Additive manufacturing in medical technology – manufacturing methods and rapid prototyping

Have you decided on 3D printing, but aren't sure which process is right for your application? In the following blog post, we'll explore the common processes and ask ourselves which application areas they are best suited for. Let's first clarify: What exactly is additive manufacturing, and why is it so hyped?

Additive Manufacturing & Rapid Prototyping

Additive manufacturing, also known as 3D printing, revolutionizes the production of components and products by applying material layer by layer instead of established, often machining-based manufacturing methods. This innovation enables the production of complex geometries and customized products with high precision, negligible time expenditure, and minimal material waste.

Rapid prototyping is a key application area of additive manufacturing. It involves the rapid production of prototypes to evaluate design, form, and functionality in early development stages. By using advanced processes such as fused deposition modeling (FDM), stereolithography (SLA), selective laser sintering (SLS), and selective laser melting (SLM), engineers can create, test, and iterate physical models in a very short time.

Additive manufacturing opens up entirely new possibilities, especially in medical technology – from patient-specific implants to optimally adapted surgical instruments. These technologies not only promote innovation but also accelerate development cycles and reduce costs, while simultaneously enhancing customization options.

Which additive manufacturing methods are used in medical technology?

1. Fused Deposition Modeling (FDM)

Fused Deposition Modeling (FDM) is an additive manufacturing process widely used in the consumer sector.

A thermoplastic filament wire is extruded through a nozzle heated to 200 to 300 °C. The material is applied layer by layer to a build platform, where it quickly cools and hardens.

By repeatedly applying these layers, the desired object is created (see Fig. 1-A). This technique is particularly popular due to its ease of use and the quick commissioning of a new 3D printer. The large and easily scalable print volume compared to SLA printers is also a particular advantage.

Devices from the manufacturers “Bambu Lab” or “Prusa3D” are widely used because they offer very high speed, an excellent print image directly from the factory, a low failure rate and high dimensional accuracy of the printed parts.

Since the consumer market in particular is saturated with a multitude of cheap offers – especially from China – not all manufacturers are able to shine with these qualities, which damages the reputation of FDM printing in the professional environment.

Thanks to rapid advances in recent years, it's increasingly possible to tackle most prototyping tasks with an affordable system (approximately €2,000). Multi-filament systems are also increasingly entering the market, which can also significantly reduce the disadvantages of support structures through the use of specially developed plastic types.

Likewise, different types of plastic can be combined, such as PLA and PETG, as they do not stick to each other and thus leave a smoother surface than with support structures made of the same material.

2. Stereolithography (SLA)

In this process, a liquid photopolymer resin is selectively cured using a UV laser or UV LEDs. Unlike FDM production, the print platform moves from above into a tank containing the corresponding photopolymer and is raised by one layer height for each curing process.

Curing then takes place at the interface between the tank floor and the print bed or workpiece. This layer is then raised by one layer height, and the process is repeated. Typically, layer heights of at least 0.02 mm to 0.05 mm are used, resulting in high resolution and low visibility of individual layers.

After the printing process, the object must be freed of any support structure and cleaned with ethanol to remove any remaining resin residue. This is followed by a final curing step under a UV light source. Only after this process is the object ready for use and can it come into contact with skin, as most polymer resins can cause skin irritation in their liquid, uncured state.

3. SLS & SLM

The basic processing between selective laser sintering and selective laser melting (SLS and SLM) is related and differs mainly in the choice of material (polymer powder or metal powder), the processing temperature and the associated energy required.

Both processes use a laser to selectively fuse the powder onto a powder bed. The main difference lies in the intensity of the laser energy: While SLS heats the polymer powder just above its melting point, thus sintering the particles, SLM completely melts the metal powder, creating dense, homogeneous metal parts. After each layer, a roller moves over the powder bed and applies a new layer of powder.

Both technologies enable the production of complex geometries without additional support structures and offer high precision and flexibility.

What is rapid prototyping?

Rapid prototyping refers to the rapid production of prototypes, including through additive manufacturing technologies. It enables designers and engineers to quickly and cost-effectively create and test physical models of their designs. This significantly accelerates the development process, as iterative design changes and functional testing can be performed early on. Subsystems can also be tested, which can further reduce iteration time.

In medical technology, rapid prototyping in combination with additive manufacturing plays a particularly fundamental role: It enables the creation of patient-specific models for preoperative planning as well as the generation of individual implants and tailor-made prostheses and orthoses as well as specifically adapted surgical instruments based on case-specific diagnostic data.

These customized solutions not only improve the precision and efficiency of surgical procedures, but also significantly increase patient comfort and quality of life, while simultaneously reducing manufacturing costs as well as production and delivery times.

These new manufacturing techniques also make completely new approaches possible, such as a splint that stabilizes the arm after a fracture and at the same time allows more light and air to reach the skin than the classic plaster cast.

By using plastic instead of the usual plaster, the splint is also water-resistant and thus does not compromise the wearer's hygiene. It is also lighter and can be easily removed for examinations and reused afterwards. Such a splint can be generated quickly and easily using a 3D scanner, a mobile phone with an integrated lidar sensor, or even photogrammetry. Production is then best achieved using the SLS process to ensure consistent force absorption.

So, that's it for now. I hope you were able to gain a good overview of the different processes and choose the right method for your prototyping project. In the second blog post, I'll build on this and explain what to consider when choosing materials and the associated regulations. We'll also briefly look at bio-3D printing. Follow us on social media or subscribe to our newsletter so you don't miss the second part!