Category Archives: Technology

3D Printing: Slicing with Non-Planar Geometries

by Rene K. Mueller · published March 26, 2022 Technology EnochSlicer, MetatronSlicer, Non-Planar Printing, Non-Planar Slicing, Research Paper, Universal Slicing

Updates:

2022/04/25: added single photo with various 20mm cube prints
2022/04/01: rewording to avoid confusion of “planar slicing” with non-planar geometries
2022/03/26: finally published
2022/03/25: adding “Benefits of Non-Planar Printing” and “Blind Spots of CAD Systems” and “Scale and Functional Quality”
2022/02/18: getting ready to publish
2022/02/15: adding different slicing geometries and the resulting G-code
2022/02/12: starting write-up

Introduction

After researching non-planar slicing using planar slicers it was obvious to find a way to slice with any kind of geometry, and it meant to step back and formalize slicing procedure in a general manner like “Universal Slicing” – and look at the procedure of slicing itself.

Two classes were defined:

Class 1: using a geometry, either planar or non-planar, and slicing with a static slicing path
Class 2: slicing with variable slicing path and/or variable slicing geometry while slicing

This document/blog-post features a solution for Class 1 Universal Slicing.

My video Non-Planar 3D Printing: Slicing with Non-Planar Geometries goes through this information in an animated form, this is the textual form.

Slicing with Non-Planar Geometry (Class 1 Universal Slicing)

When using a static planar slicing vector one usually uses a plane, hence the term “planar slicing”, yet, there is also the possibility to use a non-planar geometry and slice in a planar direction (introducing ambiguity what planar and non-planar slicing actually mean). Regardless which slicing geometry is used in this procedure, the thickness of the sliced layer stays the same.

Slicing 20mm cube with wave-like geometry

In order to explore non-planar slices, using a wave-like geometry composed by Bezier curves and slice a 20mm cube:

20mm cube wave-like sliced: wave-like geometry itself, partial complete, complete and even slices only

Note: OpenSCAD is used solely used as 3D viewer, the slicing itself is performed by an experimental slicer.

Routing a single non-planar slice

A single slice is routed to wall/perimeter and infill extrusion:

There are several approaches to achieve this:

slice non-planar, map single slice 3d to 2d, route with 2d offsetting, and map back to 3d space (MetatronSlicer)
map entire mesh and slice planar, and map routes or resulting G-code back again (EnochSlicer)

and likely other more complex means.

Non-planar Printed Wave-like Sliced 20mm Cube

Preview of the complete G-code:

Preview the non-planar G-code of 20mm cube sliced with wave-like geometry

and a brief and fast printing simulation showing the entire print:

The computed G-code printed with a 3D printer, e.g. an ordinary 3-axis FDM:

Non-Planar 3D Printing: 20mm cube sliced with wave-like geometry (1x speed with a few skips)

and produces output like this:

left-to-right: wave-like geometry itself, progressive state of 20mm cube sliced with wave-like geometry at 0.25mm layer height

Implementing Non-Planar Slicing Geometries Slicer

The illustrations and actual G-code above were produced by two new in-house slicers which are in early development (2022/03):

20mm cube sliced with wave-like geometry
left-to-right: MetatronSlicer (0.0.7), EnochSlicer (0.0.2)

MetatronSlicer: boundary-based (BREP / OpenCASCADE) and voxel-based (OpenVDB) geometry engine, performing true non-planar slicing, and LabSlicer performing routing and G-code creation; slower slicing yet precise G-code
EnochSlicer: mesh and G-code transformation approach, fast slicing yet less accurate G-code

The extrusion precision is still rough, but overall concept and algorithms have been proven to work.

Results & Achievement

This work as presented here resolves a long pending issue of slicing meshs “non-planar”, or general “non-planar slicing” with all its inherent ambiguity – consider it as given that

one can use any 3D geometry with sufficient upper “surface” to slice a mesh with

and create printable G-code for 3- and 5-axis FDM:

using a block as planar blueprint
hemisphere, convex
hemisphere reverse, concave
cone, slicing conical like for Rotating Tilted Nozzle
wave-like defined via Bezier curves
wave-like defined via NURBS (Non-Uniform Rational B-Splines) curves
tilted plane, slicing for belt printer with 45° tilted XY frame toward Z belt
pimple-like

Along with volume segmentation as presented previously and conical, cylindrical and spherical slicing now any kind of slicing geometry can be used.

**20mm cube** sliced with various non-planar geometries:
1. conic (EnochSlicer), 2. wave (MetatronSlicer), 3. wave (EnochSlicer), 4. pimple (EnochSlicer), 5. pimple 2x tiled (EnochSlicer), 6. hemisphere (EnochSlicer), 7. tetrahedron 2x tiled (EnochSlicer)
limited to 3mm Z amplitude, printed on 3-axis FDM (Ashtar K #2)

As pointed out in Universal Slicing, this “Planar Slicing with Non-Planar Geometries” is Class 1 of Universal Slicing whereas Class 2 covers changing slicing geometry and/or flexible slicing path along the slicing.

Limiting Non-Planar Height for 3-axis FDM

When using non-planar geometries to slice a model also non-planar G-code is produced and possibly significant Z motion occurs, and when printing with an ordinary 3-axis FDM 3D printer it may be suitable to limit the Z motion aka Z amplitude to 2-3mm in order to avoid part-cooler or other parts of the print head to collide with the already printed part:

left column: wave-like slicing, right column: hemisphere slicing
top row: full range, bottom row: limited to ~3mm Z amplitude

Future blog-posts will go into further details implementing Universal Slicing using those two slicers MetatronSlicer and EnochSlicer.

Regarding naming the slicers: Metatron is an archangel in jewish mythology – consider an “angel” as a fundamental intelligence, and in esoteric context Metatron is the being responsible for Form or Geometry itself – separating one into many in a spatial manner; whereas Enoch as a human, who ascended to become the archangel Metatron. I use those names in deep reverence for these two projects.

Blind Spot of CAD Systems

Current CAD systems (2022) neglect or actually are unaware of the inner vs outer structure – because only one kind of the “structure” is known, e.g. a piece is designed because of a certain function, which defines its outer form, e.g. a wrench to use a simple example – but how about the inner structure? This isn’t defined in the CAD, it is defined at the manufacturing stage, yet with 3D printing this can be described and designed even in a parametric way as well, the slicing or general 3D printing stage with different materials.

We require 2 or 3 abstraction layers to design a functional piece:

the functional description (doesn’t exist yet)
the inner structure (description how material is deposited in Additive Manufacturing, e.g. the infill geometry as of with FDM, incl. non-planar printing, or lattice structures as with SLA or SLS)
the outer structure (e.g. mesh, boundaries)

So far CAD systems only covers the 3rd point, the outer structure.

The functional description is almost non-existent in the CAD world, and only becomes some attention when Finite Element Analysis is made and the form is changed, it is kind of hidden in plain sight.

In future blog-posts I will address and elaborate on these issues further.

Scale and Functional Qualities

To put the flexible slicing geometry in the grander context of 3D printing engineering:

3D printing engineering starts at nanometer scale (10^-6mm) with material science level, over to filament composition at 1 to 10 micrometer scale (10^-2mm) such as fibers, inner geometry where slicing geometry & procedure and infill geometry define strength properties at millimeter scale (10⁰mm), and outer geometry with the shape of the object itself provide the final stage of mechanical properties.

This entire “scale chain” as a whole defines the mechanical property of the final 3D printed object.

That’s it.

References

Universal Slicing
Video: Mastering Non-Planar Printing: Slicing with Non-Planar Geometries
MetatronSlicer (Class 1, partial Class 2 Universal Slicer)
EnochSlicer (Class 1, partial Class 2 Universal Slicer)
3D Printing: Sub-Volume Segmenting & (Non-)Planar Slicing
Involved tools: YAGV, G-code Previewer, Gcode2png, LabSlicer
HackaDay: 3D Printering: Non-Planar Layer FDM (2016), brief overview
Inner Structure Approaches
- Hyperganic: software designing parts based on actual function and strength properties, voxel-based, output for SLS, SLA, FDM – very little information available on the net (2022/02), secretively operating company
- nTopology: generative design using implicit modeling, more open company, they even have a Github presence

EnochSlicer

by Rene K. Mueller · published March 26, 2022 Technology EnochSlicer, Non-Planar Slicing, Universal Slicing

Status: early development, not available yet

Updates:

2022/03/26: published with little information
2022/02/28: starting write-up

Introduction

EnochSlicer is aiming to be a fast Universal Slicer by taking research results from development of MetatronSlicer.

MetatronSlicer vs EnochSlicer

MetatronSlicer implements true non-planar slicing and routes each slice exact, whereas EnochSlicer using pre- and post transformation of mesh and routes (pre g-code).

As development of an Universal Slicer is in early stage (2022/03), both projects are pushed forward to see which one is more fit and suitable and cross-fertilize each other.

	MetatronSlicer	EnochSlicer
mesh	plain	transformation
slicing	non-planar	planar
route	dedicated ¹⁾	–
gcode	dedicated ¹⁾	native²⁾
post processing	plain	transformation

Footnotes:

utilizing LabSlicerCore library
native via planar slicer (direct mesh to gcode) like CuraEngine

In-House Slicers

LabSlicer	Vox3lSlicer	VoxGLSlicer	MetatronSlicer	EnochSlicer
– full planar slicer – 4 stages: mesh, slice, route, gcode – experimental – API defined – LabSlicerCore library – import/export data of each stage	– voxel-based planar slicer – fast slicing – uses LabSlicerCore library for route and gcode stage	– OpenGL based planar slicer – fast slicing – uses LabSlicerCore library for route and g-code stage	– non-planar slicer – implements Class 1 + 2¹⁾ Universal Slicing – uses OpenZCAD²⁾ engine to slice non-planar	– non-planar slicer – implements Class 1 + 2¹⁾ Universal Slicing – uses mesh & gcode transformation

Footnotes:

Class 2 Universal Slicing only partially implemented (status 2022/03)
OpenZCAD is alike OpenSCAD but with Python as base-language with multiple backends (OpenCASCADE, LibFive, Fogleman’s SDF)

Availability

See MetatronSlicer

References

MetatronSlicer

by Rene K. Mueller · published March 26, 2022 Technology MetatronSlicer, Non-Planar Printing, Non-Planar Slicing, Universal Slicing

Status: early development, not yet available

Updates:

2022/04/01: bringing terms/wording in-sync with Universal Slicing
2022/02/26: published finally with basic information
2022/02/18: copying content from “Universal Slicing” page start to focus on the slicer itself

Introduction

MetatronSlicer aims to become full functional Universal Slicer:

Universal slicing means free slicing geometry along a free path.

“free (definable) slicing geometry”: any kind of geometry, may it may a solid or just a surface defining the slicing geometry.

“free (definable) path”: the slicing procedure can go in any direction, curvature and steps.

See Universal Slicing for more thorough description and theoretical examples.

Implementing Universal Slicing

As I was proposing the concept of “Universal Slicing”, I had the impulse to start an implementation right away in order to produce illustrations for the concept.

MetatronSlicer aims to become full Universal Slicer, it’s not optimized for speed but to be capable as of completeness.
EnochSlicer is a sister project which takes research results from development of MetatronSlicer and tries to find a more efficient way to achieve the same or a subset.

Universal Slicer: MetatronSlicer

MetatronSlicer is the first attempt of an Universal Slicer (2022/02), which implements for a start planar-slicing of non-planar slicing geometries, for example a wave-like geometry:

The wave-like geometry was defined via Bezier curves.

Via some transformations back and forth the in-house LabSlicer and g-code produced non-planar slice:

the green represents the ideal 3D slice,
the yellow/golden are the extrusions,
the red dots indicate the start of a G1 extrusion segment.

As of MetatronSlicer 0.0.8 (still very experimental as of 2022/02) it was possible to produce printable G-code:

and then printed on a 3-axis FDM (Ashtar K #2 Prusa-Mendel style) machine with apprx. 3mm vertical nozzle spacing ²⁾, the wave-like reference geometry was slighted scaled in Z to comply to this physical contraint:

full print at 1x speed with a few skips

MetatronSlicer: toward implementing Universal Slicing capabilities

A few samples of non-planar geometries slicing 20mm cube:

Convex hemispherical slice geometry slicing 20mm cube:

Concave hemispherical slice geometry slicing 20mm cube:

Conic slice geometry slicing 20mm cube:

which essentially replaces Slicer4RTN.

As of 2022/02 MetatronSlicer is still in very early development, but eventually aims to implement also variable slicing geometries and variable slicing vector such as:

Class 2 Universal Slicing: Variable Slice Geometry / Variable Slicing Path

MetatronSlicer vs EnochSlicer

MetatronSlicer implements true non-planar slicing and routes each slice exact, whereas EnochSlicer using pre- and post transformation of mesh and routes (pre g-code).

As development of an Universal Slicer is in early stage (2022/03), both projects are pushed forward to see which one is more fit and suitable and cross-fertilize each other.

	MetatronSlicer	EnochSlicer
mesh	plain	transformation
slicing	non-planar	planar
route	dedicated ¹⁾	–
gcode	dedicated ¹⁾	native²⁾
post processing	plain	transformation

Footnotes:

utilizing LabSlicerCore library
native via planar slicer (direct mesh to gcode) like CuraEngine

Availability

MetatronSlicer and alike EnochSlicer are in early development, and will be tuned for industrial 3D printing applications for 3- and 5-axis FDM.

Sometime during 2022 one or both might become available as commercial products in order to fund future development, unless I find another way to fund the research and development – in that case an open source “community edition” is possible.

References

Universal Slicing
3D Printing: Slicing with Non-Planar Geometries
Video: Mastering Non-Planar Printing: Slicing with Non-Planar Geometries
LabSlicer: in-house slicer & slicing library
Slicer4RTN: conic slicer or Rotating Tilted Nozzle

In-House Slicers

LabSlicer	Vox3lSlicer	VoxGLSlicer	MetatronSlicer	EnochSlicer
– full planar slicer – 4 stages: mesh, slice, route, gcode – experimental – API defined – LabSlicerCore library – import/export data of each stage	– voxel-based planar slicer – fast slicing – uses LabSlicerCore library for route and gcode stage	– OpenGL based planar slicer – fast slicing – uses LabSlicerCore library for route and g-code stage	– non-planar slicer – implements Class 1 + 2¹⁾ Universal Slicing – uses OpenZCAD²⁾ engine to slice non-planar	– non-planar slicer – implements Class 1 + 2¹⁾ Universal Slicing – uses mesh & gcode transformation

Footnotes:

Class 2 Universal Slicing only partially implemented (status 2022/03)
OpenZCAD is alike OpenSCAD but with Python as base-language with multiple backends (OpenCASCADE, LibFive, Fogleman’s SDF)

LabSlicer, Vox3lSlicer, VoxGLSlicer

by Rene K. Mueller · published March 26, 2022 Technology In-House, LabSlicer, Vox3lSlicer, VoxGLSlicer

Updates:

2022/03/26: published
2022/03/03: starting write-up, based on internal documentation

Introduction

As part of getting to know the inner working of a slicer and have a toolkit for advanced non-planar slicer I had in mind, I started to code my own “laboratory slicer” or simply “LabSlicer” as an in-house project.

Its main features are:

Python-based, it’s slow for production but good enough to test new algorithms
PyClipper as offsetting & clipping engine
four stages clearly defined with API and file-format export/import:
- mesh: import & export meshs
- slice: slices 3d objects into 2d slices/polygons
- route: routes polygons with wall/perimeter and infills, bottom/top layers, skirts/brims
- gcode: takes routes and converts into G-code
LabSlicerCore: slicer available as library, with clear defined & simple API
easy to extend to non-planar slicing/routing/g-code, incl. 5-axis FDM

Motivation

It may look like redundant to code another slicer and define those rather simple steps as such, but the benefits came days after I finished the basic layout and was able to exchange the mesh and slicing stage with voxel-based engine, or use OpenGL screenbuffer to slice and then hand over polygons to route and gcode stage – within 2-3 weeks I had 3 working slicers with different slicing engines.

By having a clear API the integration into various in-house projects was truly swift and the cross-fertilization paid off quickly and immensely. I might have taken me more time to learn to memorize Slic3r or CuraEngine API than writing a basic slicer myself. Granted that coding a slicer in Python limits its overall performance, compared to an optimized slicer like Cura; but to research and develop new slicing and routing algorithm coding with Python is fast, a couple of hundred lines in Python can represent ten thousands of lines of C++ code, not to mention wait time for compiling.

Four Stages of Slicing

It may appear to be simplistic at first sight, but it’s worth to clearly layout the main stages of slicing:

Mesh

One has to import the geometry such as a mesh which circumscribes a volume.

Slice

The slicing stage takes the geometry and slices it into slices, which are a set of polygons which also describe holes – essentially an array of arrays of polygons.

Route

The real work of the slicer is actually the routing, which means to plan extrusion paths:

walls or perimeters: offsetting or rather insetting 2D polygons
infill pattern: offsetting and clipping of 2D polylines
skirts and brims: offsetting at bottom via 2D polygons
bottom and top layers, also intermediary: difference & intersecting previous and next layers to determine delta areas (polygons) were, are or becoming bottom/top layers
support structures (not yet implemented)

Routes are held in an array of arrays of routes (polylines).

Off- and Insetting Polygons

At first sight it looks trivial, but in the details this isn’t trivial at all as offsetting or insetting can clash with itself or other polygons and fork into two or more polygons. Clipper as developed Angus Johnson has laid the ground for many slicers and does the heavy lifting and therefore unloads some of the burden and one can focus on higher level algorithms.

Gcode

At this stage now all the slicing settings like travel and extrusion speeds, retraction and so on are factored in and further optimizations are done, given we know now all routes at a given (planar-)layer.

It’s easier to separate routing and actual creation of G-code as transforming routing, like for non-planar slicing, is more efficient than parsing G-code with more overhead.

From a development point of view the routing results is the most precious and worthwhile data; the other stages are rather simple, but routing is where the magick happens.

History

To give you a bit insight to how I coded it, I started with the API in mind, defined the 4 stages roughly, then the parameters and the data-structures and import/export file-formats, essentially all is encoded in JSON to keep things simple.

Within 2 days I had basic wall routing coded using PyClipper – I had some experience with coding with it at Mandoline (fork) but felt to start from scratch anyway – and I did not even try to slice yet but had a simple function returning the same square (polygon) no matter which slicing height – yes, starting with the simple 20mm cube.

Once I had the routing done, I coded the gcode stage, to create basic extrusion and preview the gcode with a G-code viewer – and added support start- and end-gcode with some sane defaults and sent it to my 3D printer – and the first print outs were bad, no retraction, no infill, single wall, no path/routing optimization.

LabSlicer early tests 2021/12 (left to right, bottom to top): 20mm cube, wall, top/bottom layers, cylinder;
20mm cube with square hole, openscad logo, 3D benchy (retraction not yet coded)

After I matured routing and gcode stage, I focused on the slicing from mesh to polygons, which took most of the time, as I had to decide on the notion how holes are defined in a set of polygons, using clock-wise (CW) and counter-clock-wise (CCW) notion – the code grew quickly complex as I coded those polygon processing from scratch instead to use shapely library right away; but it was good to look so closely at the details, as when one wants to carry metadata of facets of the mesh to the polygon slice and routing stage to the final gcode, e.g. changing color, material or other special G-code, this chain or pipe to hand over metadata had to be possible.

I also kept the file format of routing somewhat open to support easily also non-planar routes, means, the coordinate could be more than x, y, z but also u, v, w (nozzle vector for 4-, 5- or 6-axis FDM) and layer thickness for non-planar slicing.

Cross-Fertilization

Vox3lSlicer: as I experimented with voxel-based geometries, such as reliable CSG operations when slicing with voxels, I replaced the mesh– and slice-stage with voxel-based functions, and then use the next two stages of route and gcode to create G-code; it was truly a matter of a couple of hours
VoxGLSlicer: utilizing OpenGL screenbuffer to “render” volume and easily slice within the GL engine, vectorize and feed the polygons into LabSlicerCore; the same, after a few hours I had another slicer

Examples

Vox3lSlicer, printing tilted Voronoi Bear to avoid supports

In-House Slicers

LabSlicer	Vox3lSlicer	VoxGLSlicer	MetatronSlicer	EnochSlicer
– full planar slicer – 4 stages: mesh, slice, route, gcode – experimental – API defined – LabSlicerCore library – import/export data of each stage	– voxel-based planar slicer – fast slicing – uses LabSlicerCore library for route and gcode stage	– OpenGL based planar slicer – fast slicing – uses LabSlicerCore library for route and g-code stage	– non-planar slicer – implements Class 1 + 2¹⁾ Universal Slicing – uses OpenZCAD²⁾ engine to slice non-planar	– non-planar slicer – implements Class 1 + 2¹⁾ Universal Slicing – uses mesh & gcode transformation

Footnotes:

Class 2 Universal Slicing only partially implemented (status 2022/03)
OpenZCAD is alike OpenSCAD but with Python as base-language with multiple backends (OpenCASCADE, LibFive, Fogleman’s SDF)

Availability

All three slicers are in-house slicers where I do a lot of experimenting, changing rapidly and testing new algorithms, such as mapping coordinate systems and new routing procedures – for now there are no plans to publish them.

I recommend to look at my fork of Mandoline to learn about slicing, which is available at github but I have stopped to work on, it actually produces printable G-code unlike the original code of it.

References

MetatronSlicer & EnochSlicer (universal slicers)
Slicer4RTN (conic slicer)
Cura CLI Wrapper
Mandoline (fork)

Universal Slicing

by Rene K. Mueller · published March 26, 2022 Technology Non-Planar Printing, Non-Planar Slicing, Research Paper, Universal Slicing

Updates:

2022/04/01: changing wording of “non-planar” vs “planar” slicing but describe actual slicing vector and geometry
2022/03/26: published finally
2022/03/24: added “Tensile & Shearing Force” illustration
2022/03/10: added “Scale & Functional Qualities”
2022/02/27: added Class 2 example
2022/02/18: removed MetatronSlicer example and move to new page, keeping page focused on general and theoretical aspect of Universal Slicing
2022/02/12: adding MetatronSlicer example as first attempt of an Universal Slicer
2022/01/28: separating from another blog-post, solely focusing on Universal Slicing
2022/01/16: starting write-up

Introduction

While conceptualizing the in-house LabSlicer (2021/2022) and the two subsequent slicers afterwards (Vox3lSlicer & VoxGLSlicer), I realized it would be useful to formulate a general or universal description of slicing, hence I propose an universal definition of slicing as such:

Universal slicing means free slicing geometry along a free path.

“free (definable) slicing geometry”: any kind of geometry, may it be a solid or just a surface defining the slicing geometry.

“free (definable) path”: the slicing procedure can go in any direction, curvature and steps.

To put this in context:

“planar slicing” is plane or quasi box geometry with layer height thickness, sliced along a static 3D path vector of [ 0, 0, 1 ], aka “planar” or “Z-planar” with vector steps of [ 0, 0, layer height ], whereas layer height can change in that case it’s “variable” or “adaptive layer height”
“conic slicing” is a cone geometry with layer height thickness, sliced along a static path vector of [ 0, 0, 1 ] with vector steps of [ 0, 0, cos( layer height )] or scaling a stationary conic to match layer height
“cylindrical slicing” is a cylinder which stays positioned static at [ 0, 0, 0 ] and variable scaled to match layer height with [ s, s, 1 ], slicing pipe-like layers
“spherical slicing” is a sphere geometry with scales in size to match layer height, the position stays [ 0, 0, 0 ], whereas the geometry is scaled by [ s, s, s ], slicing thin sphere layers

Slicing	Slicing Geometry	Slicing Vector	Vector Steps	Geometry Scale
planar	plane	[ 0, 0, 1 ]	[ 0, 0, t ]	[ 1, 1, 1 ]
conic	cone	[ 0, 0, 1 ]	[ 0, 0, t ]	[ 1, 1, 1 ]
	cone	[ 0, 0, 0 ]	[ 0, 0, 0 ]	[ s, s, s ]
cylindrical	cylinder	[ 0, 0, 0 ]	[ 0, 0, 0 ]	[ s, s, 1 ]
spherical	sphere	[ 0, 0, 0 ]	[ 0, 0, 0 ]	[ s, s, s ]

The actual implementation, how slices are routed and then G-code is created, is up to the slicer; an Universal Slicer is a slicer which implements Universal Slicing paradigm.

Class 1: Static Slicing Vector, Static Slicing Geometry

There are two distinct cases of class 1 slicing:

slicing with planar geometry, a plane – also known as “planar slicing”
slicing with non-planar geometry, like a wave, a hemisphere, a cone, etc.

Static slicing vector means here, there is an equal distance among all points of a slice to the next or previous slice at the same [ x, y ] position according the slicing vector:

Class 1 Universal Slicing: Static Slicing Vector with Planar and Non-Planar Geometries

Regardless of the slicing geometry, the layer height or thickness remains the same along the slice or layer itself.

The layer height or thickness may vary from layer to layer, this is known as “variable layer height” or “adaptive layer height” but only means among layers or slices, but not within a single layer or slice.

Class 1 Examples

Examples of Class 1 Universal Slicing with planar and non-planar geometries and the respective G-code outputs (produced by MetatronSlicer and EnochSlicer):

Class 1 Universal Slicing: Planar Slicing with Non-Planar Geometries: planar, hemisphere convex, hemisphere concave, conic, wave-like Bezier & NURBS, tilted, pimple-like

using a block as planar blueprint
hemisphere, convex
hemisphere reverse, concave
cone, slicing conical like for Rotating Tilted Nozzle
wave-like defined via Bezier curves
wave-like defined via NURBS (Non-Uniform Rational B-Splines) curves
tilted plane, slicing for belt printer with 45° tilted XY frame toward Z belt
pimple-like

Class 2: Variable Slicing Vector or Variable Slicing Geometry

Variable slicing vector or changing slicing geometry (often refered as “non-planar slicing” without the specifics) means the slice itself has variable layer height or thickness – to be more precise:

change of slicing geometry, e.g. transitioning from one slicing geometry to another
change of slicing vector, e.g. change in steps, or curvature

Class 2 Universal Slicing: Variable Slicing Geometry, Variable Slicing Vector

It may not be always clear at first sight whether there is a transition of a slicing geometry or a change of slicing vector, as the changed slicing vector can also be looked as another slicing geometry – yet I think it makes more sense to differentiate between a slicing vector and slicing geometry when laying out a slicing procedure.

Class 2 Examples

Example of Class 2 of Universal Slicing (produced by EnochSlicer):

Example 1: Non-planar slicing of 20mm cube

It is important to realize, that change of slicing geometry and/or slicing vector implies the slice or layer has variable thickness, hence, might have to comply with physical limits like maximum layer height printable with FDM and a given nozzle diameter – the actual implementation of an Universal Slicer has to adhere this.

Slicing Vector vs Slicing Geometry

Slicing Vector	Slicing Geometry	Slices / 3D Printing	Slice Thickness
static	planar	planar	static
	non-planar	non-planar	static
variable	planar	non-planar	variable
	non-planar	non-planar	variable

Implementing Universal Slicing

The implementation of such Universal Slicing can be achieved in many ways and procedures. It is important to name features and describe what it they mean, such as:

Universal Slicing: is the ability to choose slice geometry and slice path freely
Universal Slicer: slicer which implements Universal Slicing in parts or fully – if it only implements part it shall be declared so
Class 1 Universal Slicing: static slicing path of [ 0, 0, 1 ], but with any kind of slicing geometry, static planar or static non-planar
Class 2 Universal Slicing: flexible slicing path, ability to change slicing geometry while slicing

Class	Slicing Path	Slicing Geometry
Class 1	static	static (planar or non-planar)
Class 2	flexible	flexible (planar or non-planar)

Universal Slicers

MetatronSlicer (in-house XYZdims, status 2022/03):
- slicing with (non-)planar geometries (Class 1)
- partial support for slicing with change of slicing geometry (Class 2)
EnochSlicer (in-house XYZdims, status 2022/03):
- slicing with (non-)planar geometries (Class 1)
- partial support for slicing with change of slicing path & geometry (Class 2)
DotXControl 5-Axis Slicer (status 2022/03): supposedly supports Class 1 + 2 based on illustrations on the web-site
AI-Build (AI Build): requires NDA to even see a demo (!!) therefore difficult to conclude capabilities, might supports Class 1 + 2 based on illustrations and brief videos

MetatronSlicer: slicing with wave-like geometry a 20mm cube, printed with 3-axis FDM

Benefits of Non-Planar 3D Printing FDM

**Layer adhesion tensile and shearing forces of planar and non-planar FDM**
Fa = attacking force; Ft = tensile component of Fa; Fs = shearing component of Fa; β = tangent angle

One advantage resides in the ability to address FDM Z-layer adhesion issues by distributing force or stress vectors along any kind of trajectory and optimize material vs strength of the overall printed piece, e.g. when using continuous fiber filament and lay it along most stressed locations.

Further, the ability to have top layers align to object’s surface directly, no more layer lines. Essentially being able to define and manufacture a piece based on inner structure requirements and its outer form requirements.

References

3D Printing: Slicing with Non-Planar Geometries
Video: Mastering Non-Planar Printing: Slicing with Non-Planar Geometries
MetatronSlicer (Class 1+2 Universal Slicer)
EnochSlicer (Class 1+2 Universal Slicer)
LabSlicer (planar slicer)
Slicer4RTN: conic slicer for Rotating Tilted Nozzle
HackaDay: 3D Printering: Non-Planar Layer FDM (2016), brief overview
Inner Structure Approaches
- Hyperganic: software designing parts based on actual function and strength properties, voxel-based, output for SLS, SLA, FDM – very little information available on the net (2022/02), secretively operating company
- nTopology: generative design using implicit modeling, more open company, they even have a Github presence
Papers:
- [Coupek, Friedrich, Battran, Riedel] Reduction of support structures and building time by optimized path planning algorithms in multi-axis additive manufacturing (2018) – free PDF
- [Wuethrich, Elspass, Bos, Holdener] Novel 4-axis 3D printing process to print overhangs without support material (2020) – non-free PDF
- [Khurama, Dina, Simpson] Active-Z Printing: A New Approach to Increasing 3D Printed Part Strength (2016) – free PDF

Misc: XYZdims State 2022/02

by Rene K. Mueller · published February 20, 2022 Technology LabSlicer, OpenGL Slicing, Vox3lSlicer, Voxel Slicing, VoxGLSlicer, YAGV

Updates:

2022/02/20: finally published
2022/02/08: ready to publish finally with some delay
2022/01/28: not yet published, removed Universal Slicing details for future blog-post, added more photos and illustrations
2022/01/16: starting write-up

Introduction

Aside of the technical detailed filled blog-posts I like to start to post about the larger context of my inner motivations doing XYZdims.com – this is the first post “XYZdims State 2022/02”:

More Slicers

Recent in-house developments having more slicers to experiment with, in regards of slicing techniques as well lay the ground for more complex slicing and mapping/transformation operations to support arbitrary non-planar slicing (coming soon).

LabSlicer: The Mother

Big Picture of XYZdims – State 2022/02
(click on it and then zoom in, it’s a large image)

As I was working with Slicer4RTN and wrappers like Cura-CLI-Wrapper and Kiri:Moto Slicer (CLI wrapper), and adopting Mandoline fork – I realized I need to have my own slicer, so in November 2021 I started from scratch, as I thought I need to know every detail and so I exposed each step or stage:

mesh: load mesh, vertices & faces
slice: slice layers into sets of polygons
route: route the layer polygons with walls, infills etc
gcode: convert routes to G-code

A “lab(oratory) slicer” or simply LabSlicer was born – I defined each stage: API and file-format it takes in and spits out.

After a couple of weeks I had slicing into polygons, and routing of walls, basic infills, skirts, brims and eventually intermediary top & bottom layers resolved, and I was able to generate printable gcode:

Early tests of LabSlicer 0.0.1, getting extrusion right – static slicing

Meanwhile LabSlicer as of version 0.1.5 has matured to print complex models reliably but rather performs slow compared to Slic3r or Cura.

As of 2022/02 I’m even use LabSlicer and its relatives (featured below) for productive 3D prints.

Vox3lSlicer: Voxels

Aside of LabSlicer I began to develop Vox3lSlicer which utilizes internally the OpenVDB voxel library, in order to slice planar and in the future non-planar as well, and also permit to slice voxel-based models efficiently.

A few tests with OpenSCAD Logo model (~20mm height) with various amount voxel samples, from low resolution to high resolution:

10K samples
100K samples
1M samples
10M samples (default)
100M samples

and with defined voxel sizes:

voxel 0.05mm (default)
voxel 0.1mm
voxel 0.25mm
voxel 0.5mm
voxel 1.0mm

As LabSlicer matured and LabSlicerCore library came to life, Vox3lSlicer (2011/11) utilizes the stage route and gcode of LabSlicerCore to actually produce printable G-code.

Testing the retraction code and settings of Vox3lSlicer, rotating the model in order to avoid support structure altogether:

VoxGLSlicer: OpenGL Slicing

As I was looking for other slicing procedures I came across OpenGL-ST-Slicer, which utilizes a clever OpenGL setup with GLSL (Shader Language) to render a mesh to a framebuffer with the volume information, and so slicing is done solely in the GPU almost instantly – I extended this approach and glued it together with LabSlicerCore and I was able to produce also printable G-code – VoxGLSlicer was born (2022/01).

Due the limitation of the internal framebuffer width & height the resolution of the slicing changes with the size of the model aka “relative resolution”:

model width [mm]	pixel size [mm] @ 2560 pixels
20	0.008 or 8 μm
50	0.019 or 19 μm
100	0.039 or 39 μm
200	0.078 or 78 μm
500	0.19 or 195 μm
1000	0.39 or 390 μm

and just for illustration about “pixel size” related to a ~20mm model:

pixel 1mm
pixel 0.5mm
pixel 0.25mm
pixel 0.1mm
pixel 0.05mm (default)

3 Slicers

After a few weeks coding (2021/11-2022/01), I was able to raise 3 slicers, each with their unique slicing approaches to create printable G-code, by having a common API and use symbiotic advantage of each other:

	LabSlicer	Vox3lSlicer	VoxGLSlicer
mesh	mesh.py¹⁾ multi-format mesh importer	openvdb STL importer	mesh.py¹⁾ multi-format mesh importer
slice	slicing mesh to polygons (vectorizing)	slice voxels into polygons (vectorizing)	screenbuffer into polygons (vectorizing)
route	route polygons to routes	LabSlicerCore’s route	LabSlicerCore’s route
gcode	convert routes to G-code	LabSlicerCore’s gcode	LabSlicerCore’s gcode
	+ traditional slicer with polygons + all stages fully implemented – slow slicing²⁾	+ fast slicing + flexible resolution + reliable	+ fast slicing – fixed screenbuffer size – relative resolution

All three slicers are very experimental and play a significant role for the next step – Universal Slicing.

Footnotes:

mesh.py is loading/saving 3d meshs/models and some simple manipulations tuned toward my use cases
mesh slicing not yet optimized

So any optimizing of routing (wall, infill, intermediary top/bottom layers etc) and gcode optimizing all three slicers benefit from.

YAGV & Nautilus Thumbnailer Supporting ArcWelder

After the implementing G2/G3 emulation for gcode2png as part of the G-code thumbnailer, I also added it to G-code viewer yagv fork of mine:

3DBenchy G-code (Cura 4.4.1): 7MB G-code

Print3r

And just for sake of giving a bit of context, adding ArcWelderLib in the pipeline of Print3r via the configuration:

# first declare new post-processor named "arcwelder":
post_arcwelder = ArcWelder %i %o
# optionally, define it to be active (all the time):
post = arcwelder

or optionally enable it on the command-line:

% print3r print cube.stl --post=arcwelder

That’s it for now.

References

IotaSlicer, OpenGL Z-buffer slicing with multi-color, coded in C++
OpenGL-STL-Slicer, OpenGL Z-buffer slicing coded in Python
OpenVDB, Voxel library

3D Printing: Mandoline Slicer

by Rene K. Mueller · published September 16, 2021 Technology Mandoline, Python, Slicer, Slicing

Updates:

2021/09/16: publishing this blog-post finally
2021/09/04: 0.8.6: supporting OFF, OBJ, AMF, 3MF and 3MJ in addition to STL
2021/04/11: 0.8.5: more tests and Makefiles added
2021/04/06: 0.8.4: SVG export working with example, various bug fixes
2021/04/04: 0.8.3: first print actually working (extrusion calculation fixed, removed most un/retract for now)
2021/04/02: starting write-up

20mm xyzHollowCalibrationCubeV2 sliced with Mandoline 0.8.5

Introduction

Since I started to develop on the conic slicer slicer4rtn for the RTN, and starting to work on the more complex PAXSlicer for 5-axis printer like PAX option. So I was searching for a slicer to adapt for future projects to have more control of the slicer stage and learn of the actual details and so I came across Mandoline Py, a slicer coded in Python utilizing at its core pyclipper and at first glance it was well thought out, clean code, yet not many comments but function names and variables were explanatory – I was quite impressed by Revar Desmera, who was able to put this together in such a consistent manner.

There wasn’t much information available otherwise, and the author did not reply to my emails, so I looked at past closed issues at github, which gave me a bit background information, and the challenges Revar faced.

So, after a couple of weeks pondering and waiting for Revar to respond, April 4 2021 I began to adopt it and push it forward to become usable for me. I will document all future changes (or possible a fork of it) on this blog-post.

Features

purely written in Python, compact source code, easy to read & understand
- vector.py: base vector operations
- point3d.py: x,y,z to index to x,y,z
- line_segment3d.py: two points making a line, with caching
- facet3d.py: three points making a triangle/facet, with caching
  - facet.slice_at_z(z)
- geometry2d.py: uses pyclipper
  - provides path operations like offset, union, diff, clip, paths_contain (point in paths)
  - makes infill patterns like lines, grid, triangles, hexagons
- model3d.py: STL reader & writer, OBJ, OFF, 3MF, AMF, 3MJ reader
  - indexing points, edges and facets
  - model.slice_at_z(z, lh) results in polygons/paths
- slicer.py: slicing the model
  - generating perimeters
  - generating support
  - generating adhesion (skirt, brim, raft)
  - generating solid & sparse infill
  - pathing: coordinates perimeters, support, adhesion, infill paths
  - converting paths into Gcode (or SVG)
- __init__.py: main entry point of mandoline program:
  - process arguments
  - load model and relevel, apply model operations (scale), check manifoldness
  - slice model
slice model into Gcode to print via FDM 3D printer
slice model to SVG slices (very experimental) for debugging purposes and possibly to post-process to pixel-based slices for SLA or SLS 3D printer (not yet tested)
load mutiple configs in sequence with -l config.ini, e.g. printer specifics, material settings
simple to query features/settings with -Q <term>

Usage

% mandoline
== Mandoline Py 0.8.5 == https://github.com/(Spiritdude|revarbat)/mandoline-py
usage: mandoline [-h] [-o OUTFILE] [-n] [-g] [-v] [-d] [--no-raft] [--raft] [--brim] [--no-support] [--support] [--support-all]
                 [-f MATERIAL,...] [-F FORMAT] [-l OPTNAME] [-M OPTNAME=VALUE] [-S OPTNAME=VALUE] [-Q OPTNAME] [-w]
                 [--help-configs] [--show-configs]
                 [infile]

positional arguments:
  infile                Input model filename (STL).

optional arguments:
  -h, --help            show this help message and exit
  -o OUTFILE, --outfile OUTFILE
                        Slices model (STL) and write GCode or SVGs to file.
  -n, --no-validation   Skip performing model validation.
  -g, --gui-display     Show sliced paths output in GUI.
  -v, --verbose         Show verbose output.
  -d, --debug           Show debug output.
  --no-raft             Force adhesion to not be generated.
  --raft                Force raft generation.
  --brim                Force brim generation.
  --no-support          Force external support structure generation.
  --support             Force external support structure generation.
  --support-all         Force external support structure generation.
  -f MATERIAL,..., --filament MATERIAL,...
                        Configures extruder(s) for given materials, in order. Ex: -f PLA,TPU,PVA
  -F FORMAT, --format FORMAT
                        Set output format (gcode, svg)
  -l OPTNAME, --load OPTNAME
                        Load config file, containing <k>=<v> lines
  -M OPTNAME=VALUE, --model OPTNAME=VALUE
                        Set model manipulation operation(s) (scale).
  -S OPTNAME=VALUE, --set-option OPTNAME=VALUE
                        Set a slicing config option.
  -Q OPTNAME, --query-option OPTNAME
                        Display a slicing config option value.
  -w, --write-configs   Save any changed slicing config options.
  --help-configs        Display help for all slicing options.
  --show-configs        Display values of all slicing options.

examples:
   mandoline cube.stl
   mandoline -l myprinter.ini cube.stl
   mandoline -l myprinter.ini -S layer_height=0.3 cube.stl
   mandoline -l myprinter.ini -l petg.ini -S infill_type=Triangles cube.stl -o test.gcode
   mandoline -Q skirt

Download

https://github.com/Spiritdude/mandoline-py

Formats

Gcode

By default Mandoline slices STL into 3D printable Gcode:

% mandoline -l y3228.ini hollowCube.stl -S layer_height=0.3 -o test.gcode
== Mandoline Py 0.8.4 == https://github.com/revarbat/mandoline-py
Loading model "hollowCube.stl"
Loading configs from "y3228.ini"                                              
Slicing starting
+ Random offset -78,34
- Perimeters
- Support                                                                     
- Raft[ ], Brim[ ], and Skirt[x]                                              
- Infill (Grid)                                                               
- Pathing                                                                     
- Export GCode to "test.gcode"                                                
Took 0.85s total. Estimated build time: 0h 08m, filament used: 1.394m

SVG

Mandoline (0.8.4+) also supports slicing into SVG, for debugging purpose and possibly can be post-processed into PNG to feed into a SLA or SLS 3D printer (no support-structure included yet).

% mandoline hollowCube.stl -o test.svg
== Mandoline Py 0.8.4 == https://github.com/revarbat/mandoline-py
Loading model "hollowCube.stl"                                              
Slicing starting
- Perimeters
- Export 66x SVGs to "test-*.svg"                                             
Took 0.23s total.

Issues to Resolve

model slicing problems:
- 3D Benchy incomplete, get more linient or auto-fix regarding non-manifolds:
  - 3DBenchy.stl loaded with manifold checking, 10x “non-manifold hole edges”:
    - Z = 9.087, 5.87
  - when disregarding that check with -n, then it results in various warnings “Incomplete Polygon …” which results in missing slices – major degration of 3D print
  - sliced with many warnings (Incomplete Polygon at z=... => missing layers) @0.2mm layer height: 240 layers, 4.011m with 1.75mm filament
  - sliced with many warnings (=> missing layers) @0.25mm layer height: 192 layers, 4.461m with 1.75mm filament
  - -M scale=0.5 with
    - @0.2mm layer height with warnings (=> missing layers): 120 layers, 0.674m with 1.75mm filament
    - @0.25mm layer height with warnings (=> missing layers): 96 layers, 0.634m with 1.75mm filament- fixing
- Voron Design Cube v7 wrong sliced layers without warnings
random crashs of pyclipper: I noticed a basic model with random_pos=True enabled slices correct and another time when moved to another position fails to slice
properly do un/retract:
- find out if perimeters/walls are crossed, if not, do not un/retract no matter what TYPE of extrusion is done
allow case-insensitive settings:
- infill_type
- support_type
- adhesion_type
- bed_geometry
brim, raft and skirt properly done (*_width vs *_lines and *_offset)
bottom_layer_extrusion_width
bottom_layer_speed
top_layer_speed
wall/shell/perimeter_speed
resolve “shell” vs “wall” vs “perimeter” in source variables, source comments and config
infill_type=Hexagons doesn’t work reliable, often infill is missing entirely
~~support 3MF, 3MJ input format beside STL~~, since 0.8.6: obj, off, amf, 3mf and 3mj
- properly support multi-volume -> multi-material -> multi-tool
- 3MF: ~~examples, Debian package: python3-savitar~~, since 0.8.6 using XML parser
clean up multi-nozzle setup, remove GUI, remove material config but hand it over to a collection of .ini files to be selectable with -l my.ini … (not yet finalized how to achieve simple multi-nozzle config easy)
testing, testing and testing more
future developement
- integrate geometry3d union, intersection for segmenting sub-volumes
- analyze geometry from non-planar slicing perspective
- integrate non-planar slicing: tilted, cyclindrical, conic and spherical at a deeper level
- mature it to become optional for PAXSlicer 5-axis slicer
- process metadata from .3mj either piece, sub-volume or face exact within the slicing (tool changing, fill density, slicing settings etc)

Changes

2021/09/04: 0.8.6:
- experimental OFF, OBJ, 3MF, 3MJ support
2021/04/08: 0.8.5:
- cli: -S shell_speed=s [mm/s]

2021/04/06: 0.8.4:
- SVG output: supporting slicing to SVG, using “-o test.svg“, very experimental
- intern: model.scale([x,y,z]) implemented
- cli: support for -M scale=s or -M scale=x,y,z
- intern: fixed vector.py normalize() and __truediv__() supporting STL with bad normals
- un/retract enabled again in code

2021/04/04: 0.8.3:
- cli & extending configs:
  - cool_fan_speed_{min/max}
  - cool_fan_full_layer=2, e.g. starting fan after e.g. layer 2 is reached, first layer is 0
  - start_gcode and end_gcode and new config type ‘str‘ as well
  - skirt_lines=3 only considered if skirt_layers != 0
  - gcode_comments=True|False: adding various useful info in Gcode
  - random_pos=True|False: randomize position of model on the build-plate
- all the config included in Gcode given gcode_comments enabled
- intern: carrying over ‘typ‘ (‘type’ in python 😉 ) of the extrusion in _raw_add_paths, to refine the retract/unretract, this allowed to
- have output Gcode more descriptive with ;TYPE:.. like PERIMETER, INFILL, PRIME, BRIM, SKIRT, SUPPORT etc, given gcode_comments is enabled
- cli: support -l or --load to load more configs (e.g. per printer, or material)
- cli: support -Q <term> partial match
- output “filament used …[m]” at the end of slicing
- most un/retract disabled for now to confirm extrusion calculation working
- prints simple models like 10/20mm cube and xyzHollowCalibrationCubeV2

References

Mandoline Py, original repository
Mandoline Py, my repo with my changes
Gcode 2 PNG

3D Printing: Sub-Volume Segmenting & (Non-)Planar Slicing

by Rene K. Mueller · published April 19, 2021 Technology Non-Planar Slicing, Overhang Printing, Penta Axis (PAX), Research Paper, Rotating Tilted Nozzle, Rotating Variable Tilting Nozzle, Sub-Volume Segmenting

Introduction

In order to take advantage of 4- and 5-axis non-planar FDM¹⁾ printing (e.g. tilted, conic, cylindrical, spherical) the model may be segmented and then dedicate slicing methods can be assigned to such sub-volumes.

A few basic examples combining planar and non-planar slicing methods on sub-volume segmented models illustrating the possibilities printing without support structures:

Fused Deposition Modeling (FDM) also known as Fused Filament Fabrication (FFF)

T-Model: 2 Segments: Z-planar & Conic

Utilizing novel conic slicing as introduced by ZHAW researchers in 2020/2021:

*2 segments: z-planar, conic* (outside-cone)

T-model segmented into 2 sub-volumes, sliced z-planar and conic (outside-cone mode)

Conic slices can be printed with 4-axis Rotating Tilted Nozzle (RTN) although printing the Z-planar sliced part might not give goods surface results but rather using a 5-axis Penta Axis (PAX) printhead to cover both cases easily.

T-Model: 3 Segments: Z-planar & 2x Tilted

Using non-rotating but tilted sliced (like used with belt-printers) but in two distinct directions:

T-model segmented into 2 sub-volumes, sliced z-planar and twice tilted in opposite directions

Tilted slices can be printed with 4-axis Rotating Tilted Nozzle (RTN) but the first Z-planar part, as mentioned above, might not provide sufficient surface quality, whereas a 5-axis Penta Axis (PAX) printhead can print both segments easily.

T-Model: 3 Segments: Z-planar & 2x X-planar

A more classic planar approach but with different planes as reference, first Z-planar then twice X-planar in different directions:

T-model segmented into 3 sub-volumes, sliced z-planar and twice x-planar

X-planar printing requires either 5-axis Penta Axis (PAX) printhead or the ability to tilt the bed.

Overhang In/Out: 2 Segments: 2x Conic

Lower part is sliced with conic slicing with inside-cone mode to print in-going overhang, whereas the upper part is sliced with outside-cone mode to cover the out-going overhang:

*bottom: inside-cone, top: outside-cone*

Overhang in/out model segmented into 2 sub-volumes: lower part is sliced conic (inside-cone mode) and upper part conic (outside-cone mode)

This model covers the classic case of 4-axis Rotating Tilted Nozzle (RTN) application: rotating 45° tilted nozzle printing in two different modes (outside-cone and inside-cone); a 5-axis Penta Axis (PAX) printhead also can print such.

Overhang Out No 5: 2 Segments: Z-planar & Conic

Another overhang piece, stretching out into one direction; the lower part Z-planar, and the overhang conic (outside-cone mode) with an offset to align better with the lower segment:

*2 segments: planar (bottom), conic with center offset (top)*

Overhang Out No 5 model segmented into 2 sub-volumes: z-planar at the bottom and overhang segment conic (outside-cone mode)

Overhang Out No 5: 3 Segments: 2x Z-planar & Conic

Perhaps a more realistic approach using the conic part as a “balcony” just for the overhang part sufficiently thick to carry next segment and switching back to Z-planar:

*3 segments: planar (bottom), conic (middle) and planar (top)*

*Overhang Out No 5 model segmented into 3 sub-volumes: z-planar first, then conic (outside-cone) building a thin “balcony” as support for the z-planar part on top again*

Early tests have shown the thickness of the conic overhang “balcony” depends on the actual length of the in-air overhang, where print speed, part-cooling capacity and extrusion consistency determine the geometrical accuracy. More examples with “balcony” printed with 3-axis FDM printer followed.

Conclusion

Unlike with ordinary Z-planar slicing, it may be suitable to dedicate a particular slicing method and orientation for sub-volumes in order to take advantage of the possibilities like avoiding support structure, particular strength properties or surface quality.

*solely z-planar sliced, support structure required using 3-axis FDM printer*

This of course opens a wide-range of possibilities and complexity therefore:

where to segment
which slicing method to use
in which orientation the slicing is performed

but I think it’s worth it, in particular when a piece is printed more than once like with small series manufacturing / production.

The examples have been produced with various slicers and combined with a new application coordinating the segmenting and dedicated slicing methods, which currently (2021/04) is in development; it also involves a new file-format describing the segmenting and its slicing settings. The segment positioning was done manually as a start, but I expect with more experience and research some cases can be detected automatically.

Sub-volume segmenting is just one approach to take advantage of 5-axis FDM printing, another is continuous slicing along the form.

References

[Coyetaux, Crook, Pauwels, Whelan] 5-Axis 3D Printing (2018) – free paper (PDF)
[Wuethrich, Elspass, Bos, Holdener] Novel 4-axis 3D printing process to print overhangs without support material (2020) – non-free paper (PDF)

3D Printing: YAGV: Yet Another G-code Viewer Fork

by Rene K. Mueller · published April 15, 2021 Technology Gcode, Gcode-Preview, YAGV

One of the oldest standalone G-code viewers yagv (Yet Another G-code Viewer) I forked and added following features:

ported to Python3
new color scheme (white background)
parsing G-code comments, determining wall, infill, support structure and render with different colors
support for Slic3r, PrusaSlicer, Cura/cura-slicer, Mandoline and Slicer4RTN (non-planar)
panning implemented (properly works with zoom and rotation)
- same mouse button layout as OpenSCAD
more test G-code included in tests/

Example of non-planar G-code:

Download

https://github.com/Spiritdude/yagv

Note: I opened a Pull Request (PR) but not sure if it’s accepted.

3D Printing: Non-Planar Slicing with Planar Slicer

by Rene K. Mueller · published April 10, 2021 Technology Conic Slicing, Cylinderical Slicing, Non-Planar Slicing, Research Paper, Spherical Slicing, Tilted Slicing

Updates:

2021/04/09: spherical slicing redone, slightly better than before
2021/04/03: cylindrical & spherical slices added
2021/03/26: refocusing to non-planar slicing with planar slicing
2021/03/14: starting write-up with basic illustrations

Introduction

After discovering the 4-axis Rotating Tilted Nozzle (RTN) and its prototype of RotBot as developed by ZHAW and their conic slicing method, it became clear to me a 5-axis 3D printer with variable tilting nozzle is the way to go as it is a superset of 4-axis and 3-axis 3D printing.

With that in mind, I realized there was time to explore non-planar slicing with planar slicers in more details.

Slicing Methods

Let’s provide an overview of various slicing methods:

horizontal slice, printable on 3-, 4- and 5-axis 3D printer

Horizontal Slices

Vertical slicing creates horizontal slices, the traditional aka planar slicing method, so issues and limitations are well known:

simple to slice
only challenge is to create support structure for overhangs to ensure all printed layers have layers beneath
no collision detection needed, as all already printed layers are beneath

Tilted Slices

Tilted slices are kind of new(er) and became known with belt printers, usually 45° tilted:

Transformation is [ x, y, z – y ]

simple to slice
belt-printer: no collision detection is needed
can print 90° overhangs in one direction only

There are patches for Cura available to slice for belt printer, additional the experimental Slicer4RTN also provides tilted slicing.

Conical Slices

New slicing method as introduced by ZHAW researchers and announced in 2021/01 utilizing planar slicer:

requires a center of the conic layers
can print 90° overhangs, two distinct modes: inside out (outside cone), or outside in (inside cone) depending on direction to a central slicing cone center
requires rotating and tilted nozzle aka Rotating Tilted Nozzle (RTN)
angle of conic slicing can be changed from 45° to 20° and models become printable with vertical nozzle with reduced print quality

Transformation is [ x, y, z + sqrt(x² + y²) ]

I implemented a conic slicer named Slicer4RTN in 2021/03. There are more complex conic transformations possible, e.g. map the x/y angle via atan(y/x) but just adding sqrt(x² + y²) to z does achieve a conic slice.

Cylindrical Slices

Early tests using planar slicers to slice also cylindrical, like this:

Transformation is [ atan(y/x), z, sqrt(x² + y²) ]

It can be printed on a fixed vertical rod, with a rotating and tilting nozzle, or horizontal rotating rod (like a lathe) and vertical nozzle then:

I came up with this way by myself based on the study on conic(al) slicing but I was made aware researchers Coupek, Friedrich, Battran, Riedel back in 2018 published a paper on this method already.

(Hemi-)Spherical Slices

Early tests using planar slicers to slice also spherical, like this:

Transformation is [ sqrt(x² + y² + z²), atan(y/x), atan(z/sqrt(x² + y²)) ]

It can be printed with a 5-axis like PAX printhead, it’s main advantage is to getting close to print continuous overhangs of any angle.

I suspect at least one more suitable and simpler sphere transformation, as soon I came up with such I add it on this blog-post.

Conclusion

It is possible to slice non-planar with planar slicers by mapping to and from the space of the slicing you like to have; yet in the slicing procedure some margins are introduced which need to be compensated – the planar slicer needs to work reliable, Slic3r 1.2.9 and CuraEngine 4.4.1 / cura-slicer perform reliable, whereas PrusaSlicer 2.1.1 makes assumptions of the printability and exits when no printable G-code can be produced, not recommended for this case therefore.

The simpler the transformation forward and backward, the more precise G-code can be obtained, e.g. tilted and conic slices provide precise G-code, whereas cylindrical and spherical slices are harder to tune with the planar slicer.

References

Conic Slicing for Rotating Tilted Nozzle (RTN)
Multi-Axis Printing & Overhangs
Sub-Volume Segmenting & (Non-)Planar Slicing
- Non-Planar “Balcony” Overhang with 3-axis FDM Printer
Papers
- Cylinder Slicing: [Coupek, Friedrich, Battran, Riedel] Reduction of support structures and building time by optimized path planning algorithms in multi-axis additive manufacturing (2018) – free PDF
- Conic Slicing: [Wuethrich, Elspass, Bos, Holdener] Novel 4-axis 3D printing process to print overhangs without support material (2020) – non-free PDF, does not reveal actual transformation for conic slicing; future paper in 2021 will explain conic slicing though

Introduction

Slicing with Non-Planar Geometry (Class 1 Universal Slicing)

Slicing 20mm cube with wave-like geometry

Routing a single non-planar slice

Non-planar Printed Wave-like Sliced 20mm Cube

Implementing Non-Planar Slicing Geometries Slicer

Results & Achievement

Limiting Non-Planar Height for 3-axis FDM

Blind Spot of CAD Systems

Scale and Functional Qualities

References

Introduction

MetatronSlicer vs EnochSlicer

In-House Slicers

Availability

References

Introduction

Implementing Universal Slicing

Universal Slicer: MetatronSlicer

MetatronSlicer vs EnochSlicer

Availability

References

In-House Slicers

Introduction

Motivation

Four Stages of Slicing

Mesh

Slice

Route

Off- and Insetting Polygons

Gcode

History

Cross-Fertilization

Examples

In-House Slicers

Availability

References

Introduction

Class 1: Static Slicing Vector, Static Slicing Geometry

Class 1 Examples

Class 2: Variable Slicing Vector or Variable Slicing Geometry

Class 2 Examples

Slicing Vector vs Slicing Geometry

Implementing Universal Slicing

Universal Slicers

Benefits of Non-Planar 3D Printing FDM

References

Introduction

More Slicers

LabSlicer: The Mother

Vox3lSlicer: Voxels

VoxGLSlicer: OpenGL Slicing

3 Slicers

YAGV & Nautilus Thumbnailer Supporting ArcWelder

Print3r

References

Introduction

Features

Usage

Download

Formats

Gcode

SVG

Issues to Resolve

Changes

References

Introduction

T-Model: 2 Segments: Z-planar & Conic

T-Model: 3 Segments: Z-planar & 2x Tilted

T-Model: 3 Segments: Z-planar & 2x X-planar

Overhang In/Out: 2 Segments: 2x Conic

Overhang Out No 5: 2 Segments: Z-planar & Conic

Overhang Out No 5: 3 Segments: 2x Z-planar & Conic

Conclusion

References

See Also

Download

See Also

Introduction

Slicing Methods