某零件聚氨酯橡胶弯曲模设计

本文通过对聚氨酯橡胶弯曲模具的设计,与传统钢模弯曲成型作了比较,介绍了凸模、聚氨酯橡胶垫、容框的设计要点及注意事项等。     

扁形钛铜复合棒挤压模具设计与应用

对长宽比较大的扁形截面钛铜复合棒的挤压模具进行了设计研究。通过合理选材,并选择使挤压力最小的模具模腔轮廓曲线和半模角,改变模孔工作带的几何形状与尺寸,选择适当的挤压速度等,优化设计制备出扁形钛铜复合棒专用挤压模具。增加工作带长度可以增大摩擦阻力,使向该处流动的供应体的流动静压力增大,迫使金属向阻力小的方向流动,从而使型材整个断面上金属流量更加均匀。挤压实验结果表明,合理的模具设计对挤压材的挤压过程和挤压制品质量有重要影响,锥形模具更适合于扁形钛铜复合棒的挤压。解决了科研生产实际对大的长宽比扁型钛铜复合棒的需求。     

注射垫圈模具设计

本文分析了模具的形状特点和技术要求,设计了一付普通浇注系统三层注射模具,并解决了该注射模的自动脱模问题。介绍了模具结构和动作过程。实现了在小型注射机生产多腔较大型的塑件。实践证明该模具安全可靠,提高了生产效率。     

转轴弯曲模的设计

设计了一种防止回弹和提高制件刚性的转轴弯曲模,阐述了其模具结构及工作过程.     

基于CAE某发动机加强板成形模具的设计

对某发动机加强板零件进行分析,通过计算及运用相关软件确定其展开尺寸.对弯曲成形模具凹、凸模工作部分运用CAE技术进行设计,并用Mastercam软件来模拟加工,加工时合理选择铣刀与参数设置,可得到较为理想的走刀路线.这样可获得凹、凸模的详细加工过程平面录像,同时可设计出模具的总装图及零件图.     

基于模具创新设计的高强钛管小半径加热绕弯扁化控制

目的 发展小直径高强钛管小弯曲半径(R=1.5D)加热弯曲成形的截面扁化缺陷控制技术.方法 基于对管材弯曲前预变形和弯曲过程中施加有效约束的原理,设计变曲率型腔的反变形压力模结构、勺形芯模结构和带芯球的柔性芯模结构,结合有限元仿真分析,研究探索不同模具结构设计对弯管截面扁化的影响.结果 与"压力模+圆形芯棒"模具组合相...     

异形闭合件弯曲成形模的设计与制造

根据一种异形闭合件的产品要求,对其弯曲工艺作了具体分析,克服了技术难点,设计制造了一套简单实用的弯曲成形模,达到了产品质量要求,也为类似形状制件的弯曲成形模的设计提供了一种新方法.     

汽车覆盖件模具模块化快速设计技术的研究

汽车覆盖件模具具有型面形状复杂、精度要求高、设计周期长、单件生产等特点 ,本文通过功能分类 ,模具体模块分解 ,利用参数化模板等技术 ,实现了模具的快速设计 .     

夹箍类零件的成形工艺和模具设计

介绍了2种夹箍形冲压件。根据零件结构上的差异制定了相应的工艺方案并设计了弯曲模具。对2种弯曲模的工艺原理和工作过程进行了详细的分析和描述。     

带径向扭曲叶片转子精密塑性成形技术的研究

设计了一套带有组合凹模的等温闭塞式成形试验模具，利用模拟试验方法研究了模具形状、坯料形状和成形力等对金属变性流动规律的影响。研究结果表明；采用等温成形和闭塞式成形复合技术可以整体精密成形带径向扭曲叶片的转子锻件；利用组合凹模结构能够解决转子锻后的顺利脱模问题，等温变形条件使薄而长的铝合金叶片的成形性大大提高，而锥底凸模和分流原理可以有效地降低模压力和提高金属充填模腔能力，所成形的锻件的叶片部分接近零件的形状和尺寸，金属的流线方向完全沿零件的几何外形分布，可以有效地提高构件的强度。     

纸盒模切板设计的几个问题

分析讨论了对纸盒模切板设计的影响因素，如纸板纹向、盒坯外形、搭桥、模切工艺等；分析了通过拼接提高原材料利用率的方法，给出了几种愤况的数学公式。     

无机粘接技术在模具结构上的应用

通过探讨无机粘接的原理及其在模具结构上的应用，在降低制造要求和成本的前提下，解决了复杂模具加工和装配中精度低的难题，提高了模具的使用寿命     

Powder deposition in three parallel-oriented dies of cylindrical and E shapes

The second generation pressure deposition tester (PDT-II) was used to evaluate the die filling process in multiple dies. Three parallel-oriented dies of cylinder and E-shape were filled with an alumina powder at different feed shoe speeds. The results indicated that for cylindrical dies at lower feed shoe speed, the center area had the highest pressures; at higher speed, pressure distribution was irregular, complicated, and varied more. One reason for this was relatively low bulk density and small particle size of the powder, which led to relatively poor flowability. For E-shaped dies, due to wider opening of the middle leg, its pressures were higher than those of the other legs. Compared to another powder (BPM) with denser, bigger, and less spherical particles, the alumina powder had the highest final pressures closer to the middle leg, instead of being closer to the back as for the BPM. This was basically due to its physical properties (such as particle size and shape). This research demonstrated that powder physical properties, such as particle size and shape, had pronounced effect on powder deposition. Also, die shape complexity could affect the pattern of powder flow and deposition.     

Computer aided foundry die-design

In the design of die casting dies, the object is to produce sound casting as cheaply and rapidly as possible. At the same time consideration must be given to suitable die size, locations of gating system, and selection of an appropriate die casting machine. Foundries in many cases encounter difficulties to ensure shortened lead-time in designing a new die for new product. A lot of estimations have to be done which use fundamentally based on previous experience and application of various mathematical and empirical equations. In this work, main die design procedures and related equations are presented in a logical way. A computer program is developed to estimate main die elements based on the geometry input of casting shape. After initial inputs have been given, the system does full calculations, optimizes selections, and lists main die element sizes. The program can present die characteristics and casting machine characteristics. From both characteristics the optimum die elements were optimized. Optimum filling time and gating dimensions among other elements of die are estimated. Cooling time, cooling channel locations, and flow rates relations are estimated and presented.     

HD钢在气门热精锻模具的生产应用初步试验

气门热精锻模具失效的主要形式为热磨损和压塌，提高模具使用寿命的关键是使材料具有更高的室温和高温的硬度，磨损抗力，屈服强度和热稳定性。ＨＤ（４Ｃｒ３Ｍｏ２ＮｉｖＮｂ）钢比传统应用的３Ｃｒ２Ｗ８Ｖ钢具有更高的上述性能及足够的韧塑性，因而其模具在理论上具有更长的工作寿命。生产应用试验表明，ＨＤ钢制气门热精锻模具的使用寿命是３Ｃｒ２Ｗ８Ｖ钢的２．２倍。     

Fracture life prediction and sensitivity analysis for hollow extrusion dies

It has been reported in literature that extrusion dies most often fail by fatigue fracture. Experimental studies have shown that cracks pre‐exist in dies because of various factors including machining, heat treatment and surface hardening. High levels of repeated mechanical and thermal loads result in crack propagation leading to ultimate fracture failure. In an earlier work by the authors, a simplified approach of plate‐with‐edge‐crack was used to develop a fracture mechanics based fatigue life prediction model for tube dies. In the current work, extrusion die is modeled as a pressurized‐cylinder‐with‐internal‐crack, a more realistic approach for a hollow (tube) die. Stochastic nature of various fatigue‐related die parameters has been used to reflect their variability. Monte Carlo simulation has been performed to forecast fracture failure of extrusion dies under a given set of operating conditions and mechanical properties. Predicted mean‐time‐to‐failure is quite close to actual average extrusion die life data from the industry. Using tube die as a basis, fracture life of other hollow profiles can be estimated through their shape complexity values. Analysis has also been carried out to evaluate how sensitive fracture life of hollow extrusion dies is to material and process parameters. Major findings are that die life is highly sensitive to initial crack size, wall thickness, profile outer diameter and billet length; moderately sensitive to Paris constant and extrusion ratio; and only slightly sensitive to fracture toughness and ram speed. These results can contribute to a deeper understanding of the factors responsible for fracture failure of an extrusion die exposed to thermo‐mechanical fatigue environment.     

Defining Shape Complexity of Extrusion Dies—A Reliabilistic View

Complexity of the profile being extruded plays a critical role in die design, die reliability, process aberrations, and product defects. Engineering common sense dictates that a more complex die should require a larger amount of extrusion force or pressure. This has been experimentally substantiated by the authors in a recent study. According to a basic definition, therefore, extrusion shape complexity is the ratio of the pressure required to extrude a complex profile to the pressure required for a solid circular profile of the same area. Most of the complexity definitions reported in published literature are based on this interrelationship between extrusion pressure and profile complexity. From a die reliability viewpoint, a complex profile is more difficult to extrude than a simple one, and it generates more stresses in the die. It should therefore lead to an earlier die failure. Another study by the authors confirms that the working life of hot extrusion dies is definitely affected by profile complexity. Reported complexity definitions provide some sort of index to measure extrudability, and can thus be used for pressure prediction to a certain degree. Unfortunately, none of these definitions addresses the very important issue of die reliability, and they generally yield a counterintuitive trend of increasing die life with increasing complexity. None of these definitions includes all the significant geometrical features of a die profile. This article reports the development of two new definitions of shape complexity (linear and power-law) incorporating all significant geometrical features of an extrusion die profile. Die failure data from a large commercial extrusion facility have been collected and analyzed. Regression-based models have been developed for prediction of die failure on the basis of complexity.     

Measurement of Normal Stress Distribution on Work Punches During One-Sided Die Compaction

Modeling of the powder compaction process in dies requires the determination of characteristics for use as input to the model or for confirmation of the output from the assumed model. The distributions of normal stress on work punches were determined during one-sided die compaction of a ceramic powder using an experimental device comprised of split punches and equipped with strain gauges. The effect of presence or absence of lubrication and its influence on powder conditioning were studied. The experimental data obtained were mathematically processed using spline functions that confirmed the previous theoretical observations. The distributions of normal stress on the punches presented in this study are much more detailed than those reported in the literature. For all test cases studied, stress distribution on the upper punch shows the same shape with close numerical values. On the lower punch, the largest decrease of the normal stress is noticed when the "as received" powder is compacted without lubrication. The beneficial effect of lubrication and powder conditioning for homogeneity was demonstrated with respect to the distribution of normal stress on the lower punch. Results showed that the spline functions better represent the experimental data. ceramic powder die compaction normal stress distribution     

Measurement of Normal Stress Distribution on Work Punches During One-Sided Die Compaction

Modeling of the powder compaction process in dies requires the determination of characteristics for use as input to the model or for confirmation of the output from the assumed model. The distributions of normal stress on work punches were determined during one-sided die compaction of a ceramic powder using an experimental device comprised of split punches and equipped with strain gauges. The effect of presence or absence of lubrication and its influence on powder conditioning were studied. The experimental data obtained were mathematically processed using spline functions that confirmed the previous theoretical observations. The distributions of normal stress on the punches presented in this study are much more detailed than those reported in the literature. For all test cases studied, stress distribution on the upper punch shows the same shape with close numerical values. On the lower punch, the largest decrease of the normal stress is noticed when the "as received" powder is compacted without lubrication. The beneficial effect of lubrication and powder conditioning for homogeneity was demonstrated with respect to the distribution of normal stress on the lower punch. Results showed that the spline functions better represent the experimental data.

ceramic powder die compaction normal stress distribution     

Impact of Repeated Nitriding Cycles on Extrusion Die Life—Some Statistical and Metallurgical Observations

This paper presents some observations about die failure patterns in commercial aluminum extrusions. A total of 97 dies were analyzed to observe the nature of scatter in the life of these commonly used dies. Each die in its complete life cycle passes through a number of nitriding treatments. The number of these nitriding treatments generally ranges from 5 to 10 in most cases. Each nitriding event is equivalent to die surface renewal, and a new time between failures is calculated after each renewal. This article analyzes the performance of both solid and hollow dies to first failure and to subsequent failures after nitriding. The Weibull model describes the time to first failure and cumulative time to nth failure of this group of dies and indicates an overall wearout pattern. The median time to failure, scatter in cumulative life, and progress of die death rate are discussed. A die is considered to fail when the surface must be nitrided. The interarrival time between failures (nitriding events) is analyzed for both solid and hollow dies. It is shown that interarrival time is also Weibull distributed. Based on these observations, it is concluded that if die is treated as a repairable system and the die surface nitriding makes the die as good as new, the failure can essentially be modeled as a nonhomogeneous Poisson process with a nonlinear intensity of failure. The results presented are of the first phase of an ongoing project dealing with life improvement of extrusion dies. The analyses presented provide a starting point for subsequent in-depth study of die-life reliability, optimal nitriding interval determination, and optimal cumulative time before die replacement.