I do quite a bit of 3d printing of functional parts and am trying to understand how this would fundamentally differ from printing at 100% infill? What type of part requirements are causing failures when something is just solid? Just curious what problem space this is targeting?
Show HN: 3D print Z reinforcement via injected loops
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Re: Show HN: 3D print Z reinforcement via injected loops
#42Interlocking 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 tempe…
Everything about that readme quote screams LLM. All it's missing is the user responding, "that doesn't make any sense, this won't work at all", and Claude responding back, "you're absolutely right".
Re: Show HN: 3D print Z reinforcement via injected loops
#43Earlier quoted context omitted.
It doesn’t have to be a large cavity in order to be useful. Imagine being able to reliably fill a hole that’s 5mm deep. Not amazing, but that could mean 25 layers. That’s 24 layers more than what we can fuse together now.
> Imagine being able to reliably fill a hole that’s 5mm deep You can’t inject filament into a hole without it cooling and solidifying at the top. That’s the problem with this whole idea.
I own a 3D pen and I use it to repair and tweak prints. Sometimes I use it to fill small cavities with material. The surrounding area usually doesn’t enjoy the heat, but PLA definitely can be injected to a degree. Maybe not to fill thin channels in the infill, but to fill a few strategically placed and shaped voids, yes.
Re: Show HN: 3D print Z reinforcement via injected loops
#44Earlier quoted context omitted.
> 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.
> 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 he…
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.
Re: Show HN: 3D print Z reinforcement via injected loops
#45Interlocking 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 tempe…
The filament is injected into tiny triangular U shaped channels, about twice as wide as the filament diameter. The depth of the channels is configurable and you can go as shallow as ~4mm. If you inject at a high rate that's not nearly enough time for the filament to cool off.
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.
Re: Show HN: 3D print Z reinforcement via injected loops
#46Interlocking 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 tempe…
So I'm pretty skeptical about this as well (see my other comment on this), but the particular failure mode you're discussing is not what's happening in reality. > 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 y…
> 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.
Yes exactly. And it may be a solved problem.
I need someone with a dual nozzle printer to try injecting something like PLA in a CF-Nylon part. I anticipated this and added support for dual nozzle and multi-material with a different material selectible for the injected channels. But be warned, it hasn't been tested it at all.
Re: Show HN: 3D print Z reinforcement via injected loops
#47Earlier quoted context omitted.
So I'm pretty skeptical about this as well (see my other comment on this), but the particular failure mode you're discussing is not what's happening in reality. > 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 y…
> 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 filament will cool on contact with the part. Think about it: How are you expecting this filament to stay…
The injection probably happens faster than you think. With a high flow hot-end and 5mm deep channels its reasonable for the injection to complete in less than a second.
> How are you expecting this filament to stay as hot as the inside of your nozzle while it’s flowing through the part and touching all of those walls? How are you expecting the walls to not melt, but the melted filament to flow through them?
Specially formulated injection materials with viscosity near water at injection temps. Dual nozzle setups where PLA is injected near its breakdown temperature into a heat resistant shell like CF-Nylon or Ultem. I need people with more time and hardware to test this. This was a side project for me, out of a dozen I'm working on. And I already spent a bunch of time on it.
For a years there's been talk about doing some kind of 3D injection on the GCODE level, like Z-pinning https://github.com/OrcaSlicer/OrcaSlicer/discussions/4815 . But it was hard to experiment because slicers don't support it. Now there's a codebase with dozens of different knobs to play with.
I added support for dual nozzle printers and using a different material for the injection stage. I just don't have the hardware to test it
Re: Show HN: 3D print Z reinforcement via injected loops
#48Interlocking 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 tempe…
Everything about that readme quote screams LLM. All it's missing is the user responding, "that doesn't make any sense, this won't work at all", and Claude responding back, "you're absolutely right".
The post was from a week ago. Must have been refreshed by the algo (or admins) for more visibility. Originally never got any comments.
Have you looked at the code or tried the binaries? I can assure you it very much exists as described.
Maybe I should have spent more time on the docs. I had LLM write some of the settings pages and other boring stuff.
Re: Show HN: 3D print Z reinforcement via injected loops
#49Interlocking 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 tempe…
It doesn’t have to be a large cavity in order to be useful. Imagine being able to reliably fill a hole that’s 5mm deep. Not amazing, but that could mean 25 layers. That’s 24 layers more than what we can fuse together now.
It's more than that.
I added a SAT solver to refine the tube endpoints so that nearby tubes don't start or end on the same layers. Even the default greedy solver (CP-SAT is SLOW) does a pretty good job at "staggering" the tube ends.
The part is "knitted" together in 3D at different Z layers.
Try the binaries. They've only been tested in Linux but they build fine for all platforms.
Slice something with MAGMA infill turned on and flip off the visibility of everything but injection lines. You'll see how the U shaped tubes knit the part together
Re: Show HN: 3D print Z reinforcement via injected loops
#50Earlier quoted context omitted.
It doesn’t have to be a large cavity in order to be useful. Imagine being able to reliably fill a hole that’s 5mm deep. Not amazing, but that could mean 25 layers. That’s 24 layers more than what we can fuse together now.
> Imagine being able to reliably fill a hole that’s 5mm deep You can’t inject filament into a hole without it cooling and solidifying at the top. That’s the problem with this whole idea.
I did some basic calculations on isotropic heat loss in a circular tube. I don't have the knowledge to model it in detail but I don't think this is correct.
You can set tube height to something tiny like 5mm. It takes a fraction of a second to fill that.
As someone who's printed a lot, on fast printers you have to set a minimum layer time because it takes up to 20 seconds for the layer below to solidify, cool to below the glass transition. Plastic is a bad conductor so heat loss through the walls probably isn't as bad as you'd think