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《Virtual and Physical Prototyping》2013,8(4):195-202
Hybrid moulds with mouldings blocks made with epoxy composites are being used in injection mouldings of precision parts. In the last decade developments were made in view of applying these production series of thermoplastics injection mouldings. This paper reviews some of the outcomes of research activity on specific issues of manufacturing and utilisation of these tools. Most of the results refer to moulding blocks produced in epoxy composites that were manufactured using the vacuum casting technique. Some references are also made to rapid tooling techniques based on laser sintering. 相似文献
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Rapid tooling (RT) processes driven by rapid prototyping (such as stereolithography and selective laser sintering) can reduce mold development lead-time by 50% or more, though there are certain limitations in terms of mold materials, accuracy, and surface finish. This paper presents a systematic approach for manufacturability analysis of molds produced by rapid tooling methods, based on three aspects: mold feature manufacturability, secondary elements compatibility, and cost effectiveness. The geometric features of functional elements of the mold (core, cavity, side core, etc.) are evaluated for manufacturability using fuzzy-analytic hierarchy process (Fuzzy-AHP) methodology. The secondary elements of mold (parting surface, ejectors, cooling lines, etc.) are checked for compatibility with RT mold properties (machinability, wear resistance, and surface evenness). Finally, the cost of RT mold is estimated using a semi-empirical model based on cost drivers and cost modifiers, and compared with that of a conventional mold. The methodology has been demonstrated with an experimental mold. It is useful not only for RT mold process selection, but also for identifying minor modifications to a mold design to improve its manufacturability and economy. 相似文献
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《Virtual and Physical Prototyping》2013,8(4):197-207
Today, a number of direct routes using rapid prototyping (RP) processes (fused deposition modelling (FDM), laminated object manufacturing (LOM), stereolithography apparatus (SLA), selective laser sintering (SLS), etc.), as well as indirect routes (RP coupled with secondary or soft-tooling processes like RTV vacuum casting) are available for rapid fabrication of tooling for sand and investment casting processes. Each route is unique in terms of geometric, material, quality and cost characteristics; no comprehensive database of their capabilities has been reported, especially for metal casting applications. The problem of selecting the optimal rapid tooling (RT) route is a complex multi-criteria decision-making problem. This paper describes a systematic approach for RT route selection and planning. A database of RT process capabilities was generated through benchmarking experiments, covering 20 different widely used RT routes (both direct and indirect: two- and three-step processes) involving an impeller pattern. In this approach, RT process route selection involves translating the tooling requirements specified by the casting engineer into weighted tooling attributes using quality function deployment and analytic network process (QFD-ANP), which along with part specifications is used for RT route selection by calculating the overall process compatibility indices. The routes are ranked as per the value of the overall compatibility index. Once the optimal route is selected, process planning is carried out by retrieving a similar process plan using case-based reasoning (CBR). The methodology has been implemented in a software program using Visual C + + programming language in a Windows environment. The methodology is demonstrated and validated with an industrial example of a separator body casting. It has proved to be a robust evaluation and decision-making tool for selecting appropriate tooling route for a given casting based on customer requirements. 相似文献
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In this paper, we report recent work in cranial plate manufacturing using incremental sheet forming (ISF) process. With a typical cranial shape, the ISF process was used to manufacture the titanium cranial shape by using different ISF tooling solutions with and without backing plates. Detailed evaluation of the ISF process including material deformation and thinning, geometric accuracy and surface finish was conducted by using a combination of experimental testing and Finite Element (FE) simulation. The results show that satisfactory cranial shape can be achieved with sufficient accuracy and surface finish by using a feature based tool path generation method and new ISF tooling design. The results also demonstrate that the ISF based cranial reconstruction has the potential to achieve considerable lead time reduction as compared to conventional methods for cranial plate manufacturing. This outcome indicates that there is a potential for the ISF process to achieve technological advances and economic benefits as well as improvement to quality of life. 相似文献
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Rapid hard tooling by plasma spraying for injection molding and sheet metal forming 总被引:23,自引:0,他引:23
Amidst the harsh competition over the development of new products around the world, rapid prototyping, especially rapid tooling methods have received widespread attention. Amongst the rapid hard tooling methods, thermal spraying can manufacture metal molds without limitation of pattern size. However, it has the disadvantage that only soft metals with low melting points such as zinc alloy can be sprayed to original mold, such as a rapid prototyping model or a natural material pattern, due to their lack of heat resistance and shrinkage of spray metals. So the wear resistance of spray tool is poor, it can be used only for trial or small-lot production. In this study, attempts were made to improve the heat resistance by using composite materials made of ceramic and metal powders as the sprayed original mold materials, and using stainless steel, tungsten carbide alloy, iron–nickel–chromium alloy with excellent wear resistance as spraying materials, respectively. The results show that injection molding spray mold and sheet metal forming spray die can be made by transferring from natural patterns and rapid prototyping models. As the durability and dimensional accuracy of the sprayed tools has sharply improved, the tools can be used for mass production. 相似文献
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Similarity measurement (SM) between pairs of features plays an essential role in the tooling retrieval. However, the number of tooling is usually large and difficult to retrieve. What’s more, the most similar tooling model is not always optimal in the case-based reasoning (CBR). To refine this situation, we propose a novel module-based similarity measurement method. Through dividing each tooling model into different modules, a new similarity is obtained by integrating all the most similar modules (MSMs) from existing tooling models. As a result, the new similarity is superior or at least equal to the result which is derived from previous methods. With the proposed method in this paper, feature similarities of modules between a new tooling ontology and each similar tooling ontology are calculated by fuzzy similarity measurement, and the MSMs are restructured to form a new tooling model after conflict resolution. A case study on forming mould is provided to illustrate the applications and prove the higher similarity by comparing with CBR. The proposed method has been adopted in an aircraft manufacturing company. 相似文献
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杨锦辉 《制冷空调与电力机械》2010,31(3):100-102,44
介绍了丹麦MICON风力发电机组塔架的制作工装设计、制作工序安排、塔段组装及焊接等制作工艺全过程,可为提高风电机组的国产化率提供有益的帮助,为类似产品如压力钢管、移动通讯发射塔等的制作提供有效参考。 相似文献
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陶瓷以其优异的热物理化学性能在航空航天、能源、环保以及生物医疗等领域具有极大的应用潜力。随着这些领域相关技术的快速发展, 其核心零件部件外形结构设计日益复杂、内部组织逐步走向定制化、梯度化。陶瓷具有硬度高、脆性大等特点, 较难通过传统的加工成形方法实现异形结构零件的制造, 最终限制了陶瓷材料的工程应用范围。激光增材制造技术作为一种快速发展的增材制造技术, 在复杂精密陶瓷零部件的制造中具有显著优势: 无模、精度高、响应快以及周期短, 同时能够实现陶瓷零件组织结构灵活调配, 有望解决上述异形结构陶瓷零件成形问题。本文综述了多种基于粉末成形的激光增材制造陶瓷技术: 基于粉末床熔融的激光选区烧结和激光选区熔化; 基于定向能量沉积的激光近净成形技术。主要讨论了各类激光增材陶瓷技术的成形原理与特点, 综述了激光选区烧结技术中陶瓷坯体后处理致密化工艺以及激光选区熔化和激光近净成形技术这两种技术中所打印陶瓷坯体基体裂纹开裂行为分析及其控制方法的研究进展, 对比分析了激光选区烧结、激光选区熔化以及激光近净成形技术在成形陶瓷零件的技术特征, 最后展望了激光增材制造陶瓷技术的未来发展趋势。 相似文献
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Rapid tooling is the process of directly or indirectly employing rapid prototyping technologies in tool and mold fabrication. By combining rapid tooling and temperature induced forming (TIF) a novel near-net shape process for the rapid production of complex-shaped prototypes of advanced ceramics has been developed. Rapid tooling via stereolithography quickly produces complex-shaped molds with precise surface quality and the TIF technology enables the forming and consolidation of Al2O3 green bodies in nonporous molds. Thus Al2O3 green parts with high density and without any cracks are realized. This novel process shows excellent potential for near-net shape production of advanced ceramics with complex geometry, fine surface finish and reliable mechanical properties. 相似文献
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《Virtual and Physical Prototyping》2013,8(3):177-188
Selective laser sintering (SLS) is a powder-based rapid prototyping process in which parts are built by sintering of selected areas of layers of powder using laser. Nowadays, SLS is emerging as a rapid manufacturing technique, which produces functional parts in small batches, particularly in aerospace application and rapid tooling. Therefore, SLS prototypes should have sufficient strength to satisfy functional requirements. Apart from the energy density which is the combination of laser power, beam speed and hatch spacing, various other parameters like refresh rate, layer thickness and hatch pattern influence part strength. In the present work, relationship between strength and the various process parameters namely layer thickness, refresh rate, part bed temperature and hatch pattern have been investigated. Experiments are conducted based on Taguchi method using L16 modified orthogonal array. Tensile specimens of polyamide (PA2200) material as per the standard ‘ASTM D638’ are fabricated on SLS machine with constant energy density and tested on a universal testing machine for tensile strength. Optimum strength conditions are obtained by maximising signal to noise (S/N) ratio and analysis of variance (ANOVA) is used to understand the significance of process variables affecting part strength. A regression model to predict part strength has been developed. Confirmation test conducted subsequently has revealed that the results are within the confidence interval. 相似文献
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A. T. Clare P. R. Chalker S. Davies C. J. Sutcliffe S. Tsopanos 《Journal of Materials Science》2008,43(9):3197-3202
A selective laser sintering process has been used to consolidate electro-ceramic thin films on silicon substrates. Methods
of forming pre-positioned layers of barium titanate were investigated by spin-coating the feedstock powder mixed with a commercial
polymer photo-resist. The ceramic–polymer composite was deposited directly onto a nickel film which was evaporated onto a
silicon substrate, pre-oxidised to form an electrically insulating layer. A range of laser processing parameters was identified
in which consolidated barium titanate layers could be formed. The laser power was found to be more influential in forming
sintered microstructures than laser exposure time. The microstructure of barium titanate films is sensitive to the SLS laser-processing
conditions, with the optimum laser powers for the processing of the BaTiO3–polymer found to be in the range 17–20 W. This article highlights the possibility of using ‘direct write’ techniques to produce
piezoelectric materials upon silicon substrates. 相似文献
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精益生产技术在汽车制造业的应用 总被引:6,自引:0,他引:6
针对国内汽车制造业精益生产实施的现状,结合多年来在上海通用汽车供应商中推广精益生产的经验和教训,提出了精益生产的推进应按照精益原则、精益组织、精益现场、精益价值流、精益布局、精益设备和工装、精益物流的方法和原则进行,从而推进企业的不断改善.适应当前汽车业多品种、小批量的生产特点和趋势。 相似文献
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Original equipment manufacturers (among others) from several industries experience the vulcanising planning decision problem (VPDP) on a periodical basis. VPDP assumes tooling capacity (number of tools per part-number) as input data, but when these companies face the possibility of manufacturing a new family of part-numbers satisfying VPDP conditions tooling capacity has to be determined. Tooling costs per part number are significant: design, capacity, maintenance and salvage value. Strategic business profit is impacted since these contracts tend to have a life time that includes several years. The contribution of this work is fourfold: the definition of the tooling capacity problem (TCP) for VPDP, the development of part-number wise lower bounds on tooling capacity, a heuristic (along with an upper bound on optimality gap) to find tooling capacity values and preliminary results on sensitivity analysis over contract demand changes. Numerical experimentation demonstrates the efficiency of the heuristic. 相似文献
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Traditionally, a mold made of gypsum can only be used in a low-pressure molding, e.g. casting, due to the weak strength of gypsum material. This study addresses the potential of gypsum as a candidate for rapid tooling used in injection molding. The ingredients for the gypsum mold were decided upon, and an additional compression with a vibration process was introduced to enhance the mechanical strength of the gypsum mold. Scanning electron microscope (SEM) results show that the amount of void inside the gypsum mold is reduced, and more interlocking of the microstructure of gypsum is formed by increasing the intensity of the compression with a vibration process. A higher degree of interlocking produces a significant enhancement of the compressive strength of the gypsum. Two samples were selected as master designs for testing the replication performance and lifetime of the gypsum mold. The dimensional replication accuracy of the molded part was over 99.9%. The maximum lifetime of the gypsum mold is about 210 cycles of injection shots. This work provides an alternative tooling for injection molding that can allow manufacturers to produce a small quantity of prototypes in an efficient and cost-effective way in the early stages of product development. 相似文献
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Z轴"盈余"是选择性激光烧结(SLS)成形中广泛存在并影响成形件精度的问题。文中分析了Z轴"盈余"的形成原因,并通过尼龙12对SLS成形过程中影响Z轴"盈余"的因素进行了实验研究。结果表明,Z轴"盈余"是由于烧结第一层粉末材料时,激光烧结深度大于切片厚度而产生的,表现在烧结件在Z方向上尺寸变大;提高预热温度和激光能量密度及降低切片厚度都会增大Z轴"盈余"。研究结果对控制高分子SLS成形过程中的Z轴"盈余",提高SLS成形件精度具有重要的参考价值。 相似文献
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Rapid Pattern Based Powder Sintering (RPBPS) is a new rapid tooling technique proposed by the authors. It is an integration of three techniques: rapid prototyping; lost wax casting; and powder sintering. The main advantages of the RPBPS technique compared with other tooling techniques are low investment and production cost, short production cycle and a variety of materials of products. One of the key technical problems is how to calculate and control the shrinkage during three processes in the RPBPS to improve the accuracy of products. The total linear shrinkage of the products made with the RPBPS can be controlled within 3.5% by using the selected binder type and binder ratio, suitable compacting pressure and specially designed ramp temperature program in the sintering and infiltration processes. 相似文献