I recently submitted a book manuscript to MIT Press trying to give an intelligent layperson an overview of 3D printing and additive manufacturing. I learned a lot in a short time, so here are 5 surprising things to consider.
1) There are many technologies bundled into an oversimplified metaphorUnlike your text printer, 3D printers do not usually spit out objects that are fully formed and immediately ready to use. Post-processing can be delicate, extensive, and complex, and it took me quite a while to appreciate just how much may need to be done after printing. In metal builds especially, management of thermal history (how much and how fast things heat up and cool down) to prevent physical distortion often involves the use of support structures that much be properly designed up front and carefully machined off after the build has cooled down. These support structures also constitute waste that gives lie to the stereotype of “printed” net-shape parts. In addition, heat-treating, polishing, milling, and other operations typically need to be performed.
In addition to the familiar filament-based melting of plastic in consumer-grade machines like the Makerbot, there are powder-bed metal and plastic systems where laser or electron beams melt or almost-melt (sinter) powder that is laid down in precise, thin layers as the build plate drops between passes of the beam. In contrast, direct metal deposition uses a jet of metal powder melted with a laser and deposited in free-standing shapes: a major advantage over powder-bed systems is the ability to repair worn or broken metal parts. Binder jetting, meanwhile, uses an adhesive to hold together sand (for casting), metal, or other powders before various forms of post-processing finish the job. Finally, light-sensitive polymers can be cured into precise, smooth shapes: this technology is now used to make almost all hearing aids worldwide.
2) Lots of skill is requiredOne reason household 3D printers have not become ubiquitous is because CAD files are tricky to generate and work with. At the industrial level, here are some of the skills required to make additive manufacturing work:
- Mechanical engineering, to ensure the part is strong and light enough for its job
- Metallurgy and/or polymer chemistry: Materials science is evolving rapidly
- Big data analytics: an unexceptional build can generate a terabyte of data
- Industrial engineering: where do additive manufacturing processes fit into existing workflows? How are workplace safety considerations addressed? Just as an example, aluminum powder is highly pyrophoric, nor do you want workers breathing it.
- Solid-state physics: much is still being learned about the evolution of microstructures in printed materials
- Supply-chain management: if fabrication can be moved closer to end demand, where are facilities, raw materials, and parts located and moved?
- Optics: Lasers can be shaped and their power adjusted with effects on the build’s speed and quality
- Computer science: CAD is translated into another form (historically STL format) and that in turn is translated into the code that drives the machine (often G-code). The transformation of CT or MRI scans into biomedical printed objects is more complex still.
- Legal and regulatory: How do parts get certified by the FAA, FDA, or other body? How are IP concerns addressed: copyright, patent, and trade secrets all have their place.
- Shopfloor: Machine operators have much to do with the success of a build, from advising on orientation of the build through knowing the subtleties of post-processing.
4) Emerging uses are exciting but a long way off3D-printed buildings, foods, and organs get media attention, and for good reason. If autonomous cars reduce deaths among young healthy adults, for example, where will organ donations come from? These emerging applications are a long way off: building codes do not get rewritten quickly, and until we have 30 years of history on, say, 3D-printed concrete or polyurethane, the codes won’t change very much, banks won’t lend money, and zoning authorities won’t issue permits. Food currently takes far too long for anyone to be interested in production volumes; some restaurants solve the problem by letting you watch your dessert being printed during the rest of your dinner. Finally, while tissues (skin most notably) are being printed, organs require capillaries that are too small in scale for current bio printing to resolve.
5) Business cases need to be madeBroadly speaking, there are a few known areas where 3D printing can be economically advantageous. First, remote locations badly served by conventional supply chains: think of the wrench printed on the International Space Station, or of an aircraft carrier. Second, custom items. These can be dental crowns and other appliances (Invisalign braces), hearing aids, and prostheses, whether orthotics or artificial limbs. Wheelchairs may be coming soon. Custom bikes and ski boots made using 3D printing are available to passionate, wealthy sports enthusiasts. Third, short production runs (whether for spare parts, prototypes, or custom variations) make sense on paper. Finally, mass production works where there is performance pressure (aircraft parts) that makes conventional manufacturing impossible. Here’s the most famous example.
Taken together, these surprises point to several limiting factors. First, prices will need to come down, whether for powders or machines. Second, the business cases for mass customization are such a challenge to conventional manufacturing economics that very few have been successfully commercialized. This challenge is as much cultural as it is technical. Third, the skills and freshness of perspective required at all junctures — CAD, R & D, finance, workflow design, marketing, shop floor experts — are to some extent a matter of demographics, of getting a critical mass of people whose definition of “impossible” has been recalibrated. Once talent, economies of scale, regulatory familiarity and approval, and materials science breakthroughs to identify heretofore impractical polymers, alloys, and composites converge, 3D printing will help revolutionize and in fact define the 21st-century factory.
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