Zhe-Zhu Xu

A Study on Effect of Various Cooling Methods in Motion of High-Precision Ball Screw

Ball screw system is widely used as a precision mechanical linear actuator that translates rotational motion to linear motion for its high efficiency, great stiffness and long life. Recently, according to the requirements of high accuracy and stiffness, the pre-load on the ball screw which means of remove the backlash in the ball screw is usually used. Because of the preload which means the frictional resistance between the screw and nut, becomes a dominating heat source and it generates thermal deformation of ball screw which is the reason for low accuracy of the positioning decision. There are several methods to solve the problem that includes temperature control, thermal stable design and error compensation. In the past years, researchers focused on the error compensation technique for its ability to correct ball screw error effectively rather than the capabilities of careful machine design and manufacturing. Significant amounts of researches have been done to real-time error compensation. But in this paper, we developed a series of cooling methods to get thermal equilibrium in the ball screw system. So we find the optimum cooling type for improving positioning error which caused by thermal deformation in the ball screw system.

Effect of MoS2-based composite coatings on tribological behavior and efficiency of gear

MoS2 -based Ti composite coatings were deposited on the AISI 4118 alloy and gears using an RF magnetron sputtering (RFMS) system. While MoS2 coating had been coated on the silicon substrate. The coatings structures were compared to each other to find the effect of Ti. The composite coatings have been performed by a ball-on-disk tribometer to investigate tribological behavior at various conditions. The structure of the coatings has been extensively studied by a variety of techniques, including X-ray diffraction (XRD) and scanning electron microscopy (SEM), etc, respectively. The composite coatings were also applied the gears of a reduction gearbox. The efficiencies of uncoated and coated gear with MoS2 based Ti coatings were measured and compared at various input rotating speed under absorption oil film condition. It was found that the efficiency of gear had significantly improved after MoS2 -based Ti composite coatings deposition.Copyright

Study on the Transmission Error Prediction for a Spur Gear Pair

Nowadays, lower gear vibration and noise are necessary for drivers in automotive gearbox, which means that transmission gearbox should be optimized to avoid noise annoyance and fatigue before quantity production. Transmission error (T.E.) is the excitation factor that affects the noise level known as gear whine, and is also the dominant source of noise in the gear transmission system. In this paper, the research background, the definition of T.E. and gear micro-modification were firstly presented, and then different transmission errors of loaded torques for the spur gear pair were studied and compared by a commercial software. It was determined that the optimum gear micro-modification could be applied to optimize the transmission error of the loaded gear pair. In the future, a transmission test rig which is introduced in this paper is about to be used to study the T.E. after gear micro-geometry modification. And finally, the optimized modification can be verified by B&K testing equipment in the semi-anechoic room later.

Improvement of Positioning Error on a Ball Screw Drive System by Liquid-Cooling

The demand for higher productivity and tight part tolerances requires machine tools to have faster and more accurate feed drive system. As tried and tested technology, ball screw drive systems are still used in majority of machine tools due to their low cost and high stiffness. A high speed ball screw drive system natually generates more heat and results in greater positioning error, adversely affecting the accuracy of machined parts. In order to estimate the positioning error of the ball screw system and effectiveness of the liquid-cooling system, all possible heat gain-loss sources were analyzed and calculated as calculation factors. The following paper also presents degree of positioning error improvement which employed circulation liquid-cooling system and forced liquid-cooling system. Comparing the experimental results and the forcasts, it shows that sensational cooling performance and high consistency of reality and prediction are displayed.Copyright

A Study on Tooth Modification for Spur Gear for Articulated Hauler

Construction equipment is heavily loaded during normal operation. In recent years, there is a trend that lower gear noise levels are demanded for driver to avoid annoyance and fatigue of operation. For articulated haulers, meshing transmission error (T.E.) is the excitation that leads the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in gearbox. This paper presents a method for the analysis of the tooth modification, and the prediction of transmission error under the loaded torque for the spur gear pair of the articulated hauler’s final drive. And the transmission error, contact stress, root stress and load distribution are also calculated and compared before and after tooth modification under one torque. The simulation result shows that the transmission error and stress under the load can be minimized by the appropriate tooth modification. It is a good approach where the simulated result is used to improve the design before the prototype is available for the test.Copyright