STEM DRILLING

STEM
The stem drilling process has been developed for drilling small deep holes using acid electrolytes. The electrolyte is fed through an insulated titanium tube. The tube or electrode is carefully straightened and guided into the workpiece material.

A voltage between 6 and 20 volts applied to the electrode causes anodic dissolution of the positive metal ions to take place in the gap between electrode and workpiece. This voltage is periodically reversed to prevent the building up of undissolved metal ions on the electrode tip.

The electrolyte is pumped down the tubes to return via a narrow gap between the tube insulation and the hole wall. The return electrolyte is filtered and re-circulated. Several electrodes of various size and shape may be used simultaneously. The feedrate is constant and set such that the rate of electrode advance is matches the rate of metal ion removal.

The electrolyte temperature is held constant between 20 and 25 degrees C. The electrolyte flow through the tubes is closely monitored and controlled to prevent electrode vibration and ensure efficient flow. The voltage applied to the electrode is accurately regulated.