Nozzle end shape.

I can find much discussion about the end shape of nozzles and how it influences print surfaces.

I have put one of those ebay extruders on my new (DIY) printer and it not going too bad really, however there is room for improvement.
Thin walls and support material are printing beautifully but horizontal surfaces appear to be over extruded with lots of smudging and dragging. Im convinced its not over extruded as reducing the flow ends up with voids. Vertical holes smaller than 2mm just disappear in the smudge
The nozzle is 0.3mm but has a very wide flat base and Im wondering if that may be to blame.
Is it best to have as little metal around the hole as possible (like a point) or is it useful for smoothing the plastic a bit?

here's a photo showing the small flat on the nozzles i put on my hotends, also you'll notice the inside the orifice is chamferd slightly (this took care of burrs) and seems to give me some very nice print quality that a 0.8mm diameter flat around a 0.3mm hole,

https://www.dropbox.com/s/czb9culzsnqntlz/_DSC9114.JPG


ignore the other stuff in the photoo ...

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So was that the result of trying different size flats and were you getting the smudging befroe you did this?

i didn't notice too much of a difference, the really big flats i tried somtimes pulled up and feathered the plastic that had just been layed down,, it depended on the plastic quite a bit as well though

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I would maybe assume that with a larger flat and more contact area you may dump more heat/dump heat longer into filament already extruded and it may cause issues on stepper overhangs or slower bridging. I know for a fact that Cura repositions the head when layer time is faster than X seconds instead of slowing the print down like Kiss and Slic3r(maybe, haven't tried 1.x) so you may also put more heat in when the printer slows down(which is counter intuitive I think to slow the printer down rather than do what Cura does now).

Well the print has much improved throughout the day as various problems have come to light.
The nozzle turned out to be 0.4 not the 0.3 I had set the slicer for!
Also I think my hot end thermister is under-reading. The ABS still flows OK at 200deg and the print looks better for it.
I am getting massive curl up on steep overhangs so may try to reshape the nozzle in the lathe tomorrow.
The least now the prints are useable bits of engineering.

During development of my Merlin Hotend i tried various nozzle shapes. What it boiled down to for me was that flatter nozzles make it easier to produce smooth top layers, but have difficulties printing good bridges. Sharp pointed nozzles, like the airbrush nozzles i use mostly nowadays, can print beautiful bridges, but need more precise calibration to create smooth surfaces.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Quote
Srek
During development of my Merlin Hotend i tried various nozzle shapes. What it boiled down to for me was that flatter nozzles make it easier to produce smooth top layers, but have difficulties printing good bridges. Sharp pointed nozzles, like the airbrush nozzles i use mostly nowadays, can print beautiful bridges, but need more precise calibration to create smooth surfaces.

Did you try to make your nozzle stainless steel?

I use this kind of nozzle . I think it's very good . Not easy get block . Have 0.36 and 0.5 size . Can print 0.02 precision . Look at my printing model :

It's very good .

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Quote
karabas

Quote
Srek
During development of my Merlin Hotend i tried various nozzle shapes. What it boiled down to for me was that flatter nozzles make it easier to produce smooth top layers, but have difficulties printing good bridges. Sharp pointed nozzles, like the airbrush nozzles i use mostly nowadays, can print beautiful bridges, but need more precise calibration to create smooth surfaces.

Did you try to make your nozzle stainless steel?

Yes, but i did not follow that route further since i did not see any advantage. Steel is much harder to machine with my equipment and it distributes heat much worse than brass. From the few tests i did it seems that the actual material of the nozzle does not have nearly as much impact as the shape.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Quote
thejollygrimreaper
here's a photo showing the small flat on the nozzles i put on my hotends, also you'll notice the inside the orifice is chamferd slightly (this took care of burrs) and seems to give me some very nice print quality that a 0.8mm diameter flat around a 0.3mm hole,

https://www.dropbox.com/s/czb9culzsnqntlz/_DSC9114.JPG


ignore the other stuff in the photoo ...

I see you chamfered nozzle about 45 degrees so the flats around orifice are about 0.1-0.15mm. Do you recommend such mod?

Edited 1 time(s). Last edit at 12/14/2013 10:37AM by karabas.

it's made quite the difference to print quality, i'll post a picture in a few hours so you can see

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Part of my problem with the wide nozzle was that it was not perfectly vertical so one side dragged the new plastic. Worse in one direction obliviously. I have just slightly relieved the material immediately around the hole and its now very nice indeed. I seem to get a nicer finish with colder extrusion but the trade off is worse layer adhesion.

Quote
thejollygrimreaper
it's made quite the difference to print quality, i'll post a picture in a few hours so you can see

Please!?