GB2270645A

GB2270645A - Electrode alignment

Info

Publication number: GB2270645A
Application number: GB9220001A
Authority: GB
Inventors: Colin George Radnedge
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1992-09-22
Filing date: 1992-09-22
Publication date: 1994-03-23
Also published as: GB9220001D0

Abstract

A row of worn electrodischarge drilling electrodes 10 held in a holder 14 and guide member 12 is reset by abutting the guide member against a fixed stop 16 located over a reference surface 18. The electrodes are moved by means of the holder down through the guide member so that the ends of the electrodes contact the reference surface, and are clamped in a pair of jaws 20. The holder is disengaged from the electrodes and then moved away from the reference surface, to be re-engaging onto the electrodes in its original position relative to the reference surface. The jaws 20 are unclamped from the electrodes, and the electrodes, holder and guide member are removed from the reference surface. <IMAGE>

Description

IMPROVEMENTS IN ELECTRODISCRARGE MACHINING This invention concerns improvements in electrodischarge machining, and in particular to a method of advancing electrodes in a holder and guide arrangement of an electrochemical drilling machine.

It is a requirement in high performance gas turbine engines for use in aircraft that at least some of the blades and vanes in the engine must be provided with apertures in edges or surfaces, the apertures communicating with hollow interiors of the blades, so that under high temperature operating conditions cooling air may be ejected through the apertures over the operating surfaces of the blades.

The apertures are generally of small dimensions and must be very accurately located and drilled in order to provide effective cooling. One way of providing the required degree of accuracy is by the well known process of electrochemical drilling. In this process a row of flexible electrodes is held in a predetermined configuration and presented to the work piece that is to be drilled. During the drilling operation the electrodes are subject to wear, not necessarily evenly along the row, so that on the next occasion of use there may be an insufficient electrode length available to one or more electrodes for drilling to be carried out effectively.

It would therefore be necessary to reset the electrodes in their holder before further use. Hitherto, this resetting operation has been carried out by hand, a procedure that is time-consuming, requires a high degree of dexterity and skill, and is labour intensive.

It is an object of the present invention to provide a method of automatically resetting electrodes in an electrodischarge machine (which may be referred to hereinafter as "EDM") after use at a work station.

In general, the invention concerns a method of resetting a row of electrodes in an electrodischarge machine by advancing the row a predetermined distance in a holder and guide member of the machine and abutting the electrodes against a reference surface so as to provide a required length of electrode extending beyond the guide member.

According to the present invention there is provided, in an electrodischarge machine comprising an apparatus consisting of an electrode holder, an electrode guide member and a row of electrodes held in the holder and passing through guide channels in the guide member, a method of resetting the electrodes after use of the apparatus at a work station, the method comprising the steps of, (a) moving the apparatus from the work station to a gauging station which includes a reference surface and a fixed stop member located over the reference surface, (b) causing the guide member to abut against the fixed stop member so as to locate the holder in a first position with respect to the guide member, (c) moving the holder in the direction of the guide member to a second position with respect to the guide member so that the ends of the electrodes abut the reference surface, (d) clamping the electrodes so as to render them immovable with respect to the reference surface, (e) disengaging the holder from the electrodes, (f) returning the holder to the first position, (g) causing the holder to re-engage and hold the electrodes, (h) unclamping the electrodes, and (i) returning the apparatus from the gauging station to the work station.

The invention will now be described by way of example only with reference to the accompanying diagrammatic non-scale drawings in which Figures 1-9 show schematically successive stages in a method for setting a row of electrodes in a holder and guide system.

The method of the invention will now be described with reference to Figures 1-9.

In Figure 1 there is shown in side view a row of EDM electrodes 10 gripped by a holder 14 and passing at its lower end through a free-running guide 12. After use, the lower ends of the electrodes 10 are found to be worn away and an insufficient length of each electrode projects beyond the guide 12 for the net usage to be effective. Furthermore, it may be found that electrode wear is uneven, so the next set of holes will not be drilled to the required depths.

In Figure 2 the electrode assembly is shown moved from its work station to a gauging unit which comprises a fixed stop 16, a reference base 18, and a pair of movable jaws 20. The reference base 18 may be flat, or it may be contoured to match a required profile of the row of electrodes. The assembly is located on the gauging unit so that the guide 12 abuts the fixed stop 16.

In Figure 3 the EDM electrodes 10 are shown moved downwards (arrow 4) through the guide 12 by moving the holder 14 towards the guide so that the bottom end of the electrodes passes between the jaws 90, and the ends of the electrodes contact the reference base 18. The reference base 18 may be planar, or it may have a predefined contour so as to suit the requirements of the work piece to be drilled by the electrode assembly 10. A required length of each electrode now projects beyond the guide so that the electrodes may be used effectively in the next drilling operation.

In Figure 4 the end portion of the row of electrodes 10 is shown clamped by the jaws 20 (arrows 5) so that the row of electrodes is immobilised.

In Figure 5 the holder 14 is shown disengaged (arrows 6) from the row of electrodes 10.

In Figure 6 the holder 14 is shown moved upwards through a predetermined distance (arrow 7) so as to re-establish the original spacing between the holder and the guide 12.

In Figure 7 the holder 14 is shown re-engaging the electrodes (arrows 8).

In Figure 8 the jaws 20 are shown disengaged from the electrodes (arrows 9).

In Figure 9 the electrode assembly is shown removed from the gauging unit and returned to the work station for further use.

Claims

1. In an electrdischarge machine comprising an apparatus consisting of an electrode holder, an electrode guide member and a row of electrodes held in the holder and passing through guide channels in the guide member, a method of resetting the electrodes after use of the apparatus at a work station, the method comprising the steps of, (a) moving the apparatus from the work station to a gauging station which includes a reference surface and a fixed stop member located over the reference surface, (b) causing the guide member to abut against the fixed stop member so as to locate the holder in a first position with respect to the guide member, (c) moving the holder in the direction of the guide member to a second position with respect to the guide member so that the ends of the electrodes abut the reference surface, (d) clamping the electrodes so as to render them immovable with respect to the reference surface, (e) disengaging the holder from the electrodes, (f) returning the holder to the first position, (g) causing the holder to re-engage and hold the electrodes, (h) unclamping the electrodes, and (i) returning the apparatus from the gauging station to the work station.

2. A method of resetting a row of electrodischarge machine electrodes substantially as hereinbefore described with reference to the accompanying drawings.