초록 ▼

To drill small holes in a metal component having a non-conductive, e.g. ceramic, surface layer apparatus is provided capable of carrying out both ultrasonic and EDM drilling operations without dismounting the component. The drilling operation commences with an ultrasonic drilling phase and change ov

To drill small holes in a metal component having a non-conductive, e.g. ceramic, surface layer apparatus is provided capable of carrying out both ultrasonic and EDM drilling operations without dismounting the component. The drilling operation commences with an ultrasonic drilling phase and change over to essentially EDM operation when breakthrough of the ceramic surface layer is detected. Breakthrough is detected by applying a low voltage pulse signal to a drilling electrode and sensing when current starts to flow between the electrode and the workpiece. When a multiplicity of holes are drilled simultaneously the changeover to EDM is triggered by breakthrough of the first electrode but may be delayed to permit the remaining electrodes to breakthrough.

대표청구항 ▼

An apparatus electro discharge machining a small hole in an electricall conductive workpiece having a substantially non-conductive surface, comprising EDM electrode means the position of which relative to the workpiece is adjustable to form a machining gap, dielectric supply means for supplying diel

An apparatus electro discharge machining a small hole in an electricall conductive workpiece having a substantially non-conductive surface, comprising EDM electrode means the position of which relative to the workpiece is adjustable to form a machining gap, dielectric supply means for supplying dielectric fluid into the region of the machining gap, power supply means connected in use between the electrode means and the workpiece and arranged when operative to produce machining pulses for electro-discharge machining through the conductive workpiece, ultrasonic means for imparting to the electrode means ultrasonic vibrartions in an axial direction for ultrasonically machining through the non-conductive layer, control means for sequencing the ultrasonic and EDM maching operations in separate phases, and detection means responsive to establishment of electrical continuity between the EDM electrode means and the conductive substrate to commence the electro-discharge machining phase of the conductive workpiece after breakthrough of the non-conductive layer is detected in the ultrasonic machining phase.