Thoughts on the future of 3d printing
I'm pretty bullish on 3d printing. This bullishness seems to be spreading, with recent articles in the Wall Street Journal and The Guardian proclaiming that 3d printing is finally ready to transform the world. Before expanding on this, it’s important to clarify what “3d printing” means. Technically, “3d printing” specifically refers to additive manufacturing as an alternative to traditional subtractive manufacturing methods. Traditionally, parts have been made subtractively. A manufacturer will typically buy raw materials that have been prepared into larger, standardized forms; they will then cut these (with CNC milling machines or laser cutters) into the parts for their manufactured products. In contrast, “3d printing” usually involves a material extrusion method such as fused deposition modeling where the raw material hardens in its final form. However, I’ll also be using “3d printing” as a synecdoche for a variety of methods where you bring manufacturing of parts in-house by having an automated system which manufactures physical objects from CAD designs.
First, I don't think it's fully appreciated that manufacturers are not simply an intermediary between raw materials & components and finished goods: they are also an intermediary between suppliers and vendors who are difficult to work with, and customers who expect a nice and simple purchasing experience. Just as enterprise SaaS has closed the gap between pleasant consumer software and unpleasant business software, 3d printing is trying to close the experience gap. These days, companies are more serious about closing the experience gap, partly because the traditional experience has gotten worse, and partly because the alternative (3d printing and related methods) has gotten better. Setting aside the Covid-related supply chain issues, there are longer-term issues with the traditional system, due to rising wages in China and retiring Boomers in the US.
Second, 3d printing has improved in terms of the variety of parts which can be produced with high quality and reliability. This is especially due to “network effects” among the different methods and materials. In addition to plastics, one can now do 3d printing of certain metals (eg Desktop Metal) and carbon fiber (eg Markforged). Another example is how Rack Robotics has an electrical discharge machining (EDM) system for cutting through solid metal, and their system incorporates (and can be further customized using) 3d printed plastic parts. They can also now fill in gaps in their in-house capabilities (eg low-volume custom parts where unit costs matter less) by buying from 3d printing “foundries” where you simply upload your CAD file. I've done this as a hobbyist for metal parts that my Creality Ender can't make, and it's mind-blowingly simple. Finally, the rise of the open-source hardware community (eg Printables and Thingiverse for designs, LaserWeb for generating G-code instructions from CAD designs, and numerous forums where one can ask for help) makes it so much easier to bring manufacturing in-house.
Regarding 3d printing vs machining, the bear case for 3d printing is that it's nearly reached its asymptotic limit of adoption. And here we get back to the additive versus subtractive manufacturing distinction. Strictly speaking, the PowerCore EDM system of Rack Robotics is not 3d printing, even though it uses 3d printers for its kinematics, because it is subtractive in nature. And there are some fundamental tradeoffs between additive and subtractive manufacturing. The recent article in The Guardian correctly notes that additive manufacturing has lower material costs due to the absence of wasted material. However, it has an energy cost roughly proportional to the volume of the produced part. Milling, laser cutting, and EDM approaches to machining have energy cost roughly proportional to the surface area of the produced part, while ECM has energy cost roughly proportional to the volume-removed of the produced part. (The production time varies similarly to the energy cost.) If all these approaches equalize in terms of quality and automatability, what's left are material costs and energy costs. And one can see that additive and subtractive approaches will have their respective niches.
Furthermore, 3d printing currently enjoys an automation advantage, because it has been developed more recently by innovative startups, whereas machining tool companies are behind the times. One would expect machining systems to eventually support automation equally well, and thus for this advantage to erode. There's also an interesting AI angle to automation. CNC machining requires humans to generate G-code from a CAD design, whereas 3d printers generally require only the CAD design. However, ChatGPT can already generate G-code, and I expect rapid improvements in conditionally generating G-code from CAD drawings.
Overall, I’m extremely bullish on automated, vertically-integrated manufacturing. But I think there’s nuance on the extent to which this will involve additive versus subtractive approaches.
Disclosure: I am long SHPW, DM, MKFG, and an angel investor in Rack Robotics.
April 15, 2023 update:
Further evidence of the asymptotic advantages of machining is Relativity Space’s shift from its 3d-printed Terran 1 rocket to its traditionally-manufactured (and much larger) Terran R rocket:
Since Ellis unveiled plans for Terran R two years ago, the rocket’s design has continued to evolve. But Relativity’s update on Wednesday features its most dramatic change yet, with the 3D-printing specialist incorporating an aluminum alloy into the rocket’s initial models through manufacturing “tank straight-section barrels” – a practice that is more traditionally common in aerospace.
Relativity made a name for itself with its 3D-printing approach to manufacturing rockets, building massive additive manufacturing machines. The company 3D-printed about 85% of the mass of its Terran 1 rocket, and previously planned to get that number above 90%. Ellis declined to specify what percent of Terran R will now be 3D-printed in the company’s new “hybrid manufacturing approach,” emphasizing instead that the shift is to prioritize its timeline to first launch.
“We’re using printing everywhere else strategically to really reduce the vehicle complexity,” Ellis said. “We can actually take the more simple, straight sections of the vehicle and build them traditionally and not have a huge decrement to the amount of difficulty that it is to build.”