Condition-based maintenance in punching/blanking of sheet metal

This paper provides a review and proposal for condition-based maintenance (CBM) in blanking of sheet metal. To date, little research on this topic can be found in literature, which is probably due to the complex nature of the process. Previous statistical, artificial intelligence (AI) and model-based approaches are analysed. Special attention is given to inherent assumptions and other sources of inaccuracy. In addition, it is demonstrated how the signature of the force–displacement relation changes significantly with increasing tool wear in a typical configuration of sheet steel blanking. An analysis follows as to how such behaviour could be used in CBM. A practical implementation of CBM in sheet metal blanking is proposed based on a hybrid solution.     

板材剪切与冲裁加工实验的位移测量系统

针对板材剪切与冲裁加工的特点，设计了一种应变片式位移传感器。传感器可根据需要对量程进行调节，且相对精度不变，特别适于中小位移的测量。结合数据采集系统，在材料试验机上实现了板材剪切加工和精密冲裁实验的位移测量。     

Improving the sheared edge in the blanking of commercial AZ31 sheet through texture modification

Commercial rolled magnesium sheets of alloys AZ31 (Mg–3 mass%Al–1 mass%Zn) and ZE10 (Mg–1 mass% Zn–<1 mass% Rare Earths) in O-temper condition were used for blanking experiments near room temperature. A serrated fracture surface can be observed in case of AZ31 but not in case of ZE10. During the shearing process of the AZ31 sheet, many micro cracks parallel to the sheet plane are generated in the shearing zone. These micro cracks lead to the formation of loose particles during the shearing operation, which interfere with further processing of the part and incur additional costs by increasing the scrap rate.It is found that the strong basal texture of this alloy is an important reason for the generation of such serrated cracks. In this paper a new method of selective texture modification is described to locally change the mechanical properties of the AZ31 sheet. Subsequent shearing experiments show a significant change in the material behavior, especially regarding the direction of crack propagation, which leads to a better shearing performance. The commonly observed serrated crack does not occur any more after this local treatment and the sheared edge is clearly improved.     

Evaluation of ductile fracture models for different metals in blanking

This study is focussed on the evaluation of ductile fracture methodologies, which are needed to predict product shapes in the blanking process. In an earlier publication [Goijaerts et al., J. Manuf. Sci. Eng., Trans. ASME 122 (2000) 476], two approaches were elaborated using local ductile fracture models. The first strategy incorporates the characterisation of a ductile fracture model in a blanking experiment. The second methodology is more favourable for industry. In this approach, instead of a complex and elaborate blanking experiment, a tensile test is used to characterise a newly proposed criterion, which was shown to predict accurately the ductile fracture for different loading conditions. In this paper, finite element simulations and experiments are performed on both tensile testing and blanking to evaluate the validity of both approaches with corresponding criteria for five different metals. In the blanking process, different clearances as well as different cutting radii of the tools are considered. In conclusion, it can be stated that the first approach gives very good results close to, or within the experimental error for all five materials. The second approach, the more favourable one for industry, yields good results that deviate slightly more over the range of metals.     

斜刃冲裁与平刃冲裁的关系及斜刃冲裁力的计算

摘要通过比较平刃冲裁与斜刃冲裁的特点,介绍了斜刃冲裁最大冲裁力的计算公式及其在不同刃口高度与板厚关系时的应用。     

面向对象的冲压件集成信息模型研究

在总结现有级进模ＣＡＤ／ＣＡＭ系统产品信息模型的基础上,提出了集成信息模型的概念,并结构正在开发的级进模智能ＣＡＤ／ＣＡＭ系统ＣＡＭＳＬＳ,阐述了冲压零件集成信息模型的面向 对象表达,以及集成信息模型中基于消息传递的并行揄机制。     

支架板与压板套料冲裁模设计

本文以支架板和压板为例,介绍了套料冲裁模的结构形式、使用效果以及设计要点,可为类似零件的冲裁模设计提供参考.     

An analytical force model with shearing and ploughing mechanisms for end milling

An analytical force model with both shearing and ploughing mechanisms is established for the end milling processes. The elemental forces are defined as the linear combination of shearing and ploughing forces in six cutting constants. The analytical model for the total milling forces in the angular and frequency domain are derived by convolution approach and Fourier transform respectively and are expressed as the superposition of the shearing force component and ploughing force component. This dual-mechanism model is analyzed and discussed in the frequency domain and compared with the lumped shear model. An expression is derived for identifying the cutting constants of the dual-mechanism model from the average milling forces. Explicit inclusion of ploughing force in the model is shown to result in better predictive accuracy and yields a linear force model with constant cutting coefficients. Experiments verify the accuracy and the frequency analysis of the dual-mechanism model and show that cutting constants for the dual-mechanism model are fairly independent of chip thickness.     

减震器孔加工设备及其关键技术研究

针对减震器孔加工中生产节拍高、尺寸公差、位置精度要求高等特点,设计出双套导向结构的气、液相结合冲孔机构,并采用ANSYS/LS-DYNA对冲孔全过程进行数值模拟,得到工件隆起处最大位移和冲裁力与冲头进给速度的关系曲线,在节能、高效的前提下,合理确定了冲孔加工的冲头进给速度、确切的冲裁力等主要技术参数。     

Modelling and experimental analysis of the effects of tool wear on form errors in stainless steel blanking

The main defects that characterize the quality and accuracy of blanked parts are the form errors which can be found on the blanked surface. These defects are basically related to tool wear and process parameters. This work presents theoretical modelling of the effects of tool wear on the shearing mechanism and resulting form errors. To this end, a new parameter denominated effective clearance, which characterizes the distance between a punch and the die cutting edge when a tool is worn, is defined. An experimental analysis of form errors as a function of this new parameter is made, using 6 and 8 mm AISI A2 steel punches and 1 mm thick AISI 304 stainless steel sheet. Finally, design criteria are proposed for the process parameters to fulfil the quality requirements of blanked parts.     

冲裁速度对电机定转子铁芯冲裁断面质量影响规律研究

本文通过建立有限元模型,选择韧性断裂准则和断裂因子,研究冲裁速度对电机定转子铁芯冲裁断面质量影响的规律。通过实验获得电机定转子铁芯所用材料——硅钢片的真实应力应变曲线,并把此应力应变曲线运用于模拟中,通过设置不同的冲裁速度,得到不同的光亮带长度,从而可优化出最佳冲裁速度。分析对比模拟结果和实验结果,两者非常接近,可证明本研究对提高产品质量和生产效率有很好的借鉴作用。     

Comparison of one-dimensional and multi-dimensional models in stability analysis of turning operations

Chatter is one of the main problems in machining resulting in poor surface quality and low productivity. Chatter can be avoided by applying stability diagrams which are generated using stability models. The stability analysis of turning has mostly been performed using single dimensional, so-called oriented transfer function approach whereas the actual turning processes usually involve multi-dimensional dynamics. In this paper, a comparative analysis between one dimensional (1D) and multi-dimensional stability models is given for turning operations. The multi dimensional model includes the inclination and side edge cutting angles and insert nose radius in order to demonstrate their effect on absolute stable depth of cut predictions. Chatter experiments are conducted in order to compare with both model predictions. It is demonstrated that for higher inclination angles and insert nose radii 1D models result in significant errors, and multi-dimensional solutions are required.     

负间隙冲裁与普通冲裁的冲裁力研究

用实验的方法对凸、凹模负间隙冲裁与普通冲裁的冲裁力曲线进行了分析,发现负间隙冲裁冲裁力曲线与普通间隙冲裁冲裁力曲线差异很大,解释了冲裁力曲线的变化规律,得出了冲裁力与凸、凹模间隙值的变化关系,总结了影响冲裁力的因素,对了解负间隙冲裁冲裁力的变化规律与模具设计有一定的指导意义。     

Determination of forces in high speed blanking using FEM and experiments

The increasing demand for micro-formed and stamped parts such as connectors in the electronic industry is forcing manufacturers to push the speed limit of conventional press technologies to improve throughput. Designing dies/tooling for higher speeds and obtaining extended tool life requires a thorough understanding of the process. This paper discusses an experimental study of the interaction between punch, stripper plate and sheet material at various blanking velocities up to 1600 mm/s. The effect of velocity on punching force is also studied. A methodology to obtain high strain and strain rate dependent material flow stress data using blanking test and finite element modelling is presented.     

High strength-ductility of thin nanocrystalline palladium films with nanoscale twins: On-chip testing and grain aggregate model

The mechanical behaviour of thin nanocrystalline palladium films with an ∼30 nm in plane grain size has been characterized on chip under uniaxial tension. The films exhibit a large strain hardening capacity and a significant increase in the strength with decreasing thickness. Transmission electron microscopy has revealed the presence of a moderate density of growth nanotwins interacting with dislocations. A semi-analytical grain aggregate model is proposed to investigate the impact of different contributions to the flow behaviour, involving the effect of twins, of grain size and of the presence of a thin surface layer. This model provides guidelines to optimizing the strength/ductility ratio of the films.     

An investigation of energy loss mechanisms in water-jet assisted underwater laser cutting process using an analytical model

The water-jet assisted underwater laser cutting processes has relatively low overall efficiency compared to gas assisted laser cutting process due to high convective loss in water-jet from the hot melt layer and scattering loss of laser radiation by the water vapour formed at the laser–workpiece–water interaction region. However, the individual contribution of different losses and their dependency on process parameters are not fully investigated. Therefore, a lumped parameter analytical model for this cutting process has been formulated considering various laser–material–water interaction phenomena, different loss mechanisms and shear force provided by the water-jet, and has been used to predict various output parameters including the maximum cutting speed, cut front temperature, cut kerf and the loss of laser power through different mechanisms as functions of laser power and water-jet speed. The predictions of cutting speed, kerf-width and cut front temperature were validated with the experimental results. The modeling revealed that the scattering in water vapour is the dominant loss mechanism, causing ~40–50% of laser power loss. This also predicted that the percentage losses are lower for higher laser powers and lower water-jet speeds. In order to minimize the deleterious effect of vapour, dynamics of its formation due to laser heating and its removal by water-jet was experimentally studied. And, the cutting was done with modulated power laser beam of different pulse on- and off-times to determine the pulse on-time sufficiently short to disallow growth of vapour layer, still cutting be effected and the off-time enough long for water-jet to remove the vapour layer from the interaction zone before next pulse arrives. Compared to CW laser beam the modulated laser beam of same average power yielded higher process efficiency.     

一种新压力AGC控制模型的研究

介绍了BISRA -AGC系统 ,从仿真结果指出其响应速度慢的缺点 ,从而提出了一种新的压力AGC控制模型———解耦设定模型。采用该模型 ,轧件厚度达到规定误差± 0 0 0 5mm的时间由BISRA模型的374ms减少到 76ms。     

Penetration analytical model of three dimensional welding temperature field and experiment rectification

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两种类型活套的张力控制模型

介绍了带钢热连轧过程中电动活套和液压活套各自的张力控制模型，前者以电机电流作为控制对象，后者以液压缸压力作为控制对象。