I am currently working with a hobbyist robotic arm (uArm Swift Pro) which runs a modified version of Marlin 3D printing firmware.
The arm can be used as a 3D printer as well thus it has an extruder motor. I am not using it as a 3D printer, instead I am reusing the extruder motor as 4th axis to move the arm along a rail. The problem I have run into is that the extruder motor is accelerating in steps, that is accelerating up to a certain speed holds that speed for a while (1-2 s) and then accelerates up to a higher speed holds that for a while. It then decelerates in the same fashion.
So my question is where in the Marlin code is planing made for the E-axis and is it any different from planing the speed of the other axis?