Is every reverse move of the feeder a skip back? - Difference between calculated and real weight?

[MichaelB 1]

My UM2 extended has printed about 20 hours yet. After problems with strange noise (see other thread) and some adjustments in my settings the results are not to bad at all. But...

Material: supplied PLA (silver) from UM, printed with factory set 210°C, heated bed at factory 60°C.

Printer is completely stock.

From the very first start of the printer the feeder turns a few degrees "back" sometimes. This happens not always, but there is barely a minute without this "tock" noise from the rear side...

The "visual ultimaker troubleshooting guide" talks about a quarter turn back when a skip back happens. Thats way more than my feeder does. So I am asking myself: Is the "pull back" of the material for only a few degrees (I would say 10-15) intended for printing reasons? Or should this never happen and as a result I a have a problem?

My first long (about 15hrs) print yesterday ended up with a weight of 160 grams - Cura said it should have a weight of 268g. I must admit, that I used the standard speeds after changing from fast to expert mode with the result of partly high extrusion rates... which should otherwise not be a problem with a good working printer?!

A test print yesterday (after some adjustments, mainly print speed) weighs 31g, Cura says 38g. (see photo)

This was printed with max. 4.8mm3/s. I am not to sure, but it may be, that the "tock" noise came mainly while printing at the maximum (inner wall).....

How big is the differene between calculated and real weight in your experience?

Both prints were printed with 0.2mm layer height. I want / have to print large parts without the need of perfection in inclined areas etc.

So am I having a problem with skip backs / under extrusion issue? Or am I to accurate in my expections?

Could a clogged nozzle be the reason for such problems after only 20 hours of printing without any material change? In addition the "tock" noise is from the very first test print there, I thought, this is normal.

I will try the atomic cleaning method now...

[MichaelB 1]

Well, could be that I am making some kind of "over-panic". Feel free to stop me from getting mad..

Atomic cleaning: done - as predicted without any visible problems/dirt: nozzle clean

Extrusion test: done - not as bad as suspected:

Including 8 everything fine.

BUT.

"tocking" startet now and then at

7mm3/s: https://www.dropbox.com/s/xiugtssauo2bwtf/7mm3s.m4v?dl=0

But there are no visible problems in the printout, including even 8mm3/s with a little more tocking as in the video, see photos above.

"tocking" more or less permanent at

9mm3/s: https://www.dropbox.com/s/9vfc5roguu979mm/9mm3s.m4v?dl=0

Here the problems with the printout began.

At this point the tension of the feeder was about the second line from above - you can see this in the video.

After filming I reduced tension completely, indicator above first line. Tocking was reduced then and the printout was a little bit better, as you can see on the second photo above.

Forgot something: Already increased E Motor current to 1300mA!

P.S.: How do you like my invention of the word "tocking"?

Edited May 15, 2015 by Guest

[MichaelB 1]

Forgot another fact: The previous test was printed at 230°C.

After that I printed another extrusion test at 210°C. Here we go:

Everything fine until including 6mm3/s. (with "tocking" now and then)

At higher rates the noise got harder and the result shows typical under extrusion.

So, panic or not. Something must be wrong here :(

[Labern 774]

This test is meant to be done at 230deg so anything under that will have problems.

Increasing the E motor current can make it more hot and end up melting the filament at the feeder.

The "tocking" sound is due to to much pressure build up and it skips backwards to prevent the material from being ground down by the feeder.

So if this is "Tocking" regularly when printing at the correct temps and speeds means there is something causing to much force for the feeder to feed the material.

This can come from tangles in the roll or something else after the feeder.

I recently had the same issue in a new machine and found the PTFE coupler was the problem.

If you have performed a few good atomic pulls and is clear then you may want to look at what else in line could cause the issue.

[Labern 774]

A low roll of filament can also cause it as the filament is tightly wound and doesn't like going through the bowden tube.