# US 4,394,558 A · EDM Method of machining workpieces with a controlled crater configuration

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 4,394,558 A
- Document ID: US4394558A
- Status: Granted
- Kind: A
- Application number: 06/253,287
- Filed: 1981-04-13
- Granted: 1983-07-19
- Earliest claimed: 1980-04-15
- Assignees: Inoue-Japax Research Incorporated
- Inventors: Kiyoshi Inoue
- Web page: https://patentgrep.com/patent/US4394558A

## CPC

- B23H 1/00: Electrical discharge machining, i.e. removing metal with a series of rapidly recurring electrical discharges between an electrode and a workpiece in the presence of a fluid dielectric
- B23H 9/008: {Surface roughening or texturing}
- B23H: WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL (processes for the electrolytic or electrophoretic production of coatings, electroforming, or apparatus therefor C25D; processes for the electrolytic removal of material from objects C25F; manufacturing printed circuits using precipitation techniques to apply the conductive material to form the desired conductive pattern H05K3/18)

## Abstract

An EDM method wherein the surface roughness of the machined workpiece is reduced or the ratio of the removal rate to the surface roughness is increased by controlling at least one of the rate of flow of the liquid machining medium through the discharge gap and the rate of relative displacement between the tool electrode and the workpiece along the machining interface so that each individual discharge crater on the workpiece surface becomes elliptical in shape and has its major axis at least two times greater than its minor axis.

## Claims

### Claim 1

A method of machining an electrically conductive workpiece with a tool electrode juxtaposed therewith across a machining gap flooded with a liquid machining medium,
wherein a succession of time-spaced electrical pulses are passed through said gap to produce between the opposed surfaces of the tool electrode and the workpiece discrete electroerosive discharges each of which results in the formation of a discharge crater on a localized spot on the workpiece surface and the consequential localized stock removal therefrom and which, with such discharge craters formed successively and randomly throughout the workpiece surface opposed to the tool electrode surface, cumulatively remove stock from the workpiece while the tool electrode is moved relative to the workpiece along a predetermined path to advance stock removal in the workpiece;
wherein the liquid machining medium may be forced to flow through said machining gap; and
wherein the tool electrode may be displaced relative to the workpiece, independently of but simultaneously with the aforesaid relative displacement therebetween,
said method comprising: reducing the surface roughness of said machined workpiece by increasing at least one of the rate of said flow of the liquid machining medium through said gap and the rate of the second-mentioned relative displacement between the tool electrode and the workpiece to such an extent that each of said discharge craters becomes elliptical in shape and has its major axis at least two times greater than its minor axis.

### Claim 2 (depends on 1)

The method defined in claim 1 wherein said liquid machining medium is a water liquid having a specific resistivity of 10.sup.3 to 10.sup.5 ohm-cm.

### Claim 3 (depends on 1)

The method defined in claim 1 wherein the surface roughness is reduced by increasing said rate of flow of said liquid machining medium inversely as a function of the duration of said electroerosive discharge pulses.

### Claim 4 (depends on 1, 2, 3)

The method defined in claim 1, claim 2 or claim 3, further comprising facilitating the increase in said rate of flow of said liquid machining medium by imparting small mechanical vibrations to said tool electrode.

### Claim 5 (depends on 4)

The method defined in claim 4 wherein said mechanical vibrations are of a frequency between 1 kHz and 10 MHz.

### Claim 6 (depends on 1)

The method defined in claim 1 wherein the surface roughness is reduced by increasing said rate of relative displacement between said tool electrode and said workpiece inversely as a function of the duration of said electroerosive discharge pulses.

### Claim 7 (depends on 1, 6)

The method defined in claim 1 or 6 wherein said relative displacement is effected by rotating said tool electrode.

### Claim 8 (depends on 1, 6)

The method defined in claim 1 or claim 6 wherein said relative displacement is effected by vibrating said tool electrode in a direction transverse to the direction in which said tool electrode and said workpiece are opposed to one another.