Inverted FFF printer

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LoboCNC
And here are a couple of videos:

printer walk-around

Nice little setup with all the heavy parts (motors, rails) sitting on the ground. Looks like a DLP with the model going up

bridging test

This is interesting. It seems that the pressure from the nozzle makes the extruded filament go up and create that reverse sagging motion. I'm wondering whether printing slower would alleviate the issue and get you straight lines. What settings are you running at? Is that PLA?

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JamesK
I think that deserves a round of applause

I would never have guessed that the bridging would work so well, and it's completely awesome to see that big print hanging from the bed

Great job!

Hey, thanks! I don't know that I'll convince anyone that we've been printing wrong-side-up all these years, but I'm pretty happy with how it turned out, all the same.

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ipcalit
This is interesting. It seems that the pressure from the nozzle makes the extruded filament go up and create that reverse sagging motion. I'm wondering whether printing slower would alleviate the issue and get you straight lines. What settings are you running at? Is that PLA?

Good suggestion - I'll try printing a lot slower and see what happens. I had the printing speed set for 80mm/s, temp 220c. The blower also generated pretty intense airflow. And yes, this is printing with PLA.

Edited 1 time(s). Last edit at 06/17/2016 06:17PM by LoboCNC.

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LoboCNC
Hey, thanks! I don't know that I'll convince anyone that we've been printing wrong-side-up all these years, but I'm pretty happy with how it turned out, all the same.

I'd have a hard time persuading myself to build an inverted printer, but perhaps when we all start to realise how much cost is saved by eliminating 90% of the frame you might start to get a following.

I though of one more possible advantage for inverted printing: the ability to anneal-in-place with some of these new high temperature PLA filaments. From what I've read, they need a post-printing annealing phase where the printed part is heated to ~100c for about 5 min. or so to markedly increase the heat deflection temp. Alternately, annealing can be done at a lower temp (above 60c) for a longer period of time. With an inverted printer, it should be possible to build a tall, single-wall skirt a little taller than the part to act as a custom sized heat chamber, and then just leave the bed turned on for however long to anneal the print. This would eliminate the extra hassle of baking your print and risking warping in the process.

It's an interesting idea, but my gut feeling is that just using the bed won't give you an even enough heat distribution, at least over any significant print height. Given that heat rises, heating from the top is asking for a pretty intense gradient.

An inverted heat bed with a tall skirt wall should act pretty much like the old open bed freezers in the grocery stores - you'll have a trapped pocket of hot air that ends up spilling upwards over the edge of the skirt. My guess is that most of the temp gradient will be concentrated right at the bottom edge of the skirt. There will be a temp. gradient across the print, but I don't know that you need uniform heating in particular, you just need to be above some temp for some period of time for the annealing crystallization to occur.

Any actual build based on these ideas? I have been and still am interested in bringing all the heavy components down for a low center of gravity printer...
Also the idea of an inverted open box style bed is something I've been thinking about, to keep the hottest at the first layers of the print, with no hot air escaping that area.

Edited 1 time(s). Last edit at 06/25/2016 10:23AM by realthor.

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RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

Quote
realthor
Any actual build based on these ideas? I have been and still am interested in bringing all the heavy components down for a low center of gravity printer...
Also the idea of an inverted open box style bed is something I've been thinking about, to keep the hottest at the first layers of the print, with no hot air escaping that area.

Yes, I've posted some photos and links to videos earlier in this thread here and here.

Yeah, mea culpa, i've jumped to the last page and didn't see any (updated) photos/sketches.
Quite impressive, I agree this deserves applause.

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RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff