New 3D printer promises faster multi-material creations
Advances in 3D printing have made it easier for designers and engineers to customize projects, create physical prototypes at different scales, and produce structures that cannot be made with more traditional manufacturing techniques. But the technology still comes up against limitations – the process is slow and requires specific materials that, for the most part, have to be used one at a time.
Stanford researchers have developed a 3D printing method that promises to create prints faster, using multiple types of resin in a single object. Their design, recently published in Scientists progressis 5-10 times faster than the fastest high-resolution printing method currently available and could potentially allow researchers to use thicker resins with better mechanical and electrical properties.
“This new technology will help realize the full potential of 3D printing,” says Joseph DeSimone, Sanjiv Sam Gambhir Professor of Translational Medicine and Stanford Professor of Radiology and Chemical Engineering and corresponding author of the paper. “This will allow us to print much faster, which will help usher in a new era of digital manufacturing, as well as enabling complex, multi-material objects to be manufactured in one step.”
Control resin flow
The new design improves on a 3D printing method created by DeSimone and colleagues in 2015 called Continuous Liquid Interface Production, or CLIP. The CLIP print looks like it’s right out of a sci-fi movie – a rising platform gently pulls the seemingly fully formed object out of a thin pool of resin. The resin on the surface is hardened into the correct shape by a sequence of UV images projected across the pool, while a layer of oxygen prevents hardening at the bottom of the pool and creates a “dead zone” where the resin remains in liquid form.
Deadband is the key to CLIP’s speed. As the solid piece rises, the liquid resin is supposed to fill in behind it, allowing for continuous, smooth printing. But that doesn’t always happen, especially if the part rises too fast or the resin is particularly viscous. With this new method, called CLIP injection, or iCLIP, researchers mounted syringe pumps above the rising platform to add additional resin at key points.
“Resin flow in CLIP is a very passive process – you just pull the object up and hope that the suction can get the material where it’s needed,” says Gabriel Lipkowitz, a mechanical engineering PhD student at Stanford and senior author. On paper. “With this new technology, we are actively injecting resin into areas of the printer that need it.”
Resin is delivered through conduits that are printed simultaneously with the design. Conduits can be removed when the object is complete or they can be incorporated into the design in the same way that veins and arteries are built into our own bodies.
By injecting additional resin separately, iCLIP provides the ability to print with multiple resin types during the printing process – each new resin simply requires its own syringe. The researchers tested the printer with up to three different syringes, each filled with resin dyed a different color. They have successfully printed models of famous buildings from several countries in the color of each country’s flag, including St. Sophia’s Cathedral in the blue and yellow of the Ukrainian flag and Independence Hall in red, white and American blue. .
“The ability to make objects with varying materials or mechanical properties is the holy grail of 3D printing,” says Lipkowitz. “Applications range from highly efficient energy-absorbing structures to objects with different optical properties and advanced sensors.”
After successfully demonstrating that iCLIP has the potential to print with multiple resins, DeSimone, Lipkowitz and their colleagues are working on software to optimize the fluid delivery network design for each printed part. They want to ensure designers have precise control over the boundaries between resin types and potentially speed up the printing process even further.
“A designer shouldn’t have to understand fluid dynamics to print an object extremely quickly,” says Lipkowitz. “We’re trying to build efficient software that can take a part a designer wants to print and automatically generate not only the delivery network, but also determine flow rates to deliver different resins to achieve a multi-material goal.”