Solution to the problem concerning the object to be 3D printed is off center in Printrun (Pronterface)

I ran into a problem while switching from Kisslicer to Slic3r (slic3r-mswin-x86-1-2-9a-stable) to print the Twisted Spiral Vase on one of my Prusa i3 3D printer. The problem is that, no matter how I try, the object to be 3D printed always appear on the bottom left corner (see below photo).

Here is the setting for my Pronterface.

After couple hours of trial and error, here are my findings and solution to the problem.

In Slic3r, when the origin of the print bed is set to the center - in this case, X: 90, Y: 100 (see below photo) and the setting is written into the configuration file, the bed shape setting in the configuration file is "bed_shape = -90x-100,90x-100,90x100,-90x100" (see the next photo).

When the origin of the print bed is set to the bottom left corner - in this case, X: 0, Y: 0 (see below photo), the bed shape setting in the configuration file is "bed_shape = 0x0,180x0,180x200,0x200 (see the next photo).

Note,
1. Simply changing the X & Y values in the Bed Shape window and clicking the save button under "Printer Setting" won't write the setting into the configuration file. To write the new setting into the configuration file, select "Export Config.." under the File pull down menu.

2. The "Export G-code.." command can be performed immediately after the X & Y values in the Bed Shape window are changed and the Gcode generated will be based on the latest X & Y values.

With the origin set to X: 0, Y: 0 in Slic3r, the sliced model is now placed in the center of the print bed (see below photo).

It's worth to note that in Kisslicer, if the object is to be placed in the center of the print bed, the configuration is like the one shown in the red box in the photo below.

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For the Twisted Spiral Vase, here are the settings in my Slic3r configuration file (config_18x20_PETG_E3D_160323.ini).

# generated by Slic3r 1.2.9 on Thu Mar 24 09:37:45 2016
avoid_crossing_perimeters = 0
bed_shape = 0x0,180x0,180x200,0x200
bed_temperature = 0
before_layer_gcode =
bottom_solid_layers = 3
bridge_acceleration = 0
bridge_fan_speed = 100
bridge_flow_ratio = 1
bridge_speed = 60
brim_width = 0
complete_objects = 0
cooling = 1
default_acceleration = 0
disable_fan_first_layers = 3
dont_support_bridges = 1
duplicate_distance = 6
end_gcode = M104 S0 ; turn off temperature\nG28 X0  ; home X axis\nG28 Y0  ; home Y axis\nM84     ; disable motors\n
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
extruder_offset = 0x0
extrusion_axis = E
extrusion_multiplier = 1
extrusion_width = 0
fan_always_on = 0
fan_below_layer_time = 60
filament_colour = #FFFFFF
filament_diameter = 2.93
fill_angle = 45
fill_density = 0%
fill_pattern = honeycomb
first_layer_acceleration = 0
first_layer_bed_temperature = 0
first_layer_extrusion_width = 200%
first_layer_height = 0.35
first_layer_speed = 30
first_layer_temperature = 165
gap_fill_speed = 20
gcode_arcs = 0
gcode_comments = 0
gcode_flavor = reprap
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_gcode =
layer_height = 0.3
max_fan_speed = 100
max_print_speed = 80
max_volumetric_speed = 0
min_fan_speed = 35
min_print_speed = 10
min_skirt_length = 0
notes =
nozzle_diameter = 0.4
octoprint_apikey =
octoprint_host =
only_retract_when_crossing_perimeters = 1
ooze_prevention = 0
output_filename_format = [input_filename_base].gcode
overhangs = 1
perimeter_acceleration = 0
perimeter_extruder = 1
perimeter_extrusion_width = 0
perimeter_speed = 60
perimeters = 1
post_process =
pressure_advance = 0
raft_layers = 0
resolution = 0
retract_before_travel = 2
retract_layer_change = 0
retract_length = 2
retract_length_toolchange = 10
retract_lift = 0
retract_restart_extra = 0
retract_restart_extra_toolchange = 0
retract_speed = 40
seam_position = aligned
skirt_distance = 6
skirt_height = 1
skirts = 1
slowdown_below_layer_time = 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 = 1
standby_temperature_delta = -5
start_gcode = \n
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 = 60
support_material_threshold = 0
temperature = 165
thin_walls = 1
threads = 2
toolchange_gcode =
top_infill_extrusion_width = 0
top_solid_infill_speed = 15
top_solid_layers = 0
travel_speed = 130
use_firmware_retraction = 0
use_relative_e_distances = 0
use_volumetric_e = 0
vibration_limit = 0
wipe = 0
xy_size_compensation = 0
z_offset = 0

3D printing symptoms and solutions - under extrusion - using twisted spiral vase as the test model

This post is a summary of how I solve the problems with printing the Twisted Spiral Vase (the 3D model can be downloaded from here).

The Twisted Spiral Vase is an ideal model for turning 3D printer because the printer needs to extrude a thin and continuous string of filament all the way from the bottom to the top. If there is any problem with the 3D printer - especially the extruder, then it's not possible to get a good print. In the photo below, there are 3 failed prints (the 3 to the left) and 1 good print (the 1 to the right).

For my case, here are what I did to get the good print:

1. Switch from KISSlicer to the latest stable version of Slic3r (1.2.9);

2. Set the right filament width in Slic3r;

3. Make adjustments to the extruder and to the height between the hotend nozzle and the print bed to ensure continuous extrusion of filament;

4. Lower the extrusion temperature.



Below are the explanations for making the above changes.

1. Switch from KISSlicer to the latest stable version of Slic3r (1.2.9)

According to my test and research of the info. on the Internet, KISSlicer seems unable to simultaneously extruding filament and changing the layer height (lifting the Z axis). Instead, KISSlicer must first stop the extrusion, then lift the Z axis and resume the extrusion. This kind of behavior weakens the inter-layer adhesion and makes it difficult to form the wall of the Twisted Spiral Vase.

Slic3r, on the other hand, has built-in support for Spiral Vase. All one needs to do is simply enable this feature and Slic3r will automatically set the relevant settings* (see below photo).

*you still need to set other parameters such as speed, temperature, filament width, etc.

2. Set the right filament width in Slic3r

The filament that I use has about 2.67% variance in width. To ensure there is no under extrusion caused by filament width variation, I set the filament width to 2.93mm in Slic3r.

3. Make adjustments to the extruder and to the height between the hotend nozzle and the print bed to ensure continuous extrusion of filament

I noticed, occasionally, there is no filament coming out from the hotend nozzle and the gears of the extruder are making click - click sound and not turning. After checking to make sure there is no jamming of the gears, I increase the current supplied to the stepper motor by turning up the trimpot on the A4988 module and the gears start turning again. However, even when the gears are turning, sometimes there is no filament coming out from the nozzle. After checking again, I found the height between the hotend nozzle and the print bed is too narrow and it literally blocks the nozzle; hence, the hobbed bolt is unable to push the filament out of the nozzle. After adjusting the height, the filament can now be extruded continuous without interruption.

4. Lower the extrusion temperature.

The temperature of the hotend needs to be adjusted to ensure it's not too hot for the filament used. The filament that I use has a recommended extruding temperature between 210C to 260C. When the temperature of the hotend is too high, bulges are formed in the extruded filament (see below photo).

When the temperature at the hotend nozzle is lowered, the extruded filament is free of bulges and is very clear.

Reference:

Slic3r Tip: printing vases
http://slic3r.org/blog/tip-printing-vases

Spiral Vase
http://www.kisslicertalk.com/viewtopic.php?f=13&t=380