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metal_am

142 karma · joined September 14, 2021

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metal_am··on How SpaceX streamlined the Raptor engine
Beehive is 3D printing jet engines today, albeit small and potentially only going one way.
metal_am··on How SpaceX streamlined the Raptor engine
Try machining some printed 316 stainless! It’s basically pre work hardened from the thermal stresses!
metal_am··on How SpaceX streamlined the Raptor engine
Some alloys don’t like to be melted. If an alloy has a large solidification range, certain areas can partially solidify without the liquid part keeping up to fill in the gaps so to speak. This leads to solidification cracking / hot tearing. This is a simplification and only one possible cause, but there are literal books written about this kind of thing (I like Solidification by Dantzig and Rappaz). This is also why you see things like friction stir welding for rocket bodies. No melting means no solidification means no solidification issues.
metal_am··on How I use LLMs to learn complex topics
That's pretty much the Feynman technique. It absolutely works.
metal_am··on A modular impact diverting mechanism for football helmets [pdf]
MIPS is a one and done kind of thing for major impacts.
metal_am··on Gemini 3.1 Pro
I'd love to hear some examples!
metal_am··on A modern 35mm film scanner for home
Developed film has a bar code type of encoding for DX info. The talk about the whole roll is the ability to scan the entire thing in one go vs having to load in multiple strips.
metal_am··on No science, no startups: The innovation engine we're switching off
This is a very surface level analysis like saying that the automobile was just an iterative improvement over a horse. Or a computer is just a better abacus. Fundamental research is all about diving into the weeds and finding new problems to solve. It's true that some of the "low hanging fruit" no longer exists (you won't see someone like Euler or Newton who's names pop up all over the place), but I can promise you that real gains are being made on a lower level. These small gains in fundamental research snowball into bigger advancements. As an example, the transformer architecture used by LLMs was first published in 2017.
metal_am··on Figure 03, our 3rd generation humanoid robot
If you found one for that price with the controller and pendent, please send me a link. I’ve looked a lot and have not seen any UR for remotely that cheap.
metal_am··on iFixit iPhone Air teardown
Looks like spot melt laser powder bed fusion (L-PBF). Electron beam doesn’t make sense for something on a smaller scale like this; it wouldn't have the resolution. Spot melt is interesting. Renishaw is the only manufacturer I’m aware of that uses a pulsed laser vs continuous wave (and I’m not even sure if they’re still doing that for their newer machines). I would’ve guessed it would’ve been printed on a Farsoon since it’s in China. I just wish the images had scale bars to give a little more info.
metal_am··on Ask HN: What's a good 3D Printer for sub $1000?
I have both a resin and FDM printer. The FDM is hands down easier to work with than dealing with resin. FDM ABS is also a far better material than ABS-like resin. (Disclosure: I've never tried a proper industrial resin from LOCTITE or something.)
metal_am··on Ask HN: What's a good 3D Printer for sub $1000?
I've been very happy with my Qidi Q1 Pro. I paid about $350 pre-tax off Amazon almost a year ago (Black Friday). For me, it was the most machine for the lowest cost I could find. It almost fits your desired print volume (245 x 245 x 240), but it is fully enclosed and has a dedicated chamber heater. I have almost exclusively printed ABS at a 60 deg. C chamber temp. It runs open source Klipper firmware, but I'd imagine repairability wouldn't be the best. Best of all, I have not needed any calibration. It seems pretty spot on out of the box.

My Voron is hands down a better printer but also required significantly more investments in components and especially time.

metal_am··on iPhone Air
You're making me wish I still had access to a CMM. I wonder what the tolerances are on an iPhone.
metal_am··on Reverse Engineering Bambu Connect
Chamber heater is really nice for ABS
metal_am··on Inside the university AI cheating crisis
That's how grad degrees are done. But there's simply not enough time to do this at an undergrad level with potentially hundreds of students.
metal_am··on MIT Aluminum Bicycle Project 1974 (2016)
Interesting. I haven’t heard of them. Joining would still be a problem for a bike frame. Any idea on how well they work with other severe plastic deformation processes?
metal_am··on Pi Chess Board
It must be. The part about minimizing the stepper motor power consumption is nonsensical. Steppers use the same current whether moving or stationary.
metal_am··on Openpilot – Operating system for robotics
I definitely thought it was a ROS clone based on that first line.
metal_am··on Have you ever seen soldering this close? [video]
Nicest light microscope I've ever used.
metal_am··on GM electric vehicles can now access Tesla Superchargers
Where I’m located, Supercharger prices are ~4x business electric rates. That’s something like $15 profit per charge. No idea on infrastructure costs or usage though.
metal_am··on How to build a 50k ton forging press
Electromagnetic stirring is used in continuous casting for grain refinement. It’s also used sometimes in welding.
metal_am··on How to build a 50k ton forging press
Most forms of metal AM require melting, which gives solidification microstructures. There are solid state (no melting) forms of metal AM though. Look up AFSD. MELD just got (part of) a billon dollar contract from the air force for it.
metal_am··on Next gen 3D metal printing
Absolutely. Printed molds and forging dies with conformal cooling channels can decrease cycle times.
metal_am··on Next gen 3D metal printing
A line has to be drawn somewhere because this is a rabbit hole. Without going into the specifics of ASTM standards, etc., there are metal AM parts flying today in both air and space. IMO, that counts as meeting standards.
metal_am··on Next gen 3D metal printing
Texture (the statistical arrangement of all the crystal lattice arrangements that make up a metal) can play a role on mechanical properties, but current metal AM is more than able to meet material standards. It's good to be careful with blanket statements because the most accurate answer is usually "it depends."
metal_am··on Indian startup 3D prints rocket engine in 72 hours
I know for certain that defects in the powder layer can be fixed in binder jet by redoing the recoater. There has been talk in the research world about being able to fix errors in L-PBF but I’m not sure they’ve gone past the research stage. The big point is that you can know a part might be out of whatever your acceptance criteria might be.
metal_am··on Indian startup 3D prints rocket engine in 72 hours
Peregrine from Oak Ridge National Lab does exactly this. Lots of other research papers about it too.
metal_am··on Indian startup 3D prints rocket engine in 72 hours
It might sound a little wild, but a huge amount of research has been put into getting metal AM parts to be “born qualified.” L-PBF is getting to be a fairly mature technology.
metal_am··on Army soldiers not impressed with Strykers outfitted with 50-kilowatt lasers
Just because something is reflective in the visible light spectrum doesn’t mean it’s reflective for the laser’s wavelength.
metal_am··on A tiny ultrabright laser that can melt steel
Laser powder bed fusion (L-PBF) is the more standardized term. DMLS was a trademark.
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