Ultimaker 2 - is this a bad belt?

[BradLarson 0]

This printer is approx 2 years old and this problem has cropped up while trying to print something that basically fills the entire build platform. The print is 7.5"(19.05cm) X 6"(15.24cm).  The pictures are of the brim being printed along with some holes. The bad area starts at about middle of the build plate and going left while looking at the printer. The left back is the worse with the left front not as bad.  I should note that I don't hear any type of slipping or chattering. The head movement is smooth throughout.

Left back

Right Back

Edited March 27, 2017 by Guest

[BradLarson 0]

Here's the left rear after several layers has been laid down. It seems just the raft, leftmost slot, and single hole is affected. Quite puzzling on the cause.

[Dim3nsioneer 557]

Looks to me like a bad bed leveling...

[geert_2 557]

To me this looks like underextrusion. If it is only in the left back corner, I would guess it is because the friction of the filament in the bowden tube, teflon coupler and nozzle is higher when bent more in this corner. This especially when printing very hard filament like PLA, and when it is near the end of the spool.

Maybe it could also be uneven build plate calibration (too much distance at the left back). This you can visually check when starting a print: is the first line equally thick everywhere?

If it was the teflon coupler worn out, or a dirty nozzle, I would guess the problem would occur everywhere?

If the cause would be too much friction, try to unwind and straighten a bit of filament manually prior to printing, and see if that helps.

I usually unwind 20cm of PLA, wind it in the opposite direction around a 7cm skater wheel, release it (after which it is almost straight), then wind the next 20cm around the skater wheel, etc., until I have straightened a few meters. This only takes a minute or so. Then I loosely wind it up on the spool again, so now it is sitting very very loose, with a bending radius of about 50cm, and it has very little friction in the whole feeding traject. Then it does not cause underextrusion anymore.

Of course there might be other causes, but these are my first guesses.

[BradLarson 0]

geert_2, I think you have the answer. This wasn't happening until I installed a new bowden tube that I purchased from Amazon and it wasn't an official ultimaker bowden.