A) The belts were weakened after some weeks of printing. With an allen key you can tighten the belts. But don’t overtighten as that might cause clicking sounds.
B) Clean nozzles. use Nylon, heat up, put it through, cool down while doing so. Cool down COMPLETELY (nylon still in!), dan heat up again and meanwhile pull the nylon filament until it releases completely from the hot-end. (It should have a cone tip and if lucky contains dirt).
C) Maybe the feeder roll is dirty. You can fix this easily by removing the filament completely and reinstalling it.
D) Maybe your retraction is too high, try to lower the 4mm down to 2.50 in steps of 0.5 mm
E) When using simplify3D… do check “only retract when crossing open spaces”… it saves a lot of retraction and problems.
F) Use good filament… I had serious problems in layers with Innofil… 99% print correct, but 1% failed… I don’t know what you are using here ?
I use “real filament” from Holland right now and prints are awesome.
G) Is your temperature not too high? I notice blobs; maybe caused by a lack of retraction also.
H) Enough cooling ?
… 3D printing is always a hell of a job… if you use simplify3d… maybe you can send me your profile?
The standard profile delivered by Simplify3D and BCN3D technologies is not very good, they just started to cooperate.
You need to adjust some (many) parameters to make it print like it should. f.i.
Extrusion parameters : 0.4mm nozzle size; 1.0 multiplier and MANUAL extrusion with 0.4mm work fine with me (automatically it’s 0.48 which is way too big). Also perimeter overlap should be 25% (not 15% that’s simply not enough)…
Send me your profile on wim dot hulpia at gmail dot com and I look what I can do to help you.