Whether engines for vehicles or airplanes and rockets: such technical constructions consist of a multitude of highly specialized metal components. To ensure that everything fits together exactly and can withstand even the toughest loads, each individual part must be perfectly formed. "The tolerances required can be in the micrometer range," explains Professor Dirk Bähre from Saarland University. With 3D printing processes for metals, it is possible today to produce rather complex components. But what comes out of the printer layer by layer in additive manufacturing is often not sufficiently accurate to meet the highest demands. For some geometries, the 3D printing process simply reaches its limits.
Dirk Bähre and his team are researching how to refine the workpieces from the 3D printer so that they fit exactly to the thousandth of a millimeter. "With our technologies for finishing metal parts manufactured using additives, we can cost-effectively produce precision functional surfaces for high-precision applications. Even high volumes can be produced economically," he explains. The basis for this high accuracy is provided by novel processes in which the researchers combine metallic 3D printing with electrochemical ablation.
Electrochemical ablation allows even the most complicated geometries to be implemented in the hardest metal. "This is a damage-free, non-contact manufacturing technology that enables us to efficiently process complex components and high-strength materials," explains Bähre. The materials, washed away by an electrolyte solution, assume the desired geometry down to the thousandth of a millimetre. Machining takes place without any mechanical effects on the material. All the engineers need is an electric current: This flows between a cathode and the material to be processed as the anode from the 3D printer. Tiny metal particles are washed away by the electrically conductive liquid consisting of water and salt: the metal ions are released from the workpiece and the high-precision desired component is created. "Through current pulses and vibrations of the tool, we achieve a particularly even removal with very smooth surfaces and high precision," explains Bähre.
The researchers took a close look at the metals that are used, such as aluminium, titanium or steel alloys, and also at each individual process step, because a deep understanding of the material and process is necessary to optimise the finishing process. "For example, we have to understand exactly what happens to the metal during the preceding 3D printing process. That's why we are investigating what microstructure is created in the process. By researching processes and material behavior, we can use this as a basis for further developing electrochemical methods to obtain smooth surfaces or complex geometries with high precision," says Bähre.
Toward this end, the researchers produce parts in a 3D printer in numerous experiments and investigate how the appropriate electrochemical processing must be carried out. "We look closely at the interaction of the various parameters and determine how the manufacturing process is ideally put together," explains the engineer. For example, the sequence in which the process steps are carried out can be decisive. They systematically subdivide all influences, make highly precise measurements and detailed analyses. As a result of this research, the production engineers have many levers with which they can tailor their processes and adjust the process settings in a targeted manner.
More information: https://www.lft.uni-saarland.de/en/home.html