When engineering mechanical systems and carrying out value-based optimization on machines, equipment and mechanical parts, the results are often parts referred to as multifunctional components. They do what the name implies, covering a variety of functions not with five or six individual components but with just one part. One benefit: join tolerances no longer have a negative effect on quality.
Another benefit with multifunctional parts: you save costs and time, an important plus when planning and organizing production because you only have to schedule in one part rather than five or six.
As a rule it is still necessary to machine finish multifunctional components. This creates burrs and sharp edges which conventional deburring processes sometimes have problems getting to. Sometimes they can’t get to them at all. For years the solution has been to deburr the components electrochemically using an external power source. The only problem with this approach is that edges and profiles change unreliably be cause of scattering during electrolysis.
The Steinbeis Transfer Centers for Process Development, Electronic Engineering, and Chemical Engineering (all based in Reutlingen) have developed a process that provides a solution to this production problem. Experts at the transfer centers used a pulsating DC power supply in combination with a passivating electrolyte solution such as sodium nitrate. This way, between each power pulse, there is enough time for a passivation layer to form on the part connected as an anode. When the power comes on again the passivation has to be broken down again. The result is a sharper profile which ultimately culminates in a precise finish on the part just where it is needed.
In developing the new process, extremely high demands were placed on the capabilities of high-performance electronics. For example, they needed pulsed voltages ranging from 5 to 40 volts, pulse frequencies up to 10kHz, negative pulses to control the dissipation of the passivation and even cancelling short circuits within individual power pulses.
The Steinbeis experts made a number of other improvements to the process by placing tool cathodes and anodes in a pressurized chamber with a controlled input and output of the electrolyte flow. The cathode made a feed motion with adaptive controlled electrolyte pressure, independent of the distance between the tool and the part being processed. The process is also suitable for complex three dimensional shapes such as deburring turbine blades or rounding of edges thereby minimizing notch effects. Any material that conducts electricity can be processed in this way, including carbides, Inconel (metal-based alloy) and conductive ceramics.
Prof. Karl Schekulin
Steinbeis Transfer Center Process Development (Reutlingen)
stz76@stw.de
Dr.-Ing. Dirk Schekulin
Steinbeis Transfer Center Electronic Engineering (Reutlingen)
Dr. Ulrich Schekulin
Steinbeis Transfer Center Chemical Engineering (Reutlingen)
stz348@stw.de