I’ve checked my diameter multiple times and have yet to see any actually over spec - the largest I’ve noted so far has been right at 1.75, with 1.73-1.74 being the most common.
Yeah 210 is high. You might want to try 190. I print all my PLA at 193 cause that is what I’ve found to be the most efficient. I have a fan running literally right up on the hotend with a shroud so if you are suing the fan at a 45 deg then it might need more airflow at that temp to decrease heat creep.
Does your hotend use a ptfe tube?My rigidbot did and the ptfe expanded after a bad connection caused the filament to stop extruding and made it harder for the stepper to push the plastic through.replacing the ptfe fixed it.
Thanks to everyone for the ideas and suggestions - I think I’ve got it sorted. My theory is that some filaments - in particular, softer ones, or certain colours with lots of abrasive pigments (like white) - either have inherently greater friction, or are more susceptible to the amount of heat creep in my hot end. Since I’ve already got fans on the extruder motor and on the hot end heat break itself, there doesn’t appear to be much more I can do to combat heat creep.
However, light lubrication with vegetable oil seems to have really done the job. I initially just tied a small piece of lightly oiled foam directly around the filament. That worked so well I decided to tidy it up a little and printed a small in-line filament wiper/oiler box. A drop of oil in the foam with each filament change seems to have completely eliminated the jamming.
I’ve had a lot of problems with white filament in my Rep1/Dual. Sometimes it just breaks in the PTFE tube and that is that.
Another thing that I found causes the jam is retraction settings if you retract to much soft plastic is pulled far enough back to where it can get past the heat break and cause the block. Try reducing that a little and see of it changes the results. It’s a trade off of some stringing and a completed print or not needing to clean up a 1/2 done print