Ling Kang

A linear PI cross-coupled control for servo system of CNC gear hobbing machine

The rotation mismatch between the hobbing cutter and rotary workbench in CNC gear hobbing machine will produce additional vibration during the process of gearing, thus reducing the machining precision. To achieve a better speed match, this paper proposes a synchronized control scheme based on cross-coupled control with proportional-integral (PI) compensator. Permanent-magnet synchronous motors (PMSM) in the servo system are controlled by vector control, which results in the simplification of their dynamic equations. The whole system with proposed control scheme is deduced mathematically. The simulation verifies the validity of the proposed control scheme.

Effect of Machining Precision Caused by NC Gear Hobbing Deformation

Research on the effect of main spindle deformation which is caused by hobbing force of gear hobbing machine is an important way to diminish or control the machining tolerance of gear. This paper bases on the structure and technique parameter of some typical large-scale NC gear hobbing machine, and the theory of bend and deformation of beam, a novel equation was proposed in this paper to calculate the hobbing force and deformation by practical hobbing parameter. By calculating and analyzing gear hobbing force and deformation data, we can conclude a change rule between hobbing force and deformation with spindle rotative velocity and hobbing depth. And we can reach a conclusion that we should increase hob rotative velocity and feed in a small hobbing depth in several times, it will diminish cutting force, deformation of hob and workpiece spindle, which will improve the machining precision, efficiency and diminish product scrap ratio. It also prove this research approach has reference value for optimizing gear hobbingmachine structure design, choice of processing technique parameter and machining error prediction and compensation.