Monthly Archives: March 2021

3D Printing: Cura CLI Wrapper (cura-slicer)

Updates:

  • 2021/03/24: 0.0.5: public release

Introduction

I’m a great admirer of the Ultimaker Cura slicer since years, yet I predominantly have been using CuraEngine on the command-line via Print3r, which hides all the tedious configuration. But it came the point (2021/03) when I needed to have a simpler interface than CuraEngine – hence I wrote Cura CLI Wrapper, the executable cura-slicer looks like prusa-slicer or slic3r and has similar usage.

Speciality is to query all the settings from cura-slicer directly:

% cura-slicer --help
acceleration_enabled = 0 (default)
acceleration_infill = 3000 [mm/s²] (default)
acceleration_ironing = 3000 [mm/s²] (default)
acceleration_layer_0 = 3000 [mm/s²] (default)
acceleration_prime_tower = 3000 [mm/s²] (default)
acceleration_print = 3000 [mm/s²] (default)
acceleration_print_layer_0 = 3000 [mm/s²] (default)
acceleration_roofing = 3000 [mm/s²] (default)
acceleration_skirt_brim = 3000 [mm/s²] (default)
acceleration_support = 3000 [mm/s²] (default)
acceleration_support_bottom = 3000 [mm/s²] (default)
acceleration_support_infill = 3000 [mm/s²] (default)
acceleration_support_interface = 3000 [mm/s²] (default)
acceleration_support_roof = 3000 [mm/s²] (default)
...

which lists ~570 settings as of CuraEngine 4.4.1 and its defaults and from where the defaults come from (definition defaults, config or cli), and you can query also a term e.g. like ‘brim’:

% cura-slicer --help brim
acceleration_skirt_brim = 3000 [mm/s²] (default)
brim_gap = 0 [mm] (default)
brim_line_count = 0 (config)
brim_outside_only = 1 (default)
brim_replaces_support = 1 (default)
brim_width = 8 [mm] (default)
jerk_skirt_brim = 20 [mm/s] (default)
prime_tower_brim_enable = 0 (default)
skirt_brim_line_width = 0.4 [mm] (default)
skirt_brim_material_flow = 100 [%] (default)
skirt_brim_minimal_length = 250 [mm] (default)
skirt_brim_speed = 30 [mm/s] (default)
support_brim_enable = 0 (default)
support_brim_line_count = 20 (default)
support_brim_width = 8 [mm] (default)

and with -v switch you even get a more descriptive output:

% cura-slicer --help brim -v
== acceleration_skirt_brim (Skirt/Brim Acceleration) ==
   The acceleration with which the skirt and brim are printed. Normally this is done with the initial layer acceleration, but sometimes you might want to print the skirt or brim at a different acceleration.
   acceleration_skirt_brim = 3000 [mm/s²] (default)

== brim_gap (Brim Distance) ==
   The horizontal distance between the first brim line and the outline of the first layer of the print. A small gap can make the brim easier to remove while still providing the thermal benefits.
   brim_gap = 0 [mm] (default)

== brim_line_count (Brim Line Count) ==
   The number of lines used for a brim. More brim lines enhance adhesion to the build plate, but also reduces the effective print area.
   brim_line_count = 0 (config)

== brim_outside_only (Brim Only on Outside) ==
   Only print the brim on the outside of the model. This reduces the amount of brim you need to remove afterwards, while it doesn't reduce the bed adhesion that much.
   brim_outside_only = 1 (default)
....

Essentially it makes Cura and CuraEngine easy to use on the command-line and provides a way to learn of the hundreds of settings available.

Usage

USAGE Cura-Slicer 0.0.5 aka Cura-CLI-Wrapper (CuraEngine 4.4.1): [<opts>] <file.stl> ...
   options:
      -v or --verbose         increase verbosity
      -vv or --verbose=2          "       "
      --version               display version and exit
      --load=<config>         load config file
      --load <config>           "         "
      --output=<fn>           set output filename
      --output <fn>             "         "
      -o <fn>                   "         "
      --<k>=<v>               set CuraEngine settings (keys with '-' will be converted to '_')
      -h or --help            display all settings
      -h or --help <term> ..  display settings matching term

   examples:
      cura-slicer --help
      cura-slicer --help retract
      cura-slicer -hv retract 
      cura-slicer sphere.stl
      cura-slicer overhang.stl --output=sample.gcode
      cura-slicer overhang.stl --layer-height=0.1 --support-enable=true -o sample.gcode

Settings

The user settings reside in ~/.config/cura-slicer/base.ini and will not be overwritten when upgrading Cura-CLI-Wrapper, make your changes there.

The system-wide settings reside in /usr/share/cura-slicer/base.ini and should not be be changed as it will be overwritten when upgrading Cura-CLI-Wrapper.

Download

https://github.com/Spiritdude/Cura-CLI-Wrapper

Examples

% cura-slicer cube.stl
== Cura-Slicer 0.0.3 aka Cura-CLI-Wrapper (CuraEngine 4.4.1) == 
processing cube.stl, slicing to cube.gcode
   took 0.62 secs total, done.

% cura-slicer --support-enable=true overhang-inout.stl
== Cura-Slicer 0.0.3 aka Cura-CLI-Wrapper (CuraEngine 4.4.1) == 
processing overhang-inout.stl, slicing to overhang-inout.gcode
   took 0.99 secs total, done.

References

Whereever I used CuraEngine before in my existing software packages I will switch to Cura-CLI-Wrapper with cura-slicer.

3D Printing: Slicer4RTN Released 2021/03/22

Just for sake of completeness a blog-post: I just released the source-code for Slicer4RTN. All developments will be documented there.

% slicer4rtn --subdivide=5 --recenter cube.stl
== Slicer4RTN 0.4.5 == https://github.com/Spiritdude/Slicer4RTN
processing 'cube.stl':
   1/5 read stl
      1/5 subdivide (44 vertices)
      2/5 subdivide (188 vertices)
      3/5 subdivide (764 vertices)
      4/5 subdivide (3068 vertices)
      5/5 subdivide (12284 vertices)
   2/5 map vertices
   3/5 write temporary stl
   4/5 slice (slic3r) stl
=> Processing triangulated mesh
=> Generating perimeters
=> Preparing infill
=> Infilling layers
=> Exporting G-code to ./tmp-204390.gcode
Done. Process took 0 minutes and 1.313 seconds
Filament required: 758.4mm (5.4cm3)
   5/5 remap gcode to 'cube.gcode' (18932 lines)
== took 4 secs total, done.

That’s it.

3D Printing: GCode File Preview in GNOME

When dealing with a lot of G-code it comes handy to have a small thumbnail preview in the file browser under GNOME, hence I coded this package.

It supports Slic3r, Prusa Slicer and Cura.

Download

https://github.com/Spiritdude/Nautilus_Thumbnailer_GCode

gcode2png

The package includes gcode2png which can be used standalone as well.

20mm cube sliced with Slic3r and converted with gcode2png to PNG
USAGE gcode2png 0.0.7: [<opts>] <file.gcode> ... 
   options:
      --version               print version and exit
      --autolevel             level Z minimum to 0 (default: off)
      --output=<fn>           override .gcode -> .png conversion
      --size=<w>x<h>          set size of image (default: 512x512)
      --rotate=<x>,<y>,<z>    rotate model (default: 30,0,-20)
      --dist=<d>              set distance multiplier (default: 1)
      --color=<r>,<g>,<b>     set color (default: .1,.8,.1)
      --grid=0 or 1           set grid (default: 1)
      --grid_size=<s>         set grid size (default: 10)
      --nozzle=<d>            set nozzle diameter (default: 0.4)
      --complete=<i>          set completeness: 0..1 or 0%..100%
      
   examples:
      gcode2png gcube.gcode
      gcode2png --output=cube-normal.png cube.gcode
      gcode2png --color=1,0,0 3DBenchy.gcode
      gcode2png --complete=50% 3DBenchy.gcode

That’s it.

3D Printing: Multi-Axis Printing & Overhangs

Updates:

  • 2021/03/14: more detailed references, published
  • 2021/03/11: starting write-up with basic illustration

Introduction

I thought to compose a summary of the features of 3 types of 3D printers I currently work on, and its relations to print 90° overhangs – main motivation to go beyond 3-axis 3D printing:

Functionality Commonalities

  • a 5-axis printer PAX has the same features as a 4-axis printer RTN and 3-axis printer plus it can print at any tilt angle, printing 90° or more overhangs
  • a 4-axis printer RTN prints conic- or angled sliced models so it can print 90° overhangs in all directions (conic slice) from a central point or single direction (angled slice); the tilt angle is fixed at 45°; Z sliced horizontal layers must be post-processed1) to be printable in good quality
  • a 3-axis printer by default cannot print 90° overhangs without support (unless it’s tilted 45° as for belt-printer, then only in one direction), but may print conic sliced models with 20-25° cone angle, hence print 90° overhangs from a central point, and behave partially like a 4-axis printer
  1. a suitable Zrot must be calculated and added to extrusion commands of the G-code, see this example.

Printing an Conic Sliced Overhang

Conic sliced, in this case 45° conic angle, model nr 6 (table-like), with 45° tilted nozzle (simulation, animation)

Conic Sliced on 3-axis

A well tuned and well designed part-cooler is prerequisite to print conic-sliced models at cone angle of 20-25°, and currently there is no conic slicer which can properly segment sub-volumes yet (2021/03) to switch from horizontal- and conic-slicing (with two modes of outside/inside cone) where suitable.

Conic Sliced on 4-axis RTN

Conic- or angled slicing is recommended in order to print with Rotating Tilted Nozzle (RTN) or post-processing of existing horizontal sliced G-code is required to provide additional Zrot information to print in good quality.

Conic Sliced on 5-axis PAX

and nearly the same with PAX90 (tilt angle 0..90° only) with shorter arm:

A 5-axis Penta Axis (PAX) supports other slice methods than horizontal-, angled- or conic-sliced, but any variable build-orientation, but will make the slicing software very complex to recognize those sub-volumes suitable for advanced slicing methods.

This also means, a 5-axis PAX slicer with proper settings can produce G-code for 5-, 4- and 3-axis 3D printers with combining the horizontal-, angled- and cone slicing for sub-volumes or segments.

Traditionally Horizontal Layers

Slic3r 1.2.9 and Ultimaker Cura 4.8 as comparison:

References

That’s it.

3D Printing: 90° Overhangs without Support Structure with Non-Planar Slicing on 3-axis Printer

Updates:

  • 2021/03/22: slicer4rtn released, see announcement
  • 2021/03/19: some information on use of slicer4rtn (not yet released)
  • 2021/03/09: removed lengthy “Test Protocol” and extended “Gallery” section a bit
  • 2021/03/08: slicer4rtn at 0.2.4 (still unreleased) resulting in better prints, blog-post linked at hackaday
  • 2021/03/05: 95° and 100° overhangs are printable too, more bug-fixes in slicer4rtn
  • 2021/03/04: fixing various bugs in slicer4rtn as disovered printing more complex pieces, supporting prusa-slicer as well aside slic3r, pushing the limits with overhangs
  • 2021/03/02: documenting my findings, a few photos, some early conclusions (not even one day old), conic sliced and tilt sliced.
90° Overhangs without support structure on 3-axis 3D printer

Introduction

It has been target of many efforts to print 90° overhangs without support on 3-axis 3D printers as with ordinary Z slicing, each layer requires a support underneath; hence, every overhang then needs a support structure if the model itself doesn’t provide it.

But if . . . one slices non-planar? That’s what I thought about for a couple of years and kept it in the back of my mind. In January 2021 I came across Rotating Tilted Nozzle (RTN) aka RotBot as developed by ZHAW University of Applied Sciences Zurich (Switzerland). I began to design my own approach of the printhead and then started to code my own conic slicer (slicer4rtn), as the paper which might explain it wasn’t published yet by ZHAW.

While reflecting on the output of the 4-axis conic sliced models, I thought what if I simply make the cone angle flatter than 45° but 15-25° so the vertical nozzle can print it?

Overhang model conic sliced at 25° angle
slicer4rtn --angle=22.5 sliced overhang model, meant for 4-axis printer, but printed on 3-axis printer

Conic Slices Simulation

A simple overhang model (nr 3) conic sliced at 25° for 0.4mm nozzle, 0.2mm layer height:

Tilted Slices Simulation

The same overhang model (nr 3) tilt sliced at 25° for 0.4mm nozzle, 0.2mm layer height (like with belt printer):

Conic Slices Print Tests

And on the afternoon of March 1st 2021 I ran my G-code for the first time on an ordinary 3-axis printer, a cheap CTC DIY I3 Pro B (Prusa-i3 like), in the attempt to print 90° overhangs, with a conic sliced overhang model:

Wow – it seems to have worked! There were still some issues, like the nozzle without extrusion moved into the print as I forgot map linear motions without extrusion also to conic coordinates as well, and some other minor things.

You may consider this a “backport” of 4-axis slicing procedure back to a 3-axis 3D printing procedure.

Next Day Attempts

Conic Slices

The print is still pretty ugly due to the obvious under-extrusion, but the geometry seems to work overall. The overhang on the left-front isn’t evenly, as the outer wall print speed is still too high.

Tilted Slices

Very clean print so far but the overhang is limited to one direction (see below of overall considerations).

Findings

Well, it works, but here are some limitations of using non-planar slicing:

Conic Slices

  • conic sliced overhangs need to be going out- or inward from a central point
    • more complex pieces need to be volume decomposed or segmented, e.g. some sub-volume sliced ordinary vertically Z-wise, others conic sliced where needed – this is part of my research on 4-axis and 5-axis printers; and I was hoping some of the findings can be applied to 3-axis 3D printer as well (as this post shows)
  • the printhead geometry with heatblock sock, part-cooler, LED light they quickly come into way with larger pieces and larger overhangs
    • this might look minor, but part coolers play significant role for quality prints, so they need to be optimized for non-planar printing
  • cone angle
    • 15° works, sufficient space around the nozzle, but on the edge for overhangs, better surface quality
    • 20° works better, layers more stable beneath the overhang
    • 25° works too, but is the limit on my E3D V6 clone, poorer surface quality, but overhang prints better
  • print quality is sub-optiomal, as the nozzle runs over its own extruded filament and any “flat” surface becomes jittery as it’s not longer flat (toward Z) printed

Tilted Slices

  • single direction angled slice like with belt-printer
  • only one direction overhang possible, but good quality
  • tilt angle:
    • 25° works good, yet, the heatblock comes into the way rather quickly with my sample overhang model

Conic vs Tilted Slices

Issues to Resolve

  • more tests
  • more beautiful prints
    • fine tune extrusion rate: the current slicer4rtn does a simple/poor interpolation causing rough top surfaces (under- vs overextrusion)
    • fine tune outer wall of overhangs, slow them down
      • --slicer.external-perimeter-speed=10% (Slic3r)
  • support more slicers
    • Slic3r: supported since slicer4rtn 0.0.1
    • Prusa Slicer: supported since slicer4rtn 0.1.2 (0.1.1 was broken) but often refuses to slice model, e.g. cube fails in inverted cone space
    • Cura Engine: not yet
    • see Conic Slicing for RTN for up-to-date list
  • support skirts (again): due the slicer algorithm the skirt must omitted before pre-processing but be added at last stage or post-processing
  • redesign my part cooler so I can test print larger overhang pieces
  • find collision algorithm (along with given parametric printhead geometry), that’s part of the 4-axis and 5-axis slicing procedure

Gallery

2-sided overhang model nr 4 (conic sliced)

Trying out an overhang model which extends -Y and Y (as side-ways the part-cooler comes into the way)

There are still inconsistencies with extrusion calculation, but the prints getting cleaner.

4-sided overhang model nr 6 (conic sliced)

Sample print comes soon as I need to redesign my part cooler so I can print this piece.

1-sided long 4mm thick overhang model nr 3 (conic sliced)

Long 40mm overhang, just 4mm thick extending nose . . .

1-sided long 2mm thick overhang model nr 3 (conic sliced)

Long 40mm overhang, just 2mm thin extending nose, let’s push the limits of what’s possible:

OK print so far, better than anticipated, but still a way to improve it. Reprint with a newer version of slicer4rtn (0.2.3):

  • better surface, no stringing anymore
  • faster print speed but also more geometric inconsistency like bending up
  • underside is more uneven but also cleaner than all the previous (pre- 0.2.0 of slicer4rtn)

1-sided short 2mm thick 95° overhang model nr 3 (conic sliced)

Just trying more overhang, let’s see.

Obviously there is more than 95° overhang possible, so let’s try …

1-sided short 2mm thick 100° overhang model nr 3 (conic sliced)

Even steeper overhang, let’s see.

This is truly promising, up to 100° overhangs printable with vertical nozzle as mounted on most 3-axis 3D printers . . .

Slicer4RTN Settings

As of the publication of this blog-post (2021/03) no slicer is available but slicer4rtn will be made available soon which was released 2021/03/22.

  • Caution: you need to be an experienced 3D printing enthusiast to proceed, you need to know and realize what you do:
    • pay close attention of the printhead geometry, such as the nozzle and heatblock, and the part cooler which limits the non-planar printing
    • depending on the angle, and the direction of extrusion more or less extrusion distortion will occur
Issues to look at when printing conic sliced models with vertical nozzle on a 3-axis 3D printer

  • --angle=20 is a good start, you may go as low as 15°, and perhaps at max at 30° depending on your nozzle and heatblock, if you aim to print 90° overhangs
  • --layer-height=0.2 is a good start too, the thinner the layers the better overhangs can be printed
  • if you have trouble with over- or under-extrusion and your printer otherwise well tuned, then use --erate=f as extrusion-rate tuning, whereas f = 0.5..1.5 or so, if you have to go below or above, something else is wrong.
  • conic slicing is complex(er), you need to think in new terms:
    • the slicing procedure requires a conic slicing center
      • to and from that center overhangs can be printed well
      • if you have multiple centers, slicer4rtn does not yet support volume segmenting to support multiple centers
      • slicer4rtn requires manually entered conic slicing center
    • it requires fine-grained faces so the slicing works well, use --subdivide=5 or higher for simple pieces, e.g. like a cube or low-poly models in generals

Tuning 3-axis 3D Printer

Following changes are recommended:

  • increase Z axis speed: within the start G-code the line M203 Z.. (replace .. with an actual number) to increase speed of Z-axis
    • depending on the pitch of your Z-lead screw or threaded rods, you may set it to Z4, Z6, or higher, so the motion speed comes close to X- and Y-axis to improve print quality
    • if it’s set too high, your stepper motor will block and not move at all
      • my setup with M6 threaded rod for Z (200 full steps = 1mm):
        • M203 Z8, 8mm/s => 8 revolutions/s => 1600 full steps/s: FAILED (blocked motor)
        • M203 Z6, 6mm/s => 6 revolutions/s => 1200 full steps/s: FAILED (stuttering motor at times, mechanical not reliable)
        • M203 Z4, 4mm/s => 4 revolutions/s => 800 full steps/s: OK
        • M203 Z3, 3mm/s -> 3 revolutions/s => 600 full steps/s: OK
  • slow down perimeter (overhangs): use --external-perimeter-speed=20% or a bit more, it prints overhangs better, leave it at 50% if prints look good
  • X- and Y axis speed: try to match your Z speed, so the overall printing is evenly:
    • Slic3r
      • perimeter-speed
      • bridge-speed
      • infill-speed
  • miscellaneous hints:
    • slicer setting solid-infill-below-area = 10 (make infill work at small(er) pieces too)

Models

References

That’s it.