Another new 90 another beehive!

Hello all, I completed my build of Nophead's kit about ten days ago, everything went really smoothly with the build, all credit to Nophead for a great kit, easy to put together well documented. Onto the dreaded calibration, the bed leveling was made relatively easy courtesy of the dial gauge clamp (supplied by richgain via makexyz), double checked e steps per mm and z home point, all great! First of many android prints went well and the next week was taken up trying to get my head around Skeinforge settings, eventually gave in and settled for Slic3r, attached Nopheads custom start and end code and got some nice prints very reliably using Sfact's 40 x 10 stl down to 0.1, Excellent!
However yesterday after stupidly twiddling with the left z motor to threaded bar clamps and screwing up the bed level I found it necessary to recheck the calibration and since then nothing seems to have gone that well, bed relevelled, zpoint done according to instructions, extrusion e steps checked all fine but cant replicate the calibration prints I had success with a week ago, small lumps of pla and string get dragged into prints, I've noticed that excess pla is attaching itself to the nozzle in a mini beehive like the posting below, this happens when extruding by motor as well as extruding by turning the gearwheel by hand (which turns easily) The attached picture is typical of a free extrude, the pla beehives then drops then beehives again, any ideas???

I am a new Mendel90 owner as well, and have had the same problems, off and on. One thing I found about that beehiving that you show: Is the fan turned on? Or, another way of phrasing: might you have some air currents blowing through your nozzle area to that is pushing the filament as it's extruded? That was one of the things I dealt with...a breeze that I barely noticed was enough to blow the filament like you are describing. The problem didn't really happen when the nozzle was at print-level, but high up it happened. Turning on the fan might help when testing as the airflow in the room might be foiled by the stronger airflow of the fan.

@Rigsbyscat,
That effect when extruding into free air is normal with PLA and not a problem. When it is building an object it is so close to the layer below it doesn't get chance to go sideways.

If you get lumps of PLA building up on the nozzle while it is building it means the flow rate is too high, or if it is on the first layer only, the Z calibrations is too low.

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[www.hydraraptor.blogspot.com]

Hi pendragn, interesting point, I've done all I can to ensure no drafts and reinstated the fan but still get beehives, strange thing is that when doing a free extrude and waiting for temp to reach 220 I notice the nozzle oozes but in doing so the pla leaves the nozzle and immediately creats a loop and attaches itself to the nozzle rather than dropping under gravity, if you then press extrude it creates a beehive. Am I making something out of nothing or is this really an issue?

Hi Nophead, thanks for that, one less thing to be paranoid about!