Papers by Author: L.N. Sun

Abstract: In the past decade, hydroformed structural components have been widely used in industrial areas in North American and Europe and there is a large potential market in Asia with the development of automotive industry. An extraordinary feature of tube hydroforming is that a hollow component with a three dimension axis and variable closed-sections can be integrally formed, so that the number of component parts is minimized, weight is reduced and stiffness of the part is increased. The section shapes in many automotive hollow components are complex and it is usually difficult or impossible to hydroform these typical sections directly from circular section tube, so that satisfactory preforms are necessary. In this paper, a method to reduce the friction and calibration pressure through a petal-like cross-section shape preform is presented and its mechanism is analyzed. Preforms for rectangular, trapezoidal and polygonal sections used in hollow components are investigated and satisfactory preforms are obtained. Taking an engine cradle as example, satisfactory preform section shapes have been designed, by which the thickness distribution was controlled and the flash generated from the die-parting surface in the final forming was avoided. So a carefully selected preform process can contribute significantly to the reduction of friction and calibration pressure and it is a dominant factor for successful hydroforming.

Abstract: In 3-axis NC machining, most algorithms of the sculptured surface tool-path generation are valid for ball-cutter, and the axes are designed to realize pure translation. A tool-path generation algorithm using taper-cuter is proposed in this article. And one axis of the 3-axis NC tool machine is designed to realize swing motion. The Stereo Lithography (STL) model is the most popular triangular mesh approximation of the 3D surface model. Considering the special swing mechanical and taper-cutter, arc-zigzag tool-path planning and deform Z-map grid methods are proposed, which incorporate triangular vertexes method and the Z-map method. Finally, some simulation and experiment results are provided.

Abstract: Molecular techniques are transforming our understanding of cellular function and disease. However, accurate molecular analysis methods will be limited if the input DNA, RNA, or protein is not derived from pure population of cells or is contaminated by the wrong cells. A novel Ultrasonic Vibration Microdissection (UVM) method was proposed to procure pure population of targeted cells from tissue sections for subsequent analysis. The principle of the Ultrasonic Vibration Cutting is analyzed, and a novel microknife is designed. A multilayer piezoelectric actuator is used to actuate a sharp needle vibrating with high frequency and low amplitude (Approx. 16–50 kHz, and 0-3μm) to cut the tissue. Contrast experiment was done to test the feasibility of UVM method. Experimental results show that the embedded tissue can be quickly and precisely cut with the ultrasonic vibration micro-dissection method.

Abstract: In order to satisfy the requirement of advanced manufacturing equipments with high speed and high precision, two planar parallel mechanisms have been developed. Based on these mechanisms, firstly, in consideration with the velocity and the precision of the end-effector together, the dimension optimization design is performed based on conditioning index and the precision characteristics. Then a disturbance observer is designed for the purpose of restraining load disturbance in the direct-drive system, and the experimental results show that load disturbance can be effectively restrained by the disturbance observer.