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prusa3d / PrusaSlicer

G-code generator for 3D printers (RepRap, Makerbot, Ultimaker etc.)
https://www.prusa3d.com/prusaslicer/
GNU Affero General Public License v3.0
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Bug? Maybe, maybe not, but strange Machine Limits differences between MK3s+ and MK2.5s #13067

Closed Astrobirder closed 4 months ago

Astrobirder commented 4 months ago

Description of the bug

I recently sliced the exact same model for printing on both my MK2.5S and my MK3S+. What caught my eye was the difference in print time, for what I thought were nearly identical profiles: MK3S+: 3h45m and MK2.5S 2h52m! Admittedly I have made minor modifications (added ending gcode to just move the carriage up after the print finishes, but that is identical on both printers), also I increased the perimeters (but also identical on both printers). I've attached images of the slicer for the model for both printers.

I finally traced this down to what seems to be RADICALLY different Machine Limits for the two printers: The MK2.5S has accelerations of 9000 mm/s, while the MK3S+ has accelerations of only 1000 mm/s! This seems backwards (the MK3 should be faster if anything, as it is stiffer, and has 24V stepper drivers and better stepper drivers. I contacted Prusa Support, and they mentioned that they could forward my comments / questions to the slicer team, but that I might have better response if I posted here.

I also tried slicing with the pure, default profiles for the two printers, and got similar results. I am doing something wrong, or did the slicer really reduce the machine limits on the MK3S+??

Thanks!

MK3_Sliced MK3MachineLimits MK2 5MachineLimits MK2 5Sliced ShelfBracketSpacerFinal_5x_PrintVersionMK3_x2.zip

Project file & How to reproduce

ShelfBracketSpacerFinal_5x_PrintVersionMK3_x2.zip

Checklist of files included above

Version of PrusaSlicer

2.8.0+Win64

Operating system

Windows 10 version 22H2

Printer model

MK2.5S and MK3S+

rtyr commented 4 months ago

MK2.5 shares profiles/machine limits with MK2S. The values in machine limits does not mean, that those values are actually used while printing. For example, MK2.5 does not use bigger acceleration than 2000. Even if you change acceleration in print settings to bigger value, the output gcode will never use higher print accelerations than 2000 (it is automatically limited by "maximum acceleration during extruding" machine limit).

MK3 is using max acc 1000 by default. Such value was chosen mainly for reliable "crash detection" feature (which does not exist on older printers). If I remember correctly, the hardcoded limit in the firmware is 2500, so you should be able to increase acceleration/jerk a little bit, if you disable crash detection.

It is indeed possible that some prints may be faster on MK2.5 within some object/settings combo (I would guess mainly small objects).