Numerical controller for an angular slide grinding machine

Claim 1

A numerical controller for a grinding machine wherein a work table rotatably carrying a workpiece and having a dressing tool fixed thereon is movable in a first direction parallel with the rotational axis of said workpiece and wherein a wheel head rotatably carrying a grinding wheel is movable in a second direction which makes an acute angle with said first direction, comprising: a first counter for indicating a present position of said work table in a machine coordinate system which originates from an original table position spaced a predetermined distance from an original machine position in said first direction, said original machine position being defined by an end surface of said grinding wheel when a cylindrical surface of said grinding wheel reaches the axis of said workpiece; a second counter for indicating a present position of said wheel head as a distance between said axis of said workpiece and said cylindrical surface of said grinding wheel; said present positions respectively indicated by said first and second counters being for use in controlling movements of said work table and said wheel head in accordance with numerical control data; first data processing means responsive to said present positions respectively indicated by said first and second counters when said work table is moved to such a position as to bring said dressing tool into slight contact with said end surface of said grinding wheel, for calculating a dressing reference value indicative of a positional relation between said machine original position and said dressing tool; first storage means for storing said dressing reference value calculated by said first data processing means; data setting means for setting in said first counter a distance between said original machine position and a reference end surface of said workpiece in said first direction when under the control of a sizing device engageable with said workpiece said work table is positioned to present said reference end surface to a predetermined positional relation with said original machine position, so as to enable said first counter to indicate said present position of said work table in a workpiece coordinate system prior to a grinding operation of said workpiece; second data processing means for obtaining a coordinate difference between said machine coordinate system and said workpiece coordinate system when under the control of said sizing device said work table is positioned to set said reference end surface of said workpiece in said predetermined positional relation with said original machine position; second storage means for storing said coordinate difference obtained by said second data processing means; and third data processing means responsive to said dressing reference value and said coordinate difference respectively stored in said first and second storage means and said present position indicated by said second counter when said wheel head is at a dressing start position thereof, for calculating a dressing start position of said work table in said workpiece coordinate system prior to a dressing operation which is performed following said grinding operation.