erratic filament extrusion

[jon]

I have one A1 which has worked perfectly for years.  I own two more but
they do not work as well.  I call the good A1 "Jon".

The 2nd A1, which I call "Duce", prints fine for a while and then prints
very thin filament.  I have attached a picture of the most recent
failure.  The printer was doing a diagonal fill (moving from left to
right, with the diagonals going from upper left to lower right).  You
can see sections where the filament is fine interspersed with sections
where there is little or no filament extruded.  Interesting that there
are 5 sub sections with better and worse fill, almost as if something
was oscillating.

The hob is clean, and Repetier Host showed a flat and flawless extruder
temperature graph, with no glitches.  I can imagine an extruder clog,
but not one that comes and goes (unless the temperature were
fluctuating).  I have made about 5 good prints with Duce prior to seeing
this failure mode.

Any thoughts?

Thanks!

Jon

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[Jon Bondy]

Could this be due to an incorrect drive current for the extruder motor?  Not sure where the instructions are for adjusting the current.

Jon

[Jon Bondy]

The extruder driver current limit value was 0.416 rather than 0.475.  Fixed.  I hope that Ezra used the "correct" drivers.  Fingers crossed.

Jon