High-quality manufacturing method ofcomplicated castings based on multi-materialhybrid moulding process

A multi-material hybrid patternless moulding process for complicated castings has been proposed. Moulding sands used in the hybrid moulding process include silica sand, ceramic sand, chromite sand, zircon sand, and steel shot sand. Experimental method was used to study the effects of moulding sands on the temperature field, mechanical properties, and dimensional precision of the iron castings. Under the condition that the wall thickness on different sides of the casting is the same, when the wall thickness is greater than 10 mm, the heat storage capacity of the moulding sands from strong to weak is steel shot sand, zircon sand, chromite sand, ceramic foundry sand, and silica sand. Tensile strength of the obtained castings from high to low is zircon sand, chromite sand, steel shot sand, ceramic sand, and silica sand. Contraction rate of the obtained castings from high to low is steel shot sand, zircon sand, chromite sand, silica sand, and ceramic sand. Therefore, steel shot sand and zircon sand can be used as chilled sand, and even can be used instead of cold iron when the casting wall thickness is greater than 10 mm. Zircon sand and chromite sand can be used to obtain high mechanical properties, and silica sand and ceramic sand can be selected to obtain high dimensional precision of the castings. Finally, a typical iron casting piece was tested by experiment using the hybrid moulding process. Excellent performances of iron castings confirm the feasibility of the hybrid moulding process.

Effects of process parameters on warpage of rapid heat cycle moulding plastic part

The effects of process parameters in rapid heat cycle moulding(RHCM) on parts warpage were investigated.A vehicle-used blue-tooth front shell(consisting of ABS material) was considered as a part example manufactured by RHCM method.The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the J11-W-160 type precise temperature controller was proposed.During heating/cooling process,the mould was able to be heated from room temperature to 160 °C in 6 s and then cooled to 80 °C in 22 s.The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory.Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage,thus improving mouldability and enhancing part quality,whereas the overheated of mould temperature will lead to defective product.The feasible mould temperature scope in RHCM should be no higher than 140 °C,and the efficient mould temperature scope should be around the polymer heat distortion temperature.Melt temperature as well as injection pressure effects on warpage can be divided into two stages.The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend.But others affect the warpage as a V-type fluctuation,reaching to the minimum around the heat distortion temperature.Under the same mould temperature condition,the effects of process parameters on warpage decrease according to the following order,packing time,packing pressure,melt temperature,injection pressure and cooling time,respectively.

Conversion of Rapid Prototyping Models into Metallic Tools by Ceramic Moulding—an Indirect Rapid Tooling Process

A process to convert models made by rapid prototypi ng techniques like SL (stereolitography) and LOM (laminated object manufacturing) or by conventional techniques (silicones, resins, wax, etc.) into metallic mould s or tools has been developed. The main purpose of this technique is to rapidly obtain the first prototypes of parts, for plastics injection, forging or any oth er manufacturing process using the tools produced by casting a metal into a cera mic mould. Briefly, it can be said that the ceramic moulds are produced by mixing in variab le proportions, depending on the type of ceramics employed, strength and roughne ss desired, a ceramic mixture composed by alumina and/or zirconium silicates bon ded with silica coming from a liquid binder, based on ethyl silicate. A catalyst is added to the slurry in order to produce a sol-gel reaction. The liquid slur ry is poured into the box containing the mould to be reproduced. After a short p eriod of time, controlled by the amount of gelling agent, the ceramic mixture ac quires a rubber consistency. The pattern is removed from the ceramic mould, whic h is fired to stop the gelation reaction. After this stabilization the ceramic m ould is sintered at high temperatures in order to generate an inert mould wi th the desired strength in which almost all metallic alloys can be cast. The effect of ceramic materials (shape, granulometric distribution, chemical com position, etc.), processing parameters (proportion binder/ceramic/catalyst, sint ering conditions, etc.) and casting conditions (mould pre-heating temperature a nd pouring temperature) were studied in order to obtain metallic moulds or tools with tailored properties (high dimensional accuracy, low roughness and high mec hanical strength).

Numerical simulation and optimization of shell mould casting process for leaf spring bracket

Although the shell mould casting process has a wide range of application in many fields,the prediction of casting defects is still a problem.In the present work,a typical leaf spring bracket casting of ZG310-570 was fabricated by shell mold casting.The finite element model and ProCAST software were utilized for simulating the filling and solidification processes of the casting;and the formation mechanism of the gas pore,and shrinkage porosity defects were analyzed.The results indicate that the gas pore and shrinkage porosity defects are formed due to air entrapment,insufficient feeding and non-sequential solidification.Subsequently,through changing the position of risers,adding a connecting channel between the risers,and setting blind risers at the U-shaped brackets,an optimized gating and feeding system was established to improve the quality of the casting.After optimization,the gas pore and shrinkage porosity defects of the leaf spring bracket casting are effectively eliminated.The experiment results with the optimized casting process are in good agreement with the numerical simulation,which verifies the validity of the finite element model in the shell mould casting.

Relationships between the surface quality of a single crystal copper ingot and the process parameters of a heated mould continuous casting method

The relationships between the surface quality of a single crystal copper ingot and the process parameters of heated mould continuous casting method were studied experimentally using our own design of horizontal heated mould continuous casting apparatus, and the mechanism by which process parameters affect the surface quality of a single crystal copper ingot is analyzed in the present paper. The results show that the process parameters affect the surface quality of a pure copper ingot by affecting the position of the liquid-solid interface in the mould. The position of the liquid-solid interface in the mould must be controlled carefully within an appropriate range, which is determined through a series of experiments, in order to gain a single crystal copper ingot with good surface quality.

Study on roasting process of zircon-silica sol ceramic mould

Dry stock of silica sol ceramic mould was prepared by using of colloidal moulding technique with an optimized vacuum drying process.Effect of roasting process on the shrinkage rate and compressive strength of zircon-silica sol ceramic mould,and the relationship between the roasting temperature and microstructure of zircon-silica sol ceramic mould were studied.The optimum roasting temperature of zircon-silica sol ceramic mould gained by the experiments is 900℃ and the holding time is 2 h.The scanning electron microscope(SEM) observation showed the growth of refractory particles during the roasting process.The occurrence of sintering was observed in the zircon-silica sol ceramic mould when roasting temperature was above 1,000℃.

A Computer-aided Design System for Framed-mould in Autoclave Processing

The general computer-aided design （CAD） software cannot meet the mould design requirement of the autoclave process for composites, because many parameters such as temperature and pressure should be considered in the mould design process, in addition to the material and geometry of the part. A framed-mould computer-aided design system （FMCAD） used in the autoclave moulding process is proposed in this paper. A function model of the software is presented, in which influence factors such as part structure, mould structure, and process parameters are considered; a design model of the software is established using object oriented （O-O） technology to integrate the stiffness calculation, temperature field calculation, and deformation field calculation of mould in the design, and in the design model, a hybrid model of mould based on calculation feature and form feature is presented to support those calculations. A prototype system is developed, in which a mould design process wizard is built to integrate the input information, calculation, analysis, data storage, display, and design results of mould design. Finally, three design examples are used to verify the prototype.

圆弧抽芯注塑模具优化设计

基于圆弧抽芯注塑模具,根据塑件结构及材料性能特点,对浇口的位置及结构进行了优化设计,通过CAE模拟分析得到位于填充末端、最大壁厚处的塑件最大变形量为0.739 mm,变形量在设计允许范围内。以油缸作为驱动动力源,通过齿条驱动齿轮、内齿轮旋转,实现抽芯动作;将内齿轮设计为异形非标齿轮,减少了所占空间,实现了1模2腔布局。为解决圆弧型芯冷却水路难以加工的问题,设计的加工工序为先按照直型芯进行粗加工,钻孔加工型芯冷却水路,然后,将型芯加热弯曲为所需形状,并进行调质处理,最后对型芯进行精加工使其满足设计要求,达到了随形冷却效果。传动机构关键参数采用理论计算与CAE模拟分析相结合的法验证,测试结果表明,计算校核效率提高了约4倍。

基于Polyflow正压防护面罩吸塑成型过程

为探究正压防护面罩吸塑成型过程中不同工艺参数组合对其影响。结合实际设计的要求,采用PET材料作为面罩吸塑材料,基于Ployflow,分析不同压力、温度组合的工艺参数及初始板材厚度对面罩吸塑成型的影响。结果表明,利用面积延伸率、厚度均匀性及面罩成型深度综合分析面罩的吸塑成型质量发现,温度和压力对面罩成型质量的影响较显著。由于板材厚度与成型深度呈负相关,再结合面罩成型深度的要求可知,在符合设计要求的条件下,当工艺参数组合为温度114℃、压力0.65 MPa、PET板材初始厚度为1 mm时,面罩质量最佳。

基于专利视角下分析国内模具产业发展现状与分布情况

结合国家关于模具产业方面的鼓励政策和模具产业领域的专利申请趋势,对国内模具产业技术及地域分布进行分析,通过信息采集、数据处理、数据可视化等方法,分析模具产业发展态势、技术热点研发趋势、产业高端人才情况,并重点分析了模具产业领域专利申请数量排名靠前的5位申请人,为模具产业发展提供知识产权支撑。

塑料制品挤-注-压加工成型工艺的介绍(二)

本文介绍了塑料制品的一种新的加工成型工艺,暂定名为挤-注-压加工成型工艺。

高流动性滚塑聚乙烯的性能

在气相法聚乙烯装置上开发了高流动性滚塑聚乙烯R335L,采用凝胶渗透色谱仪、旋转流变仪、差示扫描量热仪、偏光显微镜等研究了其性能。结果表明:R335L呈现较宽的相对分子质量分布和较明显的剪切变稀特征,拉伸屈服应力为13.4 MPa,简支梁缺口冲击强度为65.0 kJ/m^(2),具有良好的加工成型性能、熔融结晶性能、力学性能等。

基于模压注塑一体工艺的麻纤维零件结构及模具设计

麻纤维复合材料的应用是实现汽车轻量化、汽车行业绿色、可持续发展的重要途径之一。针对麻纤维复合材料应用于汽车复杂零部件难以成型及模具成本高昂的问题,提出一种基于模压注塑一体成型的解决方案。首先将麻纤维/聚丙烯复合材料纤维板加热软化后放入模压注塑一体模具中进行模压成型,模具分型面采用插穿结构替代碰穿结构设计,模压过程通过分型面冲切零件轮廓,对于无法通过模压成型的产品背面定位安装结构和主体参数化特征采用注塑麻纤维/聚丙烯成型。模具采用倒装结构设计,模具定模侧设计热流道浇注系统及顶出机构,型腔设计可替换镶件用于冲裁和注塑主体的参数化特征。零件设计导流道连接产品背部独立的安装结构和主体参数化特征,模压结束后通过定模热流道点浇口填充导流道以成型产品背部独立的安装结构和主体参数化特征,待塑料结构冷却固化后,定模侧由油缸驱动的顶出机构将零件顶出脱离型腔。基于该成型工艺设计了一套模压注塑一体模具并运用于实际生产,通过实践证明,该模具结构稳定可靠,零件质量满足设计要求。

基于成型工艺特点的木塑家具设计现状与展望

木塑复合材料(wood plastic composites,WPCs)的物理力学性能和加工性能优异,能防水耐腐、防虫蛀,是制造家具的理想材料,在家具产品设计和制造领域已有应用,但潜力尚未得到充分开发。阐述木塑复合材料的挤出成型、注射成型、热压成型、模压成型和增材制造技术的成型原理及制品性能特点,分析利用不同成型技术生产的木塑家具造型、结构设计现状,并针对木塑家具设计开发提出参数化技术深化造型、模块化思维拆分结构、数值模拟技术验证方案与工艺可行性的建议。

医用电子检测仪支架双色成型模具设计

设计了1副双色注塑模具用于某医用电子检测仪支架双色塑件的成型。依据塑件不同材料不同颜色的生产要求,第一射基础件选用聚碳酸酯(PC)成型,第二射插片体选用PC/丙烯腈-丁二烯-苯乙烯塑料(ABS)成型,第二射材料熔体温度比第一射材料低35℃,确保第二射成型能顺利进行。在分别制定了第一射、第二射成型工艺的基础上,设计了塑件成型的双色模具,双色模具采用旋转式结构,由两副子模具构成,两副子模具都采用两板式模具,浇注系统都采用冷流道+热嘴形式。针对有滑块机构的双色模具在第二射成型时易产生飞边问题,设计了一种双色模具三角截面斜导柱第一射免抽芯滑块机构,在该机构中,通过将常用圆柱形斜导柱改进为三角截面斜导柱、增设弹销,以及将斜导柱孔改进为“U形槽”等措施,使第一射成型时侧抽芯滑块免于侧抽芯,从而确保了第二射子模具模腔封闭的严密性,将塑件的成型品质合格率提高到99%以上。

8006铝合金超大规格扁锭生产工艺研究

在8006铝合金640 mm×2400 mm超大规格扁锭生产中,熔体纯净度难以控制,铸造过程对水温变化异常敏感,导致成型困难.从原材料、熔体精炼、在线过滤三个方面采取措施保证熔体纯净度,并通过试验确定了合适的铸造工艺参数.对熔体的纯净度、扁锭的外观及内部组织检测表明,采取的措施可有效控制熔体的渣含量,保证铸锭顺利成型.

超深动水环境下模袋混凝土护岸施工技术

为解决超深动水环境下模袋混凝土护岸施工安全风险高、质量控制差且效率低下等技术难题,以广东省西江干流治理工程——高要区标段项目为研究对象,结合工程水下护岸施工特点,参考类似项目中护岸工程的施工方法,通过方案比选,决定采用先灌后铺法新工艺进行模袋混凝土施工。该工艺采用一种新型施工设备——深水护岸摊铺船,进行模袋混凝土全过程水上充灌和水下精准沉放摊铺,护岸工程施工质量和施工安全得到有效保证,施工效率显著提升,可供类似工程项目借鉴参考。

铁型覆砂铸造工艺在轨道交通电机机座类铸件上的应用

分析电机机座类铸件结构特点与技术要求,选其中一种电机机座铸件为例,根据铁型覆砂工艺特点确定半封闭式浇注系统,分析该铸件铁型覆砂工艺设计及砂芯设计要点,采用有限元软件对铁型覆砂铸造工艺方案进行验证及优化,经生产实践表明,该电机机座铸件铁型覆砂铸造工艺方案可行,铁砂比为1∶6,工艺出品率为90.8%,产品合格率为95%。经济效率显著,已实现批量生产。

压下制动盘的国产化试制

分析制动盘的结构特点,采用铁模覆砂铸造工艺,通过原料成分控制,炉前工艺控制,铁型砂箱改进等措施,均衡整个圆盘温度场分布,消除缩孔等缺陷,实现铸件内部组织致密,确保制动器试制成功。

Investigation into microstructure of spray formed V4 cold working mould steel and its roiling and annealing

The material selected for this work was the spray formed Vanadis4 high alloy cold working mould steel （abbreviated to V4 steel）. Its microstructure, hot rolling process, and annealing treatment have been investigated. Observed from the optical and electron microscopes, the as-sprayed V4 steel had the finer microstructure of uniform and equiaxial grains ,while after hot rolling for densification and spheroidized annealing, the V4 steel obtained an excellent spheroidized structure that is favorable to subsequent quenching and tempering treatment. The spheroidized structure and level of annealed hardness of the V4 steel are almost the same as expensive imported powder metallurgy the V4 steel. It is difficult to produce V4 steel with the conventional ingot metallurgical technique, so the multi-step and high-cost powder metallurgy method is generally used at present. Compared to the powder metallurgy technique, using the spray forming technique to produce the V4 steel has obvious advantages and potential market competitiveness in reducing production costs, simplifying working process, and shortening the production cycle.