[slabity]

I've seen this technique a lot, but mostly as a post-processing technique where resin, fiber, or some other type of plastic is injected into the channels after printing is completed. It would be interesting to see this done during the normal printing process.

I am a little skeptical on the technique though. FDM printed walls are known to not handle pressure well, especially during printing when its past its glass-transition temperature. This process essentially uses the pressure from the extruder to inject a channel with molten plastic. Will this pressure could cause the walls to delaminate from each other or deform?

And how does this affect plastic that tends to warp significantly during printing? The molten plastic is injected into insulated channels that will not receive any active cooling. You're also parking the nozzle at the injection points, which will cause a lot of uneven cooling at the surface as well. For high-warping plastics like ABS, that could cause a lot of issues.

So I guess the underlying question should be, does this actually work? What is the measured difference in tension strength between parts printed normally vs with MAGMA infills? Specifically when using the same amount of plastic. There's no data or even pictures that indicate this is working.

[mgunlogson]

> Will this pressure could cause the walls to delaminate from each other or deform?

Nobody knows :) . Give it a try!

> You're also parking the nozzle at the injection points, which will cause a lot of uneven cooling at the surface as well.

There's an "injection fan speed" setting that should probably be kept at 100%.

I'm not sure the "not have any cooling" will be a problem in practice. Because unlike normal printing you're not concentrating all the heat on one layer. It's going down Z dozens-hundreds of layers to already cooled areas of the part printed minutes ago. And the design tries to avoid having nearby tubes end on the same Z. So the area directly adjacent to the tube has probably been cooling for a while.

> So I guess the underlying question should be, does this actually work? What is the measured difference in tension strength between parts printed normally vs with MAGMA infills? Specifically when using the same amount of plastic. There's no data or even pictures that indicate this is working.

No one knows. And I can't test it anymore. The code is done and I have other projects to work on. I've done probably a hundred test prints on my POS Ender 3. I need testers with better hardware. No matter what I try the top of the cell gets melty. This could be the low flow rate of my hotend (limits injection speed), the fairly bad cooling, or maybe something fancier like dual material is needed. Or maybe I just haven't landed on a good combination of settings since there's dozens of them.

I particularly want someone with dual nozzle to test so they can try injecting a low melting plastic like PLA into a heat resistant shell like CF-Nylon or more exotic materials. There's printer plastics that aren't even at glass transition temp when PLA is at printing temperature.

I added dual nozzle and multi material support. Obviously hasn't been tested though

[joshvm]

The simplest option is to print the part raised at an angle so the layer lines aren't parallel to faces. Clough42 has some good videos on support/rib design in Fusion: https://www.youtube.com/watch?v=XXaLxSmtnbQ, based on https://www.youtube.com/watch?v=8NKVNwVaZU0.

But you can definitely get printers to dump a blob of filament out without worrying about cooling problems, if the extruder speed is high enough. I was debugging some issues in P2PP (a post processor for the Mosaic Palette. One problem was that the printer would extrude all the filament at the start of some travels instead of along the path.

[slabity]

> But you can definitely get printers to dump a blob of filament out without worrying about cooling problems

Yes, but we're not talking about dumping a blob of filament. We're talking about injecting filament into a well-insulated channel where it's physically impossible for it to receive any active cooling whatsoever.

That's not a situation where you can just ignore cooling.

[Aurornis]

> We're talking about injecting filament into a well-insulated channel where it's physically impossible for it to receive any active cooling whatsoever.

Look up the thermal conductivity of air.

Then look up the thermal conductivity of 3D printing filaments which form those channels that are being injected into.

The filament will be cooling faster in the channel than in free air.

This cannot work unless the part is heated to a temperature where the filament flows.

[slabity]

You cannot compare the raw thermal conductivity of a fluid like air (that pulls heat via convection) to a solid material like plastic (that pulls heat via conduction). Especially when the fluid is being actively moved with the intention of cooling down the plastic.

On top of that, the lattice structure of the infill will mean that heat will not conduct away from the channels well regardless of the material used.

[amluto]

I can imagine it working with a needle shaped nozzle that inserts into a hole and extrudes filament as it withdraws back out. This is probably much more than a software change, though.

[rao-v]

I think the way this works is with an internal structure, that houses the plastic and is expected to deform, printed first (so it cools), then outer walls with perhaps some air gaping for insulation, then injection into the inner structure at the lowest temp possible, then the next level starts.

Would print slow but might be genuinely strong vs normal infill + many walls (weight for weight).

Multi head printers like the U1 or H2D could do even better with high heat deflection temp plastics like carbon ASA or nylon for the inner structure and outer walls and strong low temp PLA for the injection.

[protocolture]

Yeah I was thinking multi head for this, wider nozzle for dropping material in the gaps. Especially if you could find something lower temp than the other walls.

That said, maybe an acetone drip or something in a strength channel to try and bond it.

Actually what I do (and I think is pretty common) is just stopping the print from time to time and filling the outer infill channels with wood glue and sand. Sometimes wooden sticks.