I'm sorry I'm not following. I have adjusted the jerk quite a bit to try to get the best/fastest performance out of the printer for a given, combination of jerk, acceleration and velocity settings. I'm a little unclear as to what the jerk setting in repetier actually means. In dynamics, jerk is the third derivative of position i.e. the instantaneous change in acceleration. I read through repetier's documentation on jerk here. If I'm understanding the the explanation correctly, which with me is always a possible source of error :), in Repetier the jerk setting refers is the allowable ratio between the velocity of the x and y axis's. To be honest this doesn't make much sense to me, but but I didn't write the path planning section of the firmware. I don't know c language well enough go through the back out exactly how the jerk variable is being used. Is there a better explanation of what the jerk variable means within the context of the repetier firmware?
I'm left trying to optimize the speed and accuracy performance by more or less blind experiment with the jerk, acceleration and velocity settings, which has been frustrating to say the least. As I describe below I have tested a wide range of combinations of velocity, acceleration and jerk settings, which has led to numerous printer stalls, jams etc. I was expecting that the path planning software would produce g code where each move in the x or y axis involves a section of constant acceleration from rest up to a set velocity, followed by a constant deceleration back to rest. and then on to the next gcode line. The sharp short jerks in the x-y movements only occur while executing a path produced by the slicer. They are generally not present when jogging the machine with the same low jerk, accel., and velocity, settings. This made me suspicious that there was some type of bug in the path planning software. I understand that there may be other explanations, however I have done my best to test and eliminate any possible mechanical and electrical sources which may be contributing to the stalling and slow speed of the machine. Once again I really appreciate your help.
In an attempt to optimize the speed and accuracy of the printer I have tested various jerk, acceleration, and velocity combinations to see if they were able to run without stalling on either the x or y axis (I did not place an accelerometer on them). Generally, I varied the jerk setting then adjusted velocity and acceleration settings until I was able to get an combination which wouldn't stall. On the x and y axis
I varied the jerk setting from approximately 10 down to .6 in steps.
I varied the acceleration in steps from 150 mm/s2 to as low as 10 mm/s2.
I varied the velocity from 30 mm/s2 down to 10 mm/s2
Setting the jerk under 1.0 led to "faceted" curves instead of smooth curves. Holding Jerk at 1.0 I then varied the x-y accelerations and the speeds and even with a x-axis stepper capable of 12.8 Nm stall torque 1800 ozfin, I would get stalling or drifting in the x-axis with acceleration settings greater than 10-25 mm/s2 and velocity greater than 20 mm/s.
