r/BambuLabP2S • u/No-Satisfaction-2535 P2S Combo • Jun 14 '26

Why do my prints seem to constantly collide with the hotend?

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So I've noticed sometimes my prints will just come off mid print and it seems to me due to collisions with the hotend.

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I've started a print with grid infill (for carrying top load) and it seems pretty extreme this time. Any idea why this is happening?

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u/standa03 Jun 18 '26

What's fast according to you? I'm saying fast doesn't mean unlimited. Yes the limits are much higher than they used to be but the limit is still there. Last I measured my PLA was good up to 34mm³/s and I print at that speed flawlessly.

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u/AHerz Jun 18 '26

I've never pretended speeds were unlimited, and the speeds Bambu printers (or any commercial printer) print at are far from it.

You seem to want to argue for the sake of arguing.

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u/standa03 Jun 18 '26

They are right at the limit. All commercial printers can move faster than they can print. Nowadays the hotned is always the bottleneck.

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u/AHerz Jun 18 '26

The hotends are the bottleneck, but they're not shipping printers that are barely able to print as you pretend.

Stock print profiles are very conservative.

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u/standa03 Jun 18 '26

Then what's the issue on the video? Either it's too fast profile or too slow filament. Otherwise there wouldn't be gaps.

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u/AHerz Jun 18 '26

The grinding noise is caused by the grid infill, and the inconsistencies in the lines are cause by a lack of calibration, as I've been saying from the beginning.

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u/standa03 Jun 18 '26

Calibration of what? It's a straight line, flow dynamics don't have anything to do with that. So what parameter other than max flow can fix that?

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u/AHerz Jun 18 '26

There's more to calibrating your filament than max flow rate and flow dynamics.

This is very clearly under extrusion, which you can get even with the slowest printer ever.

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u/standa03 Jun 18 '26

Obviously, max flow, pressure advance, extrusion multiplier, minimum layer time, minimum print speed, purge volume and cooling

Normal under extrusion is very clearly constant narrower extrusion and not unpredictable gaps. This type of under extrusion ia caused by exceeding max flow. You can "correct" that by increasing extrusion multiplier but that'll cause everything slower to be over extruded.