Hi there,
Update: solutions are in the end of this post
Currently I am experiencing blobs and even some serious stringing, specifically when using High quality settings on Cura 15.04.2.
I have been browsing forum for a while and experimenting with different retraction, print speed settings, lowering temperature, yet I did not manage to find solution.
Regarding blobs - they form where nozzle approaches new printing perimeter.
I am using Ultimaker PLA gray and bronze.
Printer is in mint condition, no mechanical problems.
Retraction works fine.
In the last photos (with bronze bracelet) I'm using freshly installed Olsson Block.
Here are the photos:
https://www.dropbox.com/s/9o6zzivh7n1p1he/DSC_0329.JPG?dl=0
https://www.dropbox.com/sc/x83brwaht2wz1gv/AACCyMvjiAIH4T_S4ObJQoq-a
https://www.dropbox.com/sc/vrtgte07z0lgrvt/AAB4WWiatzAJHT6YjMIdD52da
Solutions
Retraction did not work because I really had two problems with printer and I think this might be interesting to others.
1. After head reassembly I did not fully push bowden tube down to "slot" inside teflon coupler, the filament started grinding one side of the coupler, creating groove and thus causing more friction near nozzle. When motor wants to retract, filament is not aligned 100% to nozzle as a result friction prevents it from successfully retracting.
Had to replace teflon coupler, because even after correct reassembly and rotation of teflon coupler retraction did not work correctly.
2. When I assembling Olsson Block, I obeyed recommendations and did not fully tightened the Stainless steel coupler down to Olsson Block and left about 1 mm gap. That was mistake, I only needed to leave very tiny gap between coupler and block. (I do not want to go into details explaining why it created difficulties for retraction, You may realize by yourselves.
When I corrected these two problems, printer works perfectly.