[BUG] Delta homing incorrectly raises one motor tower at a time, causing mechanical crash

[BirkBinnard]

Bug Description

Problem homing delta printer

Configuration Files

Binnard- Configs.zip

Required: Include a ZIP file containing Configuration.h and Configuration_adv.h.

If you've made any other modifications describe them in detail here.

Specified Sensorless Homing and Probing, Mixing hotend, 2 extruders, TMC2209 stepper drivers

Steps to Reproduce

1. Home printer with hotend close to Z = max (top of printer) works OK
2. Home printer with hotend close to Z = min (near print bed) causes hotend to crash into X tower

Expected behavior:
Successful Home from any position

Actual behavior:
Hotend crashes into X tower when Home initiated from position close to printbed

Additional Information

I'm running the latest BugFix version of Marlin on a delta printer. When I Home the printer it homes the X tower first, then Y, then Z. This works fine when the hotend is close to the tops of all 3 towers.

But when the hotend is close to the print bed Home fails because the X stepper motor moves the X tower slider up until the hotend crashes into the X tower. So I cut power when this happens.

What should happen is all 3 axes should move up until the first one reaches it's top limit, then the 2nd one, and finally the 3rd one. I thought this setting in Configuration_adv.h would do this, but it doesn't:

#define HOME_Z_FIRST

Is there another parameter that allows deltas to home properly from any position?

[BirkBinnard]

This bug report is the same problem but was closed even though it did not clearly identify a fix:

#16736

[sjasonsmith]

This is not the same as #16736. Maybe the symptom is the same, but not the same root cause. That other issue was specific to the pin definitions for the Trigorilla board, which is not used here.

[sjasonsmith]

What should happen is all 3 axes should move up until the first one reaches it's top limit, then the 2nd one, and finally the 3rd one.

This is what it normally does, although I have not actually tried it since December.

#define HOME_Z_FIRST

This is probably not relevant to delta, since you only home Z.

[sjasonsmith]

I see you also filed another bug, which seems to be largely a duplicate of this. Could you please close one of them?
#20986

[BirkBinnard]

This is a duplicate of #20986 which is currently open, so this one is now closed.

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.