| 摘要 |
1,274,946. Grinding. HEALD MACHINE CO. 24 March, 1969 [1 April, 1968], No. 58755/71. Divided out of 1,274,945. Heading B3D. A grinding machine 10 comprises a base 11, a workhead 12 mounted on the base to support and rotate a workpiece 23, e.g. a ball-bearing race, having a surface of revolution to be finished, a wheelhead 13 mounted on the base and having a rotatable spindle 21 carrying an abrasive wheel 22, and feed apparatus to bring about relative movement of the workhead and wheelhead to introduce the wheel to the workpiece with controlled force for performing a grinding operation to finish the said surface, Means are also provided for monitoring during grinding the relationship between the grinding force (F N ) exerted by the wheel on the workpiece normal to the surface of revolution and the plunge velocity (V) and operative when the ratio of the plunge velocity to the normal force indicative of wheel dullness falls below a certain predetermined value to bring about renewal or dressing of the wheel surface. In the machine shown, the workhead 12 is carried on a table 14 slidable longitudinally of the base 11 under the action of a fluid feed cylinder 19, and is driven by a belt 48 from a motor 47. The wheelhead 13 is carried on a table 16 slidable transversely of the base 11 under the action of a feed cylinder 18 supplied with fluid from a conduit 42. The normal force F N between the wheel and the workpiece is measured from the pressure in conduit 42 by a transducer 46. Alternatively F N is measured by a force transducer such as a proximity pick-up adjacent the spindle 21 which operates an amplifier 56. The plunge velocity V is indicated by an amplifier 41 operated by a velocity transducer comprising a core 38, on table 16, and a fixed coil 39. Electrical circuitry is provided in a main control which compares the ratio # = V/F N with a predetermined value # 0 . When # becomes less than # 0 a signal is generated either to a coil 55 which causes grinding to be interrupted and a tool 29 to dress the wheel 22, or to a coil 45 which opens a valve 44 to permit a pulse of fluid to the cylinder 18 thus urging the wheel 22 against the workpiece to crush-dress it. |
