Z Input Shaping

Growlix

@dc42 I have a very large CoreXZ printer with an XY plane that is 45 degrees about the X axis from the XZ plane. The printhead moves in the XZ plane with the nozzle normal to the plane. The bed lies in the XY plane and slides along the Y axis.

All this to say that input shaping along the Z axis would be very helpful to me as the printhead is routinely moving at high speeds in that direction. Also, I know the duet wiki gives some good reasons why you normally wouldn't want to independently configure input shaping for each axis, but in my case this would be very helpful as well since the frequency response of my machine in the Y direction is very different than the X direction. My machine is admittedly not the norm, but seeing these features would be a big plus to me.

Also, if anyone has any ideas on workarounds to implement Z axis input shaping with the current firmware, I would love to hear them.

dc42

@Growlix when X and/or Y is moving the same input shaping is applied to all axes including Z. So you already have Z input shaping.

The more advanced shapers cover a wide frequency range (e.g. 3:1 for EI3) so you may be able to configure a single shaper that covers the major resonances of all three axes.

Growlix

@dc42 Interesting, I didn't realize it was being applied to the Z axis as well. I will experiment with different shaping parameters and see what happens. Thanks!

Kiolia

@oliof Deltas would likely want wildly different IS compensation for Z versus XY since Z is the one axis where everything's going the same direction, but assuming per-axis IS settings become a thing in RRF, there might be a case there!

chrismbp

Just adding for the record that this would be helpful for printers with large area beds. On my printer which is roughly 1x1x1m, I get a Z resonance that is similar to how a drum vibrates.

My solution now is go slow with Z motions, stiffen it up, etc.... But it would be nice to have a software firmware solution to help address this from the input side.

dc42

@chrismbp have you used an accelerometer to measure the frequency of the Z vibration? You may be able to use a single input shaper to handle the X, Y and Z resonances.

Notepad

@dc42 Is the InputShaper applied to the Z motors as well? I blindly assumed it was only on XY motors

dc42

@Notepad as mentioned in an earlier post in this thread, RRF applies IS to all axes.

Notepad

@dc42 Oh yeah. I see it now. I must have skipped that post. My bad.

chrismbp

@dc42 I hadn't taken a measurement from the bed previously. I just tried that out and you are correct, the EI3 shaper was able to cover the relevant frequencies for me on both the X/Y axes in addition to the Z resonance. There is some trade-off, but I will run some test prints next to see if the magnitude of the remaining vibration is worth worrying about.

dc42

@chrismbp thanks for your report.

We have the possibility of using separate input shaping for the Z axis in RRF 3.6 or later if it turns out to be useful.