Computer controlled machine tool contouring system

In a contouring system including a machine tool, said machine tool having a cutting element with a lateral surface which is substantially symmetrical about a first or Z axis, and a workpiece support table having a top surface substantially disposed in a plane perpendicular to said Z axis, wherein said cutting element both rotates about and translates along said Z axis, and wherein said workpiece support table both rotates about a second or C axis, said C axis being parallel to said Z axis, and translates along a third or X axis, said X axis being perpendicular to said Z axis and having points of intersection with said C and Z axes, and further including a cutting element dressing means, wherein said dressing means translates along a fourth or P axis, said P axis being perpendicular to said Z axis and having a point of intersection with said Z axis, the improvement comprising:

• a means for controlling said rotating and translating motions of said cutting element and said workpiece support table including:
• A. a cutting element drive means for rotating said cutting element at a predetermined angular velocity about said Z axis, and
• B. a positioning control means for selectively controlling:
• i. the relative position of said cutting element with respect to a sequence of predetermined spatial points, each of said spatial points bearing a predetermined spatial relationship to said top surface and each of said points having an associated reference tangent line segment passing therethrough with said tangent line segment disposed parallel to said top surface of said support table at a predetermined angle defined with respect to a reference line segment on said top surface so that said support table is synchronously translated along said X axis and rotated about said C axis and said cutting element is translated along said Z axis, said cutting element having a contact point on the periphery thereof successively located at each of said spatial points and further having the lateral surface of said cutting element at said contact point tangent to each of said reference tangent line segments at its associated spatial point, and
• ii. the position of said cutting element along said Z axis and the relative position of said dressing means with respect to said cutting element lateral surface, whereby said dressing means is selectively translated along said P axis to dress said lateral surface of said cutting element.

In a contouring system including a machine tool, said machine tool having a cutting element with a lateral surface which is substantially symmetrical about a first or Z axis, and a workpiece support table having a top surface substantially disposed in a plane perpendicular to said Z axis, wherein said cutting element both rotates about and translates along said Z axis, and wherein said workpiece support table both rotates about a second or C axis, said C axis being parallel to said Z axis, and translates along a third or X axis, said X axis being perpendicular to said Z axis and having points of intersection with said C and Z axes, and further including a cutting element dressing means, wherein said dressing means translates along a fourth or P axis, said P axis being perpendicular to said Z axis and having a point of intersection with said Z axis, the improvement comprising:

• a means for controlling said rotating and translating motions of said cutting element and said workpiece support table including:
• A. a cutting element drive means for rotating said cutting element at a predetermined angular velocity about said Z axis, and
• B. a positioning control means for selectively controlling:
• i. the relative position of said cutting element with respect to a sequence of predetermined spatial points, each of said spatial points bearing a predetermined spatial relationship to said top surface and each of said points having an associated reference tangent line segment passing therethrough with said tangent line segment disposed parallel to said top surface of said support table at a predetermined angle defined with respect to a reference line segment on said top surface so that said support table is synchronously translated along said X axis and rotated about said C axis and said cutting element is translated along said Z axis, said cutting element having a contact point on the periphery thereof successively located at one of a set of intermediate points wherein ach intermediate point is offset by a predetermined distance along said X axis from an associated one of said succession of spatial points, said predetermined offset distance being a decreasing function of time, and said cutting element further having its lateral surface at said contact point successively tangent to one of a set of offset line segments, each of said offset line segments being parallel to an associated reference tangent line segment and passing through one of said intermediate points, and
• ii. the position of said cutting element along the Z axis and the relative position of said dressing means with respect to said cutting element lateral surface, whereby said dressing means is selectively translated along the P axis to dress said lateral surface of said cutting element.

Method of generating a contour utilizing a computer controlled machine tool, said machine tool having a cutting element with a lateral surface which is substantially symmetrical about a first or Z axis, and a workpiece support table having a top surface substantially disposed in a plane perpendicular to said Z axis, wherein said cutting element both rotates about the translates along said Z axis, and wherein said workpiece support table both rotates about a second or C axis, said C axis being parallel to said Z axis, and translates along a third or X axis, said X axis being perpendicular to said Z axis and having points of intersection with said C and Z axes, said method comprising the steps of:

• A. storing R-.theta.-Z-V.sub.s -W.sub.r -.alpha. input data representative of:
• i. the coordinates of a predetermined sequence of spatial points on said contour, said coordinates being measured with respect to a reference coordinate system on said top surface,
• ii. a predetermined pressure angle associated with each of said spatial points, said pressure angle bearing a predetermined relation to said coordinate system,
• iii. the surface velocity at which a contact point on the periphery of said cutting element is to pass through each of said spatial points,
• iv. an initial radial dimension of said cutting element,
• B. periodically dressing said cutting element at predetermined dressing times whereby the radial dimension of said cutting element is reduced to a value differing by a predetermined increment from the corresponding value associated with the immediately preceding dressing time,
• C. periodically modifying said stored cutting element radial dimension data at said predetermined dressing times so that the modified radial dimension data is representative of the previously stored cutting element radial dimension data as reduced by said predetermined increment,
• D. transforming said stored data to .gamma.-C-V axis control data for each of said spatial points during a first time period associated with each of said predetermined dressing times,
• E. periodically detecting and generating sensor data representative of the actual cutting element position relative to said support table during a second time period associated with each of said predetermined dressing times, each of said second time periods following the associated one of said first time periods and ending prior to the commencement of the next of said dressing steps,
• F. transforming said .gamma.-C-V axis control data and said sensor data to X.sub.E -X.sub.V -X.sub.A -V.sub.C machine tool drive data during each of said second time periods, and
• G. controlling said support table according to said machine tool drive data to synchronously translate along said X axis and rotate about said C axis, and controlling said cutting element to translate along said Z axis, said cutting element having a contact point on the periphery thereof successively located at each of said spatial points and said cutting element being disposed at each of said spatial points at the pressure angle associated with said point, and such that the period of time between positioning said contact point at successive ones of said spatial points is directly proportional to the distance between said successive spatial points, with a predetermined constant of proportionality.