September_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 2 0 6 4 3D PRINTSHOP USING TEMPERATURE TO CONTROL DEFECTS Researchers at the U.S. Depart- ment of Energy’s (DOE) Argonne Nation- al Laboratory discovered a way to use temperature data at the time of produc- tion to predict the formation of subsur- face defects in 3D printing so they can be addressed immediately. For their research, the scientists used the extremely bright, high-pow- ered x-rays at beamline 32-ID-B at Ar- gonne’s Advanced Photon Source (APS), a DOE Office of Science User Facility. They designed an experimental rig that let them capture temperature data from a standard infrared camera viewing the printing process from above, while they simultaneously used an x-ray beam tak- ing a side-view to identify if porosity was forming below the surface. According to Noah Paulson, com- putational materials scientist, this work showed that there is in fact a correlation between surface temperature and po- rosity formation below. “Having the top and side views at the same time is really powerful. With the side view, which is what is truly unique here with the APS setup, we could see that under certain processing conditions based on differ- ent time and temperature combinations porosity forms as the laser passes over,” Paulson says. For example, they observed that thermal histories where the peak tem- perature is low and followed by a steady decline are likely to be correlated with low porosity. In contrast, thermal his- tories that start high, dip, and then lat- er increase are more likely to indicate large porosity. The ability to identify and correct defects at the time of printing would have important ramifications because it eliminates the need for costly and time-consuming inspections of each mass-produced component. energy. gov/science . ELECTRIC PULSES SHAPE PRECISE 3D-PRINTED METAL PARTS Saarland University researchers have developed a non-contact method of transforming metal parts fabricat- ed by a 3D printer into high-precision technical components. The novel meth- od combines 3D printing and electro- chemical machining (ECM) to produce precision-finished components with complex geometries and small dimen- sional tolerances. “Our nondestructive, non-contact manufacturing technology enables us to efficiently machine parts with in- tricate geometries even when made from high-strength materials,” explains Professor Dirk Bähre. The workpieces, which are bathed in a flowing electro- lyte solution, can be electrochemically machined to the required geometry working to tolerances of a few thou- sandths of a millimeter—without any mechanical contact and without im- parting any mechanical stresses to the workpiece. All the engineers need is a source of electrical power. A high elec- tric current flows between a tool (the cathode) and the conductive workpiece (the anode), which has been 3D printed. The workpiece is immersed in a con- ducting fluid (the electrolyte), an aque- ous salt solution. The electrochemical machining process causes minute par- ticles of metals to be removed from the surface of the workpiece. The metal atoms on the surface of the workpiece enter the solution as positively charged metal ions enabling the workpiece to very precisely attain the required geo- metric form. “By adjusting the duration of the current pulses and the vibration of the tool, we can remove surface ma- terial very uniformly leaving particular- ly smooth surfaces and achieving high dimensional precision,” says Bähre. uni-saarland.de . In 3D printed metallic parts, Argonne scientists found a correlation between temperatures at the surface and defects that form below. Professor Dirk Bähre, left, with Stefan Wilhelm from Saarland University, are pairing 3D printing and electrochemical machining to make intricate parts. Courtesy of Oliver Dietze. 3D PRINTING OF MICROFLUIDICS DEVICES A team from Montana State Uni- versity has developed a new method of using 3D printing to make devices for microfluidics. The researchers can 3D print directly onto glass to form thin channels, less than a millimeter wide, that contain liquid. The new process reduces manufacturing time and could allow researchers to easily produce af- fordable, customized prototypes of the devices, called microfluidics chips, in their labs. montana.edu .