Electrochemical machining tool assembly

Abstract

In an electrochemical machining tool assembly having at least one electrode arranged across a gap from a workpiece, the electrode being energized by application of a potential difference ΔV between the electrode and the workpiece, a method of monitoring machining includes exciting at least one ultrasonic sensor to direct an ultrasonic wave toward a surface of the electrode and receiving a reflected ultrasonic wave from the surface of the electrode using the ultrasonic sensor. The reflected ultrasonic wave includes a number of reflected waves from the surface of the electrode and from a surface of the workpiece. The method further includes delaying the excitation of the ultrasonic sensor a dwell time Td after a reduction of the potential difference ΔV across the electrode and the workpiece occurs.

Description

BACKGROUND [0001] The invention relates generally to electrochemical machining and, more particularly, to monitoring interelectrode gap size and workpiece thickness during electrochemical machining operations. [0002] Electrochemical machining (ECM) is a commonly used method of machining electrically conductive workpieces with one or more electrically conductive tools. During machining, a tool is located relative to the workpiece, such that a gap is defined therebetween. The gap is filled with a pressurized, flowing, aqueous electrolyte, such as a sodium nitrate aqueous solution. A direct current electrical potential is established between the tool and the workpiece to cause controlled deplating of the electrically conductive workpiece. The deplating action takes place in an electrolytic cell formed by the negatively charged electrode (cathode) and the positively charged workpiece (anode) separated by the flowing electrolyte. The deplated material is removed from the gap by the flowi...

AI Technical Summary

Benefits of technology

This approach enables reliable in-situ monitoring of gap size and workpiece thickness without compromising ECM machining quality, improving process control and reducing the need for costly adjustments by ensuring accurate and clean ultrasonic measurements.

Problems solved by technology

Too small a gap, such as less than 100 micrometers in a standard ECM operation, could lead to arcing or short-circuiting between the tool and the workpiece.

Too large a gap could lead to excessive gap variation, as well as reduction in the machining rate.

Lack of suitable means for sensing gap size or workpiece thickness may hinder ECM accuracy control.

Without such means, many rounds of costly trial-and-error experiments must be run to obtain the gap size changes that occur during the machining process.

Variation and inaccuracy in tool feed rate and tool positioning can also contribute to changes in gap size and workpiece thickness.

However, during conventional ECM operations with a continuous DC voltage, gas bubbles are constantly generated at the cathode, which significantly attenuate the ultrasonic signal propagation through the electrolyte when the ECM voltage exceeds a certain level.

However, adjusting the ECM voltage could potentially compromise ECM machining quality.

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