Many 3D printing technologies involve the use of lasers to produce both metal and plastic parts. If you’re familiar with additive manufacturing, you’re probably at least somewhat familiar with the most common laser-based 3D printing processes. In the case of stereolithography (SLA), a laser is used to cure, or harden, liquid resin material into a solid part. In selective laser sintering (SLS) and selective laser melting (SLM), the laser sinters or melts powder into a solid part. Pretty cool, yes – but laser 3D printing processes still have their limits.
In the case of powder-based 3D printing, a mirror is used to deflect a single laser, allowing the laser to hit different areas of the powder bed. The fact that only one laser is used, however, limits the speed that parts can be printed – it’s as if the parts are being drawn, and that’s going to take some time. But researchers at the University of Sheffield have developed a new process that’s less like drawing, and more like painting with several large brushes at one time.
The process, called Diode Area Melting (DAM), uses an array of laser diodes to melt several large parallel areas of powder at one time. The lasers can be carefully controlled and switched on and off as they move across the powder bed, making the process not only faster but more energy efficient.
“Our research challenges the long held belief in the industry that low power diode modules cannot achieve sufficient melting due to their low power and poor beam quality,” said Dr. Kristian Groom of the university’s Department of Electronic and Electrical Engineering. “Key to the success of the DAM process was a move to shorter wavelength laser arrays (808nm) where increased absorption of the individually collimated and focussed beams allowed melting points in excess of 1400℃ to be reached within a few milliseconds, enabling production of fully dense stainless steel 17-4 parts.”
The wavelength of the laser used in a typical SLM process, by contrast, is 1064nm. Dr. Groom and fellow inventor Dr. Kamran Mumtaz of the Department of Mechanical Engineering plan to further develop their research, scaling the new system up and eventually extending it to polymer 3D printing as well as metal. They think it might even be possible to use the process to 3D print a wide variety of materials in a single machine. Their research so far has been documented in a paper entitled “Laser diode area melting for high speed additive manufacturing of metallic components,” which you can access here.
“The current limitations of AM of metals systems (i.e. high purchase costs, high energy consumption and slow production time) may be overcome through the adoption of a diode laser module melting source,” the researchers conclude. “Previously, the use of low power diode bars for melting common SLM materials would be easily dismissed as being unable to provide the required energy density to melt these materials. This work has shown that this energy density challenge can be overcome and presents a first step in developing a novel and efficient high speed metallic additive manufacturing process.”
Additional authors of the paper include Miguel Zavala-Arredondo, Nicholas Boone, Jon Willmott, David T. D. Childs, and Pavlo Ivanov. The research was supported by proof of concept funding from an Engineering and Physical Sciences Research Council (EPSRC) allocated impact acceleration grant (IIKE). Discuss in the Diode Area Melting forum at 3DPB.com.