Core xy prints well on diagonal but not on y axisx

FlyingScot

My core xy printer driven by a duet wifi has been printing large parts on the diagonal axis for weeks without a problem.
However last night I printed a rectangular part aligned in x,y. As it was printing along the y axis I noticed it was leaving perfectly aligned verticle lines 26mm apart. At these lines you can feel the steppers pulse. (even the extruder motor)
I then printed the same part on the diagonal and it was perfect.
I have tried 2 duet wifi boards with the same results so I think it has to be configuration related.
Has anyone come across this or have any Idea what the problem may be?

Arthur

FlyingScot

I have just discovered if I dissable bed compensation the problem disappears.
So what causes this?

bot

With mesh bed compensation, the firmware divides all moves into segments to match the grid spacing of the compensation.

I'm not sure why you are seeing artefacts, but it seems to be in coincidence with the segmentation of the gcode.

Phaedrux

Can you post some more information? Firmware version? Config? A picture?

What does your heightmap look like? It's possible there is an erroneous value in the heightmap causing it to lurch.

FlyingScot

Found the problem.
It was the M566 instantaneous speed change set to slow it was set to 60 now its 600 and all is well.
Machine now very quiet and surface good.
It is strange that it printed ok on the diagonal but as soon as it was aligned withe axis and both motors needed to print a straight face on the y axis the problem showed up.

Firmware is 2.01 printer is a cross between a Dbot and a Hypercube

Art