PrusaSlicer 2.5.0-alpha2

PrusaSlicer PrusaSlicer 2.5.0-alpha2

Summary

This is the first public alpha release of PrusaSlicer 2.5.0 (alpha1 was not public), introducing new perimeter generator Arachne, improved seam placement based on visibility, pressure equalizer, lightning infill and several more improvements and bugfixes.

The new perimeter generator Arachne and the new lightning infill were ported from Cura ↗. The Arachne perimeter generator was implemented based on the paper [Kuipers et al., 2020], while the lightning infill was implemented based on [Tricard et al., 2019]. Big thanks to Ultimaker for keeping Cura open source and big kudos to Cura development team led by @nallath, to @BagelOrb for his research and majority of the Arachne implementation and to @BagelOrb and @rburema for the lightning infill implementation.

To let you enjoy the alpha without worries, the alpha builds save their profiles into PrusaSlicer-alpha directory, so you may use the alpha side by side with the current release without ruining your production configuration.

Arachne perimeter generator #5591

The 'classic' strategy for calculating perimeter extrusion paths is to offset contours of an object slice inwards by a constant extrusion width, one offset per perimeter. This was also the default algorithm in previous PrusaSlicer versions. However this simple algorithm does not handle thin regions well, as reported in these issues ↗. Namely, thin regions cannot be filled with an integer number of fixed width extrusion lines.

The classic way of handling narrow regions is to either not generate the innermost perimeter that does not quite fit, but to fill the remaining region with a gap fill algorithm, or to over-extrude the innermost perimeter. None of the two approaches are ideal: The gap fill may produce short segments of widely differing extrusion rates, while over-extruding may produce bulges on thin walls.

The developers of Cura ↗ recently implemented a new strategy named Arachne based on paper [Kuipers et al., 2020]. The Arachne generator produces perimeter loops and gap fills with varying extrusion width in such a way, that the slice area is filled without underflows and overflows with possibly continuous paths while respecting minimum / maximum extrusion width limits. The Arachne perimeter / gap fill generator really shines on objects with thin walls as thin boxes or labels.

In this PrusaSlicer version, we have ported the Arachne engine from Cura ↗ while keeping the old perimeter generator as an option. We made the Arachne perimeter generator default in our printer profiles. Thanks again to Ultimaker for developing Cura under open license.

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The following picture demonstrates Arachne benefits on thin text: The classic perimeter generator fills text contours with many thin gap fill lines, while the Arachne perimeter generator widens the perimeter lines instead, producing cleaner prints quicker and with better surface quality.

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However the Arachne perimeter generator has a tendency to round concave corners, as shown in the picture below. While the perimeter curves with circular segments at concave corners produced by Arachne are geometrically correct (they satisfy the constant offset distance requirement), they may not be optimal for FDM due to the tendency of extruded plastic to shrink into concave corners, thus the classic perimeter generator producing mitered offset curves with sharp corners may print more accurate concave corners.

For most prints the Arachne perimeter generator is superior, but for some functional prints where the accuracy of concave corners is important the classic perimeter generator may be better.

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Another case where the classic perimeter generator may be preferable are sharp corners. The classic perimeter generator with "detect thin walls" disabled trims the tips of sharp corners, but the print surface will likely be smooth due to constant extrusion width. image With "detect thin walls" enabled, the chopped off tip is filled with gap fill, which may not quite stick to the print. image Arachne generator produces connected lines with varying extrusion rate, where the extrusion rate variation will likely cause some visible artifacts on the outer surface of the print. image

Lightning infill #7344

Infill serves dual purpose: To provide structural rigidity and to support top surfaces. In case the structural rigidity is not needed, a lot of material and printing time is saved with the new lightning infill, that is optimized to supports the top surfaces only. The lighting infill is based on paper [Tricard et al., 2019]. A branching structure is generated that gets progressively denser towards the top surfaces to support them reliably. Like the Arachne perimeter generator, we have ported the Lightning infill from Cura ↗, thanks again for keeping Cura open source.

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The following table compares the print time and filament consumption when printing the famous tree frog ↗ at 100% and 400% scale. The values for a 400% scale are enclosed in braces. | Infill type | Print time [min] | Filament total [g] | Filament Infill [g] | Filament saved on Infill | | Gyroid 15% | 54 (1104) | 6.8 (204) | 1.5 (114) | 0% | | Support Cubic 15% | 51 (792) | 6.3 (152) | 1 (62) | 33% (46%) | | Lightning 15% | 55 (840) | 6.0 (111) | 0.6 (20) | 60% (82%) |