Papers by Author: Jian Zhong Fu

Abstract: Amongst the flourishing Delaunay Triangulation methods, growth algorithm has been widely accepted because of its reputation of being simple and elegant. However, the parallelization of growth algorithm has not been fully exploited. In this work, a novel Growth algorithm of Delaunay Triangulation is proposed. The point cloud is first divided into two parts by a suitable curve and the separated areas are calculated by incremental algorithm. Triangles which cross with the curve are generated by a growth algorithm associated with uniform grid. At the process of merging, these grew triangles are used to detect incorrect triangles of the incremental algorithm areas. Method about generating triangles on curve is elaborated and a simple way to detect interferential triangles is also explained. With above method, triangulation calculation can be parallelized. Unlike the traditional divide-and-conquer method, no flip operation is needed in the proposed methodology. Thus, three dimensional applications are also made possible. A comparative research between tradition incremental algorithm and the proposed method has been conducted. Results show, the algorithm has a higher performance with less computation time.

Abstract: The drop-on-demand (DOD) inkjet printing technology has been widely used in many fields and several types of droplet generators are developed. This paper presents the design, fabrication and tests of a piezoelectric bend mode drop-on-demand inkjet printhead with interchangeable nozzle. A disk-type PZT is actuated to push the liquid out of inkjet printhead by a function generator, and a droplet is formed because of surface tension. The interchangeable nozzle design enables the same printhead to be fitted with nozzles of different orifice size, thus a clogged nozzle can be easily removed for cleaning or replacement. An experimental platform for micro-droplet jetting is built in this paper. The droplet formation is recorded by a CCD camera as pictures, which can be used to measure the droplet dimension. The experiments are carried out by using the self-developed bend mode piezoelectric inkjet printing system. The influence of the drive parameters on the droplet quality is also studied by dispensing water.

Abstract: Nowadays, drop-ondemand inkjet printing technology has shown its potential in many fields. This paper presents designing and implementing of a low cost drop-ondemand inkjet printing system. Inkjet printing system can be divided into four parts, and back pressure control system and droplet observation system are two key components, both of which are described in details. In order to have a further control of accuracy and stability of the system, this paper discusses the parameters designed in the system. In pressure control system, the designed system has higher accuracy compared with the Microfabs product. Images can be taken through CCD camera instead of ultra-high-speed camera by using droplet observation system. Some experiments also have been done to verify the feasibility of the device. Accuracy of pressure control, stability of the system and reproducibility of inkjet process can be verified from the experiment.

Abstract: The error distribution of a machined NURBS surface is complex to describe since the machined surface isnt that easy to obtain. A new method for machined NURBS surface description based on inspection database of on-machine probing is presented. The main idea is to approximate the machined surface using the inspection data and the basis functions of the nominal NURBS surface and to get the error distribution of the surface. A virtual part with a NURBS surface is presented and its error caused by the interaction of the machine-tool-workpiece is obtained using the FEA method at the inspection points. A machined NURBS surface is achieved and the error distribution of the surface is expressed. This method provides a new way in error compensation and it will improve the machining accuracy of a NURBS surface.

Abstract: Cutter Engagement Region (CER) is the part of tool that contacts with stock, where a series of energy exchange and material transportation take place. A full understanding of its shape and area is indispensible for cutting force calibration, chatter analysis, and tool wear prevention. It can provide a criterion for efficient tool-path planning as well. In literature, however, there is no available modeling of CER. We hereby propose a modeling method for ball-end tool with design surface represented in triangular mesh. First, design surface is offset to form a stock surface. Next, compute the intersection between every triangular facet and the tool. Then, connect all the intersecting arcs to form the boundary of CER. Finally, compute the area of CER. Experimental validation for the proposed method is still needed.

Abstract: This paper presents an adaptive tool path generation method for Fused Deposition Modeling (FDM). The proposed method consists of three steps. First, an adaptive slicing considering both surface quality and building time is proposed for following tool path generation. Second, a hybrid tool path strategy is introduced to improve the boundary contours accuracy. This step is an adaptive process to choose an appropriate proportional relationship between the two types of tool paths according to the specific fabrication requirements. For further improvement, a tool path adjustment is employed on the original tool paths. A case study of a sliced layer is used to verify the feasibility and advantage of the proposed method.

Abstract: Thermoelectric energy harvesting is emerging as a promising alternative energy source to drive wireless sensors in mechanical, civil, and aerospace engineering systems. Typically, the waste heat from spindle units of machine tools creates obvious potential for thermoelectric generation. The structure of heat sinks on a thermoelectric generator has a great effect on the output voltage of the thermoelectric generator due to the temperature difference between hot and cold sides induced by heat transfer, so several typical structures of heat sinks are studied under different rotation speed of the spindle. According to the simulation study, the thermal resistance of heat sinks was presented. In the experiment, the output voltages of a thermoelectric generator were measured under different rotation speed with different structures of heat sinks. Experiment and simulation shows that the two pipes structure of the heat sink can help the generator to produce more power.

Abstract: The properties of polymeric components made by hot embossing are obviously affected by the geometry of the mold such as the duty ratio, the aspect ratio, width to thickness ratio and the mold cavity position. This paper focuses on numerical simulations with isothermal embossing conditions in order to observe the stress distribution and the stress concentration of the polymeric patterns. The simulation results show that stress concentration in the PMMA resist accumulates at the contact corner between the mold and the polymer, and the location of the stress distribution is mainly on the profile of the replicated patterns. Small duty ratio will result in high stress concentration at the corner of the replicated components. The stress concentration also increases rapidly while the aspect ratio of the mold increases. The thicker the polymer is, the more difficult the adequate flow of the polymer becomes, and the stress concentration rises up. A stress barrier can be used in the mold in order to reduce the stress concentration in the middle of the replicated polymeric patterns.

Abstract: Rotating spindle is the main heat source of machine tool. However, it is hard for the traditional wired sensors to get access to the temperature value in rotating environment. This is one of the largest challenges that the researchers will encounter in machine thermal analysis and machine's state monitoring, and it limits the accuracy of the machine thermal analysis and state monitoring. Recently some researcher begins to adopt wireless communication technologies into the measurement in rotating environment, which would overcome the weakness of wired sensors. This paper first describes the superiors of the popular wireless technology ZigBee. And then presents the design of a wireless temperature measurement system based on ZigBee. In the Last, the system is implemented into a wireless temperature measuring experiment. The result of the experiment proved the stability of the wireless temperature measuring system, and shows the clear advantage of wireless sensors compared with wired sensor in rotating environment.

Abstract: The geometric structures of the mold and embossing conditions can obviously influence the filling flows in the polymeric patterns. In this study, embossing stamp and substrate with different geometries are used to investigate the flow behavior under both isothermal and non-isothermal conditions. In general, for the stamp, small duty ratio cavity fills more sufficiently than large duty ratio cavity. With the same cavity duty ratio, inner cavity fills more quickly and sufficient than outer cavity. Compared to multiple cavities stamp, individual cavity fills more slowly, especially embossed with the stamp having small duty ratio cavity. Under non-isothermal embossing, the filling flow indicates a wall climbing flow and the polymer flow replaces the outer cavity better. Uncommon substrate provides a limitation of out-squeezing flow from polymer layers, so the polymer pick reaches the mold faster than common substrate like the flat. The present simulation study provides an analysis of the mold geometry especially the substrate geometry to govern filling flow and replication fidelity.