Technology suitable for small quantity production
ECF is a new technique to machine hard materials and other electrochemically active materials. The tool movements are similar to conventional milling machines. Nevertheless ECF is an electrochemical process, hence both workpiece and tool are submerged in an electrolyte and held at a constant potential to prevent corrosion. Short voltage pulses in the range of 10ns to 100ns are applied between tool and workpiece. With these pulses the electrochemical doublelayer capacitance on the surface of the workpiece is charged over the resistance of the electrolyte. Because the resistance increases with respect to the distance between tool and workpiece the time constant of the charging also changes. Since charging takes place only during the time of the pulse, the double-layer is sufficiently charged to generate an anodic dissolution of the workpiece only in a defined working distance around the tool. Surface areas further away from the tool are not affected by the ECF process. This leads to a confined milling with a high spatial resolution. Furthermore the working distance is proportional to the applied pulse width. Thus the working distance and hence the spatial resolution of the process can be varied between 10µm to 5µm and below just by adjusting the pulse width.
ECF is a pure electrochemical process, i.e. ion transport from the workpiece into the electrolyte takes place, and due to this, no remelting of the surface of the workpiece or other conversion occurs. Furthermore virtually no forces act on the tool. Thus tools with diameter down to 5µm and below and with arbitrary shapes - like grooving cutters, rounded cutters or ball cutters - can be used. The milling strategies are similar to that of conventional milling, although the tool in the ECF process does not rotate. This allows production of 3D structures and freeform surfaces. Cutting speed is achieved of about 1µm/s in stainless steel 1.4301.
| ECF Data Sheet | |
|---|---|
| Mould Materials | Stainless Steel |
| Cutting tool | 5 – 50 µm home made from tungsten |
| Machine | 3 axis, own development |
| Removal rate | about 1000 µm3/s |
| Machining of channels & ribs | |
| Minimum width | 10 µm (Literature: <200 nm) |
| Aspect ratio | about 10 with a 20 µm tool |
| Accuracy | 2 µm, no burr |
| Minimum distance between channels | <2 µm |
| Minimum distance between ribs | 10 µm |
| Machining of holes | |
| Minimum diameter | 10 µm |
| Aspect ratio | 10 |
| Accuracy | 2 µm, no burr |
| Minimum distance between holes | <2 µm |
| Is possible 3D freeform surface? | Yes |