Method of manufacturing roller

A method of manufacturing a roller including the steps of positioning a workpiece formed with a radially outer surface of a tapered roller or a convex roller, and forming an end surface of the roller having a predetermined target shape by grinding,

• wherein said method comprises preparing a five-axis control machining center comprising a spindle carrying a cutting tool and a grinder, and a spindle head carrying a mechanical chuck having jaws, fixing the workpiece in position with the jaws of the mechanical chuck, cutting said end surface to a finished cut surface approximate in shape to said predetermined target shape with the cutting tool, and grinding the thus cut end surface to said predetermined target shape with the grinder, and
• wherein the predetermined target shape is a spherical shape, and the finished cut surface is a spherical surface, wherein the grinder is a cup-shaped grinder having a cylindrical grinding portion, said five-axis control machining center having a center of the sphere containing said predetermined target shape, a Z-axis about which the grinder is rotated, and a first rotation axis about which the workpiece is rotated, and wherein the machining center is configured to grind said end surface by contouring control so as to satisfy, when considered on a plane perpendicular to a second rotation axis about which one of the spindle head and the spindle is inclined relative to an XZ plane or a YZ plane:
• condition (i):
• The workpiece is rotated with an apex of said predetermined target shape located on a line passing said center of the sphere and said second rotation axis, while being inclined at an inclination angle α;
• condition (ii):
• The second rotation axis is offset from the Z-axis in the direction of an X-axis which intersects the Z-axis at a right angle by an offset amount e;
• condition (iii):
• The workpiece and the grinder are positioned so as to satisfy the following Equations 1 and 2:
• R={(D/2)+e}/sin(α) Equation 1
• e=(D/2)−H sin(α) Equation 2
• where R is the radius of the spherical surface;
• D is the outer diameter of the grinder;
• and H is the distance between the second rotation axis and said apex;
• and
• condition (iv):
• With the workpiece and the grinder positioned so as to satisfy the conditions (i) to (iii), the workpiece is rotated about first axis, and the grinder is rotated about the Z-axis and simultaneously fed in the direction of the Z-axis toward the workpiece, thereby forming said predetermined target shape.