This doesn't seem to change anything aside from making it slightly more difficult to remove the ooze.
  .
• Changing the Z offset.
  This was my first thought, but it seems to not have any effect whatsoever. The printer will either start in midair with too high of an offset, or start by impacting the bed, and then move up above the surface with too low of an offset.
  .
• Releveling the bed so the autoleveling won't have to compensate for as much tilt.
  This resulted in a little less autoleveling action in the print, but it still hasn't solved the whole "Printing into air" issue.

First off looking at that video your first layer speed is real high. Slow it down and let it stick.

Did you get to the bottom of this? I've just set up auto leveling and i'm getting the same results. Finishes probing then raises 4mm and starts printing.

You probably both need to (re)set z offset in firmware or on lcd, and store it in eeprom. Go to menu control/motion z offset. If you don't use display/eeprom look in configuration.h of the firmware.

Just homing isn't enough, ABL may introduce a different offset. With z offset at zero, the z home position is the same as the probe, not the nozzle, unless both are at the same height.

If you have auto bed leveling, in pronterface do g28 and g29 manually without printing, then use g1 X100 Y100 Z0 F3000. Is it still too far from tge printbed? Use the pronterface controls and a sheet of paper to find what negative z position gives the correct z home position. The lcd will show the current z position or use another gcode command to display the position in the console, see gcode reprapbwiki. Set Z offset to this value. It is correct that the z offset is a positive number on the display, the higher the nunber the closer the nozzle gets to the bed. The paper should feel some resistance under the nozzle and should be easy to get the edge in under it easily.

Edited 4 time(s). Last edit at 04/16/2015 05:30PM by imqqmi.

Dear Laazarus,

I've been following your earlier thread on how to get the MKS_BASE working to drive a Servo for an AutoBed Leveler. What was the final trick /answer? Was it X-Max acting as a PWM? If so, any tips/code you can share is GREATLY appreciated! I have a MKS_BASE_V1.1, but similar enough (unused X-MAX, unused A11, A12). Looking at the Marlin F/W code, I thought you could use the "Z_PROBE_OFFSET_FROM_EXTRUDER" to compensate? But I am very new to all of this. Appreciate any help you can provide..

First thing I noticed is that your probe is not hitting the back of the bed. its homing on the edge that's probably one explanation.

Bedleveling is something you do once and not before every print normally. settings are saved in the EEPROM if you have enabled that.