Question on filament change blobs in purge block
Mk3S, MMU2S. Latest firmware.
Minding my own business and I thought I'd gotten all of the mechanical tweaks set, I found the IR sensor tower part that raises the sensor on the extruder which did a lot of good, but this week out of nowhere I'm getting blobs on the purge block. Doesn't happen in single filament mode. Haven't changed firmware or software since.
Now the printer crashes into these blobs at times which is a whole other problem, I could care less about the tiny bit extra filament. Any guesses what would suddenly cause the change or what I could try to adjust in Slic3r?
RE: Question on filament change blobs in purge block
Do you get a similar sized blob at the left edge of the plate at the start of a print?
That really looks like an IR sensor issue where the MMU is loading longer than it should.
I'm guessing that the blob is happening during the load of the new filament. From your pic it looks like it does it at every tool change, is that correct (e.g. it's not filament or tool specific)?
Have you looked at your tips to see if they give us any clues (e.g. long thick (but thinner than the filament) tail that the MMU can still move, but doesn't trip the IR sensor correctly)?
Does it do this on all layers, or starts after a certain layer? Is it consistent?
Have you played with any of your load/unload settings?
Any noises or other indications from the extruder (e.g. clicking)?
RE: Question on filament change blobs in purge block
Does it in the lower left as well, ONLY when using the MMU2S in multi mode. In single mode it does not do it.
Tips look okay upon first run or other extrusions, and the IR sensor does look like its triggering at the appropriate time (manual testing by putting in filament and removing it after disconnecting the teflon tube). For giggles I do have a spare and swapped it, no change in behavior.
What's weird is it didn't do it and then suddenly it does it constantly and I made no changes in the configuration in slic3r. No strange noises or anything that are otherwise unusual from the extruder. It "clacks" a little when grabbing the filament at first, but it's always done that.
Now I do have the IR sensor tower mod:
https://www.thingiverse.com/thing:3554066
And without it, the MMU2S was useless as it wouldn't trigger consistently... for the most part it's been behaved since the sensor got moved.
RE: Question on filament change blobs in purge block
I've never seen that mod before. I get the idea of the longer arm to provide more sweep, but I can also see it allowing for more vibration which could cause grief.
It may be tripping when you expect, but what you describe really sounds like there is some miscommunication going on. Usually this is a matter of the IR sensor not being dialed in and either vibrations or variance in the filament diameter cause enough feedback that it pushes the filament longer than it should.