NUMERICALLY CONTROLLED MACHINE TOOLS

摘要

1407525 Machine tool control REGIE NATIONALE DES USINES RENAULT and AUTOMOBILES PEUGEOT 16 Jan 1973 [20 Jan 1972] 2225/73 Headings B3B and B3C In a numerically controlled machine tool for machining, e.g. by a vertical spindle machining unit 1, at successive stations along an elongate workpiece 3, the machining unit 1 is positioned transversely of the workpiece along a gantry 7 by a control device which positions the machining unit 1 by reference to lateral reference faces 4 or 5 on opposite sides of the workpiece and which is able to change the controlling reference face from one lateral face to the other depending on the machining operation desired, and includes means for adjusting the position of the machining unit 1 relative to a reference member, e.g. a lead screw 8, in accordance with numerical control position signals, and means for shifting the reference member between a first reference position, e.g. relative to lateral face 4, and a second reference position, e.g. relative to lateral face 5. The machining unit 1 is moved by a motor 11 driven lead screw 8 and nut 13 drive with the lead screw 8, nut 13 and machining unit 1 being able to float laterally by means of a splined bearing 10 and a plain bearing 9 on the lead screw 8. A pick-up or encoder 12 monitors the rotation of the lead screw. At a given location along the workpiece one of a pair of feelers 15, 151 which are axially fixed relative to the lead screw 8 is chosen to engage one of the reference planes 4 or 5 to align a datum 16 or 17 on the lead screw therewith. At the required reference position a jaw 18 attached to the lead screw, is actuated to clamp itself to a fixed blade 19 to lock the lead screw laterally in the datum position. A control programme then controls the rotation of the lead screw to move the machining unit along the lead screw to a predetermined machining position. The feelers 15, 151 are attached to the lead screw by means of pressure operated centering devices 14, 141 (Figs. 2-4, not shown) which, when a selected one is pressurized a pair of floating pistons are forced apart to move the lead screw axially to the datum position. If a group of holes for example, are to be machined at a location along the beam a single clamping of the jaw 18 is made to avoid local irregularities on the reference faces 4 or 5 introducing errors. The workpiece may be a regular section I or H beam, an open channel or box beam, or may be a non-linear, non-constant cross-section beam, e.g. a car chassis box member. The machine tool may include machining units for operating on the lateral faces 4 and 5 (Figs. 8-10, not shown).