Electrochemical Machining & Metal 3D Printing Yield Micrometer Dimensional Tolerances

New research is emerging from Saarbrücken, Germany as Professor Dirk Bähre and his team at Saarland University work to improve 3D printing with metal. Combining electrochemical machining (ECM) with metal fabrication, their new method allows for many of the benefits of 3D printing to come together at once, with the ability to make complex geometries that may not have been possible before using conventional techniques. Strong, lightweight parts can be constructed with accuracy, “precision-finish,” and dimensional tolerances measuring at just a few thousandths of a millimeter.

Professor Dirk Bähre

While automotive companies and organizations like NASA have been enjoying the advantages of 3D printing for years—mainly with rapid prototyping in the beginning—today metal additive manufacturing processes are used to make many different, highly functional parts. More importantly though, these parts can be heavily customized to meet the needs of industrial users. Precision is key in designing and producing parts that may be responsible for auto, aircraft, or rocket performance—and in many cases, there are many different parts, most of which are specialized in terms of specific applications.

“Tolerances can be down in the micrometer range,” says Professor Dirk Bähre.

In this current research, the scientists—experienced in both precision machining and finishing—set out to improve metal fabrication further, and especially in regard to dimensional tolerances. Hoping to print parts that are even more complex, and more precise, they decided to combine electrochemical machining for improvement, using metal alloys such as aluminum, titanium, or steel.

“Our technology for post-processing additively manufactured metal parts offers a cost-effective means of producing high-precision functional surfaces for applications where extremely tight tolerances are crucial. It enables large numbers of parts to be post-processed efficiently and economically,” explained Bähre. “Our non-destructive, non-contact manufacturing technology enables us to efficiently machine parts with intricate geometries even when made from high-strength materials,”

Precision machining is a specialty of the Saarbrücken manufacturing technicians led by Professor Dirk Bähre (left, here with the technical assistant Stefan Wilhelm from his research group). Using innovative processes, they form components made of heavy-duty metals with a precision of a thousandth of a millimeter by combining 3D printing and electrochemical removal. (Photo credit: © Oliver Dietze)

Only an electrical connection is necessary for production as the 3D printed parts are bathed in an electrolyte solution and then machined to the proper specifications. No mechanical contact is required, and no mechanical stress is placed on the part. Any metal particles are eliminated during this phase.

“By adjusting the duration of the current pulses and the vibration of the tool, we can remove surface material very uniformly leaving particularly smooth surfaces and achieving high dimensional precision,’ says Bähre.

(Photo credit: © Oliver Dietze)

The performed numerous experiments, along with “rigorously examining” every step involved in the novel technique:

“Optimizing post-processing requires a thorough understanding of both the material and the process. We need to know, for example, exactly what happened to the metal during the preceding 3D printing stage. That’s why we carefully study the microstructure of the metal produced in the 3D printing process. By meticulously examining both process technology and material behavior, we can improve and optimize the electrochemical methods in order to obtain even smoother surfaces or more complex geometries at even higher levels of precision,” Bähre said. “We examine in detail how the different material and process parameters interact and then determine how the overall production process should be configured.”

While Dirk Bähre and his research team also work with numerous business and industry-related partners, some of their projects are also funded by the European Regional Development Fund.

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