Yesterday after one print of around 3 hours (small vase), when we started with new print with design from youmagine and standard UM2 blue PLA filament, initially material started to flow from the nozzle but while printing material flow became bad, and we observed only very thin layer of material was getting printed (layer was almost transparent), after couple of seconds though head kept on trying to print but no material was flowing from nozzle.
This was new thing for us, but i thought may be something is wrong with design, so we again tried with standard ultimaker robot design, this time again initial material did flow from the nozzle but while printing robot only little amount of material was coming out due to which we even noticed printing time indicated in panel kept on increasing and printing head unsuccessfully kept on trying to complete the base layer. We again stopped the print after a min of unsuccessful printing and decided to give machine a break.
We again tried after 2 -3 hours with ultimaker robot design, but this time even initial material stopped coming out of nozzle and print head kept on trying to print without any material flowing out from the nozzle, which really worried us. We also observed that now build plate took more time than usual to cool down. I'm not sure if this is a connected issue or not.
Now we decided to go through google/UM2 forums and found out that this may be common issue of nozzle clogging, so we tried following methods suggested on UM2 forums:
1. We tried changing material to gold PLA filament couple of times, but no help, material was still not flowing
2. We tried to heat the nozzle and clean it through thin wire. We initially got blue material on surface of wire and after cleaning few times, material started flowing from nozzle but this continued only for 1-2 minutes. Wire coming out of nozzle was also very thin and runny nose-like. Around 1 feet long wire came out of nozzle but then it finally stopped. We thought may be during printing, material flow will continue but again very thin layer of material came out so printing didn't happen. Then after a while like before head was moving but no material came out.
3. After this we again tried changing material and observed the currently connected gold filament had covering of blue color at the end. So we decided to cut its end and again insert the same.
4. Now even after cleaning few more times using wire or insulin needles, we were unsuccessful in getting material out of nozzle. This time when we took out the filament from machine, we found it's edge was as smooth as inserted i.e. it didn't get heat up inside the Bowden tube.
It looks like now we may have to open the nozzle head assembly and clean it manually as suggested on forum, but we prefer to get some pictures or videos to suggest steps to do so, if required as I understand extruder assembly is heart of printer and its only couple of days old printer for me. I have also raised ticket for the same but wondering if anybody on forum have such guide.