Show HN: 3D print Z reinforcement via injected loops

> Anyone who has ever cleaned blobs of filament off of a nozzle after a print failure can tell you what happens when you try to pump hot filament into empty space. Filament cools below the melt temperature quickly, especially when it comes into contact with your print.

That's completely irrelevant because this isn't printing into empty space at all. This is injecting molten plastic into confined channels, with no active cooling, made from material that doesn't conduct heat well. You're saying that the plastic will cool too quickly, but I believe the opposite will be true.

The problem that the author is describing is that the plastic is actually far too hot when injected and causes wall collapse. This is because the author isn't taking into account that FDM walls don't handle the required pressure near/above glass-transition points.

The failure mode you're describing is the complete opposite. If you were correct, it would result in cold plugs or extruder jams. It wouldn't result in wall collapse or layer delamination.

I actually had the opposite problem in testing. Plastic has bad thermal conductivity and the large volume of plastic in the channel was melting the top of the cell. That's why I asked for testers with dual nozzle printers. So they could try injecting a low melting point material into the channel while printing the rest of the part with something like Polycarbonate or CF-Nylon.

Some of the docs were written by LLM because writing docs is boring. Did you look at the code or try the binaries?

> Reading any of the research on that should make it obvious that you can't "inject" molten plastic into larger cavities, though.

There is quite a bit of research on injection molding. The pressure at the tip of a regular 3DP nozzle is around 200psi. That's actually high enough to inject a reasonably large cavity.

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

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.

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.

The tubes only need to be tall enough for a "window" at the bottom and a splitter in the middle so that plastic will flow up one side and down the other.

The window height calculations are automatic right now. To make sure the window area is as large as the tubes so it doesn't create a bottleneck that stops flow.

But if you print tiny tubes with a tiny nozzle you could probably get the tube height down to ~3mm.

There's binaries if you want to play with the settings and see it for yourself

I’m not sure I understand. In FDM printing, Z is the only direction where you currently CANNOT have long continuous strands, even if you need them. You always need to sacrifice one direction in which the part is going to suck.

For example, you can easily print an airplane wing with a beautiful, perfectly smooth and continuous airfoil, but you have to include a channel for something like a carbon fiber rod. Without it, the slightest bending force would instantly split the layers apart. Any other orientation will give you a rough surface with steps and a disgusting amount of supports. Being able to add a few strategically placed “columns” (i.e. members in the spanwise direction) could really help this particular usecase.

This is meant to knit together the part in the Z axis

This method seals the nozzle against the tube and injects under pressure (theoretically). And leaves a path for air to escape. Pretty much a micro version of injection molding

The top of cells always melt as I'm using the same material for injection and the rest of the print. Someone with a dual nozzle printer could try something like PLA injection in a polycarbonate part. I added support but don't have a printer capable of that.

It's also possible that different print settings would work. I'm releasing the features to the community as I've run out of patience with doing a hundred hours of test prints.

We need to crowd test the best settings and nozzles, materials, etc to make this work well

A solver pairs the triangle with one of its neighbors. Then cuts a window at the bottom during the slice. So plastic gets injected into the top of a triangle tube and flows through the window at the bottom of the U to its neighbor cell.

Download the binaries and try slicing with magma infill type. Turn off visibility of all the other line types and you'll see how it works

Personally, I think it's an interesting experiment. If my prints break, it's at the layer lines. This work may be a stepping stone, an easy way to reinforce prints.

It was done with manually-written gcode though.

A lot of people here took issue with the crappy docs. My mistake, I barely spent any time on them.

The reason this "came out of nowhere" is because I was working on it in secret for a long time. So that patent trolls couldn't screw the 3DP community yet again.