GB814202A - Improvements in or relating to the simultaneous spark machining of a plurality of workpieces - Google Patents

Abstract

814,202. Making turbine blades; drilling by spark erosion. BIRMINGHAM SMALL ARMS CO. Ltd. April 18, 1957 [April 18, 1956], No. 11738/56. Classes 83 (2) and 83 (4). A method of drilling by spark erosion a plurality of holes a-f in a plurality of workpieces 10, particularly turbine blades, comprises mounting the workpieces in predetermined positions one at each of a number of spaced stations A-F, drilling one hole in each workpiece simultaneously by parallel electrodes -12 and then successively interchanging the workpieces between stations and repeating the simultaneous operation drilling until each workpiece has been drilled with the desired number of holes. Gas turbine blades 10 to be drilled with parallel or non-parallel holes a-f are each adjustably mounted in a holder 28, Figs. 3-5 (not shown) which is then clamped in a fixture 43, Figs. 6, 7 (not shown) secured at each of the drilling stations A-F on a rotatable worktable 11. The location of each blade at each station thus corresponds with the vertical hole to be drilled at that station. The parallel electrodes 12, Fig. 2, are carried by a pair of support rings 22 mounted on a bar 20 slidable in a vertical slot 21 in a plate 16 on which is mounted a pair of rings 15 with insulated guide bushes 18 for the electrodes. Interrupted direct current is fed to the spark gap which may be maintained constant by a servomotor, alternatively the electrodes may be individually counterpoised whereby they are urged towards the workpieces which, together with their fixtures and the work-table 11, are vibrated vertically through a small amplitude.