Filament globbing

[9alfred99]

I am having a problem with what I call filament globbing. I played with temperature and retraction and have got stringing pretty much eliminated.

The problem that persists is ridges and globs of filament overhanging.

I printed a 12mm square tube with a 3mm wall thickness the corners have a glob. Almost like when there is hesitation at the corner direction change extra filament is being deposited.
Also, I printed Glock magazine extension,

http://www.thingiverse.com/thing:1764263

However, when printed it had a "ridge" running right where the flat side transitioned to rounded back. The ridge extended up to where the rounded back ended. This ridge is only on one side.

My retraction is set to 1mm and -.3mm return, PLA filament.

tj

[jimc]

heavy corners are somewhat normal with 3d printing BUT it can get excessive if you are over-extruding. make sure your filament dia is set right and you print a few calibration squares to adjust your ext multiplier.

[Jules]

Ridges and globs of filament will generally form on overhangs if you are printing PLA - it tends to warp and curl without any support underneath it. Pointing a desk fan at it to cool it off quickly helps. (And you'll notice the problem is worse on the part of the print that faces away from the bed fan. If you have an overhang, turn the print around on the bed so that the overhangt faces the fan directly.)

And like jim said, and you guessed, perfectly square corners do create a slight buildup - the machine has to stop and change direction at one point, giving more filament time to be extruded there. If you can slightly round the corners in the design, it cuts way down on that effect.