I thought I would buy a 3 kg spool because lazy, don't be me.
I thought I would buy a 3 kg spool because lazy, don't be me.
Just thought I would quickly share what can happen if you're not paying attention with a heavy mass spool if you're not careful. I have all my spools on a dowel rod attached to the top of my printer enclosure and fed through an opening in the top. Never had the slightest issue with 1 kg spools, and I thought I would save a little bit of money and time changing filament by trying a 3 kg spool. It spins perfectly fine without friction, but the much heavier mass is enough to cause it to have significant strain on the extruder pulling it in to the hot end. You can see in the result where I provided strain relief by hand while watching it print. 
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Others have suggested greasing the dowel or using bearings, and if the issue was friction, then they'd be right.
If the issue is inertia, then this won't help. Accelerating a given mass to a given velocity requires a certain amount of energy, no matter what.
What could help is something similar to a Huygen drive, where the filament is looped around a large wheel (large enough that the filament can curve around it without breaking) which is able to move against a spring or counterweight. This would allow the movement of the spool to be "averaged out" rather than accelerating and decelerating sharply on every extrusion and retraction.