UMO+ airprinting when print starts

[blietz 0]

Hello everyone!

I've got this little problem with my printer. It is fully explained in the video below.

https://vid.me/e/2PVL

Here is the problem in text.

When i home the printer there is no problem at all, the x y and z axis all reach their endstops and the bed is perfectly leveled.

Then i start a print, and the magic happens, the bed lowers (as it should) but it doesnt raise enough to hit the endstop and start printing. There is a gap roughly 1.3cm between the printhead and the bed.

When i change the gcode for the z axis and withdraw 1.3 everywhere the print starts perfectly.

I've been searching for the problem everywhere but i can't get my head around it.

Can any of you guys help me?

Edited September 2, 2015 by Guest

[gr5 2,097]

My UMO does the exact same thing when I create the gcode with cura and accidentally choose um2 as the machine instead of umo. Could that be it?

[blietz 0]

well i'm pretty sure that i choose the correct printer.

One thing i found out is that the printer homes on Z-12.55.

I've tried adding G92 Z0 in the gcode after a G28 but the problem remains.

[gr5 2,097]

I watched your video and it looked like it homed perfectly - right when the nozzle hits the bed. Right? not 12mm from the bed.

Can you please post the first 50 lines of your gcode file? In UMO settings it's very easy to put some bad gcodes in the "gcode start" settings that will do what you describe.

[blietz 0]

well it homes perfectly but when you look at the info screen (@ 0:25 seconds) you will see that the Z axis homes at -12.55. So even when the printhead hits the endstops which should make it think it's at 0, the Z axis homes to -12.55.

Posting the first 50 lines of code won't really help i think, but here goes nothing.

 

M190 S70.000000

M109 S210.000000

;Sliced at: Tue 25-08-2015 23:21:37

;Basic settings: Layer height: 0.1 Walls: 0.8 Fill: 20

;Print time: 3 hours 40 minutes

;Filament used: 1.901m 15.0g

;Filament cost: None

;M190 S70 ;Uncomment to add your own bed temperature line

;M109 S210 ;Uncomment to add your own temperature line

G21        ;metric values

G90        ;absolute positioning

M82        ;set extruder to absolute mode

M107       ;start with the fan off

G28 X0 Y0  ;move X/Y to min endstops

G28 Z0     ;move Z to min endstops

G1 Z15.0 F9000 ;move the platform down 15mm

G92 E0                  ;zero the extruded length

G1 F200 E3              ;extrude 3mm of feed stock

G92 E0                  ;zero the extruded length again

G1 F9000

;Put printing message on LCD screen

M117 Printing...

;Layer count: 25

;LAYER:0

M107

G0 F9000 X17.800 Y6.300 Z0.300

;TYPE:SKIRT

G1 F1200 X46.632 Y6.300 E0.54235

G1 X46.653 Y7.609 E0.56697

G1 X166.297 Y7.609 E2.81754

G1 X166.297 Y6.300 E2.84217

G1 X195.200 Y6.300 E3.38585

G1 X195.200 Y35.195 E3.92938

G1 X193.892 Y35.195 E3.95398

G1 X193.892 Y154.804 E6.20389

G1 X195.200 Y154.804 E6.22850

G1 X195.200 Y183.700 E6.77205

G1 X166.297 Y183.700 E7.31573

G1 X166.297 Y182.391 E7.34035

G1 X46.723 Y182.391 E9.58961

G1 X46.734 Y183.700 E9.61423

G1 X17.800 Y183.700 E10.15849

G1 X17.800 Y154.804 E10.70204

G1 X19.108 Y154.804 E10.72665

G1 X19.108 Y35.195 E12.97656

G1 X17.800 Y35.195 E13.00116

G1 X17.800 Y6.300 E13.54470

G1 F2400 E9.04470

G0 F9000 X21.600 Y10.100

Edited September 2, 2015 by Guest

[SandervG 1,520]

Is this the case with every print, or just some?

Has it always done this, or only recently?

In what version of Cura did you slice it?

Thank you!

[gr5 2,097]

well it homes perfectly but when you look at the info screen (@ 0:25 seconds) you will see that the Z axis homes at -12.55.

 

What the hell!!!! I've never seen that! I missed that in the video as it goes by in under a second. Yes I see that now. Very strange! This is a Marlin issue, not a Cura issue.

Somehow Marlin has this 12.55mm offset. I have no idea where that comes from - when you home with G28 Z0 it should show 0mm, not -12.55mm.

Did you build marlin yourself? Where did you get this copy? If you built it, search for "12.5" in Configuration.h (and configuration_adv.h). Also doing a "factory reset" might fix things - that number *might* be stored somewhere not in the marlin hex file but somewhere else which I believe gets cleared with factory reset command. Not sure.

[blietz 0]

it's a recently build self sourced UMO+. Some parts are original like the ulticontroller, the mainboard, stepper motors and the heated bed. The rest is gathered from different places.

So it's a new problem on a new printer, so you can say a new problem that has been happening recently

I flashed a custom firmware that clears the whole eeprom etc. then reflashed the printer with cura 15.04 (Thesame firmware i had on it before)

For some reason the printer has been functioning right untill now. Some under extrusion problems but nothing strange i can't fix myself.

So thank you everyone for the input! Let's hope the problem doesnt return

[gr5 2,097]

So thank you everyone for the input! Let's hope the problem doesnt return

 

I missed something. Did flashing the eeprom fix the problem?