Computer-controlled machine tool

DETAILED DESCRIPTION According to the invention, there is provided a control system for controlling the position of a rotating tool acting on a workpiece, the system comprising: first motor means for adjusting the position of the tool; first position sensor means for providing a first digital signal representing the actual position of the tool; comparator means responsive to any difference between the values represented by the first digital signal and a second digital signal indicative of a desired position for the tool, for controlling the first motor means so as to reduce the difference; second position sensor means for providing a third digital signal indicative of the actual angular position of the workpiece; third position sensor means for providing a fourth digital signal representative of the position of a follower engaging the machined surface of the workpiece at a position angularly spaced from the tool in relation to the axis of angular movement of the workpiece; and digital computer means having a store for information defining a desired profile for the workpiece, the second and third sensor means being coupled to feed the computer means which is programmed to produce said second digital signal in dependence upon a selected portion of said stored information, which portion is selected by use of the third signal and is modified in dependence upon the fourth digital signal to compensate for tool wear.
According to a preferred embodiment, the control system includes second motor means for moving the workpiece angularly, said computer being programmed to provide a control signal for the second motor means, e.
g.
so that the cutting speed between the tool and the surface of the workpiece is maintained substantially constant.
Alternatively the workpiece could be rotated at a constant speed set by the computer.