Contouring systems such as the continuous path type are by far the most common can be types in use today.Such as  cnc milling machine, cnc machining cneter, cnc gantry.  They have synchronised drives for of positioning anywhere within the "work envelope". feeding, providing an accura, These universal controls can used for point-to-point positioning and can rapi next; they can also be fed in a dly vector from one coordinate to the straight-line motion applications. 

    When contouring, the tool's position or be used for contour feeding and this means that the controller must frequently linear motions of two or more axes in must be continuously controlled change the relationships of the order to generate a contoured profile on the workpiece. The control path must have an interpolator, so that it can calculate con- tinuous path positions until the target point is reached. 

    To illustrate the requirements of such a contouring operation, if we consider that a contour is to be machined on a turning centre, then to discriminate between one point and the next on the X/Z plane, then the rectilinear movements must maintain an X:Z path-ratio with a speed control that governs the feed drives in the exact synchronised ratio of fx:fz, for the shape tobe successfully produced on the workpiece. 

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