Merlin Hotend infill issues

Hello all,

I was wondering if anyone else here that uses the Merlin Hotend www.merlin-hotend.de also has infill problems? When comparing the Merlin hot end to the J-head design, the airbrush nozzle tip does not have a "flat tip" and therefore cannot "fuse" perimeters/lines of plastic when printing.
I was printing an object with slicer setting for top layer = 3 layers, yet the top layer had gaps in it. I'm using 0.4mm nozzle and 1.75mm PLA.

Anyone else had this issue or has ideas on how to fix it? I tried increasing flow of plastic and temperature, but that doesn't help.

Appreciate any help.

Thanks,
Shai

It looks like a flat nozzle tip to me, it's a tiny nozzle use a loop to verify.
If it's not flat hone or file it flat.

Your perimeter looks sparse as well as the infill.
Assuming you don't have a partially blocked nozzle, check the filament tension on your extruder, and loose set screw on the hob.

Hi,
i'm 100% sure this is not a Merlin specific issue. It looks as if a to small amount of material is extruded.
Like A2 said this can be caused by slipping in the transport. Make sure to also check if the extruder is correctly calibrated and does really transport the set length of filament on command. Another option would be that the filament diameter is much smaller than it is meant to be.
Honing or filing the airbrush nozzle will very likely destroy it, so be careful with that.
Hope this helps
Björn

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

@Srek:

Quote
Srek-Björn
Honing or filing the airbrush nozzle will very likely destroy it,

Quote
Björn Marl
you could try to smoothen it with a fine whetstone

[merlin-hotend.de]

I understand the importance of an orthogonal orifice, and it's effect on extrudate flow trajectory, and I understand the role that the orifice land length plays in creating laminar flow.
Unless the orifice land length is non-existent I don't see how removing a little material would destroy the nozzle. I can see your point in the case of a non-existent orifice land length.
How long is the orifice land length of the airbrush nozzle?

I never measured that. It is vey liitle anyway and you can't expect any "ironing" from it. Becaus of that the merlin nozlle is a bit more dependent on exact calibration of the amount of extruded filament, but at the same time works better than any other nozzle i tested for bridging. During development of the hotend i found out that more land makes it easier to get smooth surfaces, but is very limiting for bridging.
I am very reluctant to modify the airbrush nozzle because you easily create very small irregular gaps that mess up your print. Any attempt i made failed to some degree.

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