GB1439373A - Method of tool control - Google Patents

Abstract

1439373 Interpolation XENEX CORP [27 July 1973 35975/73 Heading G3N In the control of a tool drive in at least X and Y co-ordinates, in which a tool path is represented by a plurality of segments{e.g. (70, 72), Fig. 3 (not shown)}, the tracking of a given segment is terminated when the value of a function representing the distance of current X & Y values from the succeeding segment changes sign. The function may include an offset allowance, to allow for tool width. If the succeeding segment is linear, the function represents the perpendicular distance from current X, Y values to the succeeding segment plus offset correction, or, for a circular succeeding segment, the length of a line from the above X,Y to the circular segment, and perpendicular thereto at the point of intersection therewith, plus offset correction. Algebraic expressions for both these distances are given. In tracking the current segment, the same functional forms, for a linear, resp. circular segment, are used as a measure of deviation of the actual path from the current segment{still including offset allowance}and are kept as close as possible to zero during incremental tool motion under control of X & Y pulses. When the sign of the distance passes through zero, the succeeding segment becomes the current segment and what was the distance signal becomes the initial deviation signal. Alternatively the register storing the deviation is reset to zero when the distance signal changes sign. Computer 22 calculates a new, initial distance signal, relative to the next succeeding segment. For providing a circular fillet between linear segments (80, 82) Fig. 22 (not shown), the actual current X,Y values may be replaced by "pseudo" values representing a line parallel to (80), and passing through the centre of arc 86. When the distance signal for the "pseudo" path changes sign, the tool then follows the arc 86. The tool may be controlled in three;axes, and segments other than circular or linear may be used. Circuitry for unit 20 is detailed in Figs. 4-21 (not shown). A computer program is disclosed.