To improve the flexibility of hourglass worm processing equipment, a specific four-axis linkage method for processing hourglass worm, which is called CZXB method, is presented in the paper. Based on the forming principle of the hourglass worm, machining principle and the traditional processing method were elaborated in detail. And then, the CZXB method that aims to apply four feed-movements linkage to simulate the conjugated rotary motions between the worm and its worm gear was proposed. According to the basic theory of rigid body kinematics, the scientific and feasibility of the CZXB method were demonstrated. Based on the computer numerical control machining simulation system, VERICUT, a virtual model of the machine tool with CZXB function, was established. A multi-thread hourglass worm was taken as an example to simulation processing by the CZXB method. Trial manufacturing was performed: tooth grooves of the hourglass worm were cut out by the traditional method, and tooth surfaces of the hourglass worm were finishing machined by the CZXB method. The result shows that machining center distance of the CZXB method is less than center distance of the worm gear pairs. Implementing the CZXB method can significantly enhance the flexibility of machining equipment of the hourglass worm.

The manufacturing method of two spatial-orthogonal rotary axis linkage is usually used to cut hourglass worm. However, the traditional processing method of roughing tooth groove depends on the special machine, specific tool, and its processing efficiency is lower. To avoid these defects, a processing method of the rough cutting hourglass worm on general NC lathe without C-axis functions was presented in the paper. Based on the forming principle of the hourglass worm and the traditional processing steps, the machining principle of the new approach was elaborated. Key techniques such as the shape of the blade, the contours of tooth groove, tool path loop and the variable lead of worm, etc. were discussed. Macro-program of the new method was programmed based on Fanuc oi mate-tc CNC system, and tooth groove of the hourglass worm were trial manufactured on general NC lathe. Addendum axial pitch and a normal tooth thickness of the trial model were measured. It is noted that measurement results can satisfy the technological requirement. In conclusion, the new processing method of roughing hourglass worm is feasible and efficient.