Z using X Y Velocity / Accel & X Y using Z Speed after Homing

[burners]

Basic Information:

Printer Model: Anycubic Kobra Go
MCU / Printerboard: Trigorilla
klippy.log Attached
klippy.zip (1.3 MB)

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Describe your issue:

When starting a print or start of bed mesh leveling, I run into an issue where the stepper makes a beeeep noise because its being driven to hard, which causes the Z to skip steps.

I’ve noticed it right after X hits the 0 spot which is 10mm from the endstop and then it happens to Z, sometimes multiple times. Doesn’t seem to matter how slow I set all the axis in both Klipper and the slicer, but it also happens during a bed mesh so I don’t think the slicer has much to do with it. I think it’s trying to apply my X Y velocity & or acceleration to the Z…

The reason I say that is because there seems to be another weird fault that uses the Z homing speed as X Y at specific times. Here’s an easy to test example, set center of bed as home with probe. Set X Y speeds to 120mm/s with 40mm/s bump, then set Z to 8mm/s with 1mm/s bump. After the endstops are hit and bumped, the X & Y will move at turtle speed, even slower than the X Y bump speed, to the center of the bed. I noticed this even without probe for Z and using the center as home but its not as pronounced because its only between Homing and start of Gcode. I can set the X Y to 300mm/s with 200mm/s bunp and it will still crawl after it completes the bump, and it will still use (what i think) my Z speed after the bump and onto whatever move is next until its told otherwise by Gcode or a command sent from Klipper.

Same Gcode works fine on Marlin with even faster speeds. The homing process works fine, its just when the print starts if the gantry is something like 10mm or higher above bed, It wants to slam down really fast when starting the very first part of your start Gcode and I can’t understand why, or why its ignoring the speeds set, where this mystery speed is coming from and so on.

If I turn the velocity down to like 40 it doesn’t happen, but that changes the velocity for everything.

My Z is a 4mm w/ non-captive stepper, you cannot hit it will full speed right away, honestly I’m shocked the default 8mm lead on the Kobra Go did it most of the time, but now I know why I had random start heights here and there. That is also the reason I changed my Z endstop to use the probe. Needless to say, my bed is wrecked crao happens, we move on.

I have tried Simplify 3D, Cura and Anycubic’s Slic3r. Different profiles and start Gcode in each.
I normally have my accel around 30, on S3D my Jerk is set to 1 with a speed of 10 for the Z. Lowered it from 14, but again this happens during a bed mesh as well which has nothing to do with the slicer.

XY were 1500 and Jerk of 7. I usually try to stay around those numbers.

[burners]

Klipper-Issue.zip (2.0 MB)

See vid file in the zip. I compressed it down to 2mb

[Sineos]

[printer]
kinematics = cartesian
max_velocity = 45
max_accel = 1000

You are missing proper velocity and acceleration settings for Z in your config. Add something like:

max_z_velocity: 5
max_z_accel: 100

to this section. As I do not know the printer you might have to find the limits, but in any case these should be workable values.

[burners]

Stepper noise
Klipper-Issue.zip (2.0 MB)

[EddyMI3D]

Keep in mind that Z is always way slower than X/Y

[burners]

Didnt mean to double post my use case, was in a hurry to get out the door.

On the other thread it sounded like that wasn’t an option but that sounds like what’s missing to me and my extremely limited Klipper knowledge.

I will make that mod when I am back home on Monday.

I could just use something closer to what I had set in S3d which was Accel of 30 and Jerk of 1 so I would need to play with velocity to get something similar.

My printer doesn’t have the stock Z lead, it’s a 4mm lead instead of 8mm, so it takes quite a bit more time to get it spinning from dead stop (in microseconds anyway), Its; also a non-captive stepper with a brass core which doesn’t help the situation. If you ramp it up, the thing will spin up to F4600, that’s the limit though before it freezes.

Thank you for taking the time to look over my issue and respond. Did you happen to see the second / similar thing in my post here about the opposite effect? After homing and at beginning of print or move to center of bed for the probe in my case, the X & Y speeds drop down to (what seems like) my z speeds. The homing speed and homing bump speed all seem to work correct but then it has this even slower speed and I have no clue where its getting the number from. I have a video I can compress and upload.

[Sineos]

WRT the Z axis:

• A 3D printer’s Z axis does not need to be highly dynamic and fast, but it needs to be very smooth and free of wobble, or you will get a lot of Z banding
• A lead-screw driven axis is very sensitive to acceleration and especially velocity
• For a lead-screw with a rotation_distance of 4, I’d go with the value posted above. A velocity of 4600 mm/min is definitively much too high

WRT movement in general:

• Klipper does not know the jerk concept
• Klipper uses “square corner velocity” and a good default is 5, and I would leave it at this value, especially for such a printer (it is default anyway if not specified otherwise)
• The acceleration and velocity values as set forth in the cfg are Klipper’s default unless overridden by the slicer → Mind your slicer settings!
• A proper basis for this printer is likely something along the lines of:

[printer]
kinematics: cartesian
max_velocity: 150
max_accel: 3000
max_z_velocity: 5 #maybe 8 
max_z_accel: 100

[burners]

I think you may have misunderstood what I meant. What I was saying is the maximum speed of my Z is 4600 federate. It’s due to the centered Z like you see in the video. It balances the gantry and offers smooth movement which also gives repeatable bed height and tramming without much adjustment. It’s also eliminating Z banding for a few different reasons but one of which is that the Z lead screw doesn’t spin.

The settings you provided look good and are about what I had it in Marlin except a lower max accell at about half that value and the Z I had set to 30 for acceleration as it seems to offer the most flexibility without stalling the stepper.

I will try these out tomorrow when I am back home, thanks again.

[burners]

That’s exactly what I needed, I stumped how those settings went missing from my config because it looks like they were in my original file I had saved,

Doesn’t really matter now, but the first prints look great, and I still have some more tweaking of settings to go so I am pretty happy with the current results.