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I was using this model at 100% infill to test extrusion:

enter image description here

The printer is an old Printrbot which I converted to Klipper, so I'm doing some tests to ensure correct parameters.

ABS filament 3 mm (not 2.85 mm, measured in multiple points), 230°C hot end (optimised with temperature tower), 100°C glass bed. The extruder was calibrated by extruding a known length of filament. The extrusion was checked by printing a single walled cube and was within tolerance of the caliper I used. I used no cooling fan (except, manually, for the first two layers on top of the support to ensure optimal bridges).I skip cooling with ABS to avoid warping, since the air around is colder (no enclosure).

The top surface comes out perfectly indicating a perfect extrusion multiplier, but the outermost perimeter doesn't bond with the second one, see photo:

enter image description here

Something I've never seen before is that the whole print is somehow thicker in a corner where the nozzle stops before raising, and the walls tend to expand with height, so in fact I may have an excessive extrusion, see photos:

enter image description here enter image description here enter image description here

After removal of support: enter image description here

The settings for slicing are (from the gcode, abridged):

; generated by PrusaSlicer 2.2.0-alpha2+win64 on 2019-12-23 at 18:44:54 UTC
; external perimeters extrusion width = 0.45mm
; perimeters extrusion width = 0.45mm
; infill extrusion width = 0.45mm
; solid infill extrusion width = 0.45mm
; top infill extrusion width = 0.40mm
; support material extrusion width = 0.40mm
; first layer extrusion width = 0.30mm
...
; avoid_crossing_perimeters = 0
; bottom_solid_layers = 3
; external_perimeter_extrusion_width = 0
; external_perimeter_speed = 50%
; external_perimeters_first = 0
; extra_loading_move = -2
; extra_perimeters = 1
; extruder_clearance_height = 20
; extruder_clearance_radius = 20
; extrusion_multiplier = 1
; extrusion_width = 0
; fill_density = 100%
; fill_pattern = rectilinear
; first_layer_extrusion_width = 150%
; first_layer_height = 100%
; first_layer_speed = 30
; gap_fill_speed = 20
; infill_every_layers = 1
; infill_extrusion_width = 0
; infill_first = 0
; infill_only_where_needed = 0
; infill_overlap = 25%
; infill_speed = 80
; interface_shells = 0
; nozzle_diameter = 0.4
; only_retract_when_crossing_perimeters = 1
; ooze_prevention = 0
; perimeter_acceleration = 0
; perimeter_extruder = 1
; perimeter_extrusion_width = 0
; perimeter_speed = 60
; perimeters = 2
; retract_before_travel = 2
; retract_length = 0.5
; seam_position = aligned
; skirt_distance = 2
; skirt_height = 500
; skirts = 1
; small_perimeter_speed = 15
; top_fill_pattern = rectilinear
; top_infill_extrusion_width = 0
; top_solid_infill_speed = 15
; top_solid_layers = 3

How can I solve the problems of the perimeters and of the irregular shape?

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    $\begingroup$ The problem looks like a heat problem, not an extrusion problem. You don't mention what material you are using, what extruder/bed temps are, no fan usage (at least I don't think I missed it in there). You are spending all this time on extrusion, yet if you're overheating, you could be leading yourself down the wrong path. $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Dec 24 '19 at 14:34
  • $\begingroup$ The extrusion width and the extruder stepper were calibrated. I also used a temperature tower to choose the optimal temperature. No cooling fan because cooling causes warping in ABS and skipping the fan was the solution I found to avoid warping, together with a tall skirt around the part to shield it from colder air. I added some of the information to the question. $\endgroup$ – FarO Dec 24 '19 at 22:36
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    $\begingroup$ All I can tell you is the part looks melted, like there's way too much heat. Solve that and you've most likely solved the issues you're seeing. $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Dec 24 '19 at 23:46
  • $\begingroup$ note the following three extrusion width seem off: ; top infill extrusion width = 0.40mm ; support material extrusion width = 0.40mm ; first layer extrusion width = 0.30mm $\endgroup$ – Trish Dec 26 '19 at 14:39
  • $\begingroup$ @Trish I set PrusaSlicer to default ("0") and that's what I got. In fact, Slic3r suggests different values: manual.slic3r.org/advanced/flow-math $\endgroup$ – FarO Dec 26 '19 at 21:45

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