issues with priting the neck

[Lukas Wall]

As you can see from the photos, I'm having a little bit of difficulty with the neck... oddly enough its only the fillet on the underside. the rest of the thing is b-e-a-utiful!

I have a new Prusa mk3, I had a Solidoodle 3 before that, I'm not great, but I have some knowledge as to what I am doing...

This Prusa is a beast! puts the Solidoodle to shame on every front... granted there's a seven year technology difference... but I digress.

I sliced it with Prusa slicer, 4 perimeters and 10% gyroid infill. (using PLA)

My initial thoughts are two fold:

1.) import the .stl into simplify3d and manually add supports along the neck. and reprint with similar density.

2.) increase the infill and decrease the perimeters. lets say, 20% infill and 3 perimeters.

I am personally more inclined to go with the first option. because I know it will work, I'll have a little bit of clean up under the support, but I can put it where I need it and it should be fine. also, it will be way nicer than what I ended up with the first time...
I am however more afraid to risk the second option, in case it fails again... that's a lot of plastic and eight hours of print time...

Has anyone else had issues on the underside of the neck, or are yours all turning out nicely?

what settings did you use?

suggestions?

[Matt Hova]

Try smaller layers and slower outer perimeters

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[David Perry]

Yeah Lukas, this is something I struggle with, too, especially if I switch to a different brand PLA or change some other variable. 

I have upgraded my stock downward cooling fan to a squirrel cage blower, and that helps. I also find that I have to orient the neck such that the blower is blowing the extrusion back onto the neck, and not away from it. 

Even with that I still have trouble if my extruder temp is too high. If I print a bad neck, I print test cubes with perimeters and no infill, and dial down the temp by 5 degrees until I get poor layer adhesion or some other cool temp issue, then go back up 10 degrees (on average). 

I have tried using supports, but have not found that they were helpful. Your results could vary tho! 

I typically print 0.25mm layers with 0.5mm nozzle and 0.6mm extrusion width. Three perimeters, about 20-30% grid infill. 

While the neck is designed to be this way to minimize the angle between neck curve and build surface, I think a design update is in order.

-David

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