An Excellent Notion of Erosion

Steinbeis experts develop measurement-based process for grinding profiles using spark erosion

No matter how complex technical units, machines, or devices are, they always share the same core function: They convert physical processes into hands-on items that can be used. To do this, they have surfaces with active properties and kinematic effects – so what could be more natural than to make components as efficient as possible and give them multi-functional features that are also economical. This can be made possible by combining several active surfaces within a single workpiece, typically produced in a non-cutting high-precision process. Prof. Karl Schekulin of the Reutlingen-based Steinbeis Transfer Center for Process Development has now developed a profile grinding technique based on measurement-controlled spark erosion.

Merging different components into a single part offers a number of important benefits. Not only does it make it easier to organize production, there are fewer or perhaps no longer any surfaces requiring joining and this can significantly improve functional performance. The ideal candidates for producing precise parts without cutting or machining are tried-and-tested manufacturing processes such as investment casting, die casting, fine casting, fine forging, and sintering. To increase the degree of molding, semi-hot processes can be used followed by cold calibration to improve accuracy.

The challenges of finishing

Despite these manufacturing options, depending on accuracy requirements it is inevitable that some degree of post-process machining or subtractive finishing will still be required. One big problem comes with hard-to-reach areas and undercuts, which make it impossible to machine the active surfaces of a multifunctional part at will due to processing parameters. In such cases, the favored option is to use conventional drilling, turning, milling, or grinding, but often this is also not possible due to workpiece complexity.

The solution: spark erosion grinding

This was the underlying motivation for Karl Schekulin to start working on a solution to this problem and develop a process called measurement-controlled spark erosion form grinding. His process involves using a three- or five-axis spark erosion machine, with one axis programmed to act as the main axis for oscillating the electrode. Explaining the technology, Schekulin says, “Actually the erosion process is quite simple: You specify the grinding depth, for example based on a certain target measurement, and the electrode senses the starting point and keeps taking readings until it determines the required machining result.” If reworking is required to compensate for electrode wear, this can be carried out automatically.

Compared to CNC machining, the spark erosion process is extremely slow. This can, however, be compensated for by arranging workpieces and electrodes in multiples, thus making it possible to use the procedure economically in mass production. To test whether the new process could be suitable for production, Schekulin converted a commercially available spark erosion machine and equipped it with additional moving axes. His machine is currently undergoing testing at the Steinbeis Transfer Center for Process Development in Reutlingen with the aim of determining process parameters for industrial application.

Contact

Prof. Karl Schekulin | Director
Steinbeis Transfer Center Process Development (Reutlingen)
www.steinbeis-transferzentren.de/