material crack and feeder stopping

[astro 0]

Hi,

We were printing over the weekend a model which was expected to complete in 40 hours on a Ultimaker II with a PLA silver roll from the Ultimaker shop.

When I came to check the progress 20 hours into the print, the printer head was moving in the air well above the printed object. From the completion of the object it looked like feeding had stopped about 4 hours into the print.

Looking at the feeding tube, I could see several cuts in the filament. The feeder was making a large dent in the filament but the motor could not make it move in either direction. The filament in the feeder had a cut in a region just below the feeder output and the part below the cut was likely misdirected and stuck against the top of the feeder housing.

We had to remove the Bowden tube to get the filament out.

Pictures can be seen here:

https://drive.google.com/folderview?id=0B-WO0RfTMNHnNnUyUmV6aGo4azg&usp=sharing

How can we avoid this problem? We have not seen this during previous prints but we are still on our first roll of material (about two third in the roll I would guess). It looks like the material is becoming more brittle. Our guess (hunch) is that this is due to the fact that the material in the inner side of the roll was subjected to higher stress due to the higher curving. But this would make 1/3 of each roll unusable...

Thank you

[gr5 963]

This is faulty material. There was a recent bad batch of UM PLA. Contact UM immediately:

http://support.ultimaker.com

At the same time you might want to order some PLA from a local distributor. Germany has some interesting filaments - google "PLA45" and "PLA90".

Once PLA breaks in the bowden it will fail on a retraction soon after because occasionally that crack will get stuck in the print head well above the hot zone and then the print just fails because the filament is ground to dust at the feeder.

If you have several spools of PLA it's easy to test it for being brittle. Bend it until it breaks. Repeat with good and bad filament. The difference is obvious!