Algorithm for automatic undercut recognition and lifter design

When having internal undercut in the ejection direction, the finished plastic product cannot be directly removed from the mold. Through lifter design, during the ejection process, the lifter can eject products in the upward direction and make lateral movements to successfully leave the undercut location to part from the mold. Under the framework of CAD software, this study developed the undercut feature recognition, integrated the mold design, and automated lifter production. Based on the geometric relationship of the internal undercut surface, edge, and point of the product model, this study summarized a set of recognition rules. Through computer programming calculation and judgment, the proposed method can automatically recognize undercuts to reduce the labeling time at the conceptual design stage and record the undercut width and length in feature parameters. At the mold design stage, through the acquisition and calculation of its parameters, it can automatically produce a suitable lifter during the architecture of the web-based mold design navigation process. Through standardized design process, it can reduce 90 % of mouse clicks and design time to guide users to quickly complete the design, while reducing design errors to improve working efficiency by the automatic integration function.     

Recognition of undercut features and parting surface of moulded parts using polyhedron face adjacency graph

An injection or die-casting mould is an assembly of parts containing an impression into which molten material is injected. In this article, the undercuts present in mould parts are divided into basically two parts: completely visible and partially visible. A graph-based approach is proposed to identify these undercuts even for the free form objects. Unlike conventional graph based methods a new polyhedron face adjacency graph (PFAG) is proposed with the key concept of visibility of undercuts by using Bezier surface. A rule-based approach is also discussed to automatically generate an optimal parting surfaceof irregular moulded parts. Since the generation of parting surface plays an important and effective role in mould – die design, thus it is essential to develop a simple and robust algorithm based on proposed methodology, which can effectively tackle the problem. Different case studies show that the proposed method can recognize various undercut features without much difficulty.     

Automated Process Planning for the Manufacture of Lifters

This paper presents the methodology of a computer-aided process planning system IMOLD  FCAPP for the manufacture of injection moulded components, which will facilitate the standardisation of process planning and significantly reduce lead-time. The main components of the mould such as the slider, the lifter and the mould base are considered in this system. In this paper, the automated process planning for the manufacture of a lifter is described. A combination of the generative and variant approach (hybrid approach) is used for the development of the system. The input to the system is a 3D lifter model. First, the system classifies the lifter types and extracts the feature parameters from the model. Each lifter type refers to a standard process plan template, in which a set of processes is presented in sequence. Secondly, the system selects the machines, cutters, fixtures, and cutting parameters for each process in the plan template, based on the actual dimensions of the features and constraints and rules defined in the system and the available machining resources. The process plan execution is then simulated on the screen step by step.     

Feature extraction from freeform molded parts for moldability analysis

In the design of plastic injection molds, the depressions and protrusions (DP) preventing the removal of molded part from mold are referred to as undercuts. This paper describes an approach to recognize DP feature within the curvature region representation based on the curvature properties of entities in B-rep model. The recognized depression features and the concave transitions between protrusion features are potential undercuts which affect the choice of parting directions of the molded part. The possible withdrawal directions of the potential undercuts are derived by geometric reasoning and visibility map computation. This method can recognize isolated and intersecting features with planar, quadric, and freeform surfaces. The identified potential undercuts with their possible withdrawal directions can provide decision support information for mold design such as selecting parting direction, parting lines and surfaces, etc. The case study is presented to verify the feasibility of the developed method.     

Three-Dimensional Kernel Development for Injection Mould Design

Today, many software "plug-ins" have been developed on high-level 3D modelling platforms to facilitate processes such as FEM analysis, CAM, injection mould design, simulation and visualisation. Such an arrangement is advantageous in many ways. However, it is not without shortcomings. Ideally, these "plug-ins" could also be developed using low-level 3D kernels for higher flexibility and better portability. This paper examines the various issues and methodologies related to the development of such 3D-based applications. The emphasis is placed on the software aspect. First, a methodology for the development of 3D-based applications is proposed. The idea is then implemented by developing an injection mould design application using a low-level 3D kernel called Parasolid. Based on design concepts used in an established mould design application, IMOLD, the development of a mould base design module is illustrated. An object-oriented programming language has been chosen for the development of the software on a Windows NT platform.     

Injection moulding optimisation of multi-class design variables using a PSO algorithm

Injection moulding optimisation seeks to achieve the highest possible moulding quality under the specified constraints. To this end, the factors (design variables) affecting the moulding quality should be adjusted, including those of process parameters, mould design, part geometry, etc. Past work in this aspect is primarily focused on tuning the process parameters and mould design (e.g., gate location, runner and cooling channel layout), with less attention on the part geometry, and none on them all. To address this problem, this paper presents a PSO (particle swarm optimisation) algorithm for the optimisation of multi-class design variables, such as the part thickness, process parameters (melt temperature, mould temperature, injection time) and gate location. The optimisation is targeted at different aspects of moulding quality, including part warpage, weld lines, air traps, and so on. In applying the PSO algorithm, the paper proposes a modified elite archiving method, which can expedite the convergence speed, hence improving the efficiency of the algorithm. A computer program was developed that automates the steps such as adjusting the part thickness, the injection moulding process parameters and the gate location, activating the CAE software to simulate the injection moulding process, retrieving the simulation results, and evaluating the objective functions. The whole procedure iterates a number of generations by following the search process of the algorithm. A case study was also presented to illustrate as well as to test the proposed methodology, which was demonstrated as both effective and efficient.     

基于 Pro／EN GIN EER 的螺纹管模具设计

介绍了利用三维设计软件Pro/ENGINEER进行螺纹管注塑模具设计的方法和过程。以一种带有螺纹结构的塑料产品为例,提出了一种合理可行的模具设计方案。     

Artificial neural network based model for computation of injection mould complexity

The cost of injection mould construction depends primarily on the mould complexity. The ability to estimate the mould complexity before releasing the final drawings for construction purposes will greatly help the designers to understand the implications of their design on cost. Mould complexity depends on several factors such as part geometry, parting line, materials, and number of cavities per mould. In most industries, the mould complexity evaluation is performed manually based on past experiences of mould makers. Faced with a shortage of experienced mould makers, there is a pressing need for development of computer-aided tools for mould complexity evaluation. In this study, a neural network-based design tool for computing the mould complexity index, which represents the degree of difficulty of mould manufacturing, has been developed and implemented using a 14-3-1 backpropagation network running on the CNAPS neuro-computer.     

注塑模数字化设计技术研究

阐述了一种注塑模数字化设计技术.运用Pro/E软件的通用功能模块和模架设计专家(EMX)模块,进行塑件及注塑模设计.以相机面壳注塑模设计为例,验证了该方法的可行性.该方法可以提高塑料注射模具的开发效率.     

UG软件在注射模具设计中的应用

UG软件实现了CAD/CAM/CAE技术在模具设计中的综合应用,其中Moldwizard模块是用于注射模具自动设计的专业模块。Moldwizard为设计模具的型芯、型腔和滑块等提供了更进一步的建模工具,使模具设计变得更快捷和更容易,其最终结果是创建出与产品参数相关的三维模具,并能用于加工。本文以电话机外壳为例,介绍了运用Moldwizard设计模具的过程,并最终设计出三维模具图,模拟了模具加工仿真过程。     

DISCRETIZATION APPROACH USING RAY-TESTING MODEL IN PARTING LINE AND PARTING SURFACE GENERATION

Surface classification, 3D parting line, parting surface generation and demoldability analysis which is helpful to select optimal parting direction and optimal parting line are involved in automatic cavity design based on the ray-testing model. A new ray-testing approach is presented to classify the part surfaces to core/cavity surfaces and undercut surfaces by automatic identifying the visibility of surfaces. A simple, direct and efficient algorithm to identify surface visibility is developed. The algorithm is robust and adapted to rather complicated geometry, so it is valuable in computer-aided mold design systems. To validate the efficiency of the approach, an experimental program is implemented. Case studies show that the approach is practical and valuable in automatic parting line and parting surface generation.     

压力容器焊缝咬边疲劳裂纹的启裂寿命

针对某企业空气球罐焊缝咬边在压力波动时的受力情况,首先建立带咬边结构的受力模型,利用西田正孝的图表方法和有限元法分别计算咬边引起的弹性应力集中系数,然后计算出咬边尖端的名义应力,进而利用小缺口启裂寿命经验估算式估算咬边的疲劳裂纹启裂寿命。再采用与实物等厚度、与真实咬边等尺寸的模拟试样,进行与实际结构等应力范围条件下的模拟疲劳试验。结果表明,试验寿命与根据经验估算式得到的估算寿命非常接近,从而为咬边疲劳裂纹启裂寿命研究提供了理论依据和试验数据。在考虑一定的安全系数后,对所分析的球罐给出的剩余总寿命为9年,至启裂的剩余寿命为6年。     

Part decomposing algorithm based on STL solid model used in shape deposition manufacturing process

Shape deposition manufacturing is an innovative rapid prototyping technology combining CNC machining and deposition processes and in which if a surface of the part is visible from the build direction it can be directly shaped into desired geometry on part material; if the part features are undercut or face away from the build direction, these part features will be sculptured into the support material in order to form a negative cavity at first, then the part material is deposited into this negative cavity in order to replicate these features into part material. This process is cyclically repeated until all segments have been built. Finally, the sacrificial material is removed, and the finished part is left. This innovative technology has the benefits of commercial rapid prototyping technology; meanwhile, it inherits the accuracy and high surface quality of traditional machining process. For this process to be realized, it is essential to decompose the CAD solid model into a series of manufacturable segments which have no undercut surfaces at the data pretreatment step. In this paper, a solid decomposing strategy is proposed with a detailed discussion on the classification of the segments based on the value of triangle face normal vector, and then an algorithm for auto-decomposing a CAD solid model in STL data format is developed.     

基于Pro/E的管接头注塑模具设计

介绍了利用Pro/E软件对管接头注塑模具进行辅助设计的过程,重点阐述了应用Pro/E模具模块分模的流程;指出了采用模具CAD/CAM软件Pro/E来实现模具三维设计,可以大大缩短设计和制造周期,提高产品设计品质,降低设计成本.     

A 3D CAD knowledge-based assisted injection mould design system

This paper presents the basic structure of an interactive knowledge-based injection mould design system (IKB-MOULD). The basis of this system arises from an analysis of the injection mould design process for mould design companies. This injection mould design system covers both the mould design process and mould knowledge management. IKB-MOULD integrates the intelligent design process and knowledge management with many developed interactive tools in a commercial solid modelling software environment.     

Image processing-based accessibility analysis method for determining undercut-free parting direction

In injection molding, demoldability of a part without the use of a side core is possible only if all of its surfaces are fully accessible in the parting direction. A mold surface may be fully accessible from some directions, but may not be accessible from other directions. Therefore, to determine the undercut-free parting direction, an algorithm is developed that evaluates the accessibility of each part surface from a set of directions (called as candidate parting directions) by using image processing techniques. In the proposed methodology, the surface accessibility is determined by comparing the projected area of each surface on the image plane in the presence of other part surfaces to that of the same surface in the absence of other part surfaces. The algorithm can be used to determine the accessibility of planar, ruled, and free-form surfaces without tessellating the part surfaces. The algorithm includes a method that can also successfully classify surfaces that are oriented perpendicular to the parting direction. The surface classification can be used to identify the undercut-free parting direction, recognize the various undercut features, and form the visibility maps. The accuracy of the algorithm depends upon the number of pixels used to represent the part on the computer screen. The method has been successfully implemented, and test results are discussed in this paper.     

盒盖模具设计

介绍了盒盖注射模的结构、各主要部件（浇注系统、成型零件、合模导向机构和推出机构）的设计思路及模具的总装配图。在该模具设计中,利用CAD软件绘图及Pro／E软件进行造型,绘制了零件图和装配图。     

电视功能排钮注射模具设计

将注塑模拟技术应用于模具设计,可以预判设计效果的优劣,及时发现模具和成型的质量,然后改进和完善设计.以电视功能排钮为例,介绍了其模具的设计要点,并利用典型CAE软件Moldflow对其浇注系统和冷却系统进行了注塑模拟分析,对分析的主要结果进行了研究和鉴定,并用之于模具设计,最终获得较为合理的设计结果.     

儿童玩具积木的注射分析及模具设计

对1种塑料儿童玩具积木进行了注射分析和模具设计,通过CAE分析软件Moldflow,对充填时间、注射压力、气穴、熔接痕和翘曲变形量进行了模拟分析,进而优化了设计方案。实践证明,通过CAE分析软件对塑料制件注射情况进行模流分析,可以在设计阶段预测成型过程中可能出现的问题,从而合理优化注射参数和模具设计,节约模具的开发时间和成本。     

基于Pro/E和MasterCAM的注射模CAD/CAM应用研究

简要介绍了注射模的CAD/CAM设计思路,通过实例用Pro/E软件对塑件进行了注射模具设计,得到了模具成型零部件,并重点阐述了其设计流程,然后运用MasterCAM软件对该塑件的型芯进行了加工刀路设计,模拟其加工过程,生成了NC代码。将2者结合使用,可显著提高模具设计及数控加工的质量和效率。