Extruder starting too high

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Extruder starting too high

Postby gwendyl » Wed May 24, 2017 3:34 am

I have successfully printed several items in both PLA and ABS over the past couple of weeks. I just switched back to PLA from ABS and suddenly now all the prints are starting with the extruder about 10mm too high, so it is printing into air. I have scoured my slic3r settings, can't see anything wrong. I have re-leveled the plate, which it didn't seem to need, but I did it anyway. Still printing into the air. I have read the wikipedia page on gcode codes to try and understand the starting code of my file, but I don't see anything wrong. Is there anything in this g-code that would explain this behaviour?

(BTW, I know the temperatures are off for PLA printing, but I reverted back to my ABS slic3r configuration because it was working just an hour before and I was trying to isolate the number of things I changed to figure out where things went awry)

Code: Select all
; generated by Slic3r 1.2.9 on 2017-05-23 at 21:58:06

; external perimeters extrusion width = 0.35mm
; perimeters extrusion width = 0.59mm
; infill extrusion width = 0.98mm
; solid infill extrusion width = 0.59mm
; top infill extrusion width = 0.59mm

M107
M190 S80 ; set bed temperature
M104 S230 ; set temperature
G28 ; home all axes
G1 Z5 F5000 ; lift nozzle

M109 S230 ; wait for temperature to be reached
G21 ; set units to millimeters
G90 ; use absolute coordinates
M82 ; use absolute distances for extrusion
G92 E0
G1 Z0.350 F7800.000
G1 E-2.00000 F2400.00000
G92 E0
G1 X86.668 Y109.274 F7800.000
G1 E2.00000 F2400.00000
G1 X88.820 Y108.481 E2.19812 F1800.000
G1 X90.000 Y108.375 E2.30044
G1 X110.000 Y108.375 E4.02810
G1 X112.259 Y108.772 E4.22622
G1 X114.247 Y109.915 E4.42433 F1800.000
G1 X115.726 Y111.668 E4.62245
G1 X116.519 Y113.820 E4.82056
G1 X116.625 Y115.000 E4.92289
G1 X116.625 Y135.000 E6.65055
G1 X116.228 Y137.259 E6.84866
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Re: Extruder starting too high

Postby ednisley » Wed May 24, 2017 3:46 pm

gwendyl wrote:reverted back to my ABS slic3r configuration


Is the G-Code you show from a failed print or from the reverted ABS settings?

If you can successfully print an old G-Code file produced with the old ABS settings (without re-slicing the STL file), then you know there's something wrong with the new PLA settings.

If you cannot print a new G-Code file produced with the old ABS settings, then you know something has changed in the printer hardware.

Comparing the startup instructions in the G-Code file for an old ABS part with the same section of the G-Code file for a new PLA part should be instructive.
Last edited by ednisley on Sun May 28, 2017 1:16 pm, edited 1 time in total.
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Re: Extruder starting too high

Postby gwendyl » Sat May 27, 2017 8:47 pm

The gcode was from a failed print (printing into air). I typically don't keep gcode files, just stl. But I was able to find one that I was pretty confident had successfully printed previously. I ran that code and it was still printing a centimeter too high (into air). I checked the bed level one more time and it passed the test, but I decided to ignore that and re-level the bed anyway. That solved it. In typing this, I am thinking that I should have tested where the printer thought z=0 was. I didn't test that, but in the process of re-leveling, I reset that. I am guessing that that was where the problem lay.

All working now.

Thanks
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Re: Extruder starting too high

Postby ednisley » Sun May 28, 2017 2:55 pm

gwendyl wrote:should have tested where the printer thought z=0 was


For those reading this in our future …

When there's a problem with the nozzle height, the first thing to check is where the printer thinks the Z=0 home position is. Could be mechanical, could be software, could be firmware.

Manually home the Z axis, jog it to a known Z position (*), and measure the distance from the nozzle to the platform. If the distance should be (say) 10 mm and it's really 18 mm, it's probably mechanical.

Print a G-Code file from back when things worked, without re-slicing it. If that fails, look for a changed configuration setting.

Basically, keep asking "What's new & different?" while trying to change only one thing at a time!

(*) I'd send a G1 Z10 command, but jogging a known amount would probably work.
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