My first spool of PLA is near the end. The set of the filament with the smaller radius is tight enough that it raised the spool support peg rather than unwinding, then the filament bound on itself around the spool and broke. A weight was placed on the peg to hold it down and a new print started. The filament again tangled due to the tight set radius allowing a loop of the filament to bind under a turn around the spool, and it broke.
Not measured how much filament is left, but it appears there is enough for several parts. Is this a common problem? How is it handled?
Check the end of the filament at the spool. Often times manufacturers will “hook” it to the spool. Cut or unhook the filament, and it should continue to unwind without the weight of the spool. Also try tightening the idler screws a tad… a full turn on each knob.
Hope that helps!
Thanks for the tip about the “hook” - the spool in question does not have one but I will look for it in the future on other spools.
Tightening the idler would not help: I could not get the filament out pulling it by hand as it was a loop locked under a winding (no idea how the tangle got there). Pulling locked the tangle tighter; I had to push the loop out from under the winding - exact detail forgotten but I will watch detail if it happens again. I started a new spool rather than risk getting into a print that breaks like the last one at about 6 hours into an 8 hour run (guessing by height of partially printed parts). The old spool now has about 1 1/2 - 1 /34 layers left now but I do not know how much was there at the start of its final run.
Has anyone tried to relax the set by wrapping the filament around a “large” cylinder (7 or 8 inches) and placing that in an oven to soak for a while a a temp that does not melt the filament?
Hmm… tangles… that’s never good. I had one at the beginning of the spool once… and I’ve had a new spools “unspool” wrapping around the spool holder. Don’t think there’s a resolution for tangles or overlapping filament. And you’re right, tightening the idler won’t help resolve tangles.
Wrapping the end of a spool around a larger diameter cylinder to increase the curve radius is a good idea… as long as you remember to do so each time. 
As long as you don’t have a tangle, the hobbed bolt will pull tightly curled filament through the feeder tube. I’ve regularly printed eSUN ABS all the way to the nub… so much that I needed tweezers/forceps to pull the exposed filament nub from the extruder.