简易阶梯凸模的妙用两例

在冲压加工中,采用阶梯凸模主要是为了提高凸模的刚性和强度,而本文介绍的阶梯凸模则是根据某些冲压加工过程的特点,巧妙地利用阶梯凸模的阶梯改善冲压加工过程所取得的良好效果。下面将阶梯凸模在冲压生产中的两例应用予以介绍。     

托板复合冲压模具的设计

托板复合冲压模是设计一复合凹模和组合凸模,通过其联动将落料、冲孔、弯曲一次成型,保证了质量,减少了误差,降低了成本,提高了生产率.     

凸模高度的几种微调方法

在多道不同冲压工序的连续模、级进模或复合模中,有时会遇到个别凸模在高度上需作微小调整的情况。例如:在汽车电器附件生产中,有一电线与接头的压接加工。它由校平接头、压接电线、剪断接头三个工序组成。如图1所示,这三道工序是在冲床上一次行程中同时完成的,其中,压接上模与剪断上模要求作高度微调,以保证压接质量。本文以解决单个上模的微调为例,介绍几种微调方法。一、垫片微调法这是一种最简单的微调方法,见图2。图中尺寸H是不变的,通过改变垫片厚度即可调整上模3的位置。这种方法简易实用,可靠性也好,缺点是调整麻烦,且不能实现无级调整。     

覆盖层密集精密小孔冲压工艺及模具设计

阐述柔性印刷线路板 (FPCB)覆盖层四排密集精密小孔的冲压工艺 ,分析冲压产生孔边毛边、凹模强度低、凸模易断等问题 ,并设计合理的冲压工艺和模具结构     

凸模快速更换的冲模设计

通过联接片复合冲压模的设计,介绍了一种快速更换小型凸模的冲模设计方法,并指出了在此类模具设计制造中应注意的问题.     

冲压组合工序对细小冲孔凸模的影响

现代冲压生产中,连续模和复合模得到了日益广泛的应用。模具的稳定性一直是影响生产的重要因素,细小凸模是整套模具中相对薄弱的环节,细小凸模折断不但增加了模具维修的工作量和模具使用成本,更干扰了生产的连续性。     

冲压小孔用凸模固定的改进

我单位实习工厂前段时间接了一批小零件,需要在1．5-2 mm薄板上冲φ3 mm圆孔和3 mm×3 mm方孔,刚开始加工时,我们采用老的方法固定凸模(如图1示),由于凸模太细小,强度又低,冲孔时凸模经常折     

介绍一种小型凸模固定法

在电子仪器仪表行业中,时常会遇见各种各样的小型薄板零件,这些小型薄板零件的加工制造通常采用冷冲压模具。图1所示是某厂生产的一种插端零件,材料为H62。该零件尺寸小、精度高、冲制中落料难,而且因零件尺寸小,凸模工作部分易损坏。过去采用环氧树脂粘接固定凸模,但修理周期长,不能满足生产需要。为解决上述问题,笔者研制了压板锥套固定凸模法,使用效果良好,现简介如下。     

薄板冲压防止落料被带起的措施

我们在冲床上冲压薄板时，落料有时被带起回弹到模具的顶面，导致生产中断，甚至使冲裁件重叠，损坏凸凹模刃口，影响生产。根据分析，落料被带起的原因是凸、凹模间隙太大，冲出的落料比凹模尺寸小，导致落料可以随着凸模退出凹模型腔，从而被带出，或因凸模和落料之间的油封、磁吸引力或者振动     

冲压模具凸凹模间隙控制与调整方法研究

模具凸模和凹模之间的间隙将直接影响制件的质量和模具的使用寿命,合理控制凸、凹模间隙并使其均匀是装配的关键。笔者深入探讨了冲压模具装配前需注意的问题,分析研究了凸、凹模间隙的控制与调整方法,并提出了模具使用后间隙变化的调整修配措施,对模具装配生产实践具有指导意义。     

基于PVDF传感器的高速圆度测量系统

针对机械加工行业圆度测量高速高效的要求,设计了一种基于聚偏氟乙烯(PVDF)压电薄膜的压电式位移传感器的高速圆度测量系统,利用此传感器高频响、高灵敏度、高信噪比的优势,通过与电荷放大器相结合,实现高速圆度测量.通过实验可知PVDF传感器测量频率响应在1200Hz以上,谐振峰频率在3000 Hz左右,解决了电感传感器在高速圆度测量中测量结果出现失真的问题.测量数据分析结果表明,此系统圆度测量误差可达到1 μm以内.多次测量证明,该系统测量结果重复性好、可信性高.     

Design and Simulation of PVDF‐MOSFET Based MEMS Hydrophone

Abstract

Modeling has become a vital tool of investigation in all fields, since experimenting with real systems is not only costly, but also time‐consuming and even impossible in some situations. This work presents the design and simulation of an integrated PVDF‐based MEMS hydrophone with improved sensitivity, which contains a MOSFET sense amplifier. The piezoelectric polymer, polyvinylidene fluoride (PVDF), senses the input acoustic signal. As hydrophone size decreases, it becomes necessary to provide an amplifier or buffer in close proximity to avoid sensitivity loss due to interconnect capacitance. This suggests the concept of hydrophones merged with electronics in an integrated circuit environment. So, the integration of PVDF with an on‐chip MOSFET is implemented. The extended gate electrode of the MOSFET is placed over an epitaxial layer isolated from the silicon substrate and is padded with a dielectric layer, SU‐8, which significantly reduces the extended gate capacitance and, therefore, increases the sensor sensitivity. The variation of the transducer output when the input acoustic signal is applied is studied. The simulation is done using the MEMS simulation software, Coventorware.     

板材多点成形不同工艺方法的数值模拟研究

介绍了板材多点成形不同工艺方法的优缺点,基于有限元方法就多点成形不同工艺对压痕、超皱、回弹以及制品成形精度的影响进行了数值模拟研究,并且对不同厚度板条多点成形模拟结果进行了实验验证。结果表明,与多点模具成形、半多点模具成形和半多点压机成形方式相比,多点压机成形能够有效地抑制压痕和皱纹的产生,并得到变形均匀的制品;反复成开法可有效减小回弹,提高成形精度;边部优先成形法能够有效地抑制制品的直边效应。     

基于PVDF的欠驱动多指手滑触觉硬件系统

为解决传统果蔬采摘欠驱动多指手抓取力控制精度不高的问题,提出了一种基于聚偏二氟乙烯(PVDF)压电薄膜技术的新型欠驱动多指手滑触觉系统,该系统由信号采集和信号处理两个模块组成;分别设计了滑触觉传感器,电荷放大、低通滤波、工频限波、电压放大等电路,并进行了捏取和抓取实验.实验结果表明,该系统能较好地控制多指手的抓取精度,实现无损伤抓取,且具有广阔的应用前景.     

A PVDF transducer for low-frequency acceleration measurements

A unique acceleration transducer, using piezoelectric PVDF, has been developed for low-frequency vibration monitoring. The paper develops the theoretical model for this low-cost, robust sensor. The theoretical model is validated using experimental results from laboratory tests. The sensor was also installed in an underground potash mine alongside a commercial geophone for a three-month in-mine test producing results that show a close correspondence between the two transducers.     

激光吸收光谱技术在工业生产过程及安全预警标识性气体监测中的应用

鉴于常规的标识性气体监测方法在响应速度、测量精度、使用寿命、实时性、监测目标种类、测量范围和应用场合等方面相比激光吸收光谱技术存在不足,本文以可调谐半导体激光吸收光谱技术为依托,选取合适的无干扰激光吸收谱线,阐述了工业管道抽取式、管道原位在线对射式、扩散探头式(全量程激光监测一体机形式与多点无源传感器探头形式)、无组织排放开放光路式等多种形式的监测方法。上述系统的测量结果显示:抽取式可实现CO、CO2、O2等不同多组分气体的同时测量;管道对射式实现了O2及10μL/L以下CO的高精度在线测量;探头式则以CH4测量为例实现了响应时间T90=15s,监测极限小于150μL/L,泄漏报警准确率达100%;开放光路形式以天然气集气站场测量CH4、C2H2、C2H4三种气体为例实现了0误报的监测能力。上述分析结果表明,TDLAS技术应用于工矿安全生产及安全预警方面的标识性气体监测是完全实用、有效、准确、可靠的。     

Theoretical characterization of a gas path debris detection monitoring system based on electrostatic sensors and charge amplifiers

The electrostatic detection of gas path debris has been proposed in literature as a tool to monitor mechanical component faults along the combustion gas path of turbo-machines. In this paper we discuss the general theoretical characterization of a debris detection monitoring system based on electrostatic sensors and charge amplifiers. We first provide the analytical expression of the time-varying charge induced by the moving debris on the sensor surface. After introducing a simplified electric model of the charge amplifier, we discuss the effects of the amplifier bandwidth on the shape of the output voltage signal. Theoretical results have been validated with experiments.     

FOULING DETECTION IN FOOD VESSELS USING INTERDIGITAL LAMB WAVE TRANSDUCER

Lamb waves are used to detect fouling in food vessels. The propagation of the Lamb waves in plates exhibits many modes and dispersion characteristics, which have great influence on fouling detection. The relative distribution of the in-plane and out-of-plane displacement of the mode across the thickness of the plate will determine the sensitivity of the mode to a particular loading condition. By considering the dispersion and multi-mode characteristics of guided waves, an interdigital polyvinylidene fluoride (PVDF) transducer is designed to realize the mode selection of guided waves, and a single a0 mode is used for guided wave detection. Fouling detection experiments are conducted in the laboratory using epoxy adhesive on a thin plate. Using the interdigital PVDF transducer, three fouled areas are detected. Using one of the time-frequency analysis methods, the waveforms are further processed. This also demonstrates the validity of this method of fouling detection.     

Evaluation of the enhanced cavitation impact energy using a PVDF transducer with an acrylic resin backing

A transducer using a PVDF (Polyvinylidene Fluoride) film as a pressure sensitive material has been developed and applied to evaluate the cavitation impact energy. However, enhanced cavitation impact used for peening destroys the PVDF film, which is directly exposed to the cavitation impact through a polyimide tape. In the present paper, a newly developed PVDF transducer is proposed, in which a PVDF film with an acrylic resin, which attenuates the burst signal, is put on the backside of a metallic base, where the front surface of the metallic base is exposed to the cavitation impact.     

脉冲压力条件下PVDF压电薄膜的动态响应特性

通过脉冲压力发生装置产生脉冲压力,研究PVDF压电薄膜的动态特性.使用PVDF压电薄膜制作一种测试脉冲压力的传感器,借助标准压阻传感器,测得PVDF压力传感器的灵敏度,计算出灵敏度的不确定度,并将PVDF压力传感器的线性度与压电传感器和压阻传感器作出对比,发现PVDF压力传感器输出稳定.通过比较PVDF压力传感器和标准的压阻传感器输出信号在时域和频域上的相关参数,证实PVDF压电薄膜具备测试动态压力的能力.