组织工程支架的低温沉积制造工艺参数研究

低温沉积制造是一种新的快速成形技术。为了将这项技术更好地应用于组织工程支架的制造,根据支架孔隙率的要求,按照一定比例将PLGA和珍珠粉混合,配制成浆料,然后利用低温沉积制造工艺制备了网格型的组织工程支架,并得出了适于加工这种材料的一组工艺参数。主要从软件设定、浆料性质、温控调节和速度匹配4个方面入手,研究了在材料配制、分层和成形机制造等一系列工艺过程中参数对成形结果的影响。实验结果表明,制造出的支架结构规则能满足孔隙率的要求。     

Cement-based additive manufacturing: experimental investigation of process quality

The International Journal of Advanced Manufacturing Technology - The interest in additive manufacturing (AM) of cement-based materials is steadily increasing. Moreover, there is a growing need for...     

高温高压临氢阀门制造工艺的分析

阐述了石化工业生产中高温高压临氢介质对阀门的要求,介绍了高温高压临氢阀门制造中,承压壳体材料、机械加工、特殊工序和整机检查试验等过程的控制要点。     

An experimental study on grinding parameters for manufacturing PCD micro-milling tool

Micromachining has become a necessary manufacturing process. Micro-milling tool and its evolution play a vital role in the development of micromachining. This study optimizes the grinding process of polycrystalline diamond (PCD) compact for manufacturing PCD micro-tool. The optimization is conducted by using four parameters, i.e., grain size of PCD compact, grain size of abrasive wheel, grinding speed, and feed rate designed by the Taguchi orthogonal array. The study then evaluates two grinding characteristics, i.e., grinding forces and cutting edge radius of the PCD compact. The results of ANOVA show that the most influential parameter on grinding PCD compact is the grain size of the PCD compact, followed by the grain size of the abrasive wheel, feed rate, and grinding speed. As an example, a quadrilateral PCD micro-milling tool with a cutting edge diameter of 80 μm is fabricated by using the optimized parameters.     

An experimental investigation on the process parameters influencing machining forces during milling of carbon and glass fiber laminates

Milling is the most feasible machining operation for producing slots and keyways with a well defined and high quality surface. Milling of composite materials is a complex task owing to its heterogeneity and the associated problems such as surface delamination, fiber pullout, burning, fuzzing and surface roughness. The machining process is dependent on the material characteristics and the cutting parameters. An attempt is made in this work to investigate the influencing cutting parameters affecting milling of composite laminates. Carbon and glass fibers were used to fabricate laminates for experimentations. The milling operation was performed with different feed rates, cutting velocity and speed. Numerically controlled vertical machining canter was used to mill slots on the laminates with different cutting speed and feed combinations. A milling tool dynamo meter was used to record the three orthogonal components of the machining force. From the experimental investigations, it was noticed that the machining force increases with increase in speed. For the same feed rate the machining force of GFRP laminates was observed to be very minimal, when compared to machining force of CFRP laminates. It is proposed to perform milling operation with lower feed rate at higher speeds for optimal milling operation.     

The failure of torispherical ends of pressure vessels due to instability and plastic deformation—An experimental investigation

Twelve model pressure vessels with torispherical ends have been tested under internal pressure to investigate failure by instability and plastic deformation. The models covered combinations of three head heights and four thicknesses. All the thicker specimens with internal diameter-thickness ratios of 53, 106 and 212 failed by plastic deformation. The three thin specimens with an internal diameter-thickness ratio of 530 failed by buckling of the torus due to the circumferential compressive stresses. The experimental results for limit pressure and instability failure are compared with theoretical values. The effect of change of geometry is significant particularly for the larger head heights. For these specimens the experimental limit pressure is higher relative to theoretical predictions than is the case for the smaller head heights. A simple approximate theory is presented for predicting the pressure at which buckling occurs in the torus. The correlation of the new predictions with the experimental values is not good, but the new predictions are lower than those previously published.     

A TEL decision method of process parameters for smart energy efficient manufacturing

Journal of Mechanical Science and Technology - By constructing a Smart energy efficient manufacturing (SEEM) process grey model, craft parameter optimization is transformed into the process of...     

An integrated planning approach for a nanodeposition manufacturing process

This paper deals with the planning problem in a nanodeposition manufacturing process, in which a toolbit that consists of a multilayer grid of micro/nanofluidic channels is used to deposit nanoscale liquid materials to desired positions on workparts to form solid patterns. The objective is to obtain a planning procedure that achieves efficient throughput for the studied nanodeposition manufacturing systems. We break down the studied problem into several sub-problems as design pattern decomposition, nanopore assignment, liquid material routing in the multilayer grid fluidic network, and toolbit path planning. Efficient algorithms are proposed to solve these sub-problems individually, and then finally integrated into a framework that systematically plans the nanodeposition manufacturing process. A software tool that plans, simulates, and controls the nanodeposition manufacturing process by implementing the proposed algorithms is reported in this paper.     

Machining process parameters optimization for heavy-duty CNC machine tools in sustainable manufacturing

Machining process parameters (MPP) directly affect the machining quality and efficiency of heavy-duty CNC machine tools (HCMT). The selection of MPP is very important to effectively improve machining performance. Machining performance has been closely related to the HCMT running state. In order to maintain HCMT sustainably manufacturing with high accuracy and low consumption after machining performance degradation for a long time running, MPP should be re-optimized according to the current state of the machine tools. Thus, this paper proposed a MPP optimization method for running HCMT to obtain optimal MPP based on current running state. A multi-objective optimization model was built, considering both the linear factors such as machining time and machining cost and nonlinear factors such as chatter in machining process. The nonlinear factors were reflected by the nonlinear dynamic model of machining process. Furthermore, a grid optimization algorithm was introduced to search the optimal MPP from the multi-objective optimization model. Finally, a case study was implemented to verify the feasibility of the nonlinear dynamic model and the superiority of the multi-objective optimization method compared with single-objective optimization method.     

A study on the manufacturing conditions of metal matrix composites by low pressure infiltration process

Metal fiber preform reinforced aluminum alloy composite as made by the infiltration of molten metal under low pressure casting process. The infiltration behavior of filling pattern and the velocity profile with low-pressure casting process was investigated. The thermocouple was inserted into the preform in order to observe the infiltration behavior. The infiltration of applied pressure time, 1, 2 and 5 s under constant pressure of 0.4 MPa was completely filled during 0.4 s. In these conditions, molten aluminum alloy has successfully infiltrated to FeCrSi metal fiber preform by low-pressure casting process. It was observed the porosity of composites for reliability of composites. The automobile piston was developed with FeCrSi reinforced aluminum alloy that is 0% porosity by the optimal applied pressure and applied pressure time.     

Experimental investigation on viscoplastic parameters of conditioned sands in earth pressure balance shield tunneling

A device was developed to determine the viscoplastic parameters of conditioned soil, which works on the principle of torsional shear applied to a standard vane with controlled strain rate. Rheological measurements were taken for three sand samples with the same bentonite slurry injection ratio (14.3%), but with different foam injection ratios (19%, 23%, and 27%), by changing the gasbag pressure levels (i.e., 0, 100, 200, 300, and 400 kPa) and vane speeds (i.e., 1/3.4, 1/4.1, 1/5, 1/6.4, 1/9, 1/15, and 1/30 RPM) to determine the effects of confining pressure and foam injection ratio on the viscoplastic parameters. The results show that the values of viscosity coefficient and yield stress for conditioned sands are in the range of 9.1–53.5 kPa·s and 1.5–10.2 kPa, respectively. The viscoplastic parameters increase with the increase of the confining pressure, and decrease with the increase of the foam injection ratio for all tested samples.     

基于加工基元的制造过程规划研究

针对现有CAM系统的自动工艺规划功能弱,难以进行有效工艺决策的缺陷,根据数控工艺的特点,提出了加工基元的概念,并在此基础上建立了产品制造信息模型,进行了制造过程规划优化研究,完善了CAM系统中的工艺规划功能。并采用XML标准对制造过程规划文件CNCML文件进行了描述,为面向网蓐化制造的CAD／CAPP／CAM系统集成提供了有效的实现方珐。     

制造信息化的分析与研究

论述了制造信息化的内涵、现状、存在的问题和对我国制造业的影响，认为制造信息化主要是指产品设计、制造及底层设备的信息化，隶属于制造业信息化范畴，进而提出制造信息化应该与管理、决策信息化等协调发展，才能推进制造业信息化。并且描述了一个建立在制造信息化基础上的未来智能工作场模型，其具有软硬件方面的快速可重构性，以知识的挖掘、应用、革新作为驱动制造、装备智能化和高效率工作的内在机制，能形成多个车间、工作场间信息的双向流通。     

制造工艺核心论

从历史和现代的角度论述了制造技术的永恒性,阐述了人类发展和制造技术的密切关系。制造技术是一个永恒的主题,是设想、概念、科学技术物化的基础和手段,是国家经济与国防实力的体现,是国家工业化的支柱产业和关键。广义制造论是20世纪制造技术的重要发展,亦称之为“大制造”,它体现了制造概念的扩展,从制造设计一体化、材料成形机理的扩展、制造技术的综合性、多样化的制造模式、产品的全生命周期和丰富的硬软件工具、平台和支撑环境等多个方面分析了制造技术的广义性。同时重点论述了制造工艺技术的核心作用和现代制造工艺理论及技术方面的发展。最后提出了机械制造科学技术的重点发展方向。     

An economic machining process model with interval parameters

The primary objective of a machining economics model is to determine the optimal cutting parameters that minimize production costs while satisfying some design constraints. When the parameters in a machining economics model have interval values, the associated problem becomes an interval machining economics problem, and the objective value will also have interval value; that is, lying in a range. This paper develops a solution method that is able to derive the interval unit production cost of a machining economic model with interval parameters. A pair of two-level machining economics problems is formulated to calculate the upper bound and lower bound of the unit production cost. Based on the duality theorem, the two-level machining economics problem is transformed into the one-level conventional geometric program. Solving the corresponding pair of geometric programs produces the interval of the unit production cost. The results indicate that the cost interval contains more information for making decisions.     

Experimental investigation of new manufacturing process chains to create micro-metal structures on polymer substrates for lab-on-chip sensors

Over the last two decades, lab-on-a-chip devices have emerged as a leading technology for life sciences, drug development, medical diagnostics, food safety, agricultural and environmental monitoring. The conventional methods used nowadays to manufacture these micro- and nano-functional surface topography are very expensive, and they do not fit the requirements for industrial production. In particular, we report an experimental investigation to link technologies as structuring process and replication processes by establishing through the proposed low-cost-based approaches new manufacturing process chains to process non-silicon materials devices, which integrate sub-μ periodic structures. Moreover, we introduce a prototype of new testing equipment working in a non-clean environment based on photolithographic procedures. μ-trenches with feature size in the order of 10?μm are integrated on cyclic olefin co-polymer substrates. The achievements authorize to consider the proposed process chain a valid option to fabricate structured surface topography in the sub-μ range for biological applications.     

An experimental investigation on passive water cooling in laser forming process

The effect of passive water cooling in laser forming of thin sheets made of AISI 304 stainless steel is experimentally investigated. Indeed, since each laser scan can produce only small bending angles, multiple laser scans are required to produce a given deformation with a significant increase of production time due to cooling between consecutive scans. Therefore, passive water cooling is tested to verify its influence on minimum time between consecutive scans (cooling time), bending angle, and surface quality. A parametric approach is involved in the investigation and main process parameters are changed among the experiments by varying laser scanning speed, laser beam power, sheet thickness, and cooling media among several levels. It was discovered that the employment of passive water cooling in laser forming of thin sheets would be beneficial since the capability to dramatically reduce the cooling time and oxidation of both irradiated and cooled surfaces. In addition, the bending angle is only marginally affected by employment of water cooling. The effect of water cooling on stress and deformations are discussed by developing a numerical model based on finite element model.