PECM Techique Brings Precision to Post-Processing of Metal 3D Printed Parts

According to the “Post-Processing for Additive Manufacturing: Market Analysis and Forecast” report from Additive Manufacturing Research, metal post-processing revenues are forecasted to reach $1.4 billion by 2031. This isn’t simply because existing techniques like CNC machining are going to be increasingly refined and automated, but because newer approaches to post-processing will be developed. Among them is electrochemical machining, in which metal is removed from a part with a combination of electricity and chemistry.

Applying its own version of the technology to the 3D printing space is Voxel Innovations, whose Pulsed Electrochemical Machining (PECM) may offer unique advantages to additively manufactured (AM) parts due to the sheer precision it provides. In a recent interview, Kirk Abolafia, Technical Sales & Marketing Manager at Voxel Innovations, Inc., provided insight into the firm’s unique process and how it can apply to 3D printing.

PECM works by creating a custom tool shaped as the inverse of the desired geometry on a part. This tool is brought close to the workpiece without physical contact, maintaining a microscopic interelectrode gap. A charged electrolytic fluid is then passed through this gap, serving dual purposes: it catalyzes the electrochemical machining reaction, effectively dissolving the workpiece material in a specific geometry, and simultaneously flushes away the resultant metal hydroxides. This process, which could be described in layman’s terms as “”electricity and chemistry removing metal atom-by-atom” eliminates heat and friction, thus avoiding thermal distortion or tool vibration.

One significant advantage of PECM is the absence of tool wear, enabling higher part volumes without concerns about tool degradation.

“Because we don’t have to worry about thermal distortion or tool vibration, we can get very unique tight tolerances and thin-walled features,” Abolafia said. “The other interesting benefit of the process isthat this lack of heat or contact in the process significantly minimizes any tool wear, so we’re able to produce higher part volumes without worrying about a worn or distorted tool.”

However, the need for custom tooling presents a drawback, often resulting in a higher initial investment and making the process more suitable for high-volume productions. This limitation notwithstanding, PECM is particularly effective for complex geometries, tough materials, and large quantities.

Because PECM requires the end part to made from conductive materials, it is unsuitable for plastics and polymers. Yet, this limitation is offset by the technique’s indifference to material hardness, allowing the machining of challenging metals like nickel superalloys. This characteristic is particularly beneficial in industries where traditional machining methods struggle with material hardness or complexity.

“If the part in question is produced at lower volumes, with normal materials, geometries, and tolerances, chances are PECM may not be the most ideal process,” Abolafia explained. “It’s better for those producing parts with complex geometries, tighter tolerances, and especially high part volumes. If your job meets at least two of the three of those, PECM is more likely to be a good fit.”

Electrochemical Machining and 3D Printing

Voxel Innovations sees a potential intersection with metal AM, where PECM can smooth layer lines and improve surface quality, especially in hard-to-reach areas or for thin, downskin walls.

“The fact that we use 3D tooling unique to each project means that we can get into those hard-to-reach areas and provide better tolerances and surface quality,” Abolafia relayed. “For example, we’ve conducted similar research  with additively manufactured inconel turbine vanes. A customer 3D printed these vanes and we used PECM to simultaneously work as a secondary machining process making the blades thinner, and as a finishing process that improved the part’s surface quality, even in downskin areas.”

PECM may be increasingly relevant as AM moves toward larger batch sizes, as Voxel Innovations is able to process multiple parts or features using a single tool motion.

“PECM excels in high-volume production because we can not only form entire surfaces of a part at one time, but the process can also be paralleled to manufacture dozens of parts, or features, side-by-side in a single operation using a custom cathode. We just need to run the electrolytic fluid through all of it,” Abolafia said.

This setup is already employed in the company’s production lines, which has enabled Voxel to process millions of parts per year. While the company does not traditionally use 3D printing to create the unique tooling needed for PECM, there have been exceptions in certain research projects, such as those with the Air Force. With that in mind, it’s easy to imagine Voxel deploying AM to create tools in the future.

From Racing to Electrochemical Engineering

Voxel’s roots are intriguing, though not entirely out of the realm of the ordinary for the AM sector. The firm’s founder, Daniel Herrington, was a racecar driver in the IndyCar and Grand-Am series before going to graduate school at Duke University and working for ARPA-E at the Department of Energy. The former race car driver turned mechanical engineer saw the potential in electrochemical machining and established Voxel Innovations in 2016 in Raleigh, North Carolina.

“There aren’t really very many companies in the United States that perform electrochemical machining. The technology is a bit more established in Europe, andbecause it is a highly technical process to utilize, a lot of companies prefer a more well-known and less technically complex manufacturing process,” Abolafia explained. “But that’s changing. In the past year, we’ve almost doubled our staff and bandwidth.  Investors are helping us expand our capabilities and bandwidth to a new facility in Q2 2024, which is going to roughly quadruple our working space. PECM has an exciting future.”

Voxel Innovations is in a prime location within the Southeastern 3D printing hub of the U.S. Oerlikon, Proto Labs, Rapid Shape, Siemens, Axtra 3D, 3D Systems, Collins Aerospace, IperionX, Keselowski Advanced Manufacturing, and Formlabs, among others, have sites in the state.

As AM becomes an increasingly essential part of the country’s strategy to maintain supply chain resilience, North Carolina is primed to benefit in particular from this growth. In turn, Voxel Innovations is situated in a key location at key time in the history of manufacturing in the U.S. and will likely have a lucrative future as the AM boom takes off.