In Figure 8 it can clearly be seen that depending on the adjustable polishing head gap and the potential difference the average area roughness Sa lies within the range of 0.049–0.180 µm. Furthermore the average area roughness decreases with increasing potential difference. It indicates that the process is more stable with increasing voltage. Additionally, it can be seen that with increasing potential difference the width of the adjustable polishing head gap has no significant influence on the average surface roughness. Sa achieves a range between 0.065 µm and 0.090 µm.