The technology has matured beyond prototyping and is ready to offer unique benefits to orthopedic device manufacturers.
At the beginning of the spring 2019 semester, we asked our students where they believe 3D printing was being used most effectively. The top answers were prototyping and hobby activities. These answers illustrated a common misconception about 3D printing—that it only has limited appeal in manufacturing. The term “rapid prototyping” is an outdated expression that doesn’t fully capture the value unlocked by 3D printing. Today, additive manufacturing is a rapidly evolving field that utilizes 3D printing to shape the entire fabrication process from an initial concept to production to a product’s end-of-life.
3D printing is considered an additive process, as a part is built one layer at a time and material is added to each layer. This is in contrast to conventional “subtractive” manufacturing methods such as machining, which removes material to create a part. This process of layer-by-layer addition can be achieved in numerous ways. Extrusion of a thermoplastic polymer filament (i.e., ABS, PEKK, or PEEK) through a nozzle is common and the most affordable way to enter the 3D printing market. Quality extrusion printers can be purchased for less than $5,000 (for options, review the companies MakerBot, Lulzbot, or Prusa).
Photopolymerization curing of acrylics can be achieved by exposing a resin bath to light and can produce parts with intricate details and smooth finish. Invisalign is a well-known manufacturer that uses this technique to produce orthodontic aligners. Entry-level photopolymerization systems can be purchased for approximately $5,000 (one company offering this type of technology is FormLabs).
Other methods can involve deposition of a curable ink or binding agent, as well as the use of lasers to sinter together a polymer or metal powder. It is exciting to note that common biomedical materials such as titanium, stainless steel, cobalt, PEEK, PLA, acrylics, and more can now be 3D printed.
The Value for Orthopedic Manufacturing
There are two features of additive manufacturing that are attractive to medical device manufacturers in order to unlock value from the process. First, the cost-per-part curve as a function of the number of parts manufactured is relatively flat (Figure 1). This enables companies only selling several thousand devices per year to keep their manufacturing costs down without the expense of machining or molding. While injection molding is currently the most cost-effective way to mass produce a large number of polymer components, the cost curve for additive manufacturing is steadily decreasing. It is expected in the next decade that additive manufacturing will rival conventional manufacturing costs at large volumes.
The second feature to unlock value is that complexity comes for free (or close to free). Traditional design for manufacturing must take into account how tooling is made (i.e., molds), the steps needed for machining, or how an assembly may fit together from individual components. These rules mostly do not apply in design for additive manufacturing (DfAM). From a part perspective, the layer-by-layer building process can easily produce complex features, such as representative trabecular networks or surface patterning. Depending upon the design, these features may improve the performance of the device and save money compared to machining (Figure 2).
By Christopher M. Yakacki, Ph.D., Samuel T. Mills and R. Dana Carpenter, Ph.D., The University of Colorado Denver | Orthopedic Design & Technology
Image Credit: Materialise