Fix wipe tower issues with SEMM and ramming turned off

[igiannakas]

Description

Fixes issues discussed here: #6894

EDIT: Reverted changes for Z issues when next layer starts over the wipe tower. Keeping the below commentary for reference only.

@SoftFever Would appreciate a review for the nozzle crash on the last wipe tower layer issue please. This was added here 13ddb38 but with the model below I get a nozzle crash on the top layer as the nozzle is forced one layer down. For some reason this:

        double current_z = gcodegen.writer().get_position().z();
        if (z == -1.) // in case no specific z was provided, print at current_z pos
            z = current_z;

Returns the previous layer Z when on the final wipe tower layer, so it pushes the nozzle down to the wipe tower.

Maybe that is expected as on the last layer of the wipe tower the nozzle finishes the layer, does the tool change and then immediately moves to the next layer while still over the wipe tower. See below:

Last layer where a toolchange is needed is printed - the grey line is the last print

The first move of the next layer is the purge tower (the fix is applied to the below screenshot so there is no z going to the prev layer):

So technically Z hasn't changed over the model, so the gcode gen function doesnt know of this new height. So when setting it to current Z we are actually setting it to the previous Z from the model...

Just a theory on this as I am really not sure. In any case, this PR appears to have resolved it for SEMM by removing the specific code segment that causes this Z move on the wipe tower.

I have not tested this with a multi toolhead profile so please do before merging anything in :)

[SoftFever]

Hey @igiannakas
I have difficulty to repro the crash issue in dev branch.
Could you highlight the problematic part?
I'm using the debug project you attached in another thread

[igiannakas]

@SoftFever Sure thing - see attached video here:
https://drive.google.com/file/d/1nLcf18R27MYpDUgg8syBBe97IOiGmPxe/view?usp=sharing

Project link: https://drive.google.com/file/d/14oXy9z96a3jdIdgVSk3iqld1MTCkvys4/view?usp=sharing

its on layer 115

Edit: with correct project link

[SoftFever]

@SoftFever Sure thing - see attached video here: https://drive.google.com/file/d/1nLcf18R27MYpDUgg8syBBe97IOiGmPxe/view?usp=sharing

Project link: https://drive.google.com/file/d/14oXy9z96a3jdIdgVSk3iqld1MTCkvys4/view?usp=sharing

its on layer 115

Edit: with correct project link

I got it now.
Thanks!

[igiannakas]

No worries and thank you for helping out with this 🙏🏻🙏🏻

[SoftFever]

LGTM
Thank you