Unless you build your own firmware, you will still get the retraction bug. Firmware currently bundled in Cura does not fix it. Even with the retraction bug fixed, speeds faster than 48mm/s are meaningless - and also subject to the 'MaxE' speed setting. See this http://umforum.ultimaker.com/index.php?/topic/1734-marlin-bug-the-myth-of-retraction-speed/?p=12079.
You'll probably get better results with the newer firmware, so that you get a properly calibrated retraction. Speeds that are too high can also be counter productive, as the filament tends to slip and get chewed, so the retraction doesn't happen, and subsequent forward movement becomes harder too.
Generally, a speed of about 25-35 (with corrected firmware) and 4.5mm works pretty well.
You should also raise your fast move speed higher - to 175mm/s or more - once your printer is well bedded-in it can probably do 250mm/s moves or more. If you have it too high, you'll get skipping, and the layers will be offset. But, faster moves help to break the thread of filament, and stop it stringing out. As Robert noted, slower print speeds will also help reduce stringing, by reducing the pressure in the head, and hence the tendency to continue oozing, even when the extruder is no longer pushing. Temperature changes may help as well - cooler will probably make threads more likely to snap and the head less likely to drip. But if you go cooler, you'll also need slower, all things being equal, as the plastic is harder to extrude. Thinner layers may also help, because that reduces the amount of extrusion per second - which also reduces the pressure, and so reduces the tendency to ooze.
What temp, speed and layer height are you printing at?
BTW, there's some debate about whether that fan duct design is actually much help overall. While it distributes the airflow, it vastly reduces the area that the air can flow out of, and the type of fan used on the head isn't very good at sustaining the pressure needed to compress the air through a smaller opening. So it might actually not be as good as your expect. I'll be interested to hear how you get on with it.
Recommended Posts
IRobertI 521
By original firmware, do you mean what came with the printer from factory or what comes with cura? IIRC there used to be a bug in the firmware that made retraction speed settings inconsistent. Try updating the firmware (Machine menu in cura).
Also, try slowing down your print speed a bit as well as lowering temperature as that can help in getting cleaner prints.
Another thing to try is to put something like this: http://www.thingiverse.com/thing:24363%20at%20the%20feeder%20end%20of%20the%20bowden%20to%20stop%20the%20bowden%20from%20moving%20up%20and%20down%20while%20retracting.
Link to post
Share on other sites