The fand duct on the part is meant to cool down the fused filament as soon as it lives the nozzle (short explaination). It helps PLA prints to stay in good shape, because PLA can loose it's shape if it stays too long between its fuse temperature and its glass temperature (basiclaly 90-190°C). Other application for all kind of plastics, is when you want to make bridges. If you cool the fused filament quicky,
it allows you to print in straight line between to high point of your part without any support. It's called bridge. For ABS i turn the fan off all the time.
Now, you're experiencing wraping. PLA wraps not often and not much, but ABS can wrap a lot, especialy pure ABS filaments. If the top layers retract more than the early layers, it makes some wrap. Wrapping happens more often with long parts, so the shape of the part is important. Sometimes you'd rather flip a part on its side to prevent wrapping.
There's a lot of things to do to avoid wrapping. First, adherence of the first layer is crucial. So you want to have a prepared printing surface to help first layer bounding. Use Painter tape, hairspray, a buildtak plate, whatever, but don't print directly on glass, or a dirty surface.
You can use a Brim (it's a printing option of your slicing program). It creates a brim around your part's first layer. The more surface, the more bound. Easy. If it's not enough, you can use a raft (another option). That creates a raft between the buildplate and the part. You loose some filament, but it can reduces wrapping to zero. Attention, with some filaments the raft may stick too much to the part, you need to adjust the parameters. Keep in mind print quality of the side laying on the raft is not as clean as if you print on your buildplate.
Edited 2 time(s). Last edit at 01/27/2015 01:11PM by Zavashier.
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Prusa i3 Folger (A lot of the parts are wrong, boring !)
