CoreXY: Strange jerk on Y axis.

[ikarisan]

On my Hypercube Evolution I am getting strange movements when I am moving the Y axis from Y0 to Y220 and back to Y0.

https://www.youtube.com/watch?v=fpgu974rDSY

Can this be a a firmware related problem?
I can move the axis by hand without any problem.

Duet WiFi 1.04
Firmware: 2.03RC1 (2019-05-08b1)
Duet WiFi Server Version: 1.23

I used this simple GCODE:
0_1557699014515_fast_y.gcode

[Phaedrux]

What is the flashing light on your tool head? The probe? Perhaps there is a wire loose and shorting in the cable harness?

Are you using mesh bed compensation? It looks like you have G29 S1 in your startup gcode. You can see stuttering like that if the Z axis jerk is too low.

[ikarisan]

@phaedrux Yes, the flashing light is a piezo probe. The sensor is very sensitive.
And yes, I am using mesh bed compensation. I will disable the compensation and try again.

[ikarisan]

@phaedrux Okay, these are the result:

1. Disabling the mesh compensation solves the problem
2. Reducing the ammount of probe points solves the problem!
   2a) On a 220x220 bed 11 probing points per axis results in the stuttering Y axis.
   2b) If I use only 5 points per axis the movements are smooth

[Phaedrux]

@ikarisan said in CoreXY: Strange jerk on Y axis.:

Disabling the mesh compensation solves the problem

Then this is the problem.

@phaedrux said in CoreXY: Strange jerk on Y axis.:

You can see stuttering like that if the Z axis jerk is too low.

Can you post your config.g?

[ikarisan]

@phaedrux Sure.... 0_1557776986379_config.g

[Phaedrux]

Z20.00 E40.00

Try increasing your jerk values for Z and E. They are super low. Remember that it's in mm/min. Try at least Z60 and E1000

[ikarisan]

@phaedrux I got the E values from: https://zestytechnology.readthedocs.io/en/latest/nimble/tuning.html but I will try your Z values.

[Phaedrux]

Ah I see. In that case leavethee as it is recommended by zesty.

[ikarisan]

It seems that there is a problem with the movement if I configure many probing points.
On a 220x220 bed these parameters work fine and the Y axis does not stutter:

Xmin: 20, Xmax: 200, Distance: 45

But if I use

Xmin: 20, Xmax: 200, Distance: 20

the movements on Y stutters again.

[Phaedrux]

Can you post the images of your heightmap?

How fast are you traveling when it does this, and what did you end up changing your Z jerk to?

[dc42]

@ikarisan said in CoreXY: Strange jerk on Y axis.:

It seems that there is a problem with the movement if I configure many probing points.
On a 220x220 bed these parameters work fine and the Y axis does not stutter:

Xmin: 20, Xmax: 200, Distance: 45

But if I use

Xmin: 20, Xmax: 200, Distance: 20

the movements on Y stutters again.

Stuttering when bed compensation is enabled is a result of the Z jerk being set too low to permit the changes in Z speed that are demanded by changes in the height map.