Different brands and blends of PET filaments seem to do this to different degrees. Esun's PETG is definitely one that tends to glob onto the nozzle. Basically, the nozzle plows through the top surface of the filament and lifts up some plastic, much like the bow of a ship lifting up some water at high speeds. PET's viscosity and stickiness seem to amplify this effect more than other filaments.

Some things you can do to minimize the globbing:

• Calibrate extrusion volume on the low end of what you'd normally use for other filaments (how you do this depends on your slicer)


• Use your slicer's "Z-hop" or "avoid perimeters" feature so you don't do travel moves across printed surfaces


• Invest in an anti-stick coated nozzle, such as are sold by Micro Swiss or Performance 3-d (these don't eliminate globbing, but they do reduce it and make the nozzle much easier to clean)


• Play with slicer settings such as extrusion width, layer height, and infill/perimeter overlap to reduce the amount of "excess material" that sticks above the print surface

Again, this is a common problem with PET blend filaments. Anecdotally, some brands seem to glob more or less than others, so switching to a different vendor may be worth trying if you want to do a lot of PETG prints.