Coating process of multi-material composite sand mold 3D printing

Sand mold 3 D printing technology is an advanced manufacturing technology which has great flexible manufacturing ability. A multi-material composite sand mold can control the temperature field of metallic parts during the pouring process, while the current sand mold 3 D printing technology can only fabricate a single material sand mold. The casting temperature field can not be adjusted by using single sand mold material with isotropous heat exchange ability during the pouring process. In this work, a kind of novel coating device was designed. Multi-material composite sand molds could be manufactured using the coating device according to the casting process demands of the final parts. The influences of curing agent content, coating velocity and scraper shape on compactness and surface roughness of the sand layer(silica sand and zircon sand) were studied. The shapes and sizes of transition intervals of two kinds of sand granules were also tested. The results show that, with the increase of the added volume of curing agent, the compactness of sand layer reduces and the surface roughness value rises. With the increase of the velocity of the coating device, the compactness of sand layer reduces and the surface roughness value rises similarly. In addition, the scraper with a dip angle of 72 degrees could increase the compactness value of the sand layer. The criteria of quality parmeters of the coating procedure are obtained. That is, the surface roughness(δ) of sand layer should be equal to or lesser than half of main size of the sand particles(Dm). The parameter H of the coating device which is the distance between the base of hopper and the surface of sand layer impacts the size of transition zone. The width of the transition zone is in direct proportion to the parameter H, qualitatively. Through the optimization of the coating device, high quality of multi-material sand layers can be obtained. This will provide a solution in manufacturing the multi-material composite sand mold.

Controlled cooling of an aluminum alloy casting based on 3D printed rib reinforced shell mold

3D printing technology has been used for sand molding and core printing, but they simply substitute the traditional molding and core making method without changing the shape or size of the sand mold(core) and their dense structure. In this study, a new type of hollow mold based on 3D printing is presented. The new type of mold is a rib reinforced thickness-varying shell mold. This mold design can realize the controlled cooling of castings, i.e., different cooling rates at different areas, and improve the temperature uniformity of a casting after its solidifi cation. Therefore, the performance of castings can be improved and their residual stress and deformation can be reduced. This kind of new mold was applied to a stress frame of A356 aluminum alloy. The 3D printed rib reinforced thickness-varying shell mold was compared with the traditional dense mold, and the castings obtained by these two kinds of molds were also compared. The experimental results showed that the rib reinforced shell mold increased the cooling rate of the casting by 30%, tensile strength by 17%, yield strength by 11%, elongation by 67%, and decreased its deformation by 43%, while sand consumption was greatly reduced by 90%.

Cooling control for castings by adopting skeletal sand mold design

The cooling control of the melt during the casting process is of great significance. A comprehensive closed-loop cooling control of castings by adopting a skeletal sand mold design was proposed. The skeletal sand mold consisting of an adaptive shell, functional cavities and a support was designed and created based on the finite difference meshes of a casting. It was applied to a round wall test casting. Two kinds of skeletal sand molds, one with lattice support and the other with enforcing ribs for this casting were designed and printed out by the 3 D printing(3 DP) method. Aluminum alloy A356 was cast by using these two sand molds. The first mold was cooled by natural convection, the other one by water spray cooling. Two sound castings were obtained. The sand mold temperature, cooling curves, microstructures, mechanical properties, residual stress and deformation were measured, compared and discussed. Water spray cooling hastened the cooling rate by 62%, increased the content of Mg and Cu in the α-Al matrix, improved the mechanical properties, and altered the surface residual stress state.

Elimination of cracks in stainless steel casings via 3D printed sand molds with an internal topology structure

The important supporting component in a gas turbine is the casing,which has the characteristics of large size,complex structure,and thin wall.In the context of existing 3DP sand casting processes,casting crack defects are prone to occur.This leads to an increase in the scrap rate of casings,causing significant resource wastage.Additionally,the presence of cracks poses a significant safety hazard after the casings are put into service.The generation of different types of crack defects in stainless steel casings is closely related to casting stress and the high-temperature concession of the sand mold.Therefore,the types and causes of cracks in stainless steel casing products,based on their structural characteristics,were systematically analyzed.Various sand molds with different internal topology designs were printed using the 3DP technology to investigate the impact of sand mold structures on high-temperature concession.The optimal sand mold structure was used to cast casings,and the crack suppression effect was verified by analyzing its eddy current testing results.The experimental results indicate that the skeleton structure has an excellent effect on suppressing cracks in the casing.This research holds important theoretical and engineering significance in improving the quality of casing castings and reducing production costs.

Insulation effect of air cavity in sand mold using 3D printing technology

The insulation effect of the air cavity surrounding the riser in a 3D printed sand mold was studied. The influence of the air cavity on heat flux was theoretically analyzed. The results demonstrated that the heat flux of the air cavity in the 3D printed sand mold was significantly less than that of resin-bonded sand. The insulation effect of the air cavity in sand molds for a cylinder casting and a stress-frame casting were simulated using software COMSOL. The results illustrated that the air cavity could be used to insulate the riser and it was more suitable for a lower melting point metal casting. An air cavity with 10-15 mm width and 5-10 mm away from the riser can significantly prolong the solidification of the riser by over 10%. Meanwhile, the sand mold for the stressframe was made by 3D printing technology and poured with aluminum alloy A356 melt. The experiment results showed that the presence of the air cavity led to a 12.5% increase of the solidification time of its riser.

Effect of gel time of 3D sand printing binder system on quality of sand mold/core

Two important factors affecting the performance of sand mold/core generated by 3D printing(3DP)are strength and dimensional accuracy,which are not only closely related to the reactivity of furan resin and the phase transition of silica sand,but also the curing agent system of furan resin.This paper studies the influence of gel time on the strength and dimensional accuracy of a 3DP sand mold/core,taking the furan resin system as an example and using a sand specimen generated by a 3DP inkjet molding machine.The experiment demonstrates that the gel time of 3 to 6 min for the sand mixture suits 3DP core-making most under the experimental condition.However,it should be noted that under the same resin condition,the strength of a no-bake sand mold/core is higher than that of a 3DP sand mold/core.The dimensional accuracy of the sand mold/core does not change significantly when the gel time is less than 15 min.Improving the activity of binder and developing ultra-strong acid with low corrosion shall be an effective way to improve the quality of the mold/core by 3D printing.

Effect of sintering temperature on microstructure and properties of 3D printing polysilazane reinforced Al_(2)O_(3)core

Ceramic cores are the key intermediate components of hollow blades for aero-engine.Conventional processes,such as hot-press molding and gel film casting,face difficulties in fabricating complex-structured ceramic cores due to the complexity of moulds and long process cycles.Stereolithography 3D printing provides a new idea for the fabrication of complex-structured ceramic cores.The effect of sintering temperature on open porosity,bulk density,weight loss rate,shrinkage rate,flexural strength and microstructure of the Al_(2)O_(3)-based ceramic core doped with 10vol.%polysilazane(PSZ)was studied.The sintering mechanism of PSZ-reinforced ceramic cores was analyzed.Results show that the optimum sintering temperature of PSZ-reinforced ceramic cores is 1,450°C.At this temperature,the open porosity of the ceramic core is 36.60%,bulk density is 2.33 g·cm^(-3),weight loss rate is 22.11%,shrinkage rate along the X,Y,Z directions is 5.72%,5.01%,9.61%,respectively;the flexural strength is 28.794 MPa at 25°C and 13.649 MPa at 1,500°C.Properties of 3D printing PSZ-reinforced ceramic cores can meet the casting requirement of superalloy hollow blades,which is expected to promote the industrial application of 3D printing complex structure ceramic cores.

砂型3D打印技术在航空发动机领域的研究与应用

随着航空工业的快速发展,行业对航空发动机的性能和制造效率提出了更高要求。传统的砂型铸造方法已难以满足现代航空发动机复杂结构的制造需求。砂型3D打印技术作为一种新兴的快速成型技术,以其高效、灵活、精确的特点,为航空发动机的设计和制造带来了革命性的变革。本文综述了砂型3D打印技术的原理、优势及其在航空发动机领域的应用现状;分析了目前砂型3D打印技术在航空发动机领域应用存在的问题,并提出了相应的解决措施;通过应用案例分析,强调了砂型3D打印技术在提高航空发动机生产效率和质量方面的重要性。最后,对砂型3D打印技术在航空发动机行业领域的未来发展趋势进行了展望。

Sand-bed defect recognition for 3D sand printing based on deep residual network

The 3D sand printing(3DSP),by binder jetting technology for rapid casting,has a pivotal role in promoting the development of the traditional casting industry as a result of producing high-quality and economical sand molds.This work presents an approach for monitoring and analyzing powder sand-bed images to serve as a real-time control system in a 3DSP machine.A deep residual network(ResNet)is used to classify the defects occurring during the powder spreading stage of the process.Firstly,a pre-trained network was applied as the initial parameter;then it was fine-tuned on the labelled defective sample dataset to accomplish the task,which defines the sand-bed defects induced in the 3DSP processing.Furthermore,the recognition and positioning of sand-bed defects were readily achieved by dividing the sand-bed images into blocks.Experiments show that the fine-tuned network has a 98.7%classification accuracy on the validation dataset of sand-bed defects and 95.4%recognition accuracy for the sand-bed images.

Digital high-efficiency print forming method and device for multi-material casting molds

Sand mold 3D printing technology based on the principle of droplet ejection has undergone rapid development in recent years and has elicited increasing attention from engineers and technicians.However,current sand mold 3D printing technology exhibits several problems,such as single-material printing molds,low manufacturing efficiency,and necessary post-process drying and heating for the manufacture of sand molds.This study proposes a novel high-efficiency print forming method and device for multi-material casting molds.The proposed method is specifically related to the integrated forming of two-way coating and printing and the shortflow manufacture of roller compaction and layered heating.These processes can realize the high-efficiency print forming of high-performance sand molds.Experimental results demonstrate that the efficiency of sand mold fabrication can be increased by 200%using the proposed two-way coating and printing method.The integrated forming method for layered heating and roller compaction presented in this study effectively shortens the manufacturing process for 3D-printed sand molds,increases sand mold strength by 63.8%,and reduces resin usage by approximately 30%.The manufacture of multi-material casting molds is demonstrated on typical wheeled cast-iron parts.This research provides theoretical guidance for the engineering application of sand mold 3D printing.

基于砂型3D打印泵体的铸造工艺研究

以泵体为研究对象,就数值模拟和砂型3D打印技术在砂型铸造中的应用进行了研究,利用Anycasting软件比较了泵体铸件侧注式、顶注式和底注式浇注方案,并确定侧注式浇注系统为最佳选择。采用3D打印技术对泵体砂型进行了制作,采用砂型铸造工艺制备出了合格铸件。结果表明,数值模拟结合砂型3D打印技术在铸造中的应用,可有效缩短零件开发周期,降低生产成本,大大提高了生产效率。

3DP打印砂型(芯)的研究及应用进展

与传统工艺相比,三维喷印技术(3DP)打印砂型(芯)在铸造工艺开发或复杂铸件的单件小批量生产时,优势明显且极具发展潜力。近年来,3DP在砂型铸造领域的研究和应用发展迅速,成为备受关注的热点。本文对3DP进行了介绍,综述了3DP打印砂型(芯)的研究和应用现状,并对存在的问题及研发应用前景进行了探讨。

基于CFD模拟的280气缸盖3D打印整型工艺研究

依据CFD仿真模拟试验,研究了280气缸盖3D打印整型工艺。研究表明:基于CFD仿真模拟对整芯浇注流道进行排气清砂参数模拟,表征了不同条件下排气清砂参数的可行性,并建立了最优的排气清砂系统方案,同时也获得了内腔壁面摩擦应力和气流清淤能力的阈值。采用3D打印技术获得整芯砂芯,有效避免了铸件因多个砂芯配合而导致的尺寸累计误差不合格,获得的铸件表面光洁,均匀一致,外观品质好,无明显缺陷,满足生产所需要的质量要求。

基于3D打印砂型的转向架套筒零件快速制造

为提高铸件质量,缩短开发周期,采用“3D打印砂型+铸造”的成形方式开发转向架套筒零件,从铸造工艺、砂型结构设计、3D打印工艺3个方面入手,分别采取了针对性的工艺措施来满足套筒铸件规定要求。在铸造工艺设计阶段,对充型流场、凝固温度场和缩松分布情况开展模拟分析,确定出合理的浇注系统;在砂型设计阶段采取随形减薄和集成设计来减少砂型的数量并提升了铸件表面质量水平;在3D打印砂型阶段,根据砂型结构特点优化激光工艺参数及打印层厚设置,保障了砂型成形效率。经检测,所开发的转向架套筒铸件完全满足设计指标要求;其开发周期和成本分析结果显示,综合效率成本显著优于传统的模具开发方式。

结构对SLS砂型次级烧结区的影响及其控制工艺研究

设计了一种包含多种常见结构的精度测试件,用于探究结构对SLS打印的砂型成形精度的影响。通过打印和尺寸测量发现,纵向椭圆结构和圆孔的次级烧结相对其他结构更加严重,且存在方向性差异。采用低密度多道次的扫描方法,相较于常规扫描方法,在0.1 J·mm·s^(-2)的总能量密度下可以将国标鼓形件的精度等级从无评级提高至5级,筋板的尺寸偏差降低到0.072 mm,显著改善了砂型的尺寸精度。

3D打印技术在箱体铸件开发中的应用

本文阐述了基于3D打印技术制造复杂箱体的铸造开发过程,包括:铸造工艺设计及模拟、砂型设计及打印、砂型组装和浇注、铸件精整和检查。结果显示,基于3D打印的铸造工艺设计不再受产品结构限制,设计方案更加灵活,铸件尺寸精度高,产品开发周期大幅度缩短。

Study on Antigravity Mold Filling by Conservative Scalar Method

By SIMPLE method and Van Leer scheme, a program on numerical simulation for 3D mold filling has been developed. The fluid flow field of gas and liquid is calculated in couples by a single phase N S equation using SIMPLE method, and free surface control equation is handled by Van Leer scheme. Then it is verified by an anti gravity mold filling of thin wall plate. In order to demonstrate its ability to simulate 3D casting, an anti gravity mould filling of a cube is computed by the program.

应用砂型3D打印技术制备复杂铝合金铸件

砂型3D打印技术使传统铸造在工艺设计、砂型分型设计方面更加开放与灵活,在实际操作方面更加精确与快捷。根据砂型3D打印技术的上述特点,针对某复杂铝合金壳体铸件,开放式的设计浇注系统,同时结合模拟仿真技术进行工艺优化,然后进行砂型设计与打印、铸件制备与检验,实现在较短的周期内研制出满足技术要求的复杂铝合金铸件。

3D打印砂模的结构优化设计方法研究

砂模3D打印是一种快速发展的砂模智能制造技术,能够对任意复杂形体进行几何造型。在实际应用中,砂模造型设计仍沿用传统设计思想,尚未充分发挥3D打印所带来的技术优势。由于传统砂模几何形体中存在冗余结构,直接影响打印效率,因此有必要结合3D打印技术优势对砂模结构进行设计优化,以提高生产效率、节约生产成本。在新工艺环境下,本文建立了一种砂模结构优化设计方法及其设计流程;以砂模壁厚作为优化参数,依据力学性能要求,建立了砂模结构优化设计模型;最终基于某厂铸造试验件进行了范例设计与仿真校核。优化设计后的试验件砂模在满足力学性能要求的前提下,体积优化率达到42.6%,有效提升3D打印砂模的生产效率与经济性。

3D打印砂型在铸造中的应用

介绍了3D打印机的工作原理及在砂型铸造中的应用,列举了3D打印技术在工程机械铸件新产品开发、汽车铸件新产品开发及航空复杂铸件上的应用,得出以下结论:(1)采用3D打印铸件砂型,浇注的铸件精度高、披缝少、易清理,新产品开发速度快,适用于新产品开发和复杂件单件小批量的生产;(2)3D打印工艺的设计更改只需要更改三维模型,因而可以快速切换、升级;(3)高端砂型依赖进口设备和原材料,3D打印成本相对较高,是传统铸造的补充,对于普通铸造无法生产的铸件砂型,可以使用3D打印来完成。