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...