Suggestion: linear speed variation option
I use PrusaSlicer for both my Mk3s+ and for another printer I have, which is a bed slinger, with a tall build volume, around 400mm. Now I experienced many times that, for tall prints, the speed when printing at the top of the part becomes an issue because of vibrations and the mass of the already printed part, that leads to ghosting and even imperfections at the top. At the bottom, once the first layer is down, the print could even go much faster than the set speed. Now, the proper solution to this would be to decrease jerk and acceleration at the top but that could become quite cumbersome to set. So the other option is to decrease the feed rate. Of course it can be done manually with custom gcode, but a dedicated option could be a nice have. Basically you can set the speed of the print and then set that it should vary from X% (from layer 2? onward) to Y% at the top (with X>Y) and change linearly in each layer.
Hope this might be considered and is helpful, Cheers
Federico
RE: Suggestion: linear speed variation option
Hi Federico. Unfortunately this is mainly a user to user forum. While the devs do pop by occassionally its not often. All feature requests and bug reports need to be made at the Prusa Slicer github repository located https://github.com/prusa3d/PrusaSlicer/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc
Please check through both open and closed issues before starting a new one. Given there are ~1700 open issues and many more closed ones its likely that there is already been one to match.
Iirc there have been several requests covering this. In general the response has been to use a speed modifier at the layer you want.
However I think what you want can actually be done by adding some custom gcode to your printer profile and saving the profile. You can do height based evaluations and apply lower speeds for each 'band'. That way you could tweak the speeds and heights to your machine.
RE: Suggestion: linear speed variation option
Thank you very much for your kind reply, I will give a look at everything you just mentioned.
RE: Suggestion: linear speed variation option
In the meantime, you can do this fairly easily using custom G-Code in the "After Layer" section.
Here are two options that start at 100% max acceleration, then reduce it to 50% max acceleration at the top of the max print height:
M201 X{machine_max_acceleration_x[0] - ((machine_max_acceleration_x[0]*(layer_z/max_print_height))/2)}
M201 Y{machine_max_acceleration_y[0] - ((machine_max_acceleration_y[0]*(layer_z/max_print_height))/2)}
You probably only need to do this for Y, since bed slingers only degrade on the Y Axis as print height increases.
You can do the same for feedrate and jerk:
M203 Y{machine_max_feedrate_y[0] - ((machine_max_feedrate_y[0]*(layer_z/max_print_height))/2)}
M205 Y{machine_max_jerk_y[0] - ((machine_max_jerk_y[0]*(layer_z/max_print_height))/2)}