Stop or jerk during high speed non extruding moves

Urban

When I start a print from the maintenance station to the first extruding position the move stops shortly or maybe it is jerky. This happens after approximately 200mm (I have to make a high speed movie because it is really almost impossible to see what is happening).

The speed is 500mm/s and M204 P2000 T6000.

I user a 20 mm lead ballscrew with 3200 steps per revolution. This gives 20mm/3200=0,0063mm per step. (The maximum speed for 180kHz would then be 1134mm/s.)

The move for 200mm is then approximately 30000 steps.

Does anyone have an idea of why this is happening?

Phaedrux

If you send M122 right after this move, do you see any hiccups?
Do you have mesh compensation active at this time?
What is your Z jerk set to?

Urban

I see what you are getting at

I will check if there are any hiccups.
Yes, I do. The mesh could fit the stops.
The Z jerk is 0. I set it to zero in an attempt to reduce ringing in the platform from z-hop. Never thought of that it could influence xy-movements.

I will test to increase the Z jerk. Thank you for the tip!

Phaedrux

the Z jerk needs to be high enough to allow for the XY motion to proceed smoothly as the Z axis adjusts the height to match the grid. If it's not high enough it will slow down suddenly to give the Z axis time to move. Z jerk of 60mm/min may be enough.

Lower acceleration on Z may help the z hop problem.