Some of the techniques give insight to what might be causing PLA to extrude poorly (i.e. Heat setting: Without heat setting PLA will have a high degree of shrinkage).
Bulked Continuous Filament (BCF Guide)
Manufacture of PLA fibers
[www.natureworksllc.com]
Bulked Continuous Filament (BCF Guide)
Manufacture of PLA fibers
[www.natureworksllc.com]