Shape generating mechanism of conical twin-screw milled by cylindrical bar cutter

In order to realize the high precision milling of screw extrusion pair with complex geometry by cylindrical bar cutter,the mathematical model was established using the actual cutting points between cylindrical tool section and workpiece as well as according to the spacial geometric relationship between tool and workpiece.The actural spiral shape milled by cylindrical bar cutter in grooving and finish machining was derived through theoretical analysis.It is proved that the shape is an approximate inverted cone instead of a cylinder.Furthermore,a correcting method for cutter swing angle by reverse calculation was proposed.The actual cutting experiments prove the validity of the theoretical analysis.The method can be used to determine the cutter swing angle by pre-calculating before actual cutting,and improve the machining precision and efficiency of conical twin-screw surface effectively.