Papers by Author: Wei Chen Lee

Abstract: The objective of this paper is to present the design and fabrication of a hybrid 5-axis machining and rapid prototyping machine tool. The rapid prototyping used for this machine was fused deposition method. The extruder of the fused deposition method and the cutting spindle were installed on each end of the rotary axis respectively to reduce the complexity of this machine. Preliminary experimental results demonstrated that the machine can increase the accuracy of the product made by low-cost fused deposition method.

Abstract: The electrical characteristics of an interconnection system, which include impedance, insertion loss, and return loss, can greatly affect its performance as the signal speed increases. The objective of this research was to understand the discrepancy between the computer-aided analysis and measurement results of an interconnection system, so that a more accurate prediction of the electrical characteristics of this system can be made during the design phase. It was discovered that in both the time and frequency domain the computer-aided analysis results were consistent with the measurement results. Given these conclusions the simulation model was modified to improve the impedance mismatch within the interconnection system. It was found that by properly designing the antipad, the impedance mismatch can be greatly reduced.

Abstract: Traditionally, three CT markers are attached to a surgical guide of dental implant surgery to correlate the implant positions in CT images and the drill positions of a drill press. To allow the drill press to know the positions of the CT markers, users need to use the press to probe the positions of them manually. This process is inaccurate and time-consuming. The objective of this research was to develop a new process to eliminate the traditional probing process. This new process uses two identical pairs of locating pins both in the plaster mold cavity and on the fixture of a CNC drill press, respectively. Since the position of the drill bit relative to the locating pins and the positions of the locating pins relative to the CT markers are designed by us, the drill press knows the positions of the CT markers without probing them. According to the preliminary evaluation results, the mean errors of the location and angle of the drilled holes were 0.696 mm and 1.23°, which indicate that this innovative idea presented in this paper is feasible and promising.

Abstract: The objective of this research was to study and improve the destructive 3D digitizer based on grinding technique that was developed previously. It is shown that the grinding technique used in the 3D digitizer generates better surface condition than the milling technique commonly used in other 3D digitizers, and this is beneficial to the subsequent image processing to obtain the profiles of the cross-sectional images. To increase the overall image resolution, an image-merging method was employed by putting a fiducial on top of the object to allow us to merge partial images into a full image. One of the key factors for the success of image processing is to have good contrast between the object and the background material, and we developed a program with a controllable power supply to automatically adjust the illumination based on the histograms of the images to obtain the maximum contrast. At the end, we performed an experiment by using Taguchi method and found out that the grinding depth is the most significant factor that can be controlled on the destructive 3D digitizer for burr length reduction.

Abstract: The objective of this research is to design and fabricate a general purpose 3D digitizer based on grinding technique to completely acquire the geometry of an object, including its inner structure, and accurately create its CAD model. How the 3D digitizer works is as follows. First a thin layer of an object that is fixed in epoxy is removed by a grinder and the image of the cross section is taken by a CCD camera. The process is repeated until the images of all the cross sections of the object are captured. Then the images are stacked up by using software 3D-DOCTOR to obtain the 3D CAD model. The accuracy of the 3D digitizer developed in the research was within 0.03 mm when measuring a length of 5.50 mm and the gauge R&R percentage was 25.99%. The performance shows that the 3D digitizer is promising for use in industry.