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I just got the modified the nozzle back from mhackney and I repeated the plug measurement so I could see the changes to the length but also the angle.

The top is the before, bottom is after the adjustment.

Aerotayl wrote:I just got the modified the nozzle back from mhackney and I repeated the plug measurement so I could see the changes to the length but also the angle.

The top is the before, bottom is after the adjustment.

That looks good, let us know how it prints PLA now.

I can say - I attempted to print with this nozzle on my Rostock before the mod and got immediate jamming (on the part that I know is difficult to print in PLA without jamming). I then made the mod and printed the part again, this time flawlessly. I then packed up the nozzle ands shipped to Aerotayl. So I'm really looking forward to his results too!

This photo clearly shows the difference in angle though. That might be an important element in all of this.

mhackney wrote:I can say - I attempted to print with this nozzle on my Rostock before the mod and got immediate jamming (on the part that I know is difficult to print in PLA without jamming). I then made the mod and printed the part again, this time flawlessly. I then packed up the nozzle ands shipped to Aerotayl. So I'm really looking forward to his results too!

This photo clearly shows the difference in angle though. That might be an important element in all of this.

The after angle is probably 118 degrees, do you know the before angle? Perhaps a drill is available that matches the before angle.

I don't and I don't think we'd want to reproduce the before angle. If anything, I'd like to grind a sharper angle and try that. It seems reasonable that a more gradual taper would be better.

Wouldn't a longer taper create more surface area and as a result, more resistance?

I'm sure there would be a sweet spot somewhere - difficult to measure me thinks.

That is true but its also true that "hitting a wall" is not good for thixotropic fluids. And a gradual taper down also aligns the flow with less turbulence.

mhackney wrote:That is true but its also true that "hitting a wall" is not good for thixotropic fluids. And a gradual taper down also aligns the flow with less turbulence.

A walking, talking dictionary! Just picking on you, again.

not seeing these nozzles for sale on your site yet Michael....

Nozzle works great! I have just completed a part that always failed at nearly the same region of the print, this time worked just fine. I just need to work on the retract and some other settings to get things dialed in. Finally some success!

Good to hear. I do 2mm retract at 20mm/s in KISS with 2mm of wipe. Works well.

Bubbasnow, not something I would want to sell! I'll help folks out though.

cheers,
Michael

FWIW I ended up with 3mm retract at 30mm/s in Cura with the modified nozzle. I still have the SeeMeCNC connector on the extruder end.
In Kiss I'm running the same with 5mm wipe, but I didn't spend a lot of time tuning it, and it's probably excessive, the wipe setting is what I generally use regardless.

@mhackney

Seems like you reached the same conclusions I did with regards to internal nozzle angle and orifice length. You can see the brief discussion about these features here in my Prometheus Hot End thread: http://forum.seemecnc.com/viewtopic.php ... 5&start=50

In my design the internal angle is 60 degrees. The idea behind this is to increase the thermal conduction to the tip while decreasing the turbulence of the molten plastic at high flow rates. This ultimately results in a higher max flow rate.

Also, I was originally going with a 1mm orifice length, but the longer orifice length tends to increase backpressure a bit too much especially in bowden setups. On the production version I changed the orifice length to 0.6mm for a 0.4mm orifice (for an orifice length 1.5X the orifice diameter). I think this gives a good balance between reducing backpressure while not significantly increasing ooze or "die swell".

One more important thing to note is that people often overlook the effect of orifice length on die swell. I am sure you are aware of this but I am posting this in case it is new info to other people here. You guys can check out this wiki article for info: http://en.wikipedia.org/wiki/Die_swell.

An alternative to increasing the orifice length is to change the internal angle (as I did with my Prometheus Hot End). However, I think a more DIY friendly approach would be to use progressively smaller drill bits to step the internal diameter down from 2mm to the 0.4mm orifice. With the E3D nozzles you can just drill out the last 0.5mm with a 1mm drill bit to ease the flow of plastic, but if you are making your own nozzles you can try drilling up to 6mm from the tip with a 2mm bit, and then step down to 1.5mm and then 1mm to ease the transition to the 0.4mm orifice while maintaining a short (~0.5mm orifice length). This should not significantly increase backpressure, but I imagine that it would really help mitigate the turbulence and die swell while increasing the material at the tip of the nozzle and therefore the thermal conduction to the tip

I hope this helps!

Eric

Thanks Eric. Good link to die swell. I've been doing extrusion for something like 30 years so know all about it, but I'm sure many don't. I do think the steeper angle is the way to go. It really is dead easy to file a 2mm drill tip to get the angle you want. We are just drilling brass, it doesn't need to be a perfect, sharp edge. I have a couple of 2mm bits coming in with another order so I plan to modify them to make steeper angles to try.

Re backpressure, yes, you can definitely feel the difference with the shorter bore. I push a new filament through by hand to purge the old filament and now with these modified nozzles, it is OBVIOUSLY less pressure to push and purge.

cheers,
Michael

Anyway, congrats on another success!

Hey all,

I print PLA with a MendelMax 2 and 3mm direct drive E3D.

I joined this forum specifically to thank you guys for all the time you've spent troubleshooting the E3D PLA issues.

Mine was jamming regularly with PLA using the 0.6mm nozzle .. retraction disabled .. just trying to squirt the friggin plastic out. Then when I tried a 0.25mm nozzle it was almost hopeless -- very finicky .. had to run at 230C and very sensitive to speed. Anyway, I almost got to the point of chucking the POS in the trash and machining my own J-head to take different size nozzles .. and then I found this thread. I stayed up until 2AM last reading all 77 pages and then implemented all of the good suggestions (not very scientific I know, but I was about to lose my mind)

I did:
canola oil
deburred inside passage
potted the thermistor and heating element
kapton taped under bottom fin to seal bottom of 30mm fan duct
wrapped hot end with extra kapton tape for better insulation
screwed nozzle all the way into the hot end for better heat conduction
drilled out the 0.25 nozzle so the tip passage is 0.5mm long

For the record, my nozzles (0.25, 0.25, 0.4, 0.6) measured 1.4 1.4 1.4 and 1.5mm respectively using electronic calipers.

I attached a picture of the spade drill I made. It's a 1/8" steel rod that I ground to a point on one end to match the external nozzle tip angle. Then I cut away the sides and sharpened it to make my own spade bit. Primitive, but it works.

Anyway, my printer is plugging along at 25mm/s, PLA, 220C, 0.25mm nozzle without a single hiccup so far.
Now that it's ACTUALLY SQUIRTING PLASTIC OUT THE POINTY END I can start to think about tuning it, going back to lower temps, and re-enabling retraction.

Thanks again.

Good job in getting the plastic to come out of the pointy end.

That's fantastic Illini_Rob1! Sorry that you had to read 77 pages though.

That's a great solution for the homemade drill, I'm making one of those tonight! People don't realize that brass is very easy to work and does not require hardened tools.

Thanks also for measuring and posting your nozzle lengths. 1.4mm is too long IMHO for a .4mm nozzle and WAY too long for a .25 for PLA.

I've now printed 1000s of parts in PLA with ABSOLUTELY NO JAMMING OR FILAMENT STARVING at high speeds (90-100mm/s) and reasonable temps (185-190°C at those speeds). There is nothing wrong with the E3D or Kraken upper-end design, in fact, it is much better for PLA than any other hot end I've used. It's just the "last mile" (almost literally!) with the nozzle. It is either out of design spec or needs a design tweak to be ready to go out of the box. I know the guys are working on it so it shouldn't be long for this hot end to rock out of the box.

Illini_Rob1, do you remember what the angle was that you ground onto the steel rod?

Eaglezsoar:
Nope I just eyeballed the angle to roughly match the outside cone. I'm printing with 3mm PLA so getting both a smooth profile and a 0.5mm length hole wouldn't have been possible with a standard 3mm drill bit -- I needed a sharper angle to avoid blowing out the corners. I can't imagine the angle would be tooooo critical.
I'm used to hand-grinding TIG welding electrodes so I got pretty good results. If someone wanted to be more scientific, they could make a simple jig clamped to the tool rest of a bench grinder (block with a hole in it clamped at the right angle). Or grind one on a lathe. Funny I have all this equipment around and I still do things by hand ...

Me too! I have CNC mills, lathes and a router, a metal band saw, etc but I still do a lot of things by hand - especially one offs.

mhackney wrote:Me too! I have CNC mills, lathes and a router, a metal band saw, etc but I still do a lot of things by hand - especially one offs.

Speaking of which, I know it will be quite some time with your schedule but I would love a short video when your CNC router is running. No rush sir, just please
don't forget.

You'll be the 2nd person to see it work after me Eagle! How's that?

I am making a little progress. I am getting most of my other projects cleared out.

I'm sending you an email about the "black box", I had a few questions!

Well keep in mind they just came out with the Kracken and in doing so may have had the nozzles resourced with different specs the time frame sounds about right

The Kraken nozzles are identical and in fact, it was on my Kraken that I discovered the issue! I had four .4mm nozzles with long (?1.5mm) bores. They are all now reduced to .5mm bores and they ALL work flawlessly.

All of this said, and as Josh and Sanjay have mentioned, they are working on a new E3D V6. I am not permitted to give any specifics but I am allowed to say that I received one in the mail yesterday! I will be allowed to discuss its printing performance once I get it setup and running. I'm really looking forward to testing this one and putting it through my torture test.

cheers,
Michael