Some new stuff to test...

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Re: Some new stuff to test...

Postby orcinus » Tue Apr 01, 2014 7:35 pm

I've tried the hotend today.

Despite the cooling (two 50mm fans, one pointing at the hotend, the other at the print), i couldn't get it to extrude for longer than a minute reliably.
The transition zone is just plain too long, at least for PLA, and even with cooling. The PLA swells quickly and, what's worse, the back pressure pushes the molten PLA back up all the way to the entry into the brass barrel. Since the diameter of the entrance hole is noticably larger than the diameter of the filament, it creates a plug and extrusion stops.

The cooling actually makes things worse when that happens, as it freezes the plug in place.

I'll give it another try without the PTFE/carbon spacer between the brass and the ceramic, but i doubt that'll do any help (it'll quite likely make things worse).
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Re: Some new stuff to test...

Postby runninfarmer » Thu Apr 03, 2014 8:10 pm

What settings (acceleration, retract speed, length, etc.) are you using for your trinity motor? My Pg35L motor is similar to that one but I had problems getting it to retract. It was actually odd because I got great looking layers at 1200 mm/s^2 acceleration but had no retraction so had a lot of artifacts. I lowered the acceleration down to 400-500 mm/s^2 and got retraction, but then I had crappy layers. Still trying to figure mine out, which is why I'm working with the geared Nema 11 currently.
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Re: Some new stuff to test...

Postby orcinus » Sat Apr 05, 2014 10:46 pm

The PG35L allegedly has delrin gears, unlike the Trinity/2engineers one. Also, supposedly, the Trinity has all brass gears, while the 2engineers one does not (some are brass, some appear to be steel).

My settings are as follows:

Code: Select all
Ve-jerk = 30 mm/s
Vmax e = 30 mm/s
Amax e = 6000 mm/s^2
Aretract = 600 mm/s^2
Esteps/mm = 570

Retract distance = 1.00 mm
Retract feedrate = 720 mm/min
Unretract feedrate = 360 mm/min
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Re: Some new stuff to test...

Postby orcinus » Sun Apr 06, 2014 2:21 am

I think i've managed to modify the hotend to work.
The only problem is, it renders any and all advantages it could've had utterly useless...

I've replaced the short PTFE+carbon spacer between the brass part and the ceramic holder with a 2x longer section of a PTFE tube.
I'm not yet sure how reliable it is (haven't printed anything with it yet, just did some free air extrusions by hand), but at least the filament doesn't get stuck within the first minute (or at all, within the 10ish minutes i've been testing it) and i can push it through by hand without too much effort.

Of course, having a PTFE tube inside renders the whole exercise pointless, because the top temperature is limited by it, instead of ceramic/brass. Also, it's not short anymore, in fact, it's longer than the Arcol.hu by quite a bit and only slightly shorter than the E3D.
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Re: Some new stuff to test...

Postby orcinus » Sun Apr 06, 2014 2:59 am

M'yeah, that didn't work either.
The heat creeped up eventually and the filament got stuck again.

The heat barrier is really badly designed on this hotend...
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Re: Some new stuff to test...

Postby fma » Sun Apr 06, 2014 9:44 am

Is there a decent bearing on the output of this geared stepper? If not, this design won't last very long...
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Re: Some new stuff to test...

Postby fma » Sun Apr 06, 2014 9:48 am

Sorry, I didn't see that you added a bearing in the printed part! Well, should be strong enough ;)
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Re: Some new stuff to test...

Postby orcinus » Sun Apr 06, 2014 4:56 pm

Yeah, i wasn't super comfortable with leaving the "naked" shaft loaded radially, so i've added a space for a bearing.
FWIW, i did take the gearbox off the stepper to check if the gears were greased/oiled. They were, all of them, but i've re-packed them with some thicker silicone grease.

It increased the friction somewhat initially, but i guess that'll subside once it gets squeezes out.

I didn't see any "proper" bearings in there, just bushings, but i admit i wasn't looking too carefully.
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Re: Some new stuff to test...

Postby orcinus » Sun Apr 06, 2014 5:04 pm

Re: hotend - at this point, the only thing i can do is recommend people to stay away from it.

It's misdesigned out of the box and, even if it were working properly, it wouldn't be worth it.
I've sent an e-mail to 2engineers complaining about it not being usable despite the cooling (i even tried sticking a 50mm fan right in front of it, 3 cm away) and received no reply. Kinda weird, considering they were very responsive up to that point (sent them the photos of the extruder, updated them when the package came in etc.).

On top of that, i've seen someone post about another ceramic hotend on the reprap forum, with a youtube clip of it in action - that one was made from Zirconia as well, but with thinner walls, fins and everything else this design is missing. Snooping around the posters channel, i realized it's the same guy (or people), i.e. 2engineers.

Meaning they've knowingly sold a defective design in order to finance a v2 for themselves.

All of this is conjecture, of course, but even so - more than a bit shady.
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