3D printing technology holds immense promise for transforming manufacturing, particularly for smaller production runs where creating expensive molds isn’t feasible. However, traditional 3D printing methods, which build objects layer by layer, have been too slow to meet typical manufacturing timelines. Researchers at the University of Michigan have introduced a groundbreaking approach that overcomes this speed barrier, achieving speeds up to 100 times faster than conventional methods by printing complex 3D shapes from liquid resin in a single step.
For industries seeking to produce batches of under 10,000 units, 3D printing offers a compelling alternative to mold-based manufacturing, which can incur costs exceeding $10,000 just for mold creation. Yet, the prevalent layer-by-layer 3D printing techniques have struggled to meet the demands of production schedules that often require turnaround times of just one to two weeks.
Examples of 3D printed models showcasing University of Michigan's rapid volumetric printing technology.
“Using current 3D printing technologies, fulfilling such production needs would necessitate a large number of machines, making it impractical,” explains Timothy Scott, an associate professor of chemical engineering at the University of Michigan. Scott, along with Mark Burns, the T.C. Chang Professor of Engineering at U-M, spearheaded the development of this innovative 3D printing technique.
Their method employs two different light sources to precisely control the solidification of liquid resin. This dual-light control allows for the hardening of resin in intricate 3D patterns, unlike the line-by-line or layer-by-layer approaches of traditional methods. The Michigan team demonstrated this capability by creating complex structures like lattices, miniature toy boats, and even the iconic block M logo of the University of Michigan, all in a single print operation.
“This is truly one of the first real volumetric 3D printers ever invented,” states Burns, emphasizing the significance of their innovation.
This true 3D volumetric approach is not merely a demonstration of capability; it’s a necessary advancement to address limitations inherent in previous vat-printing techniques. A major challenge with earlier vat-printing methods was resin solidification on the light-transmitting window, which would halt the printing process prematurely. The University of Michigan’s solution creates a substantial zone where solidification is inhibited. This larger non-solidifying region allows for the use of thicker resins, potentially incorporating strengthening additives, to fabricate more robust and durable objects. Furthermore, this method enhances structural integrity compared to filament 3D printing, which often suffers from weak points at layer interfaces.
Close-up view of a resin sample produced with the University of Michigan's advanced 3D printer, highlighting the precision and detail achievable.
“This advancement opens the door to using much stronger, more wear-resistant materials in 3D printing,” adds Scott, highlighting the expanded material possibilities.
Previous attempts to solve the window solidification issue involved using oxygen-permeable windows. Oxygen penetration into the resin inhibits solidification near the window, creating a thin fluid film that allows the printed object to detach. However, the narrow gap created by this method, roughly the thickness of transparent tape, necessitates the use of very low-viscosity resins to ensure rapid flow into the gap as the object is lifted. This limitation restricted vat printing to small, delicate products like dental devices and shoe insoles.
It’s one of the first true 3D printers ever made.
Mark Burns, the T.C. Chang Professor of Engineering at U-M
By substituting oxygen with a second light source to prevent solidification, the University of Michigan researchers can achieve a much larger gap – several millimeters thick – between the printed object and the window. This significantly enhances resin flow rates by thousands of times.
The core of this breakthrough lies in the resin’s unique chemistry. Traditional systems rely on a single photoreaction where a photoactivator hardens the resin upon light exposure. The University of Michigan system introduces a photoinhibitor, responsive to a different light wavelength. Instead of merely controlling solidification in a 2D plane, as with current vat-printing methods, the Michigan team can utilize these two light types to selectively harden resin in virtually any 3D location near the illumination window.
Diverse shapes and forms achievable with University of Michigan's new 3D printing technology, showcasing its versatility and potential for complex designs.
The University of Michigan has filed three patent applications to protect the various innovative aspects of this technology. Scott is also in the process of launching a startup company to commercialize this rapid volumetric printing method.
Further details about this research are available in a paper published in Science Advances, titled, “Rapid, continuous additive manufacturing by volumetric polymerization inhibition patterning.” Mark Burns also holds positions as a professor of chemical engineering and biomedical engineering at the University of Michigan.
This innovative 3D printing technology from the University of Michigan promises to significantly accelerate production speeds and expand material options, potentially revolutionizing various manufacturing sectors.
