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3D Printing

From Prototype to Production

3D Printing

Apr 2023
Additive Manufacturing

3D printing (also known as Additive Manufacturing) has been around since the 1980s. You’re probably familiar with it from prototyping (or from printing parts for fun), but in the last 10 years 3D printing has emerged as a large-scale production technology. It offers not only unprecedented customization, but also the ability to design complex geometries that are impossible to achieve with conventional manufacturing techniques.

Some products are 3D printed directly, and others rely on the technology to execute vital stages in the production process. In this edition of Scan of the Month, we explore cutting-edge examples of both. With dental aligners and investment-casted knee implants, 3D printing serves as an intermediate tool. For a lattice-padded hockey helmet and metal cooling plate, additive manufacturing is responsible for the final result itself.

CT scanning provides the perfect companion technology to 3D printing. 3D printing turns a digital file into a physical object, while industrial CT takes the opposite route to transform atoms to bits. Let the journey begin.

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Dental aligners

SOTM, 2023

Nothing captures 3D printing’s indispensability as an intermediate process while also demonstrating its capacity to scale better than dental aligners and nightguards. 3D printing has made it possible to customize aligners according to each patient's unique dentition, resulting in improved comfort, reduced treatment times, and better overall outcomes. An industrial CT scanner fits seamlessly into this workflow, providing accuracy and detail that a surface scanner just can’t match.

We gave the process a try in our workshop with a patient recruited from a nearby desk. The first step was taking a physical impression by having our patient bite into a tray filled with alginate. This impression created a dentition mold that we could scan to produce a model of his teeth.

Instead of using a traditional surface scanner, we popped the impression tray into our Lumafield Neptune industrial CT scanner to generate an intricate 3D digital representation of the teeth that captured not only obvious external features, but also details that were obscured by overhangs on the mold.

We converted the scan to a mesh STL file and then inverted it to get an accurate model of our patient's teeth. If we were making aligners, we’d adjust them at this point in specialized dental software.

After that, we sent our inverted STL file to a stereolithography (SLA) 3D printer and printed a physical model of our patient's teeth.

Next, we used a vacuum former to heat a thin sheet of dental-grade thermoplastic material until it became pliable. We lowered the heated sheet over the 3D printed model, flipped the vacuum switch on, and applied suction to shape the plastic around its contours. Once the plastic cooled and hardened, it retained the shape of the model, creating a custom-fit nightguard.

We then carefully trimmed and polished our formed nightguard to remove excess material and achieve a comfortable fit. It’s now ready to wear during sleep to protect our patient's teeth from grinding or clenching.
Learn more about the workflow

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Hockey helmet

Bauer, 2023

To fabricate each MyBauer RE-AKT hockey helmet, Bauer scans a player's head and generates a customized lattice structure that can be 3D printed. This personalized approach ensures optimal safety, since the most protective helmet is the one that fits best—reducing negative space between a player’s head and their helmet and moving around least during gameplay. Through "mass customization," Bauer combines the strengths of both conventional and additive manufacturing, integrating bespoke 3D printing with the efficiency and cost-effectiveness of traditional production methods.

Slicing into this helmet, we get a look at the FreeForm Adjustment system, a feature of Bauer’s entire helmet collection. It consists of two pieces of interlocking plastic shell, offering a comfortable and secure fit by adjusting independently front-to-back and side-to-side. A spring-loaded occipital pad in the back adapts to the player's head, allowing for modification as needed.

The Digital Foam inserts, produced by a 3D printing process known as Selective Laser Sintering (SLS), offer enhanced airflow and cooling properties compared to traditional helmet pads. Here we can see how the exterior shell vents allow air to flow into the varying, hexagonal lattice structure of the Digital Foam. This design enables greater breathability by effectively dissipating both heat and moisture.

The lattice struts are strategically designed, with thinner struts closer to the head for comfort and fit, and thicker struts near the helmet shell for effective impact absorption. 3D printing gives designers the flexibility to specify the performance of the pad everywhere on the volume while fitting it to the specific contours of each player's head, providing a secure fit that minimizes movement and maximizes protection.
More on CT for 3D printed parts

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Knee implant

Intrepid Automation, 2022

This knee implant is not 3D printed, but 3D printing plays an essential role in its fabrication process. Medical technology companies are transforming knee replacement surgery by designing and manufacturing patient-specific knee implants. These personalized implants, adapted to each patient's unique anatomy, offer a better fit, enhanced functionality, and reduced recovery time compared to traditional off-the-shelf options.

Intrepid Automation uses Digital Light Processing (DLP) 3D printing to create customized patterns for investment casting, guaranteeing accuracy and precision while cutting down on production times. By combining a closed-loop print process from specialized software with a wax-like resin, DLP produces complex patterns that meet the orthopedic needs of individual patients.

Our CT scan shows that the casting pattern is nearly hollow, with a sparse internal lattice and thin walls that will collapse easily when the pattern is heated. This results in a cleaner burnout and reduced chances of casting defects.

The pattern is coated, or “invested,” in a liquid ceramic slurry that hardens into a heat-resistant shell. The shell is heated in a programmable oven, melting the pattern out and leaving a cavity in the shape of the pattern.

Molten metal is then poured into the mold’s void. In this implant, cobalt-chromium alloy is used.

At the end, the sacrificial ceramic mold is broken away and the metal casting is finished by machining and polishing.
More on CT for 3D printed parts

Intro image for the scan.

Cold plate

Puntozero, 2022

This lightweight heat sink keeps the high-voltage traction inverter of an electric racecar cool. Puntozero used nTopology design software to develop lattices that imitate biological structures to increase surface area and optimize coolant flow. 3D printing puts these almost impossibly intricate structures within reach, giving designers the freedom to create a part that is truly optimal, without worrying about the limitations of traditional molding or machining methods.

This cold plate was crafted using a metal 3D printing process called Direct Metal Laser Sintering (DMLS), which uses a high-powered laser to selectively fuse aluminum alloy powder layer-by-layer. The design draws inspiration from shark scales, employing directional lamellar geometry to guide fluid flow and maximize heat transfer within the cold plate. Slicing into the part allows us to assess this complex internal geometry and see that the intended structural integrity was achieved.

CT can also be used to check that the heat sink channel is free from unfused powder and that the manufacturing process turned out a clean, obstruction-free coolant flow path. For a part like this, post-processing steps such as depowdering, ultrasonic cleaning, and post-machining are critical. Removing residual powder ensures unimpeded heat transfer and keeps the cold plate operating at top performance.
More on CT for 3D printed parts

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