Slic3r User failure = Clicking Extruder  

Slic3r User failure = Clicking Extruder

Just to tell a story in case it helps anyone else in a similar scenario...

Yesterday, I tried to print something that was, essentially, a 10cm x 10cm x 1cm cuboid.

First layer started printing perfectly. I left the room. A little while later, I heard repeated loud clicks from the printer; turned out to be the extruder.

I paused the print. Raised the extruder, and extruded "manually". No problem at all. Resumed the print; clicking resumed. Raised extruder and extruded manually; no problem.

Restarted print. First layer started printing perfectly. Second layer or so - clicking. Gah. Did a cold pull, in the theory that there must be a blockage somewhere. Restarted print from scratch. Clicking started on second (or so) layer. Gave up. Went to bed.

Woke up. Regenerated model - actually, with the intention of making it simpler on higher layers, because I had a print deadline to meet. Happy to find I'd halved the previous 4-hour print time estimate. Printed. Worked absolutely fine. But confidence somewhat blown at this point; my previously perfect printer had developed a bizarre problem the night before, that had now equally mysteriously disappeared.

Wracked brain. Recalled that, actually, there was something strange with the way that the first layer printed on the failed extruder-clicking print. It effectively printed twice. It started filling from top-left to bottom right, and then filled *again* from bottom right to top-left. No layer raising until after that second fill. At the time, I didn't think too much of it.

Checked in gcode analyser. Sure enough, *every layer* was printing twice in the failed print, and only once in the subsequent successful print. I reckon that explains the extruder clicking; it was trying to extrude into, effectively, non-free space. Back pressure prevented extrusion; hence clicking.

So how did Slic3r end up duplicating every layer? After a little playing, I found the answer: I must have added the STL model twice. Because they add directly on top of each other, it's easy to miss. But Slic3r literally tries to print them both, on top of each other. And that doesn't work in real life 🙂