PLA making grinding noise in bowden tube when retracting

[nick-leijenhorst 0]

I've been having problems with some prints that require retraction. I'm currently using 40mm/s retraction speed and 4.5mm of length.

Sometimes when I print with retraction, I notice gaps in some parts of my print. I think this happens because the filament isn't through the nozzle yet after the retraction ends... Also I'm noticing a subtle grinding noise coming from the bowden tube everytime it retracts... Is this normal?

I have found that I can usually get rid of the gaps by heating the PLA to 225 degrees, but I would love to get some feedback from a more experienced user.

Greetings,

Nick

 

[gr5 2,172]

I prefer lower temps with retraction:

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/

I haven't noticed a grinding noise but that doesn't mean I don't have it also.

Note that 40mm/sec is a little faster than the extruder can reasonably spin. But there was a bug in Marlin such that it didn't matter because Marlin was moving the filament much slower. But if you have the latest Marlin and are still using 40mm/sec for extrude/retraction speeds that might be a problem. Illuminarti wrote a blog entry about this somewhere. I'm not sure what a reasonable speed is. Probably 20mm/sec.