Papers by Author: Guang Qi Cai

Abstract: This paper proposes a novel three degrees of freedom parallel machine tool. The parallel machine tool consists of three serial chains and a fixed base and a moving platform which can be moved in a pose space corresponding to the three degrees of freedom. By using matrix methods, a error model of the parallel machine was developed. The explicit solution of the error of joint and the stroke error of telescopic link were solved for analysis of influence factors of error on the position of moving platform. It provided a theoretical foundation for error compensation of parallel machine tool.

Abstract: This paper proposes an optimization method which makes the structural parameters are minimum and the workspace is maximum based on 3-DOF parallel machine tool. By analysis the conditions of boundary, parameters optimization model is built and gives out the explicit solution of dexterous workspace. Analysis the effect of structural parameters on workspace. The results show the workspace is a unsingularity space.

Abstract: The theoretical hydrodynamic pressure modeling were presented for flow of coolant fluid through the grinding zone in flood delivery grinding using roughness surface grinding wheel. The simulation results show that the hydrodynamic pressure was proportion to grinding wheel velocity, and inverse proportion to the minimum gap between wheel and work surface and the maximum pressure value was generated just in the minimum gap region in which higher fluid pressure gradient occuring. It can also be concluded the surface roughness of grinding wheel and workpiece makes the contact zone’s hydrodynamic pressure rough and unstable, i.e. the value curve considering roughness is not smooth, leading to the micro-elastohydrodynamic lubrication phenomenon.

Abstract: Due to point contact cause, the point grinding process have the lower grinding power and heat to measure and the better cooling conditions. For green manufacturing, the point grinding process has the significance to reduce the consumption of grinding fluid and improve the ground surface integrity and the process greenness. This study analyzes the geometric configuration of the contact area between the wheel and the workpiece in point grinding process, establishes the geometric and mathematic models of the contact area, and investigates the relations between the grinding parameters. The dry point grinding experiments are performed on the ground surface integrity. These investigations show that the dry grinding can be achieved in point grinding process under less depth of cut and the higher grinding speed for the high machining greenness demand.

Abstract: This paper proposes a new 2PTT-TPT parallel machine tool, solves the kinematics equation and analyzes the actuating force and maneuverability. In order to simulate the movement trajectory and pose, the model of virtual prototype is built in Solidworks and visualNastran. As a result, the mechanism is featured by compact construction, no singularity and good maneuverability, which provides the theoretical foundation for the design of parallel machine tool.

Abstract: This paper deals with the dimensional synthesis of a 2UPS-UPR parallel mechanism tool newly designed by Northeastern University. On the basis of establishing kinematics equations and obtaining Jacobian matrix, the performance index of dimensional synthesis is given which is the average of 729 values of the condition number of Jacobian matrix corresponding to 729 positions in the workspace. With MATLAB software, the effects are simulated which the structural parameters of parallel machine tools have on dimensional synthesis, their change laws are gained, and then dimensional synthesis of parallel machine tools is conducted based on these laws.

Abstract: The purpose of MH/Ni power battery positive mill is to make it have the certain density, thickness and good tenacities. The thickness of positive battery is different, its capacity, the efficiency of charge and discharge, the utilization efficiency of the electrode material is also different. Positive battery has variable delay and variable gain in the mill process, so it is suitable for using neural networks to control.

Abstract: The dynamic performance of the grinding wheel system is one of the key factors to affect the super-high speed grinding process The excessive centrifugal stress acted on the wheel body can make the wheel rupture due to the super-high rotary speed of the wheel. And the alternating centrifugal force caused by the wheel imbalance can not only make the spindle and bearings vibration and failure, but also lower the machining precision and the wheel life, as well as make against the safety. In this paper, the centrifugal stress of the high speed grinding wheel and its effect on machining process were analyzed by means of finite element analysis and simulation. The alternating centrifugal force and its effect on the wheel spindle system were investigated. Furthermore, the balance precision of super high speed grinding wheel and system was discussed for achieving the high precision, safety and efficiency machining process.

Abstract: Based on the modeling and experiments concerning the surface roughness in abrasive jet finishing with grinding wheel as restraint, the effect of abrasive size, abrasive fluid concentration, machining cycle, wheel velocity and carrier fluid on machined surface quality was investigated. Surface grinder M7120 was employed in a jet machining experiment conducted with W18Cr4V and 40Cr materials, profilometer TALYSURF was used to measure the micro geometrical parameters after machining, and SEM was used to observe surface micro-morphology. Experimental results show that with W7 Al2O3 powder at the mass fraction of 10% and antirust lubricating liquid being adopted in jet machining for 20 to 30 cycles, not only high surface shape precision can be kept or obtained, but also defect-free machined surface with the roughness of Ra0.15～1.6µm can be obtained with high efficiency. Experimental observation and experimental results proved that the experimental results agree well with a mechanism-based machining model.

Abstract: This paper introduces the working principle of the impact mechanism which is belonging to the double-chamber scavenge oil hydraulic rock drill. On the basis of some fundamental hypothesis, a mathematical model of hydraulic impact mechanism is established, then carrying out a dynamic simulation. Focusing on the influence of supply pressure, supply flow and precharge pressure on the working performance of impact mechanism, some research is implemented, and some regularity conclusions are obtained.