GB1578779A

GB1578779A - Spark erosion

Info

Publication number: GB1578779A
Application number: GB2590977A
Authority: GB
Original assignee: Agemaspark Holdings Ltd
Current assignee: Agemaspark Holdings Ltd
Priority date: 1978-05-25
Filing date: 1978-05-25
Publication date: 1980-11-12

Description

(54) SPARK EROSION (71) We, AGEMASPARK HOLDINGS LIMITED, of Lincoln Road, Cressex Industrial Estate, High Wycombe, Buckinghamshire, a British Company, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to spark erosion apparatus and is concerned, more particuearly, with an improvement in or modification of the apparatus and method disclosed in U.K. Patent Specificaion No. 43518/73 (now Patent No. 1,494,992).

Claim 1 of the above Patent claims spark erosion apparatus which includes means for indicating when the radio-frequency radiation of the spark is below a certain level so that one or more of the operating parameters of the apparatus may be adjusted, when the radiation is below said level, until the radiation is above said certain level indicative of satisfactory machining.

Claim 3 of the above Patent claims a method of operating a spark erosion apparatus in which one or more of the operating parameters of the apparatus are adjusted when the radio-frequency radiation of the spark is below a certain level until the radiation is above said certain level indicative of satisfactory machining.

One problem which has been encountered with such an apparatus and method is in the form of interference due to radiation from the oscillator, supplying the pulsed power current to the spark gap, both at its fundamental frequency and its har monics. This problem is enhanced when two or more machines are being operated close together, and in this case there is the further problem of confusion between the radiation from the sparks of the different machines.

In the present invention it is proposed to detect the level of the radio-frequency component of the spark by providing direct electrical connection of a radio frequency detector across the spark gap and associating with the detector a filter to reject frequencies below a certain value which may be as low as 10 MHz but is preferably 100 MHz.

In carrying the invention into effect according to one convenient mode by way of example, the accompanying drawing shows diagrammatically spark erosion apparatus which includes an electrode 11 mounted in an electrode position control device 12 and arranged to be supplied with pulses of electrical power from a supply 13 so that work may be performed upon a workpiece 14 by means of sparks drawn repeatedly between the electrode 11 and workpiece 14.

The supply 13 is provided with controls for adjusting its operating parameters such as pulse current, pulse duration and the duration between pulses, and the device 12 has a control for adjusting the rate of feed of the electrode.

Connected across the spark gap between the electrode 11 and workpiece 14 is a radio-frequency detector 15 in series with a high-pass filter 16 arranged to pass frequencies above 100 MH, although useful results can be obtained if the filter 16 passes frequencies above 10 MHz.

In this way, the detector 15 detects the level of the selected radio-frequency components of the spark and the operating parameter can be adjusted until this is at a maximum or at least above a certain level indicative of satisfactory machining.

WHAT WE CLAIM IS:- 1. Spark erosion apparatus as claimed in claim 1 of U.K. Patent No. 1,494,992, wherein a radio-frequency detector is directly electrically connected across the spark gap and a filter is associated with the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. (54) SPARK EROSION (71) We, AGEMASPARK HOLDINGS LIMITED, of Lincoln Road, Cressex Industrial Estate, High Wycombe, Buckinghamshire, a British Company, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to spark erosion apparatus and is concerned, more particuearly, with an improvement in or modification of the apparatus and method disclosed in U.K. Patent Specificaion No. 43518/73 (now Patent No. 1,494,992). Claim 1 of the above Patent claims spark erosion apparatus which includes means for indicating when the radio-frequency radiation of the spark is below a certain level so that one or more of the operating parameters of the apparatus may be adjusted, when the radiation is below said level, until the radiation is above said certain level indicative of satisfactory machining. Claim 3 of the above Patent claims a method of operating a spark erosion apparatus in which one or more of the operating parameters of the apparatus are adjusted when the radio-frequency radiation of the spark is below a certain level until the radiation is above said certain level indicative of satisfactory machining. One problem which has been encountered with such an apparatus and method is in the form of interference due to radiation from the oscillator, supplying the pulsed power current to the spark gap, both at its fundamental frequency and its har monics. This problem is enhanced when two or more machines are being operated close together, and in this case there is the further problem of confusion between the radiation from the sparks of the different machines. In the present invention it is proposed to detect the level of the radio-frequency component of the spark by providing direct electrical connection of a radio frequency detector across the spark gap and associating with the detector a filter to reject frequencies below a certain value which may be as low as 10 MHz but is preferably 100 MHz. In carrying the invention into effect according to one convenient mode by way of example, the accompanying drawing shows diagrammatically spark erosion apparatus which includes an electrode 11 mounted in an electrode position control device 12 and arranged to be supplied with pulses of electrical power from a supply 13 so that work may be performed upon a workpiece 14 by means of sparks drawn repeatedly between the electrode 11 and workpiece 14. The supply 13 is provided with controls for adjusting its operating parameters such as pulse current, pulse duration and the duration between pulses, and the device 12 has a control for adjusting the rate of feed of the electrode. Connected across the spark gap between the electrode 11 and workpiece 14 is a radio-frequency detector 15 in series with a high-pass filter 16 arranged to pass frequencies above 100 MH, although useful results can be obtained if the filter 16 passes frequencies above 10 MHz. In this way, the detector 15 detects the level of the selected radio-frequency components of the spark and the operating parameter can be adjusted until this is at a maximum or at least above a certain level indicative of satisfactory machining. WHAT WE CLAIM IS:-

1. Spark erosion apparatus as claimed in claim 1 of U.K. Patent No. 1,494,992, wherein a radio-frequency detector is directly electrically connected across the spark gap and a filter is associated with the detectol to reject frequencies below at least 10 MHz.

2. Apparatus as claimed in claim 1, wherein the filter is arranged to reject frequencies below at least 100 MHz.

3. A method of operating a spark erosion apparatus, as claimed in claim 3 of U.K.

Patent No. 1,494,992, which includes directly 'electrically connecting a radio frequency detector across the spark gap and using a filter to reject frequencies below at least 10 MHz.

4. A method as claimed in claim 3, wherein the filter is used to reject frequencies below at least 100 MHz.

5. Spark erosion apparatus substantially as described with reference to the accompanying drawing.

6. A method of operating a spark erosion apparatus, substantially as described with reference to the accompanying drawing.