Piston machining

A method of machining a piston for a positive displacement machine, said piston being in a work piece formed of a rough casting having an inner cavity, said method comprising:

• fixturing said piston by gripping said piston along said inner cavity;
• rotating said piston along a longitudinal axis of said piston;
• rough cutting a side surface of said piston with a rotating cutter;
• rotating said piston and cutting into said piston side surface at least one piston ring with a cutting head;
• holding said piston stationary, machining a connection pin bore through said piston;
• finish cutting a circular surface on said side surface of said piston by rotating said piston and sequentially moving a cutter head translationally toward and away from said piston;
• and
• releasing said piston.

A machining center for machining a piston for a positive displacement machine, said piston being presented to said machining center in the form of a work piece of a rough casting having an inner cavity, said machining center comprising:

• a fixture for gripping said piston along said inner cavity of said piston;
• a spindle for rotating said piston along a longitudinal axis of said piston, said spindle being translatable along a first axis;
• a slide table positioned underneath said spindle for moving a plurality of cutting tools into contact with said piston;
• a first cutting tool for milling said piston when said piston is rotated by said spindle;
• an ovality unit for moving a cutting toward and away from a center line of said piston in sequence with the rotation of said piston to give said piston a non-circular cross-section;
• at least one stationary tool for cutting a groove in the OD of said piston while said piston is being rotated by said spindle;
• and
• a second rotating cutting tool for cutting a cross bore through said piston to facilitate insertion of a connecting pin to said piston said spindle holding said piston stationary during the cutting of said cross bore.