3D Printing is Really About Design

A quick survey of headlines of the past 18 months indicates an inflection point in the hype cycle surrounding an undeniable exciting technology: additive manufacturing. The mythical consumer 3D printing market failed to prove profitable as demonstrated by closing and floundering product lines and desktop FDM machines, while useful for many, continue to be plagued by basic engineering problems. We are at an important point in the development of this family of technologies and now that the noise around 3D printing has died down a bit, we have an opportunity to reflect on what can be learned from both the successes and failures of the past several years.

At the heart of it, I believe that there has been a fundamental misunderstanding of the technology, largely propagated by the media and by some of the first startups attempting to make consumer 3D printers. This hinges on a misunderstanding of where the value of the machine comes from. I see 3D printers as perfect machine metaphors for exploring the source of value and impact in designed objects: unstructured commodity material enters the machine and something of value exits the machine. Ultimately, a 3D printer is only as valuable as the things that it makes. And the things that a 3D printer makes are only as valuable as their design process was thoughtful.

In this post, the first of a series, I’d like to explore a perspective on additive manufacturing grounded in design rather than by novelty of applications (ie, the first 3D printed [X]), and discuss what I see as some of the biggest challenges (and opportunities) in the field.

Where does value in 3D printed things come from? An intensive/extensive framework.

An additively manufactured (AM) object’s or product’s first order value is derived from the intensive properties of its constituent material (ie, PLA, Nylon, PEEK, Ti-Al6-V4, etc) and its structure (extensive properties). Approaching an object with this framework, we can begin to develop a first order taxonomy of value in goods produced with additive. Intensive properties are driven by materials science and extensive properties are driven by design. Unlike much of materials science, design is something that can be iterated upon rapidly because geometry is something easily rendered in software, making iterative simulation/optimization workflows the logical next step.

An object could be plotted against its intensive and extensive properties.

But design requires some unpacking because it is more complex than just the ruthless, quantitative optimization of form. In creating an object that solves a problem, a designer is integrating a huge amount of both quantitative (will it break? will it fit? how stiff is it?) and qualitative (will it bring joy? does it feel good in the hand?) information. As we will discuss below, this qualitative aspect of design for 3D printing is hugely under-appreciated and under-developed, but is arguably where some of the biggest potential for AM lies. With this in mind, we can extend the initial intensive/extensive framework to include a qualitative/quantitative space.

A more comprehensive framework adds a qualitative dimension to intensive and extensive properties and in doing so makes more clear the quantitative aspects of each.

Of course, only a fraction of products that we use on a daily basis are composed of a single material, but this class of mono-material products will become more and more relevant as AM actually becomes more economical and useful for manufacturing.

Multimaterial versus Mesostructure: Re-imagining Materiality

Different materials for different functions in a conventional insole (US patent US20130000146)

Traditionally, designers have navigated the intensive-extensive dimension of product design by selecting materials for the various intensive properties that might be required to satisfy performance requirements (say loading cycles, impact energy dissipation, deflection) and then refining the form that that material will take before selecting a strategy for joining it with other pieces of material that have undergone the same treatment. What’s interesting here is that in this model, we rely on intensive, bulk material properties to dictate many product architecture and manufacturing decisions. This is not necessarily a problem given how wide the selection of intensive material properties is compared to the complexity of extensive form that we have been able to achieve to date, but there is an expansive opportunity in the extensive space.

Textile engineering long ago recognized this performance duality and capitalized on it. Fibers types are selected largely for intensive properties (though at a finer scale, extensive ones as well) and are then hierarchically structured into advanced materials with incredibly diverse properties. Made with the same base cotton fiber, a knit and a weave will have very different tensile and drape properties. Likewise, if the base fiber is changed, the behavior of both structures changes. Most importantly, different high-level performance goals (drape, hand, weight, toughness) can be achieved by effectively navigating the intensive-extensive space — multiple combinations of base material and structure can deliver the same functional outcome.

What’s exciting about AM is that this underlying principle can be applied much more broadly, trading intensive complexity for extensive complexity, material for mesostructure, which is often cheaper and simpler (more on this in later posts) due to the fact that a single process can be used to realize a target outcome. Products like shoes are typically made up of a wide variety of synthetic materials permanently bonded with adhesives that make recycling challenging if not impossible. If a shoe were instead made from hierarchically-structured TPU that delivered the same performance, there may be new opportunities for closing material-product loops, allowing a shoe to be recycled in its entirety.

Mesostructured swatch demonstrating a degree of flexibility not typically possible in the bulk material (PLA).

While there’s a lot of excitement around the multimaterial space, it is at a certain level grounded in an old-fashioned way of thinking. Multimateriality and material gradients will ultimately have niche applications (likely in bioprinting/regenerative medicine and surgical planning models), but I see far more potential for leveraging the intensive/extensive duality to achieve target performance outcomes with simpler manufacturing processes.

Not Just Lightweighting: The Art of Finding the Right Shape

The potential for AM is not exclusively to be realized from quantitative performance gains. One of the things that I am most excited about is the potential for AM to solve problems that aren’t best-solved with mass-manufacturing. Last year, I outlined this potential during a talk at Digifabcon: while there is a huge amount of excitement about distributed manufacturing, but little talk about about how what actually gets made in a distributed fashion will get designed, nor of the challenge of distributed QA (one machine making 10,000 parts is one thing, 10,000 machines each making one part is something else entirely).

There are hundred of thousands of problems around the world that fall into the category of “having the right shape in the right material in the right place at the right time”. The question of what the right shape (ie, what part) is highly contextual. In rural Tanzania it might be a neonatal aspirator. In a small auto repair shop in Illinois, it might be a wire harness clip. In a clinic in Haiti, it might be a properly proportioned prosthetic limb. However, in each of these cases, the problem can be solved if we can design the right shape for the available materials.

In order for distributed manufacturing to be truly impactful, it needs to be coupled to a system for distributed design. The humanitarian potential of the technology is of particular interest as there are clear economic incentives for the keepers of spare part CAD data to make it available to distributed manufacturing centers while there are often more market failures in the humanitarian space.

However, serious barriers stand in the way of the longer term utopian design democracy, the largest of which are that design is a scarce skillset and that design tools impede open collaboration.

The current tradeoffs between design tools, datatypes, one-way file format conversion, and the scarcity of design skills makes it very difficult to realize democratized design.

What we mean by the very word “design” and how people will design local solutions to local problems will evolve rapidly over the coming years. Teaching the world Solidworks and Inventor is not going to work (though I am very optimistic about the current generation of TinkerCAD-educated kids advancing through the education system). Design is going to be made more accessible through simple, but powerful tools that are scoped to specific applications.

At LimbForge, we are building one such tool for the rapid configuration and manufacturing of 3D printed prosthetics by local clinicians. Tools like the software that we are building for prosthetics are going to be critical for the democratization of design that is necessary to truly capitalize on democratized manufacturing.

Up Next: Systems-Level Value

The ways in which 3D printing or AM will ultimately realize value are diverse and nuanced. Design is at the heart of how value can be created with 3D printing, but there are other important dynamics at play. In the next post in this series, we’ll explore upstream implications of 3D printing in labor efficiency, supply chain, and product design.