Slic3r prints 2 layers on the same layer height

Hey,

I was wondering, why all my prints are messed up lately. Every print looked like the z axis didnt move properly, so I first thought of a mechanical problem... but everything is fine there.

I then took a look at the g-code and I believe I found the problem. Slic3r 1.29 does not change the layer height on the next layer, but instead uses the same layer height for about 2-3 layers:

; generated by Slic3r 1.2.9 on 2015-08-25 at 13:27:02

; external perimeters extrusion width = 0.50mm
; perimeters extrusion width = 0.50mm
; infill extrusion width = 0.50mm
; solid infill extrusion width = 0.50mm
; top infill extrusion width = 0.50mm

M190 S108 ; set bed temperature
M104 S240 ; set temperature
G28 Y ;
G28 X;
G28 Z;
G1 Z2 F5000;
G1 Z5 F5000 ; lift nozzle

M109 S240 ; wait for temperature to be reached
G21 ; set units to millimeters
G90 ; use absolute coordinates
M82 ; use absolute distances for extrusion
G92 E0
M106 S255

//LAYER CHANGE

G1 E-1.00000 F1800.00000
G92 E0
G1 Z-1.130 F1800.000
G1 X-0.674 Y-0.501 F1800.000
G1 E1.00000 F1800.00000
G1 X-0.132 Y-1.232 E1.03805 F1440.000
G1 X1.505 Y-2.139 E1.11627
...........
G1 X5.441 Y20.603 F1800.000
G1 E1.00000 F1800.00000
G1 X5.380 Y21.637 E1.09182 F480.000
G1 X5.441 Y22.574 E1.17505

//LAYER CHANGE

G1 E0.17505 F1800.00000
G92 E0
G1 Z-1.130 F1800.000
G1 X38.063 Y19.064 F1800.000
G1 E1.00000 F1800.00000
G1 X52.263 Y19.064 E1.59349 F960.000
G1 X52.263 Y27.864 E1.96130
.......................
G1 X29.558 Y62.245 F1800.000
G1 E1.00000 F1800.00000
G1 X29.578 Y62.712 E1.04136 F480.000
G1 X29.578 Y65.256 E1.26677
M104 S233 ; set temperature
M140 S92 ; wait for bed temperature to be reached

//LAYER CHANGE

G1 E0.26677 F1800.00000
G92 E0
G1 Z-0.830 F1800.000
G1 X25.763 Y31.867 F1800.000
G1 E1.00000 F1800.00000
....................
G1 X65.918 Y39.509 E7.52758
G1 X65.693 Y39.733 E7.53371

//LAYER CHANGE

G1 E6.53371 F1800.00000
G92 E0
G1 Z-0.830 F1800.000
G1 X61.245 Y59.725 F1800.000
G1 E1.00000 F1800.00000
........................
G1 X27.607 Y39.334 F1800.000
G1 X28.175 Y38.641 E3.40572 F1200.000

//LAYER CHANGE

G1 E2.40572 F1800.00000
G92 E0
G1 Z-0.530 F1800.000
G1 X38.784 Y19.790 F1800.000
G1 E1.00000 F1800.00000

How can that happen?

Edited 1 time(s). Last edit at 08/25/2015 07:47AM by Persephone.

Odd. I've never come across a negative Z value being commanded. It the STL flush with the bed in the plater window?

Dave

Quote
dmould
Odd. I've never come across a negative Z value being commanded. It the STL flush with the bed in the plater window?

Perhaps he has a negative Z offset configured in slic3r?

---

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].

Quote
dc42

Quote
dmould
Odd. I've never come across a negative Z value being commanded. It the STL flush with the bed in the plater window?

Perhaps he has a negative Z offset configured in slic3r?

Could be. I'm not sure why you would need to do that - setting the Z zero height to the correct base level would seem to be a better way to achieve that. Maybe there is a bug when Slic3r is working with negative Z values.

Dave

You need to turn on Verbose G-Code under Print Settings, Output Options.
Then slice and take another look.

---

My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
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I use a proximity sensor located slightly above the nozzle instead of a mechanical endstop, thats the reason for the negative z starting point. But even with the z starting point set to zero, the problem still remains.

I got this g-code with Verbose activated:

M109 S240 ; wait for temperature to be reached
G21 ; set units to millimeters
G90 ; use absolute coordinates
M82 ; use absolute distances for extrusion
G92 E0 ; reset extrusion distance
M106 S255 ; enable fan
G1 E-1.00000 F1800.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.400 F2400.000 ; move to next layer (0)
G1 X22.194 Y59.939 F2400.000 ; move to first skirt point
G1 E1.00000 F1800.00000 ; unretract
G1 X24.131 Y59.436 E1.09303 F450.000 ; skirt
G1 X72.887 Y55.827 E3.36526 ; skirt
G1 X73.300 Y55.812 E3.38444 ; skirt
G1 X64.987 Y85.350 E1.18033 ; infill
G1 E0.18033 F1800.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.400 F2400.000 ; move to next layer (1)
G1 X47.104 Y84.649 F2400.000 ; move to first perimeter point
G1 E1.00000 F1800.00000 ; unretract
G1 X56.954 Y84.649 E1.45779 F840.000 ; perimeter
G1 X56.954 Y85.769 E1.50985 ; perimeter
G1 X24.984 Y85.769 E2.99570 ; perimeter
M104 S233 ; set temperature
M140 S100 ; wait for bed temperature to be reached
G1 E0.51508 F1800.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.700 F2400.000 ; move to next layer (2)
G1 X74.421 Y85.229 F2400.000 ; move to first perimeter point
G1 E1.00000 F1800.00000 ; unretract
G1 E0.06631 F1800.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.700 F2400.000 ; move to next layer (3)
G1 X37.003 Y70.785 F2400.000 ; move to first perimeter point
G1 E1.00000 F1800.00000 ; unretract

Edited 1 time(s). Last edit at 08/31/2015 02:28PM by Persephone.

It looks to me that it is printing different objects as separate operations, and so keeping the Z height the same for each layer of each object may be correct. Do you perhaps have more than one STL loaded on the build plate? Perhaps they are overlapping? How about infill settings - is the "combine infill every:" setting set to 1?

Dave

M109 S240 ; wait for temperature to be reached
G21 ; set units to millimeters
G90 ; use absolute coordinates
M82 ; use absolute distances for extrusion
G92 E0 ; reset extrusion distance
M106 S255 ; enable fan
G1 E-1.00000 F1800.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.400 F2400.000 ; move to next layer (0)
G1 X22.194 Y59.939 F2400.000 ; move to first skirt point
G1 E1.00000 F1800.00000 ; unretract
G1 X24.131 Y59.436 E1.09303 F450.000 ; skirt
G1 X72.887 Y55.827 E3.36526 ; skirt
G1 X73.300 Y55.812 E3.38444 ; skirt
G1 X64.987 Y85.350 E1.18033 ; infill
G1 E0.18033 F1800.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.400 F2400.000 ; move to next layer (1)
G1 X47.104 Y84.649 F2400.000 ; move to first perimeter point
G1 E1.00000 F1800.00000 ; unretract
G1 X56.954 Y84.649 E1.45779 F840.000 ; perimeter
G1 X56.954 Y85.769 E1.50985 ; perimeter
G1 X24.984 Y85.769 E2.99570 ; perimeter
M104 S233 ; set temperature
M140 S100 ; wait for bed temperature to be reached
G1 E0.51508 F1800.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.700 F2400.000 ; move to next layer (2)
G1 X74.421 Y85.229 F2400.000 ; move to first perimeter point
G1 E1.00000 F1800.00000 ; unretract
G1 E0.06631 F1800.00000 ; retract
G92 E0 ; reset extrusion distance
G1 Z0.700 F2400.000 ; move to next layer (3)
G1 X37.003 Y70.785 F2400.000 ; move to first perimeter point
G1 E1.00000 F1800.00000 ; unretract

I looked for anomalies also.
The extra Z positioning at the same level seems OK here as it is not printing in the same spot. Slic3r sometimes does this when printing different kinds of features.
However the highlighted area is odd. It has extra retracts. This may not be a large enough snippet to tell what is happening.

Some options:
- You could try turning off retract on layer change.
- Do you have a photo of what is happening?
- Does it print OK on an earlier version Slic3r?
- To investigate further you may need to attach the entire gcode (old and new), and stl (or post a link)
- If you can create a test case with photo of old and new slicer results, config file, and STL, you can post the issue on Github here.