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foehnsturm

Merlin Hotend on an Ultimaker

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... inspired by the UBIS thread.

I've been happily printing with the UBIS for two weeks now. However one thing bothered me. With PLA/PHA, stringing was even a little worse than the Ulitmaker hotend (due to a longer hot zone I suppose). So I made an adapter and tried the new http://merlin-hotend.de/.

I'm stunned. Stringing and underextrusion after retractions are gone with PLA/PHA. Overall results are as good as with the UBIS. The Merlin is tiny and uses minuscule airbrush nozzles (comes with 0.5, 0.3 and 0.2 mm). So there is very little additional heat input to the part.

As it performed so well, I made a new printhead (still under development, by far not as slick as Nick's).

A short video (air is coming from the right).

 

 

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So the antenna are supposed to be cylindrical Eh. I need to get off my rear and do something about the backlash problem on my x-axis. The problem is pretty clear when printing the robot.

Really nice looking print and hot end. What is the compatible temperature range? What is material compatibility like?

 

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Well, as it's the classic brass - PEEK - PTFE setup I'd stay below 250°C. For sure it features a comparatively small hot zone, so max extrusion rate will be limited. I will run some tests to find out. On the Merlin website they show prints with ABS, PLA, HIPS and PET. I think it's fine for layer heights below 0.2 mm.

 

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Today I drilled the 1.75 mm PFA tube to 3mm, because I managed to ruin the 3 mm PFA part. Seems to work.

The brass-PFA boundary inside the PEEK is the critical part here as well. If screwed to loose against each other it gets even looser when becoming hot and eventually leaks, screwing to tight ruins the PFA.

 

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Some findings:

Maximum extrusion rate is in the range of 10-11 mm^3/s with a 0.5 mm nozzle (PLA/PHA)

Printing speed was checked with a stopwatch because gcode sliced with Cura (100mm/s & spiralize) only prints with about 60mm/s on my UM original. This should be related to the numerous z-moves but I never expected such a difference.

As the Merlin's oozing tendency is so low, 2.5 mm retraction @ 30 mm/s works as good as 4.5 mm.

 

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Hi,

I just bought the merlin hot end because it really looks very promising! =) I also bought a 4.7kOhm resistor for the thermistor. My problem is that I dont exactly know where I have to solder those? I have a dual extruder setup so I bought everything twice! ;) Are the pins I need the ones marked as: R21 and R23 near the temp sensor connections?

And my last question is: Where do I connect the new temp sensors? Do they also come on the little PCBs on the printhead?

Thanks for all answeres in advance guys! =)

 

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Hi,

R21 and R23 is correct.

The thermistor is wired between signal and ground (black and yellow wires for hotend 1), you don't need the small PCB.

Right at the moment a workshop is manufacturing custom Merlin nozzles for me. If everything works as intended, there will be 0.2, 0.4, 0,6 and 0.8 mm nozzles available soon.

 

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Actually I'm unintentionally running a "new" 12V cartridge and an "old" (I suppose 24V rated) cartridge at the same time with my tool changer. Took some time to discover that ...

PID autotune was hard ;-) Though obviously not perfect, it's working quite well, but only with reduced PID_MAX and BANG_MAX settings in Marlin.

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Was trying the Merlin was the modular printhead and it doesn't seam to fit the groove profile. My Ubis Hotend perfectly fits the Ubis version, which I printed at the same time. I also found that the groove profile in the Nema 8 worm gear version is slightly different and seems to fit correctly.

I am wondering if there was a change in the Merlin mount profile at some point.

BTW, for I have also found that the Merlin Hotend needs a little extra time for the tip to come up to temperature, after the thermistor is up to temperature. Seems like the start code could use a 1 or 2 minute pause before printing.

Edited by Guest

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