Browse Prior Art Database

Servo Control of Electric Discharge Machining Apparatus

IP.com Disclosure Number: IPCOM000076968D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Larcombe, AC: AUTHOR [+2]

Abstract

Precision screws, having a high length-to-diameter ratio, can be accurately generated without inducing mechanical or thermal stress by electric-discharge machining. Fig. 1 shows such a screw 1 positioned relative to a suitable electrode 2. The screw is formed from a workpiece blank, which is effectively rolled against the electrode during the formation of the groove. The system for ensuring that the relative positions of screw 2 and electrode 1 are accurately maintained throughout the entire machining operation is shown in Fig. 2.

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Servo Control of Electric Discharge Machining Apparatus

Precision screws, having a high length-to-diameter ratio, can be accurately generated without inducing mechanical or thermal stress by electric-discharge machining. Fig. 1 shows such a screw 1 positioned relative to a suitable electrode 2. The screw is formed from a workpiece blank, which is effectively rolled against the electrode during the formation of the groove. The system for ensuring that the relative positions of screw 2 and electrode 1 are accurately maintained throughout the entire machining operation is shown in Fig. 2.

Electrode 2 is carried by a hydraulic ram 3 and its vertical movement sensed by a linear potentiometer 4. The workpiece 1 is rotated by stepping motor 5 and the amount of rotation is sensed by rotary potentiometer 6. Initially, the workpiece is located at the lower end of electrode 2 and the two potentiometers adjusted to supply equal value inputs to sense amplifier 7. During the screw cutting operation the ram 3 moves downward, fairly rapidly at first, until the cutting starts whereafter it continues more slowly. From time-to-time the ram is automatically retracted to enable accumulated debris to clear. It is essential that the control system energizes the motor-field windings in such a way that the workpiece 1 and electrode 2 maintain the same relative positions during large and small movement, in either the forward or reverse directions.

Any movement of ram 3 immediately produces an unbalance condition at the input of sense amplifier 7. The magnitude of the unbalance condition will, of course, depend on the rate of movement of the ram 3. The sense of the unbalance condition will...