GB933731A - Improvements relating to the electrolytic removal of metal - Google Patents

Abstract

933,731. Electrolytic removal of metal. ROLLS-ROYCE Ltd. Jan. 24, 1962 [Jan. 31, 1961], No. 3714/61. Class 41. A cathodic tool for electrolytically removing metal from an anodic workpiece comprises a bundle of abutting or adjacent open-ended metallic tubes through at least some of which electrolyte is passed towards the workpiece. Electrolyte may be withdrawn through others of the tubes or through the spaces between the tubes or need not be withdrawn through the tool at all. Fig. 4 shows a tool 27 comprising tubes 22 having their upper ends cast into a layer 27<SP>1</SP> of alloy. Each tube has an outer insulating layer. To ensure that the boundary surfaces of a cavity are not uneven, due to the action of the separate tubes, relative motion may be imparted to the workpiece and tool, or, as shown in Fig. 8, the tubes may be surrounded by two layers 56, 57 of insulated metallic ribbon. The current density on the cutting face of the layers 56, 57 may be made variable to counteract a tendency to cut slower at the tool edge. Fig. 13 shows a tool 80 with a face 83 shaped by offsetting the ends of tubes 81 from each other. Fig. 7 shows apparatus for moving a workpiece 34 while a tool 33 is advanced towards the work. The work is mounted on a table 35 movable in the direction 38 over a sub-table 37 which itself is movable in direction 42 over slides 41 on a machine top 43. Motion is imparted from a rotating arm 53 via a rod 46 which is jointed to the arm at 51, spring loaded at 55 to contact an annular former plate 44, and jointed to the machine top 43 at 47 and to the table 35 at 48. Tapering cavities, e.g. frusto-conical, can be formed by apparatus similar to that shown in Fig. 7 (Fig. 9, not shown) which varies the amplitude of oscillation of the workpiece as the tool advances. To vary the amplitude, a ring similar to the ring 44 is raised and lowered by a cam plate operated through a servo link to the tool 33. By appropriate formation of the cam plate and former plate it is possible to produce different tapers on different sides of a cavity. Two tools may be used in forming a cavity as shown in Fig. 14 and the second tool could be used to form an undercut. Fig. 15 shows a tool 90 which is advanced towards a workpiece 93 by a motor 109. The tool-workpiece gap 94 may be maintained constant by controlling the motor 109 in accordance with a signal derived either from the pressure difference between electrolyte flowing towards the workpiece through the tool and that flowing away from the workpiece or from measurements both of the current density at selected portions of the tool and the conductivity of the electrolyte. The electrolyte is recirculated through a filter 103. Use of a tool without sparking, a voltage of 12, a current density of 100 amps./ sq. inch and an electrolyte pressure of 100- 150 lbs./sq. inch are referred to.