Papers by Author: Jinn Jong Sheu

Abstract: In this research, high efficiency machining tool path design of die cavities were developed using CAD/CAM and plunge roughing technology. The algorithms of cutting tool path design for ideal and non-ideal rouging area were proposed to improve the material removal rate (MRR). The proposed tool path design methods are based on the minimum numbers of rectangular or triangular patterns to cover the roughing areas. The cutting results of the traditional Z-plane and the plunge roughing were compared to show the improvement of the cutting efficiency with the proposed methods. Design of experiments (DOE) method was adopted to optimize the tool path designs and cutting conditions. Cutting experiments were carried out to verify the proposed cutting path design methods. The better material removal rate was obtained using the proposed plunge roughing method compared to the traditional Z-plane roughing. Both of the cutting simulations and the cutting experiments also showed the cutting efficiency of plunge roughing is increased with increase of cutting depth. The proposed hybrid tool path design method can further improve the cutting efficiency of plunge roughing process.

Abstract: The dimension accuracy and the too life are the major issues of the machining of hard-to-cut materials. To fulfill the requirements of accuracy and tool life needs not only well planning of cutting path but also the proper cutting conditions of cutters. The vibration and deflection of cutters caused by poor selection of cutting conditions can be predicted using models of cutting force and tool deflection. In this paper, a cutting force model considering the effect of tool helical angle and a cantilever beam model of tool deflection were proposed for the high speed machining of hard-to-cut material SKD11. The shearing force, the plowing forces, and the helical angle of cutters are considered in the elemental force model. The material of workpiece, SKD11, studied in this paper is commonly used for the die and mold industries. The cutting constants of the proposed force model are determined via the cutting experiments carried out on a high speed machining center. A dynamometer and a high frequency data acquisition system were used to measure the x-, y-, and z-direction cutting forces. The obtained cutting constants were used to predict the cutting forces and compared with the results obtained from the cutting experiment of verification using cutters with different helical angles. The theoretical and the experimental cutting forces in the x-, y-, and z- direction are in good agreement using flat cutters with 30 and 45 degrees of helical angle. The dimension deviations of the cut surface in the cutting experiment case of tool deflection were measured using a touch probe and an infrared receiver installed on the machining center. The measured average dimension deviation, 0.163mm, is close to the predicted tool deflection, 0.153mm, using the proposed cantilever beam model. The comparisons of the cutting forces and the average of the cut surface dimension deviation are in good agreement and verify the proposed cutting force and the tool deflection models are feasible and useful.

Abstract: The difficulty in forging of bevel gear with an outside diameter larger than 75mm is due to the high forming load requirement. In this paper, a new intuitive method for the punch and preform design of the bevel gear warm orbital forging is proposed to lower the forging load and improve the die filling. The geometry of the forged bevel gear are divided into characteristic features and mapped to the main dimensions of the preform design. The exact dimensions of the preform are determined utilizing constraints of the volume constancy and the section centroid balance. The surface of punch tip is designed using the section profile described by a Bezier curve with five control points which are related to the preform and the forged part geometry simultaneously. The forming process was analyzed via the FEM simulation. The die stress was also calculated to prevent die failure and improve tool life. A PXW-200 orbital forging press was adopted for the experimental tests of the proposed designs. The unfilled area at the teeth faces were examined via the laser scanner. The experimental results of the maximum unfilled distances were varied from 0.3 mm to 0.8mm depending on the different punch tip profile design. The predicted tooth profiles were in good agreement with the experimental measurements.

Abstract: In this paper, authors proposed an effective quality index of bending operation and a new punch profile design method to prevent defects. The proposed quality index is presented in terms of distance of fracture location with respect to the topmost plane of blank, the maximum von Mises stress, and the maximum shear stress. The Taguchi method with L18 orthogonal array was adopted to evaluate the effects of design parameters and find out the optimum design of punch profile. A new punch feature called “golden finger” was proposed to control the material flow and move the fracture defects out of the trimming line. The results of this study had demonstrated the optimum die design can be achieved with the proposed golden finger feature to obtain a sound product.

Abstract: The bending tool design of a cold roll-formed blank has been discussed in this paper. The cold roll-formed blanks give a up and down bending line instead of a conventional straight line, The problems of wrinkling and edge irregularity occured frequently in such bending operation. A die design and blank pre-cutting methods are proposed in this paper to eliminate the edge irregularity. The radii of die and punch, punch profile, the gap of tools are considered as the design factors. The CAE method is adopted to obtain the measurements of the design of experiments (DOE). A fourth-order Bezier curve is proposed to desing the pre-cutting curve systemtically and automaticaly. The Golden section method is adopted to improve the pre-cutting curve design. The edge iregularity of a cold roll-formed balnk can be minimised by the proposed method. The wrinkling defects can be decreased but are not able to fuly elimiated.

Abstract: An intelligent E-Manufacturing system was developed in this paper. The high speed machining center was rebuilt using 3D CAD system. The moving table (X axis), span column (Y axis), spindle (Z axis) and the tool changing system were modeled precisely. The high speed cutting (HSC) experiments of AL 6061 were carried to obtain the cutting forces and surface roughness for different cutting conditions. The backward propagation supervised artificial neural network (ANN) system was developed to predict the results of the high speed cutting. The intelligent virtual reality (VR) system of high speed cutting was developed integration the ANN and the VR environment. The users were able to learn the manual and the CNC operations of the HSC machine. The actions of users were recorded and evaluated to judge the learning results. The cutting results of forces and surface roughness of user’s NC program was predicted by the ANN system to assist the NC programmer to adopt the suitable cutting parameters. The developed VR system was deployed to the internet webpage to supply a good E-Learning and E-Manufacturing environment.