Missing extrusion at the start of some layers

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FlatEarther
Posts: 14
Joined: Sun Feb 18, 2018 1:46 pm

Missing extrusion at the start of some layers

Post by FlatEarther » Sun Feb 18, 2018 1:48 pm

Hi,

I have a custom Prusa I3 with a genuine E3D V6. I'm using Slic3R and Slic3R prusa edition as slicer. Most models print just fine. However some models have missing extrusion at the start of some layers. This looks ugly. I can' t just add an extra prime amount after retraction because that wil create blobs on models that print fine(which are most models).

I noticed on Slic3R sliced files that it prints the inner perimeter first, then it moves to a different location and prints the outer perimter. This only happens on the layers with missing extrusions at the start. I think this is the cause of the issue. If the slicer would just loop twice without moving to a different location for the outer perimeter, this issue wouldn't exist. Isn't there an option in slic3r to disable this behaviour?

I will post some examples tonight when I'm home.

Thanks!

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Missing extrusion at the start of some layers

Post by slippyr4 » Sun Feb 18, 2018 2:44 pm

This is probably a symptom of either temperature issues (possibly way too hot) or inappropriate retraction settings.

What’s. happening, by the sound of it, is that after a travel move there is a small deficit of plastic in the nozzle, which causes underextrusion.

What temperature / plastic and retraction settings do you use?
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

FlatEarther
Posts: 14
Joined: Sun Feb 18, 2018 1:46 pm

Re: Missing extrusion at the start of some layers

Post by FlatEarther » Sun Feb 18, 2018 3:20 pm

I'm using das filament PLA, temperature 210. Retraction 1 mm at 40mm/s.

Print speed is 50/60 mms/s except for the outer perimeter which is printed at 30 mm/s. Travels happen at 120 mm/s.

The thing is, it doesn't always do this. If I observer a print for a minute, I can see that it primes the nozzle correctly, the inner perimeters seem to start exactly where they supposed to. The issue is only there when moving somewhere else to start the outer perimeter. It almost seems like it accelerates to quickly, nog allowing the extruder to have enough time to extrude enough plastic. I'm probably wrong. Acceleration is 1000 mm/s.

Do You know of a model that tests your theory? I did try lots of test models from thingiverse, like the make retraction test:

Image

But they don't show this issue.

All my settings:

Code: Select all

# generated by Slic3r Prusa Edition 1.38.5-prusa3d-win64 on 2018-02-18 at 15:25:25

[b][print:NORMAL][/b]
avoid_crossing_perimeters = 0
bottom_solid_layers = 3
bridge_acceleration = 0
bridge_angle = 0
bridge_flow_ratio = 1
bridge_speed = 60
brim_width = 15
clip_multipart_objects = 0
compatible_printers = 
compatible_printers_condition = 
complete_objects = 0
default_acceleration = 0
dont_support_bridges = 1
elefant_foot_compensation = 0
ensure_vertical_shell_thickness = 0
external_fill_pattern = rectilinear
external_perimeter_extrusion_width = 0.55
external_perimeter_speed = 30
external_perimeters_first = 0
extra_perimeters = 0
extruder_clearance_height = 20
extruder_clearance_radius = 20
extrusion_width = 0.55
fill_angle = 45
fill_density = 10%
fill_pattern = rectilinear
first_layer_acceleration = 0
first_layer_extrusion_width = 0.55
first_layer_height = 0.2
first_layer_speed = 30
gap_fill_speed = 20
gcode_comments = 0
infill_acceleration = 0
infill_every_layers = 1
infill_extruder = 1
infill_extrusion_width = 0.55
infill_first = 0
infill_only_where_needed = 0
infill_overlap = 25%
infill_speed = 60
interface_shells = 0
layer_height = 0.2
max_print_speed = 80
max_volumetric_extrusion_rate_slope_negative = 0
max_volumetric_extrusion_rate_slope_positive = 0
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 = 0.55
perimeter_speed = 50
perimeters = 2
post_process = 
raft_layers = 0
resolution = 0
seam_position = nearest
skirt_distance = 6
skirt_height = 1
skirts = 1
small_perimeter_speed = 30
solid_infill_below_area = 70
solid_infill_every_layers = 0
solid_infill_extruder = 1
solid_infill_extrusion_width = 0.55
solid_infill_speed = 40
spiral_vase = 0
standby_temperature_delta = -5
support_material = 0
support_material_angle = 0
support_material_buildplate_only = 0
support_material_contact_distance = 0.2
support_material_enforce_layers = 0
support_material_extruder = 1
support_material_extrusion_width = 0
support_material_interface_contact_loops = 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 = 5
support_material_speed = 60
support_material_synchronize_layers = 0
support_material_threshold = 15
support_material_with_sheath = 0
support_material_xy_spacing = 50%
thin_walls = 0
threads = 8
top_infill_extrusion_width = 0.55
top_solid_infill_speed = 40
top_solid_layers = 4
travel_speed = 130
wipe_tower = 0
wipe_tower_per_color_wipe = 15
wipe_tower_width = 60
wipe_tower_x = 180
wipe_tower_y = 140
xy_size_compensation = 0

[b][filament:FlexD][/b]
bed_temperature = 70
bridge_fan_speed = 100
compatible_printers = 
compatible_printers_condition = 
cooling = 1
disable_fan_first_layers = 3
end_filament_gcode = "; Filament-specific end gcode \n;END gcode for filament\n"
extrusion_multiplier = 1
fan_always_on = 1
fan_below_layer_time = 60
filament_colour = #29b2b2
filament_cost = 0
filament_density = 0
filament_diameter = 1.75
filament_max_volumetric_speed = 0
filament_notes = ""
filament_soluble = 0
filament_type = PLA
first_layer_bed_temperature = 70
first_layer_temperature = 220
max_fan_speed = 100
min_fan_speed = 100
min_print_speed = 10
slowdown_below_layer_time = 5
start_filament_gcode = "; Filament gcode\n"
temperature = 220

[b][filament:PETG][/b]
bed_temperature = 65
bridge_fan_speed = 100
compatible_printers = 
compatible_printers_condition = 
cooling = 1
disable_fan_first_layers = 3
end_filament_gcode = "; Filament-specific end gcode \n;END gcode for filament\n"
extrusion_multiplier = 1
fan_always_on = 0
fan_below_layer_time = 60
filament_colour = #29b2b2
filament_cost = 0
filament_density = 0
filament_diameter = 1.75
filament_max_volumetric_speed = 0
filament_notes = ""
filament_soluble = 0
filament_type = PLA
first_layer_bed_temperature = 65
first_layer_temperature = 240
max_fan_speed = 80
min_fan_speed = 40
min_print_speed = 10
slowdown_below_layer_time = 5
start_filament_gcode = "; Filament gcode\n"
temperature = 240

[b][filament:PLA][/b]
bed_temperature = 60
bridge_fan_speed = 100
compatible_printers = 
compatible_printers_condition = 
cooling = 1
disable_fan_first_layers = 3
end_filament_gcode = "; Filament-specific end gcode \n;END gcode for filament\n"
extrusion_multiplier = 1
fan_always_on = 1
fan_below_layer_time = 60
filament_colour = #29b2b2
filament_cost = 0
filament_density = 0
filament_diameter = 1.75
filament_max_volumetric_speed = 0
filament_notes = ""
filament_soluble = 0
filament_type = PLA
first_layer_bed_temperature = 60
first_layer_temperature = 215
max_fan_speed = 100
min_fan_speed = 100
min_print_speed = 10
slowdown_below_layer_time = 5
start_filament_gcode = "; Filament gcode\n"
temperature = 215

[b][printer:I3][/b]
bed_shape = 0x0,200x0,200x200,0x200
before_layer_gcode = 
between_objects_gcode = 
deretract_speed = 0
end_gcode = M104 S0 ; turn off temperature\nM140 S0;\nG28 X0  ; home X axis\nM84     ; disable motors\n
extruder_colour = ""
extruder_offset = 0x0
gcode_flavor = reprap
layer_gcode = 
max_layer_height = 0.4
min_layer_height = 0.2
nozzle_diameter = 0.5
octoprint_apikey = 80085
octoprint_host = 192.168.178.11
printer_notes = 
retract_before_travel = 2
retract_before_wipe = 0%
retract_layer_change = 0
retract_length = 1
retract_length_toolchange = 10
retract_lift = 0.5
retract_lift_above = 0
retract_lift_below = 0
retract_restart_extra = 0
retract_restart_extra_toolchange = 0
retract_speed = 40
serial_port = 
serial_speed = 250000
single_extruder_multi_material = 0
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
variable_layer_height = 0
wipe = 0
z_offset = 0


[presets]
print = NORMAL
printer = I3
filament = PLA


chumm
Posts: 176
Joined: Thu Jun 15, 2017 11:24 am

Re: Missing extrusion at the start of some layers

Post by chumm » Mon Feb 19, 2018 3:28 am

Worth comparing it to default Prusa Slic3r retraction settings, which I've always found really solid. You have several of the binary options set the other way.
Image

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