In the medical arena, identifying the right manufacturing tools for complex product and device design is critical.
A complex silver fan part, created by direct metal laser sintering.
Technologies like 3D printing let engineers and designers combine multipart part assemblies into a few components. This can accelerate development and create a more user-centric device for both surgeon and patient. More traditional manufacturing technologies like overmolding and insert molding again accommodate complex designs while keeping the end-user—the patient—in mind. For example, 3D-printed spine cages are used in spinal surgeries can be tailored to be a perfect fit for the patient. The implants are all the same, but that perfect fit offers performance characteristics that far exceed traditionally manufactured devices.
3D printing complex components
Industrial 3D printing is uniquely suited to designing for complexity, particularly at low volumes. Depending on the specs of a part, machining suppliers will advise particularly challenging designs be built through additive manufacturing, with secondary finishing, micro-hole drilling, or laser machining to achieve the final part.
3D printing opens up new design possibilities like hollow parts and complex organic geometries, but it’s important to keep a few fundamentals in mind to take full advantage of 3D printing’s capabilities. Understanding material properties and differences between technologies, as well as design considerations like support structures and feature resolution, are crucial for success.
But 3D printing isn’t the only way to tackle part complexity. Low-volume molding has evolved to provide more than simple parts. Experts have the ability to manufacture complicated parts using side-actions and hand-loaded inserts along with multi-material processes such as overmolding and insert molding.
Overmolding and insert molding complexity
Proto Labs recently started beta testing insert molding process, says Tony Holtz, technical specialist for Proto Labs, who regularly blogs about manufacturing design for the company. “Insert molding allows you to build added strength into parts with prefabricated components,” says Holtz.
Insert molded parts, such as this knob, use threaded inserts to shore up mechanical properties.
He says that instead of a mold that produces a final part using two separate shots like overmolding, insert molding generally consists of a preformed part—usually metal—that is loaded into a mold, where it is then overmolded with plastic to create a part with improved functional or mechanical properties.
One way insert molding is leveraged is with threaded inserts, which reinforce the mechanical properties of plastic parts’ ability to be fastened together, especially over repeated assembly, Holtz explains. “Self-tapping screws work well with softer plastics, but they can become easily worn or cross-threaded.” These may fail to perform well, which results in damaged parts that need to be replaced.
Incorporating metal bushings or sleeves is similar to threaded inserts, requiring an operator to slide the threaded insert over a pin before plastic is molded. Bushings and sleeves are a great way to increase part durability for mating components that need more abrasion resistance due to moving parts.
