E3D mentions on their own wiki:
Excessively long retractions will cause issues by dragging soft filament into cold areas. [...] for bowden systems you might want to go up to 2mm. Retraction beyond 2mm is likely to cause issues.
I have retraction set to the recommended maximum of 2mm, but I still get a lot of stringing and blobs. My printer is set up with a relatively long Bowden tube (500-600mm). I wonder if I need to push my retraction setting slightly beyond 2mm to take up some of the slack. Is the 2mm a conservative rating (I guess they don't want dissatisfied customers with clogging problems) or is it really the maximum? Is there anything else I can do to improve retraction performance? (I already have a small coasting distance of 0.1mm set.)
To my experience, there is absolutely no problem in increasing retraction in E3D assemblies up to at least 5mm. Typical retraction distance for my Bowden system is 3.5 mm (ABS). Clogging may occur after a series of retracts when thermal break doesn't have enough time to cool itself down. To avoid clogging when there is a real need in long retracts (printing with filaments like PLA or PETG) you need to:
- keep amount of retracts at possible minimum
- make sure that thermal break is properly cooled. You may want to use thermal grease and extra cooling for that