Adapting Whirling Process for CNC Manufacture of Bespoke Screws with Variable Pitch and Diameters

Widely increased use of screws with variable pitch, flight and core in contemporary machinery makes it of great significance to explore an efficient way for manufacturing them. This paper proposes a whirling-based approach to manufacturing bespoke screws of kind. The machining is performed on a 3-axis CNC whirling machine. Unlike conventional whirling process which uses profiled cutters to cut the helical grooves, this approach employs tipped cutters which follow complicated toolpath to cut the screw out of a blank. In order to determine a continuous toolpath to approximate the screws cross-section profiles, one after another, the screw's cross-section profiles are considered as the envelope of the tipped cutters' trajectory and m CC points on each cross-section are relocated at several hypothetical cutting planes evenly. Finally, machining test using an example screw part is conducted to demonstrate the feasibility of the proposed approach. [Submitted 29 December 2018; Accepted 27 February 2019]