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Layers 2-5 form a gap

Posted by RepMike 
Layers 2-5 form a gap
September 23, 2017 02:10PM
Hi, I got a little problem, when printing ABS on my custom built i3 Rework, I get this effect:


Luckily, the first layer sticks as hell (Elmers Glue Stick on top of Hairspray), but the second layer and approximately layers 3-5 are not right, they build a gap between the first layer and the rest.

Below you can see my settings in Slic3r.

I've tried with a raft layer, but THAT won't stick so well, it curls up. A brim is also not helping. I've increased skirt loops to 5, because I thought the filament sitting in the extruder for a longer time should not be used. I'm printing at very low speeds as you can see in the settings, but that gives me those wals with which I'm satisfied with; I rather wait a little longer for better prints. I'm not using a fan although you can see it in the settings, because I'm limiting the time per layer via the fan settings.

Any idea on how I could get rid of the gap?
TIA
Michael

P.S.: Slic3r settings:
Filament:
bed_temperature = 94
bridge_fan_speed = 0
cooling = 1
disable_fan_first_layers = 3
extrusion_multiplier = 0.97
fan_always_on = 0
fan_below_layer_time = 15
filament_colour = #FFFFFF
filament_diameter = 1.75
first_layer_bed_temperature = 90
first_layer_temperature = 235
max_fan_speed = 5
min_fan_speed = 0
min_print_speed = 10
slowdown_below_layer_time = 10
temperature = 235


Print:
avoid_crossing_perimeters = 1
bottom_solid_layers = 3
bridge_acceleration = 0
bridge_flow_ratio = 1
bridge_speed = 30
brim_width = 0
complete_objects = 0
default_acceleration = 0
dont_support_bridges = 1
external_fill_pattern = rectilinear
external_perimeter_extrusion_width = 0
external_perimeter_speed = 45%
external_perimeters_first = 0
extra_perimeters = 1
extruder_clearance_height = 20
extruder_clearance_radius = 20
extrusion_width = 0
fill_angle = 45
fill_density = 30%
fill_pattern = rectilinear
first_layer_acceleration = 0
first_layer_extrusion_width = 200%
first_layer_height = 0.4
first_layer_speed = 40%
gap_fill_speed = 5
gcode_comments = 0
infill_acceleration = 0
infill_every_layers = 1
infill_extruder = 1
infill_extrusion_width = 0
infill_first = 0
infill_only_where_needed = 0
infill_overlap = 15%
infill_speed = 10
interface_shells = 0
layer_height = 0.15
max_print_speed = 80
max_volumetric_speed = 0
min_skirt_length = 0
notes = 
only_retract_when_crossing_perimeters = 1
ooze_prevention = 0
output_filename_format = [input_filename_base].gcode
overhangs = 0
perimeter_acceleration = 0
perimeter_extruder = 1
perimeter_extrusion_width = 0
perimeter_speed = 30
perimeters = 3
post_process = 
raft_layers = 0
resolution = 0
seam_position = aligned
skirt_distance = 6
skirt_height = 1
skirts = 5
small_perimeter_speed = 12
solid_infill_below_area = 70
solid_infill_every_layers = 0
solid_infill_extruder = 1
solid_infill_extrusion_width = 0
solid_infill_speed = 10
spiral_vase = 0
standby_temperature_delta = -5
support_material = 0
support_material_angle = 0
support_material_contact_distance = 0.2
support_material_enforce_layers = 0
support_material_extruder = 1
support_material_extrusion_width = 0
support_material_interface_extruder = 1
support_material_interface_layers = 3
support_material_interface_spacing = 0
support_material_interface_speed = 100%
support_material_pattern = pillars
support_material_spacing = 2.5
support_material_speed = 40
support_material_threshold = 80
thin_walls = 1
threads = 2
top_infill_extrusion_width = 0
top_solid_infill_speed = 10
top_solid_layers = 3
travel_speed = 60
xy_size_compensation = 0


Printer:
bed_shape = 0x0,193x0,193x176,0x176
before_layer_gcode = 
end_gcode = M104 S0 ; turn off temperature\nM140 S0; turn off heatbed\nG28 X0  ; home X axis\nG28 Y0; home X axis\nG0 Y150;  Pull heated bed forward\nM84     ; disable motors\n;StarWars/Imp\nM300 S1174 P401\nM300 S0 P133\nM300 S1174 P401\nM300 S0 P133\nM300 S1174 P401\nM300 S0 P133\nM300 S466 P267\nM300 S0 P133\nM300 S1396 P133\nM300 S1174 P401\nM300 S0 P133\nM300 S466 P267\nM300 S0 P133\nM300 S1396 P133\nM300 S1174 P802\nM300 S0 P267\nM300 S880 P401\nM300 S0 P133\nM300 S880 P401\nM300 S0 P133\nM300 S880 P401\nM300 S0 P133\nM300 S932 P267\nM300 S0 P133\nM300 S1396 P133\nM300 S1108 P401\nM300 S0 P133\nM300 S466 P267\nM300 S0 P133\nM300 S1396 P133\nM300 S1174 P802\nM300 S0 P267\nM300 S2349 P401\nM300 S0 P133\nM300 S1174 P267\nM300 S0 P133\nM300 S1174 P133\nM300 S2349 P267\nM300 S0 P267\nM300 S2217 P267\nM300 S0 P133\nM300 S2093 P133\nM300 S987 P133\nM300 S932 P133\nM300 S987 P267\nM300 S0 P267\nM300 S1244 P133\nM300 S0 P133\nM300 S1661 P267\nM300 S0 P267\nM300 S1567 P267\nM300 S0 P133\nM300 S1479 P133\nM300 S1396 P133\nM300 S1318 P133\nM300 S1396 P267\nM300 S0 P267\nM300 S466 P133\nM300 S0 P133\nM300 S1108 P1070
extruder_offset = 0x0
gcode_flavor = reprap
layer_gcode = 
nozzle_diameter = 0.4
octoprint_apikey = .....
octoprint_host = octoprint
pressure_advance = 0
retract_before_travel = 2
retract_layer_change = 0
retract_length = 1
retract_length_toolchange = 10
retract_lift = 0.1
retract_restart_extra = 0
retract_restart_extra_toolchange = 0
retract_speed = 40
start_gcode = G28 ; home all axes\nG1 Z5 F5000 ; lift nozzle\n
toolchange_gcode = 
use_firmware_retraction = 0
use_relative_e_distances = 0
use_volumetric_e = 0
vibration_limit = 0
wipe = 0
z_offset = 0

Re: Layers 2-5 form a gap
September 25, 2017 07:25AM
May not be the problem but I suspect your Z height calibration may be out.
I can't see much evidence of squish on the skirt layers.
Do the bed levelling and ensure you put the Z-offset in the slicer. The bed is below the nozzle so its a negative (-) value.
Reduce 1st layer height to 0.35.
Reduce 1st layer extrusion width to 150%.

Hope that helps
Re: Layers 2-5 form a gap
September 25, 2017 04:20PM
In fact, before every print, I do a manual bed leveling using a piece of paper. I have a Z axis endstop which triggers when I am at minimal height above homing position and the rest will be done by the bed leveling procedure, which verifies 9 spots and I test them with a piece of paper: I lower the nozzle until the paper nicely draws with a gentle force and the texture of the paper can be felt. The bed leveling procedure mostly subtracts around 0.5-0.6mm from the actual Z.

As regards the Z offset setting in Slic3r's printer settings, I will start testing by adding little amounts to that setting (e.g. half the layer height). I will also try modifying 1st layer height and 1st layer extrusion width, as you suggested. I will provide feedback about those tuning measures, but it will take me a while.

Thanks so far for your advice
VDX
Re: Layers 2-5 form a gap
September 25, 2017 05:53PM
... heatbed too hot?


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org]
Call for the project "garbage-free seas" - [reprap.org]
Re: Layers 2-5 form a gap
September 26, 2017 07:27AM
Sorry I don't follow your bed levelling procedure.
For I3s with fixed homing switches you home the Z axis so the switch triggers. That sets the Z height to Zero. Then you adjust the bed height to a small gap - paper thickness, then you have to put the paper thickness in the slicer as the Z offset (negative value). You should never set the gap to more than the layer height. Don't know what paper you are using but it typical values are from 0.15 to 0.25.
Rule of thumb for Max layer height is 75/80% of nozzle diameter - hence I suggested you reduce it.
200% over extrusion hides a lot of inaccuracies but gives people problems with the surface for layer 2 - this is particularly true for small layer heights like 0.15 that you are using.
Your extrusion multiplier is 0.97 - I assume you set this or it will under extrude.
Obviously I assume you calibrated the extruder = request 100mm and it extrudes 100mm.

Im still not sure this is your current problem as I would have expected the layers to be stacked better but varying in width. Your picture looks like severe shrinkage but im not sure that can be true. Having said that I suppose if the first layer is held by the glue may be it is. Hot end temp could be to high allowing more time for shrinkage. Try reducing to 225. Try putting the bed temp up?
Watch while printing to see if layer 2 is printed right on top of layer 1.
Obviously I don't know if your temperatures are accurate. Thermistors are usually under the bed heater so the print surface can be a lower temperature.
VDX
Re: Layers 2-5 form a gap
September 26, 2017 10:31AM
... search for "elephant foot" - it's mostly affecting an higher count of bottom layers, but will show a similar effect -- see the attached images in the start post:

[forums.reprap.org]


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org]
Call for the project "garbage-free seas" - [reprap.org]
Re: Layers 2-5 form a gap
September 26, 2017 01:19PM
Thanks, @MCcarman for your detailed feedback, I will go through those points as well. As regards the Leveling procedure, I follow this guide where it notably says: "The Z-endstop should be set slightly above the bed. An opto endstop is preferable but a switch with a metal arm that allow some travel though should also work" ... and I'm taking the metal arm route; I know, it's not ideal.

And Thanks @VDX ... I will also go through your advice.

Meanwhile, I made one print in higher speed (80 mm/s) and I must say, for that, it came out quite satisfying, except for the "elephant foot" problem. (see photo below).
That was only to exclude speed issues, in other words: The speed is irrelevant to my problem.

As I said, it takes me a while to implement your advice.
I'll report on the progress later...

Re: Layers 2-5 form a gap
September 27, 2017 01:09PM
As an initial test, reduce your FlowRate setting to 80%, Adjust the home Z height down until you see a good vertical surface on test prints. I think you are slightly over extruding, and the nozzle is about 0.75mm too high.

Measure your skirt area thickness, and see how far off you are from the expected layer height.
Re: Layers 2-5 form a gap
September 29, 2017 05:01PM
Ok, I've changed a lot, and I think it came out pretty good. Any comments to the outcome or the parameters are welcome, it still can be improved in lots of points, always. But: the initial problem is more or less gone. Current setup of bed adhesion: Painters tape from ALDI Süd (German Grovery Store, they have painters tape from time to time), Elmers Glue Stick on top. Printing the ABS at 235°C and the bed is at 70°C, no fan for the layers. I've also started using a brim to reduce warping (not enitrely gone, but ok).

Next I will develop a little snippet of gcode which blobs a little piece of plastic in a corner to get rid of some oozing Filament at the beginning of a print, because that causes ugly strings in the first layer and forces me to sit next to it and catch the oozing plastic with a pair of pliers.

End goal: Get the Part fitting calibration successful, not there yet. I think I'm still over-extruding. But that would be another thread. I'll work on that.

Thank you for your valuable input
Michael



Filament:
# generated by Slic3r 1.2.9 on Fri Sep 29 21:20:50 2017
bed_temperature = 70
bridge_fan_speed = 0
cooling = 0
disable_fan_first_layers = 3
extrusion_multiplier = 0.97
fan_always_on = 0
fan_below_layer_time = 15
filament_colour = #FFFFFF
filament_diameter = 1.75
first_layer_bed_temperature = 70
first_layer_temperature = 235
max_fan_speed = 5
min_fan_speed = 0
min_print_speed = 10
slowdown_below_layer_time = 10
temperature = 235


Print Settings:
# generated by Slic3r 1.2.9 on Fri Sep 29 20:42:18 2017
avoid_crossing_perimeters = 1
bottom_solid_layers = 3
bridge_acceleration = 0
bridge_flow_ratio = 1
bridge_speed = 60
brim_width = 5
complete_objects = 0
default_acceleration = 0
dont_support_bridges = 1
external_fill_pattern = rectilinear
external_perimeter_extrusion_width = 0
external_perimeter_speed = 50%
external_perimeters_first = 0
extra_perimeters = 1
extruder_clearance_height = 20
extruder_clearance_radius = 20
extrusion_width = 0
fill_angle = 45
fill_density = 30%
fill_pattern = rectilinear
first_layer_acceleration = 0
first_layer_extrusion_width = 150%
first_layer_height = 0.3
first_layer_speed = 10
gap_fill_speed = 5
gcode_comments = 0
infill_acceleration = 0
infill_every_layers = 1
infill_extruder = 1
infill_extrusion_width = 0
infill_first = 0
infill_only_where_needed = 0
infill_overlap = 15%
infill_speed = 80
interface_shells = 0
layer_height = 0.15
max_print_speed = 100
max_volumetric_speed = 0
min_skirt_length = 0
notes = 
only_retract_when_crossing_perimeters = 1
ooze_prevention = 0
output_filename_format = [input_filename_base].gcode
overhangs = 0
perimeter_acceleration = 0
perimeter_extruder = 1
perimeter_extrusion_width = 0
perimeter_speed = 60
perimeters = 3
post_process = 
raft_layers = 0
resolution = 0
seam_position = aligned
skirt_distance = 6
skirt_height = 1
skirts = 5
small_perimeter_speed = 15
solid_infill_below_area = 70
solid_infill_every_layers = 0
solid_infill_extruder = 1
solid_infill_extrusion_width = 0
solid_infill_speed = 20
spiral_vase = 0
standby_temperature_delta = -5
support_material = 0
support_material_angle = 0
support_material_contact_distance = 0.2
support_material_enforce_layers = 0
support_material_extruder = 1
support_material_extrusion_width = 0
support_material_interface_extruder = 1
support_material_interface_layers = 3
support_material_interface_spacing = 0
support_material_interface_speed = 100%
support_material_pattern = rectilinear
support_material_spacing = 2.5
support_material_speed = 60
support_material_threshold = 80
thin_walls = 1
threads = 2
top_infill_extrusion_width = 0
top_solid_infill_speed = 15
top_solid_layers = 3
travel_speed = 130
xy_size_compensation = 0


Printer Settings:
# generated by Slic3r 1.2.9 on Wed Sep 27 00:02:43 2017
bed_shape = 0x0,193x0,193x176,0x176
before_layer_gcode = 
end_gcode = M104 S0 ; turn off temperature\nM140 S0; turn off heatbed\nG28 X0  ; home X axis\nG28 Y0; home X axis\nG0 Y150;  Pull heated bed forward\nG0 X85; Pull X in Center\nM106 S255; turn on Fan\nM84     ; disable motors\n;StarWars/Imp\nM300 S1174 P401\nM300 S0 P133\nM300 S1174 P401\nM300 S0 P133\nM300 S1174 P401\nM300 S0 P133\nM300 S466 P267\nM300 S0 P133\nM300 S1396 P133\nM300 S1174 P401\nM300 S0 P133\nM300 S466 P267\nM300 S0 P133\nM300 S1396 P133\nM300 S1174 P802\nM300 S0 P267\nM300 S880 P401\nM300 S0 P133\nM300 S880 P401\nM300 S0 P133\nM300 S880 P401\nM300 S0 P133\nM300 S932 P267\nM300 S0 P133\nM300 S1396 P133\nM300 S1108 P401\nM300 S0 P133\nM300 S466 P267\nM300 S0 P133\nM300 S1396 P133\nM300 S1174 P802\nM300 S0 P267\nM300 S2349 P401\nM300 S0 P133\nM300 S1174 P267\nM300 S0 P133\nM300 S1174 P133\nM300 S2349 P267\nM300 S0 P267\nM300 S2217 P267\nM300 S0 P133\nM300 S2093 P133\nM300 S987 P133\nM300 S932 P133\nM300 S987 P267\nM300 S0 P267\nM300 S1244 P133\nM300 S0 P133\nM300 S1661 P267\nM300 S0 P267\nM300 S1567 P267\nM300 S0 P133\nM300 S1479 P133\nM300 S1396 P133\nM300 S1318 P133\nM300 S1396 P267\nM300 S0 P267\nM300 S466 P133\nM300 S0 P133\nM300 S1108 P1070
extruder_offset = 0x0
gcode_flavor = reprap
layer_gcode = 
nozzle_diameter = 0.4
octoprint_apikey = ....
octoprint_host = octoprint
pressure_advance = 0
retract_before_travel = 2
retract_layer_change = 0
retract_length = 1
retract_length_toolchange = 10
retract_lift = 0.1
retract_restart_extra = 0
retract_restart_extra_toolchange = 0
retract_speed = 40
start_gcode = G28 ; home all axes\nG1 Z5 F5000 ; lift nozzle\n
toolchange_gcode = 
use_firmware_retraction = 0
use_relative_e_distances = 0
use_volumetric_e = 0
vibration_limit = 0
wipe = 0
z_offset = -0.25

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