Plaster casting process for prototyping of die casting based on rapid tooling

Rapid prototyping (RP) combined with a gravity casting process can provide a suitable substitute with steel tool die casting for prototyping metal casting. Due to differences between die casting and gravity casting, there are several drawbacks in RP simulated die casting. This paper is concerned with the development of a new plaster die casting process that combines pressurization and vibration for prototyping of die castings, and with a plaster die casting machine that has a structure similar to that of a die casting machine. The machine utilizes an oil cylinder for pressurization and a magnetic actuator for vibration. A rapid prototyped pattern is made by the laminated object manufacturing (LOM) process to prepare a plaster mold. In the process, a plunger in the developed machine simultaneously pressurizes and vibrates the molten metal to fill the plaster mold completely and to facilitate the creation of nuclei in the molten metal, respectively. The developed machine has produced a prototype of an end clutch cover with remarkable improvement in mechanical properties.     

金属型铝合金重力浇注装置及其模具设计的研究

为适应较小规模铸造企业的生产模式、有效提高铸件质苎．对铝合金重力浇注装置及其模具结构进行设计研究。在装置上采用简单的机械结构使之方便手动操作，使用完全金属型模具并使之具有倾转功能。研究发现在浇注过程中具有操作简单方便、易于维护，并且制造成本低廉、模具设计制造周期短的特点。铝合金液体在模具中的充型和排气效果良好，可减少气孔、缩孔等铸造缺陷。特别适用与中小型企业的小批量铸件的生产和产品零件的试制加工。     

浅析棘轮本体金属模低压铸造工艺与模具设计

低压铸造是介于金属型铸造和压力铸造之间的一种铸造方法。其是在一定的压力作用下,将金属熔液注入铸型型腔。并在压力的作用下凝固以获得铸件的方法,本文主要是对棘轮本体金属模低压铸造工艺与模具设计进行探寻和改进,根据以往的各种铸造方法的优势和劣势不断总结经验,不断的探索挖掘,使模具设计及铸造工艺得到了更全面的改进。     

基于RP工艺的直接铸型制造方法探讨

快速成形 (RP)发展的重心已转向快速制造 (RM)。RP技术与铸造工艺结合产生的快速铸造 (QC)是 RM的主要研究领域之一。本文介绍了基于 RP工艺的直接铸型制造的工艺方法 ,对其成形精度、效率、适用范围和主要特点进行了分析比较 ,指出直接铸型制造工艺是实现铸造过程的自动化、柔性化、敏捷化的重要途径。 PCM工艺具有独特的优越性 ,应用前景广阔     

Thermal analysis of casting dies with local temperature controller

In high pressure die casting processes, a die plays a critical role in removing heat from the molten metal during the cavity filling and solidification stages. Proper control of die temperature is essential for producing superior quality components and yielding high production rates. In this paper, a computerized intelligent real-time monitoring and control system (IRMCS) is developed for die casting processes involving cooling of a die with multiple channels. A local temperature controller is designed to monitor temperature signals from the die insert and flow rate signals from the cooling lines. The performance of the controller is evaluated, and the effect of the controller on local temperature and heat transfer of casting dies is analyzed. The experimental results obtained from a laboratory die casting process simulator indicate that the developed control system is capable of adjusting the desired supply of cooling water into multiple cooling lines, which effectively controls the local temperature of the die insert within a given range. Hence, the desired thermal pattern of the die becomes achievable.     

复合铸造技术在特种产品上的应用

介绍了将复合铸造技术运用到航空炸弹中的复杂工件,特别是大型薄壁铝合金舱体的优势。分析了石膏型熔模铸造结合真空增压技术的特点,同时,采用该技术研制大型复杂薄壁铝合金铸件,通过合理设计铸件浇注系统,选择铸型工艺,优化浇注工艺参数和严格控制固溶处理温度与校形时机,提高了铝合金的充型能力,改善了铸件的致密度和针孔度,解决了大型薄壁铸件充型及内部质量难以控制的难题。     

新的激光快速成形方法及应用

针对目前主要激光快速成形方法的优缺点,提出一种基于三维实体边界分割的激光快速成形新方法.该方法将叠层实体制造(LOM)法主要进行激光二维轮廓线扫描和选择性激光烧结(SLS)法能够加工多种覆膜粉末材料的优点有机结合,能够克服SLS法加工效率低,成形件致密度、硬度、精度和表面粗糙度等性能较低的缺点.利用自主开发的快速成形系统,采用热像仪测温与Ansys模拟激光能量输入模型相结合的方法对工艺参数进行确定,对基于三维实体边界分割激光快速成形方法进行应用研究,实现三维实体的快速成形及金属零件的快速铸造,并通过无模具快速铸造的手段获得金属齿轮铸件.     

Dimensional accuracy and surface roughness of rapid freeze prototyping ice patterns and investment casting metal parts

The dimensional accuracy and surface finish of ice patterns generated by rapid freeze prototyping were first investigated. The dimensional accuracy and surface finish of metal parts made by investment casting with ice patterns were then investigated and compared with those made by conventional investment casting with wax patterns. The selection of binder, ceramic powder, and catalyst material for ceramic slurries in the process of investment casting with ice patterns and the need for an interface agent to separate the ice pattern from the ceramic slurry in the mold making process are discussed. The parts used in the investigation included circular cylinders with vertical and slant walls and a turbine impeller. This revised version was published online in October 2004 with a correction to the issue number.     

消失模铸造充型与凝固过程的计算机仿真

根据消失模铸造液态金属充型及液态金属—模样界面的推进机制,提出了充型过程界面推移位置的人工神经网络算法。根据计算得出的界面位置,用SOLA算法计算了充型过程中液态金属的流场,并耦合计算了充型过程中的温度场。根据计算得到的充型结束时铸件及铸型温度场,求解三维导热微分方程,计算了铸件凝固过程的温度场。结合消失模铸造型壁移动的规律,预测了球墨铸铁件消失模铸造的收缩缺陷。计算模拟结果与充型过程实际测试结果及铸件解剖结果一致。     

Rapid investment casting: direct and indirect approaches via fused deposition modelling

Investment casting (IC) offers an economical method for mass producing complex, shaped metal parts. However, high tooling cost and lead times associated with the fabrication of metal moulds for producing IC wax (sacrificial) patterns result in cost justification problems for customised single casting, small- and medium-quantity production. Rapid prototyping (RP) techniques can reduce the costs associated with single-part or small-quantity production as they can be applied to the fabrication of sacrificial IC patterns containing complex and intricate designs with significant cost and lead-time savings. In this project, a benchmark model is designed to assess the fused deposition modelling (FDM) process for creating sacrificial IC patterns. In addition, an indirect approach toward producing wax patterns via silicone rubber moulding is investigated. Cost and lead time comparisons between the two IC pattern production methods were carried out and presented. The dimensional accuracies of metal castings generated from the RP-produced patterns are also presented.     

Maximizing average efficiency of process time for pressure die casting in real foundries

Scheduling of casting processes is the problem of determining the number of products that will be manufactured in each casting shift so as to optimize a predetermined objective function. In this paper, we propose a linear programming (LP) model that maximizes the average efficiency of process time for casting in real foundries. The considered casting process is pressure die casting, the most prevalent permanent mold casting process, equipped with an automated die exchange device. In permanent mold casting, the use of a mold or die installed on a casting machine requires a significant process time for casting. The objective function of the proposed LP model is defined as the average ratio of the actual process time to the pre-assigned operating time in a shift. A solution that minimizes the objective function will provide the maximum surplus time, hence optimizing the efficiency of casting operations in terms of process time. Numerical examples are presented to illustrate the applicability and reliability of the proposed model. The results demonstrate that this model is an effective and conveniently implemented tool for solving real casting sequences in a simple and practical framework.     

蓄电池板栅连铸机研制

设计了一种蓄电池板栅连铸机,该连铸机可实现蓄电池板栅的连续铸造。针对蓄电池板栅连铸过程中铅液在模具内快速凝固结晶的特点,分别进行了动模表面连续板栅型腔结构设计、定模内部供铅结构设计、模具温度控制结构设计、浇注过程气体保护结构设计,并进行了样机试制及板栅连铸试验,获得了蓄电池连铸板栅样品。     

Rapid investment casting: direct and indirect approaches via model maker II

Although investment casting (IC) provides an economical method for the mass production of metal parts with complex and intricate features, the relatively long lead times and high tooling costs involved in the manufacture of metal moulds for the fabrication of sacrificial IC wax patterns lead to cost justification problems for customised single casting, small and medium quantity production. The application of rapid prototyping (RP) technologies to fabricate complex sacrificial IC patterns can result in significant reduction in the costs and lead times associated with single part or small quantity production. Previously, the authors assessed the suitability of the fused deposition modelling process, in particular ABS models, for creating sacrificial IC patterns [1]. The current research looks into the feasibility of employing patterns fabricated by Model Maker II (MMII) as sacrificial IC patterns to produce metal castings rapidly. In addition, an indirect approach involving the utilisation of silicone rubber moulding with an MMII-fabricated master pattern to produce sacrificial IC wax patterns is investigated. The dimensional accuracies and surface qualities of the final metal castings generated from the RP-produced patterns are presented. Cost and lead time comparisons are also carried out and presented .     

快速铸造金属模具整体精度补偿的试验研究

介绍了基于快速成型技术的快速铸造金属模具的工艺流程和影响模具尺寸精度的主要误差因素。对鼠标注塑模尺寸精度的整体补偿进行了试验研究,通过对制品尺寸的整体补偿,显著提高了金属注塑模的尺寸精度。     

Vibration-assisted filling capability in thin wall investment casting

Understanding the mechanism of the vibration needed to fill thin section and clarifying the dominant control parameters of the vibration in thin wall investment casting are the keys to producing sound casting. The filling capability in thin wall investment casting method can be assessed by the metal head. It was found that the effect of the vibration on the metal head is markedly dependent on acceleration of applied vibration. Two potential mechanisms were observed from the experimental results during the filling process in thin wall casting: discontinuous propagation flow in vibration conditions and continuous propagation flow without vibration. These mechanisms can modify the contact angles between liquid metal and a wall of the mold. Experiments also showed that two features of the transition can be observed from the front of the morphology: coherent liquid metal front, this occurs in thin wall investment casting when the acceleration due to vibration is less than (1?g) and jetting at the free surface, this occurs in thin wall investment casting when the acceleration due to vibration exceeds 1?g.     

快速成型技术在熔模精密铸造中的应用

快速成型技术是具有高柔性的先进制造技术,无需任何专用工具,由零件的CAD模型直接完成零件或零件原型的成型制造。将快速成型技术与铸造技术结合起来,采用快速成型技术制造铸型或铸模,可极大提高铸造的柔性和生产效率,满足新品试制和小批量生产的需求,这也是快速成型技术的一个主要发展方向。本文通过几种快速成型模在熔模精密铸造中的实际应用和试验得出,采用SLA法制作的蜂窝结构快速成型模在尺寸波动方面满足精铸需要,并能实现铸件的快速制造。     

Rapid prototyping and tooling techniques: a review of applications for rapid investment casting

Investment casting (IC) has benefited numerous industries as an economical means for mass producing quality near net shape metal parts with high geometric complexity and acceptable tolerances. The economic benefits of IC are limited to mass production. The high costs and long lead-time associated with the development of hard tooling for wax pattern moulding renders IC uneconomical for low-volume production. The outstanding manufacturing capabilities of rapid prototyping (RP) and rapid tooling (RT) technologies (RP&T) are exploited to provide cost-effective solutions for low-volume IC runs. RP parts substitute traditional wax patterns for IC or serve as production moulds for wax injection moulding. This paper reviews the application and potential application of state-of-the-art RP&T techniques in IC. The techniques are examined by introducing their concepts, strengths and weaknesses. Related research carried out worldwide by different organisations and academic institutions are discussed.     

A new shell casting process based on expendable pattern with vacuum and low-pressure casting for aluminum and magnesium alloys

A new shell casting process, with the adoption of the foam pattern of lost foam casting (LFC) as prototype and the combination of the thin shell fabrication technology of investment casting and vacuum and low-pressure casting process, was proposed for manufacturing complicated and thin-walled aluminum and magnesium alloy precision castings. Loose-sand uniting vacuum was used in the new process to further reinforce the thin shell, and the new process proves to be a process with simple process, low cost, and high thin shell strength. Because the molten metal filling and solidification are completed under air pressure and vacuum level, the filling capability and feeding capacity of the molten metal are greatly improved, and the castings become denser. This paper mainly investigated the fabrication technology of thin shell based on foam pattern prototype, the removing foam and roasting shell process and vacuum and low-pressure casting process. The few-layer compound thin shell of silica sol–sodium silicate was adopted for the new process. Removing foam pattern was carried out at 250°C for 30 min, and the shell was roasted at 800°C for 1 h. Combined with the vacuum and low-pressure casting process, this new shell casting process has successfully produced thin wall and complex aluminum and magnesium alloy parts with high quality. In addition, comparisons in terms of filling ability, microstructure, mechanical properties, porosity, and surface roughness among this new shell casting, gravity casting, and LFC were also made to show the characterization of this new shell casting process.     

压铸机压射速度自适应模糊控制与仿真研究

压铸机是有色金属铸件生产的重要装备，广泛地应用在汽车、摩托车、家电、仪表、电子信息等各行业的制造业中，其压射系统的性能的优劣对压铸件的质量起着决定性的作用。针对卧式冷室压铸机二级压射速度控制工艺技术特点。采用自适应模糊控制技术对二级压射进行控制．通过控制增压阀对增压时间进行控制。采用具有典型二阶过程的电液伺服阀系统进行了仿真研究。仿真结果表明了该方法的有效性。     

压铸机压射机构的改造及其压射控制

如何在现存压铸机的基础上,进行压射机构的改造并对压射实现自动控制,这是一个很有研究意义的问题。为此,本文研究了液态金属压铸机压射结构的重新设计及其实时控制,在理论上设计 一套对压射进行实时控制的系统,文章重点研究了该系统的组成、基本原理及其特点。