Extruder jamming with blue PLA

[Merad]

On Friday I installed Rsilver's extruder housing on our M2 and in the process put blue loctite on the screws that hold the extruder housing in place as well as the filament tension screw (not sure if that's its official name?). After letting the loctite cure for 24 hours I've done 2 medium size prints with orange PLA and 2 with white PLA both of which worked perfectly. Yesterday evening I swapped to blue PLA, Makergear brand 1.75mm that I have used plenty of times before, and tried to start a print. It made it about halfway through the 1st layer before the print started getting spotty (photo) and when I retracted the filament there was an obvious "flat" where the extruder had jammed and caused the extruder drive to strip the filament.

I've tried restarting that same print 3 times, tinkering with temperature settings and the tension screw every time but without fail it doesn't make it more than halfway through the first layer without jamming. So far all of my PLA has worked great with a 1st layer temp of 215 dropping to 205 after that (V3b hotend) but yesterday I did try pushing the temp as high as 225 with the blue PLA. Right before I started typing this post I switched back to white PLA and restarted the print from the pic, it is just now starting the 3rd layer and working great.

Any idea why my printer has started hating blue?

[Dale Reed]

Merad,

Usually when we see this, it's caused by the first layer printing with the nozzle too close to the bed. Try starting the print and immediately turning the knob for the Z axis a click or two to lower the bed (increase the gap) -- then let us know if it finishes. May need to tweak the Z limit switch bump screw a smidge, or alternatively, add a small positive Z offset (say, 0.05 mm?) when slicing.

If printing the first layer with a larger nozzle gap doesn't fix it, come back and we'll think of something else!

Dale

[Merad]

Is there some reason it would only affect one color of PLA? I'll have to re-check the bed height and leveling when the current print finishes (30 hours!) but I just adjusted the Z height a week ago because I was having that exact problem, and like I said all other colors are printing ok.

[Tim]

I think Dale is suggesting that the color of filament may just be a coincidence. If you swap in the blue PLA again and it jams, again, then it starts becoming less likely to be a coincidence.

[Dale Reed]

What Tim said!

[Merad]

Ok, have another question that is probably related, so I'll piggyback it onto this thread. When I went to check the bed leveling, I noticed that the hotend is slightly loose in the extruder housing. It can rotate around the Z axis and move front to back slightly in the Y axis, probably 1mm of travel or so at the tip of the nozzle.

1. Is this considered a problem (I assume yes)?
2. How to fix it? I noticed it was loose in the same manner about a day after installing rsilver's extruder housing, so I took the hotend out and wrapped the top with ptfe tape until it snapped in snugly. But now only 4 days later it's loose again...

[Toby]

Rsilver's extruder housing gives an even tighter fit than the stock makergear extruder housing. The hot end should snap into place and be a bit difficult to remove, especially at first.

I think there was more than one version of it though. Which one are you using and what did you print it in?

[Merad]

I got the stl off of Thingiverse maybe 2 weeks ago? I thought I remembered reading that it should be tighter, though. I can't remember what settings I used when I printer that first housing, but I made two extras more recently that I know were done on very high quality settings. Maybe that first one was just a bad print. I swapped to one of the newer ones this morning and the fit is very tight. Also, I re-leveled the bed after installing it and the bed was actually too far from the nozzle at every point. We'll see how it works today.

[Merad]

Well I think I finally discovered the real cause of our issues. After having more problems on the day that I made my last post, I disassembled the hotend and cleaned it out with paint stripper. This morning I was reassembling everything, and discovered that our extruder motor mount was broken. Lucky, I printed one of those as part of a batch of spare parts a couple weeks ago. Definitely does not seem like a part that should be made out of PLA, considering ours lasted barely a month...

[Merad]

Alright, I am seriously about to take this thing out and recreate the fax machine smashing scene from office space...

I got everything back together, did about 4-5 100mm manual extrudes tweaking the filament tension until it was extruding smoothly with none of the slipping noise. Then I started a print. And almost immediately the drive started slipping and once again before end of the first layer the extruder was jammed. And this time it's really jammed, the filament will move back and forth maybe 10mm but it will neither extrude or retract beyond that.

The Z height is DEFINITELY not the problem. I releveled the bed and double checked the height before starting the print. The skirt and the outlines of the first parts looked great, before the slipping started. I'm out of ideas...