Z Homing/printing problem - *Solved*

Hello, Im new to 3d printing and I have no idea whats causing this problem, But I will try to provide as much information as I can.

This is what i do to print something:

1. I set the Z axis using a paper between the bed and extruder to get the height just right then I send the G92 Z0 command to set Z as 0.
2. I set the heat for the extruder to 200*c and the bed for 65*c and wait for them to heat up.
3. Then I select a G code file for print and the machine starts to print it, raising the extruder 5mm, moves it to the middle, lowers the extruder 5mm and starts to print.

I have printed 2 things so far, a mini-figure and a whistle


But now i get this wierd problem

The nozzle raises about 5 mm (like it does all the time before a print) and then it should lower itself 5mm (To Z=0) and start to print right?
But my nozzle seems to go 4-10 mm under what i set Z=0 to be, and pressing against the glass so the extruder bends and the other side of the bed lifts.
It then starts to move like normal but scraping against the glass, I always press the emergency stop before that happens tho.

I didnt have this problem before and i have no damn clue whats causing it, im sure its something simple.

Printer: Ormerod
Firmware: FIRMWARE_NAME:RepRapFirmware FIRMWARE_VERSION:0.78 ELECTRONICSuet + Extension DATE:2014-06-11


I can provide more information but i hope this is enough

Edited 2 time(s). Last edit at 08/09/2014 11:02AM by victhor.

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Does the gcode file you are trying to print have a G28 homing command in it? If so, then it will ignore the homing you have already done and try to use the IR sensor for Z-homing.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I guess so, and the easy fix would be to remove that line in the gcode, or turn it off in the slic3r software if there is such option?

-----------------------------
; generated by Slic3r 1.1.6 on 2014-08-03 at 01:44:31

; perimeters extrusion width = 0.50mm
; infill extrusion width = 0.52mm
; solid infill extrusion width = 0.52mm
; top infill extrusion width = 0.52mm
; support material extrusion width = 0.50mm

G21 ; set units to millimeters
M107
M190 S70 ; wait for bed temperature to be reached
M104 S245 ; set temperature
G28 ; home all axes
G1 Z5 F5000 ; lift nozzle

M109 S245 ; wait for temperature to be reached
G90 ; use absolute coordinates
G92 E0
M82 ; use absolute distances for extrusion
G1 F1800.000 E-1.00000
G92 E0
G1 Z0.500 F7800.000
G1 X40.586 Y42.546 F7800.000
G1 E1.00000 F1800.000
G1 X42.348 Y41.007 E1.43418 F1080.000
(((( And so on )))

Edited 2 time(s). Last edit at 08/08/2014 05:44PM by victhor.

Yes that's it. I suggest you remove the G28 line from the custom start gcode in your slic3r settings and re-slice. Alternatively, use an editor such as Notepad++ to edit the gcode file, removing the G28 line.

[Edit: or get a good zprobe such as my differential IR board, which works anywhere on the bed and allows you to do 5-point bed compensation thanks to RRP's latest code. But I prefer to do Z homing and bed compensation separately from printing.]

Edited 1 time(s). Last edit at 08/08/2014 04:54PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

delete the codeline in slicer and reslice your object.

Thanks for both your help, it turns out that was the problem.. my ir sensor seems to bee a bit "joggy" or what word i should use.. The Zprobe numbers jump between 700 and 900

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Youtube: [www.youtube.com] 3D printing videos
3D Hub: [www.3dhubs.com] Pictures of stuff I've printed
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Quote
victhor
Thanks for both your help, it turns out that was the problem.. my ir sensor seems to bee a bit "joggy" or what word i should use.. The Zprobe numbers jump between 700 and 900

Three suggestions:

1 If you are using aluminium tape for the z-probe targets, replace it with white PVC tape or white paper;

2. Shield the printer from direct sunlight, and replace any incandescent light bulbs above the printer by LED or CFL ones;

3. Order one of my differential IR hot end boards

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hello, I've already done that part with the paper & Its now listed in the build guide for the ormerod

2: I will do that! i got un used led-strips

3: im interested but i dont have any money right now I'll come back to you next month

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Youtube: [www.youtube.com] 3D printing videos
3D Hub: [www.3dhubs.com] Pictures of stuff I've printed
Thingyverse: [www.thingiverse.com] More pictures
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As an aside, the nozzle does not drop to zero when starting the first layer, but drops to the height of that layer. If your first layer height is set to be larger than the rest in Slic3r (I usually use double the layer height for the first layer), your Z zero calibration is far more forgiving, because any errors will be a smaller percentage of the layer height.

Dave
(#106)