Computer controlled grinding machine for producing objects with complex shapes

The method for machining a workpiece to conform with a model of predetermined shape comprising the steps of

• providing a computer control means having stored therein blocks of data tables representing said predetermined shape,
• rotating said workpiece about a Y axis therethrough,
• providing an abrasive machining tool including an abrasive belt having a generally cylindrical moving surface,
• mounting said abrasive machine tool for angular adjustment about a C axis and translational movement along a Z axis perpendicular to said Y axis,
• adjusting said abrasive machine tool along said Z axis to engage the surface of said workpiece at a contact point, and
• angularly adjusting the rotational position of said abrasive machine tool about said C axis and said C axis about said contact point thereby to position said abrasive machine tool to engage said workpiece along a linear contact line corresponding to the surface of said predetermined shape,
• continually and automatically determining the position of the surface of said workpiece along said C axis,
• continually and automatically determining the position of said abrasive belt at the point where said belt makes contact with said workpiece, thereby to determine the thickness of said belt, and
• continually and automatically readjusting the translational position of said abrasive belt relative to said workpiece to compensate for changes in the thickness of said belt caused by wear during the finishing process.

A grinding machine for finishing a workpiece to correspond to a model having a predetermined complex shape comprising

• means for supporting said workpiece and rotating it about a Y axis,
• an abrasion tool having an abrasive belt positioned to engage the surface of said workpiece along a linear contact line,
• support means for supporting said abrasion tool,
• first control means for producing relative translational movement between said abrasion tool and said workpiece along a Z axis extending perpendicular to said Y axis,
• means for angularly adjusting said support means about an X axis perpendicular to said Z axis and passing through a fixed point on said contact line,
• drive means for angularly adjusting said support means about a C axis parallel with the plane of the Y and Z axes and extending through said point to position said contact line along a surface of said predetermined shape,
• second control means for angularly adjusting said C axis about a fixed point on said contact line to maintain said C axis in a plane parallel with a local normal and passing through said fixed point,
• continually and automatically determining the position of the surface of said workpiece along said C axis,
• continually and automatically determining the position of said belt at the point where said belt makes contact with said workpiece, thereby to determine the thickness of said belt, and
• continually and automatically readjusting the translational position of said abrasion tool relative to said workpiece to compensate for changes in the thickness of said belt caused by wear during the finishing process.

Machining apparatus for automatically machining a workpiece to conform with a predetermined shape, comprising

• a machine base,
• a Z-axis table mounted no said machine base,
• first displacement means for displacing said Z-axis table along a Z axis with respect to said machine base,
• a Y-axis table mounted on said Y-axis table;
• second displacement means for displacing said Y-axis table along a Y axis with respect to said Z-axis table, said Y axis being orthogonal to said Z axis,
• an X-axis table mounted on said Y-axis table,
• third displacement means for displacing said X-axis table along an X axis with respect to said Y-axis table, said X axis being orthogonal to said Y and Z axes,
• means on said X-axis table for rotating said workpiece about said Y axis,
• an abrasive belt machine assembly including
• a belt drive motor, and
• a drive wheel and nose roller for supporting and rotating an abrasive belt,
• means controlling said assembly to move said abrasive belt into engagement with said workpiece along a linear contact line,
• first contact line control means for rotating said abrasive belt and nose roller about a C axis parallel with the plane of said Y and Z axes and passing through a fixed point on said linear contact line,
• second contact line control means for rotating said abrasive belt and nose roller about an A axis parallel with said X axis and passing through said fixed point, whereby said first and second contact line control means are effective for rotating said linear contact line while said fixed point remains stationary,
• a control system under computer control including
• means for (a) displacing said workpiece along said Y and Z axes, (b) angularly adjusting said C axis about said A axis to maintain said linear contact line nearest the surface of said predetermined shape at the finishing point, and (c) angularly adjusting said assembly about said fixed point to maintain said linear contact line perpendicular to a local normal of said predetermined shape at the point of finishing as said workpiece is rotated about said Y axis,
• continually and automatically determining the position of the surface of said workpiece along said C axis,
• continually and automatically determining the position of said belt at the point where said belt makes contact with said workpiece, thereby to determine the thickness of said belt, and
• continually and automatically readjusting the translational position of said abrasion tool relative to said workpiece to compensate for change in the thickness of said belt caused by wear during the finishing process.

Apparatus for machining a workpiece to conform to the shape of a mathematical model comprising

• a machine base,
• a Z-axis table mounted on said machine base,
• first displacement means for displacing said Z-axis table along a Z axis with respect to said machine base,
• a Y-axis table mounted on said Z-axis table,
• second displacement means for displacing said Y-axis table along a Y axis perpendicular to said Z axis,
• an X-axis table mounted on said Y-axis table,
• third displacement means for displacing said X-axis table along an X axis perpendicular to said first and second displacement axes,
• drive means on said X-axis table for rotating said workpiece about a Y axis passing through said workpiece,
• an abrasive-belt machine assembly including
• a drive wheel,
• a nose roller,
• an abrasive belt positioned over said drive wheel and said nose roller, and
• a drive motor for driving said drive wheel,
• said abrasive belt being movable to engage said workpiece along a linear contact line extending across said belt,
• first contact line control means for angularly adjusting said abrasive belt and said nose roller about a C axis in a plane parallel with the plane of said Y and Z axes and extending through a fixed point on said linear contact line,
• second contact line control means for angularly adjusting said abrasive belt and nose roller about an A axis parallel with said X axis and passing through said fixed point, whereby said control means are effective for angular adjustment of said abrasive belt while said fixed point remains stationary,
• a control system including means for displacing said workpiece along said X, Y and Z axes while angularly adjusting said linear contact line about said fixed point to maintain said contact line along the surface of said predetermined shape at the point of finishing,
• continually and automatically determining the position of the surface of said workpiece along said C axis,
• continually and automatically determining the position of said belt at the point where said belt makes contact with said workpiece, thereby to determine the thickness of said belt, and
• continually and automatically readjusting the translational position of said abrasion tool relative to said workpiece to compensate for changes in the thickness of said belt caused by wear during the finishing process.

A grinding machine for grinding a complexly curved workpiece comprising in combination:

• an abrasive belt assembly for supporting an abrasive belt, said belt assembly having a longitudinal axis through its center and a nose supporting belt to define a contact point, said belt assembly having means to rotate said nose about said longitudinal axis and means to maintain said longitudinal axis normal to said workpiece at said contact point during grinding operations;
• means for rotatably supporting said workpiece and for moving said workpiece and said belt assembly relative to one another to engage said belt and said workpiece at said contact point;
• and
• computer-controlled means for coordinating said belt assembly and said workpiece so as to grind multiple instantaneous linear contact lines on the surface of said workpiece.

A grinding machine for grinding a complexly curved workpiece comprising in combination:

• a horizontally-oriented belt assembly for supporting an abrasive belt, said belt assembly having a longitudinal axis through its center and a nose supporting said belt at a workpiece contact point, said belt assembly having means to maintain said longitudinal axis normal to said workpiece at said workpiece contact point during abrasive grinding operations;
• means for rotatably supporting said workpiece and for horizontally moving said workpiece and said belt assembly relative to one another to engage said belt and said workpiece at said workpiece contact point;
• and
• computer-controlled means for coordinating said belt assembly and said workpiece so as to grind multiple instantaneous linear control lines on the surface of said workpiece, the length of each of said linear contact lines being determined by the radius of curvature of said workpiece surface at said contact point and the predetermined finish tolerance of the dimensions of said workpiece.

A grinding machine for grinding a complexly curved workpiece comprising in combination:

• a horizontally-oriented belt assembly for supporting an abrasive belt, said belt assembly having a nose supporting said belt at a contact point, and aid belt assembly having means to rotate said nose;
• means for rotatably supporting said workpiece and for horizontally moving one of the belt assembly and workpiece relative to the other to make contact between said belt and said workpiece at said contact point;
• support means for said belt assembly, said support means being pivotable so as to ensure that said nose is normal to the surface of said workpiece at the contact point;
• and
• computer-controlled means for coordinating the relative motion of said workpiece and said belt assembly nose at said contact point, said means utilizing said contact point as the reference point for calculating instantaneous linear contact lines on the surface of said workpiece to be traced by said contact point, the length of each of said linear contact lines being dependent upon the radius of curvature of said workpiece in the area of said lines and the desired finish tolerance of the workpiece, said linear contact lines lengths being calculated by employing point-to-point methodology.