Cycling system for tracer-controlled machine tools

A method of operating a machine tool of the type which includes a frame and a movable machine element for supporting a pattern for movement along first, second and third mutually perpendicular axes, a first, second and third axis bi-directional motor adapted to drive the machine element along said first, second and third axes, respectively, a tracer mechanism mounted to the frame and including a body and a stylus having a tip adapted to trace over the surface of a pattern, mounting means mounting said stylus to the body, the stylus having a longitudinal axis which is generally aligned with the first axis, and which is mounted for axial shifting movement along the first axis, and for lateral movement of its tip in all lateral directions from the first axis, first axis power control means, second axis power control means, and third axis power control means mounted to the body and responsive to components of stylus tip deflection along the respective first, second and third axes to control the application of power to the respective first, second and third axis motor in response to said stylus deflection, axis selector means for selecting two of the power control means and respective motors to establish a tracing plane in which the stylus traces the pattern at a substantially constant surface rate of travel over the surface of the pattern in response to the two selected power control means, limit means defining the limit of travel of the stylus along the second and third axes and adapted to cause the axis selector means to select the previously-unselected one of the power control means and its respective motor and one of the previously selected power control means and its respective motor after said limit is reached, thereby selecting a new cutting plane for pick movement at a substantially constant surface rate of travel over the surface of the pattern in response to the two power control means which are respective to the newly-selected axes, distance measuring means for terminating said pick movement at the conclusion of a predetermined distance of movement along one of the newly-selected axes, and adapted to cause the axis selector means again to select the first-named pair of power control means and their respective motors, said method comprising:

• using said axis selector means, selecting said first two power control means and causing the stylus tip to trace the pattern in a trace cut at a substantially constant surface speed until a limit switch is encountered terminating the trace cut;
• using said axis selector means to select said second pair of power control means and causing the stylus tip to trace the pattern in a pick movement at a substantially constant surface speed until said distance measuring means indicates a predetermined distance movement, and using said selector means, again selecting said first two power control means and causing the stylus tip to trace the pattern in a trace cut parallel to from the first trace cut at a substantially constant surface speed.