Show HN: 3D print Z reinforcement via injected loops

zargon · 2026-06-14T23:03:04 1781478184

I came across a method of printing that attempts to make the extrusion of two adjacent layers overlap each other by 50%, with the goal of creating stronger layer adhesion. They called it HexWAM and it seemed more likely to work than this one. There were also some test prints available. The website with the full description seems to be down and archive.org unfortunately didn't get the images.

https://www.printables.com/model/438863-supper-strong-layers...

https://www.printables.com/model/437584-qualitative-layer-ad...

https://web.archive.org/web/20251008223152/https://bcarvercr...

Aurornis · 2026-06-14T18:59:15 1781463555

Interlocking layers is an interesting idea, but I don't see how this is supposed to work.

You can't use the nozzle to inject that much filament into a large cavity because it will cool and solidify right out of the nozzle. 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.

At least the README admits that it doesn't work:

> What’s NOT yet working: the physical print. On my Ender, same-material plastic injected into freshly-printed cells melts the cell walls before they can seal. The math says this should work; the materials science is the open question.

I like seeing experimentation, but this is a lot of software work dedicated to something that couldn't possibly work. I'm curious about "the math says this should work" combined with the large number of em-dashes and other LLM tells. Was this experiment largely driven by an LLM?

There is some interesting work on the topic of staggered interlocking layers: https://github.com/OrcaSlicer/OrcaSlicer/pull/8181

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

warumdarum · 2026-06-14T22:14:48 1781475288

Secondary epoxxy nuzzle?

xnyan · 2026-06-14T22:43:18 1781476998

It's always a balance of tradeoffs and benefit. That might work, but there are already alternatives. If possible, change the design so that the anticipated load is acting on the x and y axis of the print. If that's not possible, another common tactic is to do something like partial print > insert metal rod in printed channel along y axis > resume print.

slabity · 2026-06-14T17:10:49 1781457049

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.

rao-v · 2026-06-14T18:12:42 1781460762

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.

dwallin · 2026-06-14T16:03:17 1781452997

Instead of one large channel throughout the whole print, why not multiple small 2-4 layer bridges?

boothby · 2026-06-14T20:44:13 1781469853

I had the same thought -- with a checkerboard pattern of 1:1:2 "brick" voids where each brick would be surrounded by bricks of a differing offset, one could conceivably calibrate the injection step and the print might have less propensity to cleave along xy planes. But, given the complexity of that calibration (and need for a high-flow head) I'd rather use the brick infill available today.

blacksmith_tb · 2026-06-14T21:16:49 1781471809

Hmm, I wonder if a simpler room-temp alternative would be to fill a low-infill print with 2-part resin. In a way that would be a bit like casting, except you wouldn't ever remove "the mold".

notduncansmith · 2026-06-14T20:47:03 1781470023

> What’s NOT yet working:

Oh Claude~

coryrc · 2026-06-14T16:07:51 1781453271

Why do you think this is better than the old practice of filling straight holes a few layers deep?

ricardobeat · 2026-06-14T20:37:07 1781469427

Is that available in any of the standard slicers?

stirfish · 2026-06-14T20:53:23 1781470403

I think that's called z-pinning, and it might not be because of patents. I'm not sure though.

deckar01 · 2026-06-14T17:51:11 1781459471

When you say continuous interlocking U shape, are you saying it fills one channel from the top until the connected channel fills from the bottom?

gus_massa · 2026-06-10T01:23:54 1781054634

Do you have a photos of objects you build with this? A video?

mgunlogson · 2026-06-14T14:50:22 1781448622

No, unfortunately. I've printed a ton of objects but nothing clean enough to be interesting.

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

smallpipe · 2026-06-14T20:21:08 1781468468

I’m surprised you bothered writing software instead of writing some G code by hand for testing

q3k · 2026-06-14T20:50:49 1781470249

when you have claude everything looks like a software problem :)

mgunlogson · 2026-06-09T13:54:18 1781013258

Here for any questions about how it all works :).

alterom · 2026-06-14T19:32:32 1781465552

>What’s NOT yet working: the physical print

So, nothing to show.

Next.

ricardobeat · 2026-06-14T20:38:00 1781469480

This is how science works. Share your failed experiments, someone else picks it up. Eventually it may work, or not.