Here’s a little tip that would have saved me some grief and troubleshooting when printing with PLA on painters’ tape with my MakerBot Replicator 1.
The orientation of the tape matters.
Lay your tape front-to-back on your build platform, not side-to-side.
Look at this photo (of blue PLA on blue painters’ tape, so click to embiggen):
See where the front-to-back tape ends, and the side-to-side tape creates a rats’ nest of tangled PLA filaments?
Now look at the same print, but with front-to-back tape covering the print surface:
Much, much better adhesion. Fun new model coming soon, so watch this space.