Snapmaker 2.0 Printing Defects - Z Feed Rate too high - Skipping Z steps

[jalapenopuzzle]

Description of the bug

I have experienced several issues using PrusaSlicer 2.8.0 with Snapmaker 2.0 A350T.

1. First layer speed 50mm/s is too fast and has poor adhesion. I reduced it to 20mm/s and had much better results, but I did not tune this value.
2. First Layer Height 0.3mm seems to be too high. I had better results with 0.2mm.
3. I have had HUGE issues with missing Z steps while printing. PrusaSlicer produced the following benchy: This benchy is only 35mm high (should be 48mm high). I did a lot of testing with this one. The Snapmaker 2.0 uses linear actuators with different screw pitches per axis: https://shop.snapmaker.com/products/linear-module-with-tmc2209-a350t-f350 The consequence of this is that the Z axis has a lower feed rate limit than the X and Y axes. Feed Rate Limits (reference: Snapmaker's Luban slicer v4.13.0):

• X+Y: Slow: 40mm/s Medium: 50mm/s Fast: 60mm/s
• Z: 10mm/s (F600) - (Reference: Luban generated G-Code)

PrusaSlicer generates G-Code with Z feed rate of F7200 (120mm/s). It appears that this is causing the Z axis to skip steps. PrusaSlicer appears to have the following parameters affecting the z speed:

• Print Settings -> Speed -> Speed for non-print moves -> Travel (default: 120mm/s -> F7200)
• Print Settings -> Speed -> Speed for non-print moves -> Z travel (default: 0, causes "Travel" value to be used)

I found that setting 10mm/s for the Z travel speed had no effect. PrusaSlicer continues to generate G code with F7200 on Z movements. The only way that I could reduce the Z speed was to reduce the Travel speed.

I performed some manual Z movement tests with increasing speeds such as: G1 Z50 F1000 G1 Z150 F2000 I found that the speed (and stepper tone) did not seem to increase after about F3400 (56.7mm/s) (but I only tested in units of 100).

It appears that faster speeds are coming to the Snapmaker 2.0 with the vibration compensation firmware currently in beta testing https://forum.snapmaker.com/t/vibration-compensation-firmware-open-beta-for-2-0-series-a-at-f-models/35729. I mention this because they claim a speed increase, depending on which linear modules (20mm or 8mm lead) are installed, from 100mm/s (no VC) to 120mm/s (with VC). I don't think this applies to Z axis.

Project file & How to reproduce

20240921_3DBenchy_One_Colour_Z_Speed_10mm_s.zip I sliced and exported the G-Code. To save time I have been checking the G-Code using sed: sed --quiet -e "s/^G1 .* Z(-?[.0-9]+).* F(-?[.0-9]+)/\2/p" file.gcode | sort -u This prints the Z feed speeds used in the G-Code file. I get: F200 F7200 The F200 comes from the initial movements to approach the bed. F7200 is used while printing, including for Z-hop movements.

Checklist of files included above

• [X] Project file
• [ ] Screenshot

Version of PrusaSlicer

2.8.1

Operating system

Ubuntu 22.04

Printer model

Snapmaker 2.0 A350T with upgraded linear modules TMC2209