Processes: The Fundamentals of 3D Printing

Stereolithography creates solid print objects in a vat of liquid photopolymer.

Current additive fabrication processes—or 3D printing, as it is widely known—rely on one of several layering approaches.

The oldest of these, stereolithography, involves using laser light to solidify layers of a photo-sensitive liquid polymer. Once the layers of polymer have hardened, the platform is raised out of the remaining liquid to reveal the completed structure. By making automated fabrication of whole objects possible, this groundbreaking approach kicked off the 3D printing revolution in the mid-1980s.

Successive approaches have similarly involved building up layers of material. Sintering, for example, uses lasers to actually melt layers of metal, glass, or plastic into place.

Laser sintering melts layers of fine metal filings into a solid object.

A parallel suite of technologies is taking shape that may move more easily into widespread home use. Fused deposition modeling, for example, actually squirts precise layers of melted plastic, sugar, or even ice to build a freestanding structure. Another process uses a binder or glue to fuse layers of modeling powder.

While 3D printing technologies continue to spread, at present, actual high-quality printers are very expensive and available to only a small collection of organizations. However, a number of commercial “print centers” have emerged to address this gap. Services like Ponoko and Shapeways allow users to send digital models for printing. The models are printed and then shipped to the user.

Fused deposition modeling prints by depositing layers of material.

Beyond this, wildcards in this space include marginal applications taking shape for use in construction, electronic circuitry, and stem cell applications. One of these may ultimately turn out to be the true “killer app” for additive fabrication.

Overall, however, while the potential for additive fabrication is now becoming clear, new techniques will need to be introduced for the field to truly mature. Each of the existing approaches will experience marginal technical advances over the next several years. But they also each have fundamental limitations that inhibit the easy expansion of 3D printing into the creation of complex forms involving a diverse array of materials and properties — that is, into mainstream production of final products.

As they exist today, most 3D printing technologies might more readily be classified as sophisticated sculpting techniques than as mature manufacturing technologies. However, this will begin to change over the coming decade.

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