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3D Printed Shoes, Food, Homes & More - What to Know

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Meet the Expert: Robert MacCurdy PhD

Robert MacCurdy

Dr. Robert MacCurdy is an assistant professor of mechanical engineering at the University of Colorado Boulder, where he leads the Matter Assembly Computation Lab (MACLab). He is developing new algorithms, materials, and fabrication tools to automatically design and manufacture electromechanical systems, focusing on robotics.

Dr. MacCurdy did his PhD work with Hod Lipson at Cornell University and his postdoctoral work at MIT with Daniela Rus. He holds a BA in physics from Ithaca College, a BS in electrical engineering from Cornell University, and an MS and PhD in mechanical engineering from Cornell University.

The History of 3D Printing

While 3D printing technology may seem like a recent development, its origins can actually be traced back to the 1980s when Chuck Hull invented stereolithography (SLA). This process involved using UV light to solidify liquid plastic layer by layer, creating a three-dimensional object. However, it wasn’t until the early 2000s that 3D printing became more widely accessible and affordable due to advancements in materials and printing techniques.

“In the early days, it was single material, and the materials that you could fabricate with were not engineering materials,” explains Dr. MacCurdy. “We could use the method to make models representative of objects that we would then fabricate via other means. It was often referred to as rapid prototyping because it was a way of making models very quickly.”

However, despite its usefulness, early 3D printing technology encountered several limitations that hindered its broader application. The materials available during this initial phase were predominantly non-durable and lacked the mechanical properties necessary for creating functional, end-use parts. This restricted the technology primarily to prototyping, limiting its application in manufacturing.

Additionally, the resolution of early 3D printers was often insufficient for producing finely detailed objects, making them unsuitable for applications needing precision and complex geometries. The printers were costly and required significant technical expertise to operate, limiting their accessibility to larger companies with the necessary budgets and skilled personnel. As a result, while early 3D printing offered exciting possibilities, its impact was constrained by these technological and material limitations.

Since then, significant developments in 3D printing technology have occurred, including new methods such as selective laser sintering (SLS), fused deposition modeling (FDM), and digital light processing (DLP). These techniques allow for the use of various materials, including metals, plastics, and even food items. “The major revolution and evolution of 3D printing in the last 10 to 15 years has been the discovery of new materials suitable for end-use applications. Now you can directly fabricate the object, which will then be used rather than fabricating a non-functional prototype,” explains Dr. MacCurdy.

Current Applications for 3D Printing

3D printing has transcended its initial use as a prototyping tool, evolving into a versatile technology with various applications across various industries. Today, it creates consumer products, medical devices, architectural models, automotive parts, and even aerospace components. “Now, we are printing functional end products. Whether that functional end product is a piece of synthetic meat, an occupiable structure from concrete, or robot components,” says Dr. MacCurdy.

Here are some of the current applications for 3D printing.

  • Automotive: The automotive industry has been using 3D printing for prototyping and manufacturing parts such as engine components, exhaust systems, and even entire cars. “We can fabricate structures that wouldn’t be feasible via existing fabrication means or would be too expensive because of the number of fabrication steps,” he says.
  • Heat exchangers: 3D printing has also been used to create heat exchangers, which are crucial for many industrial processes. Due to their complex design, these devices are typically challenging and costly to produce using traditional methods. However, with 3D printing, manufacturers can easily fabricate intricate geometries without needing expensive molds or tooling. “They are cheaper to manufacture this way because fewer individual components need to be fabricated and then assembled manually,” notes Dr. MacCurdy.
  • Food: 3D printing technology creates customized chocolates, candies, and even entire meals. By using a paste made from ingredients such as chocolate or dough, 3D printers can produce intricate designs, making it possible to create unique and personalized food items. “It hasn’t seen a lot of commercial impact, but it’s really interesting from the perspective of being able to bring together different materials in a way that is very precisely controlled geometrically. You can print fun things like a logo or even a name directly inside a cake,” he says.
  • Shoes: “All the major shoe manufacturers are embracing additive manufacturing, not just as a way to preview their latest design, but as a way of making higher performing and individually customized footbeds and entire shoes,” explains Dr. MacCurdy. Now, shoe companies can scan a foot and create a unique sole for that person. This has tremendous performance-enhancing applications, particularly for elite athletes.
  • Cycling: 3D printing has been used to create helmets and bicycle seats in cycling: “Some manufacturers are selling bicycle seats that are entirely 3D printed. My understanding is that they’re using the Carbon 3D printer and materials that use the CLIP process, which is a version of vat photopolymerization,” he notes.
  • Dentistry: One of the most significant impacts of 3D printing can be seen in dentistry, where it is used for creating dental implants and aligners. “Invisalign dental aligners are not directly 3D printed, but the mold representing your teeth is 3D printed. There’s also an increasing interest in the dental industry in using 3D printing to make a final end-use part such as a dental prosthetic,” says Dr. MacCurdy.
  • Surgical planning: 3D printing has been used for pre-surgical planning, particularly in complex or unique cases. With the help of 3D printed models, surgeons can better visualize and plan surgeries, leading to more precise and successful outcomes. “The idea is to print a structure representing the patient’s unique anatomy, making it easier for the patient and the surgeon to understand the interior structure,” he says.
  • Housing: The construction industry is also exploring 3D printing for creating homes and buildings. With the ability to print in various materials, including concrete, companies are developing large-scale 3D printers that can create entire houses in hours.

Advances in Materials Used for 3D Printing

Traditionally, most 3D printing applications have relied on single-material usage, often limiting the functionality and durability of the printed items. This conventional approach was primarily due to the technological constraints of early 3D printers, which could not handle the complexity of simultaneously processing multiple materials. However, a significant shift towards multi-material 3D printing is on the horizon. The development of multi-material capabilities is expected to revolutionize the industry, creating intricate structures that integrate diverse materials within a single print.

“It’s one thing to make a 3D printed bracket that’s all the same material and has a lot of intelligence in the design. It’s another thing entirely to make, an entire aircraft seat with one manufacturing process that would potentially involve many dissimilar materials,” posits MacCurdy. “I’m not forecasting that we will be making entire seats, ever. It could be that there are lots of good reasons not to do that, but in the quest to make higher-performing objects cheaper, multimaterial integration will be inevitable.”

The quest to develop multi-material manufacturing processes also involves discovering how to use new materials in 3D printing. “The range of materials available via additive manufacturing has expanded in the last 15 years,” notes Dr. MacCurdy. “We’ve expanded the range into powder versions of engineering thermoplastics and metals. That allows for fabrication via laser melting or laser sintering to create end products that are mostly bulk plastic or almost fully solid metal. The final product is either a titanium alloy, steel alloy, or similar that has all the properties of metal rather than plastic so that you can use them for higher temperature or force applications.”

New Desing Tools for 3D Printing

With new materials and processes, new tools and software are needed to manage them. “We need design tools that allow us to leverage multi-material fabrication capabilities,” notes D. MacCurdy. “My lab is designing tools. These new software developments will allow designers to specify what material goes where in a multi-material design and use multi-material 3D printing tools to fabricate that design.” While these new tools are still in development, they show much promise.

He continues, “We’ve been making our software tools as flexible as possible to be relatively agnostic of 3D printing modality. So, our latest design tool can leverage multi-material inkjet and multi-material extrusion. Multi-material 3D vat-photopolymerization is still a research curiosity that’s coming, along with multi-material powder bed fusion.”

Current design tools for 3D printing think within predefined boundaries, focusing primarily on an object’s exterior or surface shape rather than considering the internal structure’s potential. “Our traditional design tools model an object by describing its surface. If you have a cube, you think about the six faces of the cube. And that’s called a boundary representation. Virtually all of our CAD tools use boundary surface representations. Those boundary representations do not describe what is inside the boundary. They just described the boundary,” explains Dr. MacCurdy.

“That was fine when we were making everything from machining materials because everything inside would be the same material as the outside. With multi-material added manufacturing, we can fabricate precise interior microstructures with wildly dissimilar materials, but we don’t have a good way of describing those designs, so my software tools are designed to do just that.”

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