Apparatus and method of machining article of eccentric configuration

An eccentric-shape machining apparatus for machining a workpiece, including boring, contour shaping, threading and so on, about a position different from the rotational center of the workpiece, comprising:

• (1) a main spindle on which a chuck for holding said workpiece is mounted and which is controllably rotatable about a C-axis;
• (2) a turret type cutting head controllably movable in a direction perpendicular to said C-axis (X-axis direction);
• (3) a turret mounted on said turret type cutting head and controllably rotatable about a Ct-axis parallel to said C-axis, said turret including a cutting tool mounted thereon in a direction perpendicular to said Ct-axis;
• (4) a rotating tool spindle mounted on said turret in a direction parallel to the Ct-axis of said turret and controllably rotatable about an Ma-axis parallel to said Ct-axis, said rotating tool spindle including a cutting tool mounted thereon in a direction perpendicular to said Ct-axis;
• (5) main spindle drive means for rotatably driving said main spindle while controlling the rotational phase (.theta.1) of said workpiece about said C-axis;
• (6) turret type cutting head drive means for controllably moving said turret type cutting head in said X-axis direction;
• (7) turret drive means for rotatably driving said turret while controlling the rotational phase (.theta.5) of said turret about said Ct-axis;
• (8) rotating tool spindle drive means for rotatably driving said rotating tool spindle while controlling the rotational phase (.theta.4) of said rotating tool spindle about said Ma-axis;
• and
• (9) numerical control means for controlling all said drive means such that the tip of said cutting tool is positioned on said X-axis and the rake angle of said cutting tool is maintained at a constant angle relative to a tangent line at a cutting point on a cutting plane.

An eccentric-shape machining method for machining a workpiece, including boring, contour shaping, threading and so on, about a position different from the rotational center of the workpiece, to form a surface having a radius, comprising the steps of:

• generating a composite motion by simultaneously controlling motions in the C-axis being a control axis for controlling the rotational phase of said workpiece, in the X-axis being a control axis for controlling the position of a turret type cutting head in a direction perpendicular to said C-axis, in the Y-axis being a control axis that extends in a direction perpendicular to both said C- and X-axis directions and is used to control the position of said turret type cutting head and in the Ct-axis being a rotatable control axis extending parallel to said C-axis and used to control the rotational phase of a turret that is mounted on said turret type cutting head and on which a tool is mounted;
• and
• using said composite motion to control the cutting operation such that the cutting tip of said tool is positioned in place on said X-axis and the rake angle of said cutting edge is maintained at a given angle relative to a tangent line at a cutting point on a cutting plane
• wherein the C-axis is spaced from the Ct-axis by a distance X along the X-axis and a distance Y along the Y-axis, the cutting tip of said tool is spaced a distance Z from a reference point along the Z-axis, the position about which the workpiece is machined is offset from the C-axis by a non-zero distance A,
• X=A cos .theta.1+r cos (.theta.3-.theta.1)+L1 cos .theta.2;
• Y=L1 sin .theta.2;
• Z=(.theta.3/360.degree.)p;
• r=the radius of the surface being machined;
• L1=the distance between the Ct-axis and the cutting tip of said tool;
• .theta.1=the rotational phase of the workpiece about the C-axis;
• .theta.3=.theta.1+.theta.2;
• and
• p=the displacement of the cutting tip of said tool along the Z-axis during each revolution of the workpiece relative to the cutting tip of said tool.

An eccentric-shape machining apparatus for machining a workpiece, including boring, contour shaping, threading and so on, about a position different from the rotational center of the workpiece, said apparatus comprising:

• (1) a main spindle on which a chuck for holding the workpiece is mounted;
• (2) a rotating tool spindle on which a cutting tool can be mounted in a direction perpendicular to the axis of the cutting tool;
• (3) main spindle drive means for rotatably driving the main spindle while controlling the rotational phase (.theta.1) of the workpiece;
• (4) rotating tool spindle drive means for rotatably driving the rotating tool spindle while controlling the rotational phase (.theta.2) of the rotating tool spindle;
• (5) feed drive means for feeding the rotating tool spindle relative to the workpiece in a biting direction (X-axis direction) and in a feed direction (Z-axis direction) while controlling the position of the rotating tool spindle;
• and
• (6) numerical control means for controlling the rotational phases of the workpiece and rotating tool spindle in synchronism with the biting movement of the rotating tool spindle such that the cutting tool is brought into contact with the inner or outer periphery of the workpiece with a given depth of cut during one complete revolution of said rotating tool spindle and for simultaneously controlling the feed of the rotating tool spindle.