Experimental study of sand filling process of aeration filling and high pressure squeezing flaskless moulding machine

Abstract

Aeration filling is a new flask (or moulding chamber) filling method, which has been developed from the shooting/blowing process. As a sand filling stage, aeration filling determines the ultimate quality of mould in a sense, such as integrality and uniformity. If the moulding sand can be filled in every part of the mould cavity, an accurate shape would be replicated after the finial compaction stage, otherwise the mould may have weak regions. This paper focuses on the study of the sand filling process and its influential factors. From experiments and comparison with conventional shooting (or blowing) process, it can be seen that this method has the advantages of better sand filling effect and less energy consumption.     

Industrial treatment processes for recycling of green foundry sands

Abstract

Three treatment processes for the reclamation of green moulding sands coming out from a cast iron foundry located in Northern Italy are considered in this study. A wet mechanical treatment, a dry mechanical treatment and a dry mechanical plus heat treatment are compared to evaluate the efficiency of each process and to point out the best regeneration solution for the recycling of reclaimed sand in foundry operations. The inflow and the outflow samples of each process were characterised by means of particle size analysis and the determination of silica, loss on ignition, acid request, oolitic and some metals contents. A final evaluation of the three processes was performed taking into account the obtained quality of recovered silica sand and the economical aspects; the wet mechanical and the dry mechanical plus thermal treatments are most effective for the recovery of green moulding sands coming out from the considered foundry plant for cold box core production.     

用气冲气推成形触头造型机制造电机壳铸型的试验研究

扼要介绍了用气冲气推成形触头造型机制造电机壳铸型的成型过程及其实砂效果,试验结果表明,在工作气压为0,4￣0.45MPa的条件下,气冲气推成形触头造型机对电机壳类铸型的紧实,实砂效果十分理想,砂型紧实度高而且均匀。     

A new numerical simulation model for high pressure squeezing moulding

High pressure squeeze is the most popular moulding process applied in modern moulding machines.Because of the unique characters of moulding sand and nonlinearity of squeezing process,the mechanical model is of key importance for computer simulation.Drucker-Prager/Cap is a typical soil mechanical theory model and it was used to simulate the squeezing process in this study,while ABAQUS software is used to simulate dynamic stress/strain evolution during the process.The simulation agrees well with the experimen...     

飞轮壳的铸造工艺设计

HT250飞轮壳铸件采用HWS静压线造型、湿型砂铸造工艺。根据铸件的结构特点,把整个铸件放置在下型,法兰边向上,每型布置两件,上型砂胎喷涂涂料防止粘砂。浇注系统各单元截面尺寸为:∑F阻=13.5 cm2,F直=19.63 cm2,∑F内=31.68 cm2,∑F网=77 cm2。生产结果表明,飞轮壳铸件满足顾客要求。     

Experimental investigation and numerical analysis of compaction behaviour of moulding sand

Abstract

The compaction behaviour of green sand was studied to assess the applicability of the Cooper–Eaton equation under conditions close to those of real foundry operations. The results indicate that the Cooper–Eaton equation describes the behaviour reasonably well, allowing prediction of the pressure required to achieve sand moulds of reasonable density. A corresponding distinct element method numerical simulation was also attempted. The study contributes useful information to the understanding of green sand compaction. It is clear that spherical sand is preferable to improve filling behaviour and that the gap between mould wall and pattern must be sufficiently large to avoid prevent weak sand compaction.     

Sequence control of pressing velocity for pressure in press casting process using greensand mould

Abstract

Recently, a press casting process using a greensand mould was actively developed by the authors' group to improve productivity and casting quality. This process consists mainly of two parts: in the first, molten metal is poured in the lower mould by a ladle, and in the second, the upper mould falls down toward the lower mould to press the molten metal. The feature based advantages of this greensand casting are an astonishing increase in casting yield (over 90%) and energy saving. A rapid pressing process should be realised as a vital task to achieve an increase in productivity. In addition, the advanced technique of this process will also suppress casting defects such as a cold shut and the inclusion of generated oxide film due to the temperature decrease in molten metal. As the technical problem on high speed pressing, the other defects are caused by increased pressure. Metal penetration, in which the solidified molten metal is soaked among the sand particles in greensand, often occurs. Hence, the authors propose controlling the pressing velocity in order to realise high production competence and to suppress the rapid increase in pressure. In this paper, a pressure suppression method in high speed pressing is proposed in which the sequential velocity control of the press can be applied to various casting moulds. The control design is conducted simply and theoretically, and a brief mathematical model of the fluid pressure is built using a complicated, exact model of CFD. Then, the permitted range of pressure fluctuation is given for the production of high quality casting. Considering the upper limit of the pressure constraint for defect free pressing, the switching velocity pattern of multisteps is derived using the proposed mathematical model without trial and error adjustment. The control performance for pressure fluctuation using the obtained velocity reference is checked by CFD simulations.     

射压造型数值模拟

射压造型是铸件生产中的现代化造型方法之一.射压造型包括用射砂进行充填及预紧实和高压压实进行砂型最终紧实.本文利用两相流理论模拟出射砂预紧实后的密度场分布;并采用分区建模的思想,结合型砂的本构关系试验,利用有限元方法,计算出砂型内二维的应力分布状况.     

Evaluation of green compressive strength of clay bonded moulding sand mix: neural network and neuro-fuzzy based approaches

Abstract

An attempt has been made to develop neural network and neuro-fuzzy based models to predict the green compressive strength of clay bonded moulding sand mixtures and to analyse the properties of the mixed sand. Data for the models were generated following standard experimental procedure in the sand laboratory. Process parameters such as clay content, moisture, coal dust and mulling time were varied. The collected data were used in developing these models. The predicted green compressive strengths by neural network and neuro-fuzzy based models have been found to be in good agreement with the experimental values. Furthermore, it has been observed from the results that the predicted values from the neuro-fuzzy model are more accurate than those predicted from the neural network model.     

Back Matter

Abstract

This paper is concerned with the experimental determination of thermomechanical properties of a cold box sand, which have a strong influence during the solidification in a sand casting process. To this end, the uniaxial behaviour for different temperatures up to the casting temperature of an aluminium alloy is investigated. For the tests at room temperature, the authors use optical measurement equipment, which is ideally suited to measure inhomogeneous deformations and strains within the material specimens. Furthermore, different strain rates are applied to analyse rate dependent behaviour. The storage time of the sand is also varied, since it influences the material characteristic of the binder in the cold box. An effective heating procedure is developed to characterise the mechanical material behaviour due to different isothermal loadings. The pressure dependence of multiaxial stress states is investigated in a pressure cell. The experimental data are intended to develop and identify a material model for sand, taking into account the strength–differential effect (S–D effect), rate and temperature dependence and the effect of hydrostatic stress states.     

Benchmarking commercial aluminium sand gating systems

The results of a study to identify the range of commercial gating systems used in American aluminium foundries are reported. Fifteen foundries using green sand moulding methods participated in the study by producing moulds of test castings using their “normal” shop gating systems. The foundries were asked to rig a common test pattern for a target volume of 1,500 pieces per month, produced to a “commercial” quality standard, and with an absence of visible porosity on machined surfaces. Information was also requested on essential melt and moulding media conditions, as well as a selling price for the castings.

The evaluations included gating ratio and yield measurements, radiographic evaluations of subsurface quality, machining of cope and drag surfaces to reveal gating induced trapped air and dross, pressure testing of two drilled bosses, and a final liquid penetrant examination of the machined surfaces.

Those features in the individual systems that appeared to produce the best results are summarised, as well as some undesirable practices that might have a negative influence upon casting quality.     

用覆砂铁型铸造工艺生产球铁轮毂

介绍了用于QT450-10轮毂铸件的覆砂铁型铸造工艺:覆砂层厚度控制在7～10 mm,铁型壁厚20～30 mm;采用双工位覆砂造型机造型,模具温度控制在240±10℃;铸件采用边冒口补缩,浇注温度控制在1 420～1 350℃。生产结果显示:轮毂铸件表面粗糙度达到Ra12.5μm,尺寸公差等级CT7～8,工艺出品率88%,球化等级1～2级,石墨球大小6～7级,内部组织致密,产品合格率在95%以上。     

FS粉代替型砂中煤粉的生产应用

采用FS粉取代煤粉配制高压造型线用型砂。两年多的生产使用结果表明,型砂的含泥量和水分降低、湿拉强度提高,因而铸件夹砂、冲砂、粘砂等缺陷减少。此外,由于粉尘较少,生产条件和工作环境也得到改善。     

Rapid fabricating process of zinc alloy moulds based on vacuum casting process

Abstract

A rapid fabrication process was developed by combining stereolithography prototype, silicone rubber mould and vacuum casting process for zinc alloy moulds. Transfer coating mould was introduced as casting moulds reproduced from silicone rubber moulds. Vacuum casting process was applied to improve filling ability of complicated mould with fine pattern surface. Vacuum reduces the gas counterpressure in the casting mould cavity and then improves the filling ability.     

钢铁零件挤压铸造的工业化应用

我国钢铁零件挤压铸造目前已经进入针对具体零件推广应用的新时期,主要生产设备和工艺技术正在向专业化方向发展,轮盘盖、叉架座和箱体类钢铁零件的挤压铸造都已获得成功应用。实践证明,该工艺适用性强、成本低、绿色度高,适于生产高品质要求的中小工件。今后的研究重点是钢铁零件挤压铸造工艺设计准则研究和从热.力.材三方耦合的角度进行专用涂料的系列化研究、模具设计的科学化和模具材料的最优化研究。     

新型碳纤维复合材料手机电池盖IML注射工艺研究

介绍了新型碳纤维复合材料的特性,结合IML工艺,通过模流分析、模具结构设计、注塑机螺杆要求分析和制品表面处理技术,成功地将碳纤维新型复合材料注射工艺应用于手机电池盖,使得同等强度条件下,制品外壳厚度减薄50%,质量减轻42%。     

年产2.5万t铸件的砂型铸造车间设计

介绍了年产2.5万t制动鼓铸件的砂型铸造车间的设计过程:(1)明确砂型铸造车间的生产纲领和设计原则;(2)选择合适的造型工部、熔化工部、砂处理工部、清理工部设备和工艺方案;(3)完成车间总体部署和物流方案设计。最后确定,造型线选用国产水平分型造型线,设计造型速度为90整型/h,配套选用一拖二IGBT熔化电炉,铁液熔化速度为15 t/h。     

Some demands on rapid prototypes used as master patterns in rapid tooling for injection moulding

Injection moulded components are finding vigorously increasing applications in numerous sectors. The flexibility of the process allows complex components to be manufactured in high volumes in fully automated environments. Associated with such components are equally complex tools whose manufacture is both expensive and time consuming. It is therefore vital that the component design be evaluated thoroughly with regard to both performance and manufacturability before commitment is made to expensive production tooling. The use of a physical prototype often provides the best method of design evaluation. The major routes to prototype manufacture are; material removal, rapid prototyping and rapid tooling. Rapid tooling techniques provide the most representative route, with the ability to produce polymeric prototypes (often in final material) by an injection moulding process.

Research has been undertaken into two rapid tooling processes; enhanced silicone moulding and sand moulding. Both processes involve casting material against a rapid prototype (master pattern) to form a mould which is then used in the manufacture of product prototypes by injection moulding. The focus of this paper is on the demands of these tooling techniques placed on rapid prototypes when used as master patterns. The demands are discussed in terms of surface finish, surface porosity, dimensional accuracy, thermal resistance and thermal expansion.     

基于注塑机螺杆位置与压力曲线的注射成型过程监测方法

提出基于注塑机螺杆位置与压力信号，采用非线性数据降维方法提取成型特征，建立原材料、模具温度与制品成型质量之间的神经网络模型，实现注射成型过程的故障监测和质量预测。试验结果表明：与未降维的数据和主成分分析等线性降维方法相比，拉普拉斯映射法和扩散系数图法相结合的非线性降维方法可从螺杆位置与压力信号中判断制品原材料、模具温度的异常及预测制品成型质量，在验证集和测试集均获得了高于0.92的回归系数，所提出的方法提取了原始曲线数据内在的高维度、非线性、强耦合的数据关系，有效进行了数据降维，提高了故障监测与质量预测模型的精度与效率。     

铸铁用湿型砂取消煤粉的理论与实践

介绍了湿型砂中煤粉的作用和机理，分析了湿型砂取消煤粉的可能性，通过实例，证明在手工造型的情况下，只需在砂型表面喷涂一薄层固砂剂，煤粉是完全可以取消的。