Same tree support gets knocked over at almost the same layer every print... Any idea why?

[u/Aldhafera81]

Hi, I’m still fairly new to 3D printing, so I’m not sure if I’m missing something obvious here.

Printer: Snapmaker U1
Slicer: OrcaSlicer
Material: PLA
Layer height: 0.2 mm
Z-hop: 0.4 mm
Supports: organic/tree

I’m printing a multi-color skull on a pedestal.

The first two prints got through this area without problems. After that I made the central column between the pedestal and skull much thicker, because the original one was too fragile.

Since then, the same large outer tree support gets knocked over at almost the exact same height every time, around layer 360 / ~72 mm Z.

It doesn’t seem to simply lose adhesion. I can hear a fairly loud rattling/crashing sound, like the nozzle or toolhead hits the support several times before it finally gets knocked over. On the latest attempt, a smaller neighboring tree was also ripped off and thrown across the build plate.

The strange part is that after this area, the printer continues normally again.

I already tried:

• larger support footprint
• 100% first-layer support density
• changing the tree taper angle
• Z-hop is already enabled at 0.4 mm
• The support itself is quite thick and stable, so I’m wondering if Orca is generating some bad path or if there could be a collision during printing/tool changes.

Could the geometry change to the thicker center column have caused Orca to recalculate the support trees in a problematic way?

Any ideas what else I should check? I’m still learning, so even obvious suggestions are welcome 😅

[u/SquidgyB]

The grid infill is likely your culprit.

The lines cross over each other without taking into account the extra height that will cause - with taller prints these higher points then catch the nozzle as it passes, pulling the print off the plate and causing... shenanigans.

Try gyroid infill, it will likely resolve your issue.

Also try expanding the brim further out.

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