Shinn-Liang Chang

Computerized Tooth Profile Generation and Undercut Analysis of Noncircular Gears Manufactured With Shaper Cutters

Pitch curves of a conjugate noncircular gear pair are derived based on kinematic considerations. A method for considering the inverse mechanism relationship and the equation of meshing, is proposed here to derive a complete mathematical model of noncircular gears manufactured with involute-shaped shaper-cutters. The proposed method is similar to the contact line method and the envelope method, but is easier to apply to the determination of tooth profiles. A computer program is developed for generation the tooth profile with backlashes. Undercutting analysis is also investigated by considering the relative velocity and equation of meshing. Finally, modified elliptical gears are presented to illustrate the tooth profile generation when the proposed mathematical model is applied, and to investigate the phenomenon of tooth undercutting.

Mathematical model and undercutting analysis of elliptical gears generated by rack cutters

The theory of gearing and geometry of the straight-sided rack cutter are employed to develop a mathematical model of elliptical gears that takes backlash into consideration. The mathematical model also includes the bottom land of the elliptical gear, which is equidistant from the pitch ellipse. A computer program is developed to generate the tooth profile of elliptical gears. The profile of elliptical gears obtained by applying the proposed method is compared with that obtained by the evolute method. Undercutting of elliptical gears is also investigated. The results of this research should be helpful in the design, manufacture, and measurement of elliptical gears. Copyright 1996 Elsevier Science Ltd

A general mathematical model for gears cut by CNC hobbing machines

A hobbing machines cutting mechanism is a mechanism with multi-degree offreedom during the cutting process. In this paper, we propose a general gear mathematical model simulating the generation process of a 6-axis CNC hobbing machine based on the cutting mechanism of CNC hobbing machine and worm-type hob cutter. The proposed gear mathematical model can be applied to simulate different types of gear cutting. Some examples are included to verify the mathematical model. Also, a novel type of gear named Helipoid which can be used in crossed axes transmission is proposed. The proposed general gear mathematical model can facilitate a more thorough understanding of generation processes and toward the development of novel types of gears.

Kinematic optimization of a modified helical gear train

A mathematical model of a modified helical gear train (MHGT), manufactured with a practical hobbing machine using a curved-template guide, and which takes considerations of center-distance variation and axial misalignment into account, is developed. Tooth contact analysis (TCA) and kinematic errors of a MHGT due to mis-assembly are investigated. A multiple optimization method is applied to reduce the level of MHGT kinematic errors, and to investigate optimal gear tooth modifications. Computer simulation programs for TCA and optimization are also developed. Two numerical examples are presented to illustrate the kinematic optimization of the proposed helical gear train. The results of this study are most helpful in designing and analyzing a MHGT.

Development of a CAD/CAE/CAM system for a robot manipulator

Abstract In this study, a CAD/CAE/CAM integrated system for a robot manipulator was developed. The D–H (Denavit–Hartenberg) coordinate transformation method was used to perform the robot position analysis, according to the transformation matrices, we used Matlab to calculate the robot position analysis. Pro/ENGINEER (Pro/E) was used to construct the robot manipulator parametric solid models, Pro/Mechanica was used to simulate the dynamic simulation and working space, MasterCAM was used to implement the cutting simulation, and the prototype was manufactured using a CNC milling machine. Finally, a CAD/CAE/CAM integrated system for a robot manipulator was developed. A demonstration example is presented to verify the design, analysis, and manufacture results (the demonstration is located at the website of http://www.sparc.nhit.edu.tw/∼jennifer/robot1/index.htm ). This integrated system not only promotes automation capabilities for robot manipulator production, but also simplifies the CAD/CAE/CAM process for a robot manipulator. This integrated system is useful for developing a supplementary teaching tool for practical computer-aided mechanism design courses.

Helix gash of hob cutter manufactured by milling

Abstract Hob cutters with a helix gash are frequently used in worm-type and straight-sided hob cutters with large lead angles. A milling cutter is the main tool in the manufacture of gashes of hob cutters. However, if a hob cutter has helix gashes, the actual cutting faces may deviate from the theoretical form due to generation motion. Sharpening errors can also contribute to both profile and lead errors if the work piece is exposed to the cutting edge in a different plane. In this paper, the mathematical models of the theoretical and the actual gashes manufactured by milling cutters are developed. A numerical example is also given to demonstrate the significance of profile deviation of the cutting faces. The models can be used to predict actual cutting profiles and assist in the design and manufacture of high precision hob cutters.

The influence of serration on a shaving cutter with a pre-designed relief portion

In this paper, a shaving cutter with serration and a pre-designed relief portion manufactured by a hob cutter was designed. Due to the non-conventional manufacturing process, standard manufacturing problems were avoided and the production efficiency was enhanced as was the stiffness of the shaving cutter. Two solid models of the shaving cutter, one with the novel relief portion and the other a relief hole, were set up for stress analysis using the finite element method. The models confirmed that the shaving cutter with the novel relief portion had a higher stiffness compared to that with a relief hole in the presence of serration.

Studies on Epitrochoid Gear for Cycloid Drives

Cycloid drives are widely used in the industries because of their excellent characteristics, namely, high gear ratio, smooth transmission, compact size, high efficiency, low noise and long service life. In this paper, a mathematical model of an epitrochoid gear for a cycloid drive with a small tooth number difference has been proposed. Computerized simulation of the generated epitrochoid gear has also been developed. In this paper, the pressure angle, which has an important role in the analysis of cycloid drives as it influences the direction and magnitude of force transmission in gears, is derived based on the theory of differential geometry. The rack cutter profile, which is the fundamental tooth profile of a hob cutter, which in turn is the main manufacturing process of epitrochoid gear, has been obtained based on the theory of gearing. It is anticipated that the results from this paper will be beneficial to the design, analysis and manufacture of cycloid drives.

Surface Modification of High Density Ceramic Powder for Increasing Suspension Capacity in Three-Dimensional Printing Application

Three-dimensional slurry printing is a promising tool for making ceramic object but it limits in high dense ceramic powder because of poor suspension capacity. This study uses zirconia powder with an average diameter of 2 μm because its density is 5.67 g/cm3. A treatment protocol is proposed to improve the suspension capacity of zirconia powder including the ball milling, surface modification and resin blending. Experimental results show that adding 1% of isostearyl titanate, a coupling agent, for surface modification can enhance the lipophilicity of zirconia powder. Mixing surface modification powder in resin with a weight ratio of 7:3 and carrying on ball milling with 100 RPM for 6 hours can obtain the diameter of powder less than 400 nm. As a result, the zirconia slurry can obtain good suspension capacity which is over 48 hours.

Computer –Aided Design of Helical Cutting Tools

The helical cutting tools have complex geometries. A rack cutter is the most economical tool that has been used for manufacturing helical cutting tool. In this paper, the computer program has been designed to evaluate the manufacture abilities following design concept and analyze the technical parameters of helical cutting tool. The program can simulate the sections of helical cutting tool and the rack cutter, analyze the clearance angle, relief angle, width top of the helical cutting tool, and modify the rack cutter profile to show the helical cutting tool profile suitably. This program can predict the differences during manufacture process and offer the best solution for economical consideration.