After being a big fan of the All Metal Ubis I've found an issue and downgraded it from Most Wonderful to Recommended with Reservations.
I have an All Metal Ubis, purchased when it first became available in the 2014 Black Friday Sale, connected to a Beta Geared Extruder kit installed in the V2 (printed, gears in fixed position) extruder, driven with a recycled stepper replaced in an upgrade. I noticed some stepper skipping issues when it was first installed, wrote them off to the stepper (the me part of ass-u-me, as it turns out), and ignored them. While recently printing a large object in ABS where I tweaked the extrusion width to reduce curling I noticed that it was leaving gaps in the inside of the lower (not first) layers and did some investigation. Turns out that somewhere just short of 20mm of manual "high" speed (30mm/sec in Repetier-Host) it would start clicking at just under 20 mm of extrusion. Very repeatable, and not really speed sensitive (happened at higher speeds at about the same place), not really temperature sensitive (didn't test this one too hard). Hmm.
Brought it up with Printrbot, told that the wonderfullness came with a price, limited extrusion speed because of the short melt zone that reduced oozing. Interesting, as they never mentioned that one before, and once I discovered retraction oozing was never a problem with the 3.0mm ceramic Ubis, nor has it ever been a problem with the AMU. Time to investigate - this is more of a capacity (as in amount of plastic melted before it wonks out), not speed issue.
Attached is some quickly whipped off gcode that should work with pretty much any Printrbot, heats up the extruder to 200 degrees, homes and then moves the head up a bit so it won't end up in a giant plug of plastic. After that it waits for the extruder to come up to temp, extrudes 10mm, delays to let it settle down, and repeats the cycle incrementing a mm at a time. It's attached, give it a try (I'd really like to see how the Ubis 13, Ubis 13s (the cell phone model), and perhaps an E3D reacts. If you use PLA that'd be great, but pretty much any other filament (think of t-glase...) should do with a quick one line manual edit of the temperature. I only tried it with Repetier-Host, but if Cura will let you load gcode it should work with it's gcode sender. There's delays after every extrude for the so just count 10, 11, etc. If you'd be so gracious as to report back with your results (no skips anywhere, starts skipping at XXmm, along with your extruder type and anything, like temperature, you changed. Thanks!
I got skips starting around 18 to 19mm with my 2014 All Metal Ubis.
I didn't do any retraction/reprime between steps so the dreaded ooze will dribble out a bit and cause a small variation in the results.
I plan to do the usual automated test generator tomorrow to allow temp and speed variations. Today I need to do some American Heart Instructor Updates (they change the rules every 5 years, one theory is it sells a lot of several hundred instructor kits, but really it's because they're always looking for better ways to bring you back from the dead) and then do an ambulance standby at a hockey game (tends to be a physically aggressive and injury prone sport as you fans know). I'm a BLS (that's CPR and AED) and PALS (BLS plus drugs and other advanced stuff for kids) instructor, between them that's about 4 hours of updates and I've only done one of them. Tomorrow, if I don't procrastinate too long with the rather boring updates I'll start in on the enhanced tests. And if anybody wants to travel to the land of the eternal moose I'll do a CPR class or two for free...
Kirk