Print Head Crash/Layer Shift (travel speed too high)

[gchristopher]

Here's a nice ball of PLA fluff from a fail, maybe 16 hours into a 40 hour print.

[img]http://gchristopher.net/3dprinting/big_fail.jpg[/img]

This one is pretty easy to explain. The head collided with the print, causing horizontal layer shifts and eventually complete failure.

Here's a closeup of successively shifted layers prior to losing contact with the print entirely.

[img]http://gchristopher.net/3dprinting/big_fail_closeup.jpg[/img]

It was printing overnight and had probably about 4 hours after failing of printing into air before I checked on it and stopped the print.

I got really really lucky with the aftermath. The effector platform was pretty liberally covered with blue PLA fuzz, but none of it had hardened around the joints and it hadn't accreted into a giant solid ball around the hot end. After some manual cleanup, only the hot end remained fouled and it mostly wiped clean after being brought up to temperature. PLA tended to ooze down to the bottom of the heat block for a few hours afterward, but after cleaning that off a few times, it looks no worse for the experience!

The root cause was also pretty easy to diagnose. Switching back and forth between Slic3r and Matterslice, (both have frustrating drawbacks) I had set non-print travel speed to 200 at some point, and z-lift was only 0.2. What was interesting was that there was plenty of warning that something was wrong. The print head tended to audibly grind over infill on fast moves, and a few points farther out toward the edges of the bed had visibly poor infill.

Reducing non-print travel to 120 and increasing z-lift appears to have resolved the print issue. I wonder if the speed limit is due to RAMBo computational limitations, or mechanical acceleration limit issues?

[teoman]

Check your fan aswell. It might have sucked in some fuzz.

[gchristopher]

Good call. Thanks!