Virtual prototyping and manufacturing planning by using tri-dexel models and haptic force feedback

This paper presents a new method of using the tri-dexel volumetric models and a haptics force feedback for virtual prototyping and manufacturing planning. In the proposed method, the initial polyhedral surface model is converted to a tri-dexel volumetric model by using a depth-peeling dexelization algorithm. In the virtual prototyping process, the tri-dexel volumetric model is updated by the swept volume of a moving cutter via a haptic force feedback interface device. A collision detection algorithm is proposed for the virtual sculpting and the pencil-cut planning with real-time haptic force feedback to the users. Tool paths are generated for machining the virtual sculpted parts via the simulation and verification on a virtual CNC machine tool before they are actually machined. Computer implementation and practical examples are also presented in this paper. The proposed method enables the haptic-aided virtual prototyping and manufacturing planning of complex surface parts.     

Freeform modelling using sweep differential equation with haptic interface

This paper presents the development of a virtual sculpting system and addresses the issues of interactive freeform solid modelling with haptic interface. A virtual reality (VR) approach is taken to make the developed system more intuitive and interactive. The virtual sculpting method is based on the metaphor of carving a primitive or imported solid model into a 3D freeform object. The geometric modelling is based on the sweep differential equation method to compute the boundary of the tool swept volume. The ray-casting method is used to perform Boolean operations to simulate the sculpting process. A new method of surface reconstruction from dexel data is presented. The PHANToM? manipulator is used to provide the position and orientation data of the sculpting tool and also to provide haptic sensation to the user hand during the sculpting. An accuracy analysis is performed to determine the limitations on the sculpted geometric details.     

Freeform modelling using sweep differential equation with haptic interface

This paper presents the development of a virtual sculpting system and addresses the issues of interactive freeform solid modelling with haptic interface. A virtual reality (VR) approach is taken to make the developed system more intuitive and interactive. The virtual sculpting method is based on the metaphor of carving a primitive or imported solid model into a 3D freeform object. The geometric modelling is based on the sweep differential equation method to compute the boundary of the tool swept volume. The ray-casting method is used to perform Boolean operations to simulate the sculpting process. A new method of surface reconstruction from dexel data is presented. The PHANToM™ manipulator is used to provide the position and orientation data of the sculpting tool and also to provide haptic sensation to the user hand during the sculpting. An accuracy analysis is performed to determine the limitations on the sculpted geometric details.     

虚拟机械加工环境的建造

在研究虚拟现实技术,数控加工技术的基础,开发出一个虚拟加工环境,其中主要包括车间、机床、夹具等场景,该环境包括三坐标铣削加工中心等５台机床,机床实现了仿真加工能力,车间提供了用户漫游功能。同时该环境实现了对零件可加工性、加工参数合理性的评价。     

数控加工中的刀位干涉检查

干涉检查是数控加工的关键问题之一,本文提供了一套可靠的干涉检查算法。介绍了研制CAX系统的基本原则;说明刀位计算方法;详细讨论曲面间、曲面自身及边界部位的干涉检查算法,其方法均是首先将曲面离散为三角小平面,然后计算球头刀球心至有界三角小平面的距离。该距离即作为判断干涉与否的依据。运行表明,算法可靠,效率较高。附有若干实例。     

Titanium aluminide coating on titanium surface using three-dimensional microwelder

Feasibility of a new method of titanium aluminide coating on titanium surface based on a reaction between aluminum liquid beads and the surface of titanium substrate has been studied using a computer-aided three-dimensional microwelder (3DMW) designed by the present authors. A predetermined length of thin aluminum wire was fed onto the substrate surface, and a spark was stricken from a thin electrode of a W-Ce₂O₃ alloy to make a small aluminum liquid bead on the substrate surface and to simultaneously melt a small area of the substrate surface beneath the bead. All conditions including the length of the wire feeding, the position of the electrode, electric power, etc. had been programmed beforehand. The liquid bead containing aluminum and titanium rapidly solidified on the titanium substrate surface producing titanium aluminides on it. Repetition of the aluminum wire feeding, the electrode positioning and the spark striking produced a coating layer consisting of sub-layers of TiAl₃, TiAl and Ti₃Al from the surface side to the substrate side. Vickers hardness and wear resistance of the coated sample were remarkably improved.     

利用CAD/CAM软件确定数控编程中未知点的坐标

针对常用未知点算法繁琐易出错,提出了用CAD/CAM软件的尺寸标注、测量、目标捕捉等功能确定零件数控编程未知点坐标的方法,并通过实例介绍了这些方法的操作步骤。与常用方法相比较,该方法具有简单、准确、方便、快捷等优点。     

Five-axis machining of STL surfaces by adaptive curvilinear toolpaths

We propose a new framework for toolpath generation for five-axis machining of part surfaces represented by the StereoLithography (STL) format. The framework is based on flattening the STL part and generation of adaptive curvilinear toolpaths. The corresponding cost functions, designed to represent the accuracy and the efficiency of the toolpath, are scalar functions, such as the curvature, kinematic error, rotation angles, machining strip or material removal rate or a vector field when the tool moves along a curvilinear path partly or even entirely aligned with directions considered to be optimal. The adaptive toolpath exploits grid generation methods and biased space-filling curves, combined with adaptation to the boundary and the domain decomposition. The proposed methodology of the adaptive curvilinear toolpath (ACT) has been tested on a variety of STL surfaces, including a case study of STL dental parts. Machining crowns/implants for four basic types of human teeth, molar, premolar, canine and incisor, has been considered and analysed. The reference methods are the standard iso-parametric path, MasterCam toolpath, and advanced methods of NX9 (former UG). The experiments show that there is no universal sequence of steps applicable to every surface. However, a correct choice of the tools available within the proposed ACT-framework always leads to a substantial improvement of the toolpath, in terms of its length and the machining time.     

工业中CAD/CAM几何造型的研究与应用

通过形状复杂的水轮机转轮叶片的几何造型研究,提出了3DCAD／CAM在工业中的应用模式。