Study on Numerical Simulation of Mold Filling and Heat Transfer in Die Casting Process

A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow of mold filling process of die casting. In addition, the mathematical model for simulating the heat transfer in die casting process has also been established. The computation program has been developed by the authors with the finite difference method (FDM) recently. As verification, the mold filling process of a S-shaped die casting has been simulated and the simulation results coincide with that of the benchmark test. Finally, as a practical application, the gating design of a motorcycle component was modified by the mold filling simulation and the dies design of another motorcycle component was optimized by the heat transfer simulation. All the optimized designs were verified by the production practice.

Simulation of mold filling and prediction of gas entrapment on practical high pressure die castings

Element parameters including volume filled ratio,surface dimensionless distance,and surface filled ratio for DFDM(direct finite difference method)were proposed to describe shape and location of free surfaces in casting mold filling processes.A mathematical model of the filling process was proposed specially considering the mass,momentum and heat transfer in the vicinity of free surfaces.Furthermore,a method for gas entrapment was established by tracking flow of entrapped gas.The model and method were applied to practical ADC1 high pressure die castings.The gas entrapment prediction was compared with the fraction and maximum size of porosities in the different casting parts.The comparison shows validity of the proposed model and method.The study indicates that final porosities in high pressure die castings are dependent on both gas entrapment during mold filling process and pressure transfer within solidification period.

Theoretical modeling of cutting temperature in high-speed end milling process for die/mold machining

A parametric model of cutting temperature generated in end milling process is developed according to the thermal mechanism of end milling as an intermittent operation, which periodically repeats the cycle of heating under cutting and cooling under non-cutting. It shows that cutting speed and the tool-workpiece engagement condition are determinative for tool temperature in the operation. The suggested model was investigated by tests of AlTiN coated endmill machining hardened die steel JIS SKD61, where cutting temperature on the flank face of tool was measured with an optical fiber type radiation thermometer. Experimental results show that the tendency of cutting temperature to increase with cutting speed and engagement angle is intensified with the progressing tool wear.

Mold Wear During Die Forging Based on Variance Analysis and Prediction of Die Life

A process parameter optimization method for mold wear during die forging process is proposed and a mold life prediction method based on polynomial fitting is presented,by combining the variance analysis method in the orthogonal test with the finite element simulation test in the forging process.The process parameters with the greatest influence on the mold wear during the die forging process and the optimal solution of the process parameters to minimize the wear depth of the mold are derived.The hot die forging process is taken as an example,and a mold wear correction model for hot forging processes is derived based on the Archard wear model.Finite element simulation analysis of die wear process in hot die forging based on deform software is performed to study the relationship between the wear depth of the mold working surface and the die forging process parameters during hot forging process.The optimized process parameters suitable for hot forging are derived by orthogonal experimental design and analysis of variance.The average wear amount of the mold during the die forging process is derived by calculating the wear depth of a plurality of key nodes on the mold surface.Mold life for the entire production process is predicted based on average mold wear depth and polynomial fitting.

Low-cycle fatigue behavior of permanent mold cast and die-cast Al-Si-Cu-Mg alloys

Fatigue failure is one of the main failure forms of Al-Si-Cu-Mg aluminum alloys. To feature their mechanical aspect of fatigue behavior, the low-cycle fatigue behavior of permanent mold cast and die-cast AI-Si- Cu-Mg alloys at room temperature was investigated. The experimental results show that both permanent mold cast and die-cast AI-Si-Cu-Mg alloys mainly exhibit cyclic strain hardening. At the same total strain amplitude, the diecast AI-Si-Cu-Mg alloy shows higher cyclic deformation resistance and longer fatigue life than does the permanent mold cast AI-Si-Cu-Mg alloy. The relationship between both elastic and plastic strain amplitudes with reversals to failure shows a monotonic linear behavior, and can be described by the Basquin and Coffin-Manson equations, respectively.

Mold Filling and Prevention of Gas Entrapment in High-pressure Die-casting

This paper presents some results of direct observation of mold filling in a specially designed die-casting by X-ray diffraction, including comparison with numerical simulation. Based on such work the authors discuss how to prevent gas entrapment and propose new methods.

Microstructure and properties of nano-TiN modified Ti(C,N)-based cermets fabricated by powder injection molding and die pressing

Powder injection molding （PIM） and die pressing were employed to fabricate nano-TiN modified Ti（C,N）- based cermets. The shrinkage behavior, microstructure, porosity, and mechanical properties of the samples with and without nano-TiN addition fabricated by PIM and die pressing were analyzed. It is demonstrated that for either PIM or die pressing, the porosities are obviously reduced, the mechanical properties are significantly improved after adding nano-TiN, and the hard particles are refined; the rim phase thickness obviously becomes thinner, and the number of dimples in fracture also increases. Compared the samples fabricated by die pressing, it is difficult for PIM to obtain dense Ti（C,N）-based cermets. Due to the too much existence of pores and isolated carbon, the mechanical properties of the sintered samples by PIM are inferior to those of the sintered ones by die pressing.

Optimization strategy in end milling process for high speed machining of hardened die/mold steel

An optimization strategy for high speed machining of hardened die/mold steel based on machining feature analysis was studied. It is a further extension of the previously presented study on the thermal mechanism of end milling and constant cutting force control. An objective function concerning machining cost and associated optimization algorithm based on machining time and cutting length calculation was proposed. Constraints to satisfy specific machining strategies when high speed machining the hardened die/mold steel, trochoid tool path pattern in slot end milling to avoid over-heat and feed rate adaptation to avoid over-load, were also discussed. As a case study, the tool selection problem when machining a die part with multiple machining features was investigated.

HSM strategy study for hardened die and mold steels manufacturing based on the mechanical and thermal load reduction strategy

The paper discussed cutter-work engagement situation hidden behind the mechanical and thermal load effect on cutting edges during high speed hard machining process. The engagement situation was investigated in great detail using experimental and geometrical analytic measures. Experiments were conducted using A1TiN-coated micro-grain carbide end mill cutters to cut hardened die steel. On the basis, a general high speed hard machining strategy, which aimed at eliminating excessive engagement situation during high-speed machining （HSM） hard machining, was proposed. The strategy includes the procedures to identify prone-to-overload areas where excessive engagement situation occurs and then to create a reliable tool path, which has the effect of cutting load reduction to remove the prone-to-overload areas.

The Convention of Die Casting Industry

The 8th China International Diecasting Congress & Exhibition June 17-22,2012 Shanghai Rhea Lakeview Hotel Shanghai New International Expo Centre(SNIEC) Organized by the Foundry Institution of Chinese Mechanical Engineering Society(FICMES) and the Productivity Promotion Center of Foundry Industry of China,the 8th China International Diecasting Congress&Exhibition is to beheld on June 17-22,2012 in Shanghai.This convention will providean opportunity for the diecasting professionals from China and the rest of the world to meet and discuss frontier technical development indie casting industry。

A Tool Path Re-generation Algorithm for Die & Mold Machining

Facing the challenges of a shorter product design a nd manufacturing lead-time, many mold companies are using 3-D CAD/CAM software s ystems in design and manufacturing. A new product file is often issued to the mo ld design department before it is completely finalized and the design may have t o be iterated many times during the mold design and making processes. In practic e, if a mold has been modified, all the tool paths that cover the modified regio n must be re-generated, no matter how small the modified region may be. With th e available tool path generation systems, if a tool path needs to be re-generat ed, all the cutter location (CL) points must be re-calculated, and none of the original CL points can be re-used. It would require as much time to re-gen erate the modified tool path as in the original case. On the other hand, the mod ified region is usually quite small compared with the entire mold. The complete re-generation process is therefore highly unproductive and time-consuming. This paper proposes an efficient tool path re-generation approach for 3-axis d ie and mold machining. It is assumed in this research that a gouge-free too l path has been generated for the original mold and the same ball end-mill is to be used to generate the tool path for the modified mold. It is shown in th is work that if the boundary of the modified region is interference-free, the a ffected CL points are enclosed by a set of CL points which correspond to the poi nts on the boundary of the modified region. An efficient tool path re-generatio n algorithm was developed in this research. With this algorithm, a closed CL cur ve is first generated from the boundary of the affected region. The CL points fo r the original mold are then analyzed by comparing the x and y values with the b oundary of the affected CL points. If the CL points are not affected by the modi fication, they are output to the new CL file directly. Otherwise, they are remov ed and replaced by the new CL points. The algorithm has been tested using severa l industrial parts, and results show that it is efficient, robust, and the re-g enerated tool path is gouge-free and smooth.

Development of Online Machining and Measurement System in Die and Mold Manufacturing： Concept and Fundamental Experiments

The corrective machining to compensate the resulting errors is usually tried at plural times based on the trial-and-error process when the machining is realized in die and mold manufacturing. This corrective machining has an influence on accuracy and efficiency and is an important factor. The measurement system for measuring the forms of die and mold at all times is essential in order to machine the die and mold with high accuracy and efficiency. However, the problems of management and operation errors are found in compensating process of die and mold machining. In this paper, an online machining and measurement system in die and mold manufacturing is developed in order to overcome these problems. In this online system, 2-axis control system is added to a surface roughness measuring instrument, and both NC machining program and measured data are linked and controlled using a same computer. Therefore, the machining and measurement can be recognized for consistent process, and can be realized on the machine. This system has the advantages such as the high accuracy, low-price, and online convenience and so on. The possibility of practical use of this online system was investigated by fundamental experiments.

Polishing Techniques of Stainless Steel Molding Die for the Slumping Method of Glass Optical Components

In recent years, high precision geometric shape, surface roughness, and cost reduction are required for large glass component molding processes. In this research, the polishing process of stainless steel molding dies used to form thin glass components is investigated. The surface roughness of the polished stainless steel molding die surface is below Rz = 200 nm （P-V） at 15 h polishing with 0.5 % alumina polishing liquid. In the case of polishing process with only the weight of molding die and a polishing pressure of 0.5 kPa, polishing times are approximately 60 h and 20 h, respectively. Final surface roughness polished stainless steel molding die surface with pressure of 0.5 kPa is Rz = 7 nm （P-V）, rms -- 1.6 nm and Ra = 1.4 nm. In a thin glass component manufacturing method, ＂slumping method＂, surface roughness before glass forming is rms = 0.7 nm and Ra = 0.6 nm, and after is rms = 0.7 nm and Ra = 0.6 nm. Therefore, there were no observable changes their surface roughness.

模具设计卓越工程人才“三位一体、四方联动”产教融合培养模式探索与实践

在新时代、新经济和新工科背景下,培养大批能够适应模具产业发展和转型升级的模具设计卓越工程人才,越来越得到教育界与产业界的重视和关注。以产业需求为导向与以产教深度融合作为推进模具设计卓越工程人才培养的基本路径,创建了耦合教育链、人才链和产业链,政府搭建平台,以高校和企业为主导,第三方专业机构辅助的“三位一体、四方联动”校政企协同育人模式。该模式的创新之处是在政府、高校和企业之外,引入了既熟悉工程教育教学规律,又深谙企业生产实践的第三方专业机构,在政府的支持、调控与指导下,对接高校和企业,四方联合打造模具设计卓越工程人才培养协作共同体。该模式突破了传统校企合作的藩篱,解决了产教“联而不动、动而乏力”的问题,有效提升了材料成型和模具设计与制造专业毕业生与社会需求的契合度,促进了学生更加充分与更高质量的就业。

基于OBE理念的职教本科项目驱动式教学改革探究——以压铸模技术课程为例

依据行业发展方向,结合职业教育改革政策,从职教本科压铸模技术课程出发,以培养学生“知识+技能+创新”能力为目标,分析OBE教学理念在教学中的适用性,并从项目载体选择、项目实施、课程考核三个方面进行教学改革探索,使学生专业知识技能螺旋式提升,学习兴趣由被动变主动,创新思维得到有效锻炼,也为适应经济社会发展和技术技能的数字化设计与制造技术专业人才培养奠定基础。

基于专业教学资源库的模具拆装虚拟仿真实训构建

传统模具拆装实训受到设备条件、空间场地、安全隐患等因素影响,限制教学效果的提升。专业教学资源库、虚拟仿真系统等数字化平台的建设为该类实训的开展提供了新的载体和模式。模具专业教学资源库为该实训提供离散化、模块化的全过程数字资源支撑。虚拟仿真系统作为专业教学资源库的特色资源,为该实训提供可交互的立体操作平台。依托以上数字资源,构建了“三段式”模具拆装实训翻转课堂。

一体化大型压铸模具温度控制方法

新能源汽车的发展使一体化压铸完成了从0到1的突破,给压铸模具发展带来了新的机遇。压铸模具是一个热交换器,压铸模具成型中的热平衡问题至关重要。以压铸模具的温度控制为基础,介绍了压铸模具的基本概况与压铸成型加工过程中热平衡的重要性,阐述了目前一体化压铸模模温控制所采用的模温控制岛、异形水路、红外线成像技术、模内传感器、一体化压铸模模温控制集成化等方案。模具温度的控制有利于提高铸件质量,延长模具使用寿命,提高压铸效率。

应用型本科院校模具课程教学改革探索

结合应用型本科院校模具课程教学中存在的问题,进行了较为深入分析,提出了一些具体课程改革方法,可通过完善模具课程体系、引入3D打印、逆向技术、ANSYS、MoldFlow等新课程打造课程创新性,拓宽学生知识面。加大实践环节、深入校企合作、优化教学团队、改进教学方法、探索更适合模具课程教学的新模式。

职教本科背景下模具设计及制造专业课程体系的构建

明确了职教本科的人才培养定位,确定了模具专业人才培养目标,提炼了模具工艺及优化岗位、模具数字化设计岗位、模具智能化制造岗位、模具自动化生产岗位和模具信息化管理岗位等岗位所需的核心职业能力和职业素养,按照职业岗位能力和职业素养的需求设置相关课程内容,完成了职教本科背景下模具专业课程体系的构建。