Hi!
I’ve been using different accelerations and velocities limits for X and Y on my E3Pro for the past two years. Now that the code has been tested a bit by the community, I decided to share it here.
Installation
Here is the code: limited_cartesian.py
To download: click “Raw” then “Save As” the page. It is implemented as a kinematic implementation file. This way, you can simply put the file under klippy/kinematics/
^{[1]} and change your kinematics to kinematics: limited_cartesian
. In order to activate the changes, you must restart the klipper process: sudo systemctl restart klipper
or reboot. *RESTART
gcodes are not enough.
The syntax for the axis limits are the same that the ones for Z, max_x_accel
, max_x_velocity
, etc.
Note that X and Y always indicate the cartesian axes even on CoreXY: perpendicular and parallel to the gantry, respectively.
Cartesian printers
For optimal speedups, the primary max_accel
and max_velocity
should be set equal to or higher than the result of the square root of the sum of their axis configuration values, √(x² + y²). A new gcode command SET_KINEMATICS_LIMIT
has been introduced, which displays these values and the angle at which they are achieved. If not set accordingly, the acceleration will be capped at the maximums when they are reached. The next figure demonstrate how max_accel
abd `max_[xy]_accel`` interact with each other.
scale_xy_accel
If the slicer lowers the acceleration by utilizing the M204
gcode command to adjust max_accel
, the circle in the above figure may no longer intersect with the horizontal and vertical axis limits, resulting in the same acceleration being applied in all directions. This typically leads to printed features having constant acceleration, which is beneficial for maintaining extrusion consistency.
However, if you have previously finetuned the axis accelerations to achieve similar resonance amplitudes and smoothing in X and Y, you may want to preserve that X/Y ratio at all times by enabling scale_xy_accel: true
. This will adjust the X and Y acceleration limits by scaling M204's acceleration / √(ax² + ay²)
.
For example, if you have max_x_accel: 12000
and max_y_accel: 9000
in your config, limited_cartesian
will limit the acceleration to max possible acceleration = 15k
on 37° diagonals.
When the slicer sets acceleration of 5000 mm/s² (M204 S5000
), effective max_x_accel
and max_y_accel
values will be the third of their config values.
CoreXY
The corexy version is tested as much as the cartesian version, but it should work in principle.
Unlike Cartesian printers which may have varying motor specifications for the X and Y axes, CoreXY machines use the same steppers for both axes and thus do not have any velocity restrictions per axis. However, it is still beneficial to have a lower acceleration for the Y axis as it moves the heavier gantry. Acceleration and velocity for diagonal movements are reduced to align with the available torque and speed of the recruited stepper(s).
This time, SET_KINEMATICS_LIMIT
reports the minimum acceleration and its angle. The maximum, usually aligned with the X axis, is set by max_x_accel
.
klipper_estimator
klipper_estimator should support the limited_cartesian settings out of the box, with the exception of scale_xy_accel
.
Warning
Note that there are print quality concerns with anisotropic accelerations and velocities. Extruder pressure and lengths of accelerating segments will depends on the orientation. In theory this could lead to dimensional discrepancies. This was the main argument for rejecting previous similar PRs.
Thus, user reports of any kind are welcome!

This is intended to help people with little knowledge of git. More advanced users may cherrypick the commit or merge the branch and set the correct pull policy to follow upstream. ↩︎