Diamond machining of sinusoidal grid surface using fast tool servo system for fabrication of hydrophobic surface

Ultra-precision diamond machining with piezoelectric-assisted fast tool servo (FTS) was used to produce various free-form surfaces.A low cost,rapid and large area fabrication of uniform hydrophobic surface at room temperature which transfers the FTS fabricated sinusoidal grid surface to the flat film with UV-moulding process was described.A piezoelectric-assisted FTS with high band width of 2 kHz,travel range up to 16 μm and the compact mechanism structure was designed for the sinusoidal grid surface machining and the dynamic performance testing of FTS was described in detail.Machining results indicate that the dimensions of sinusoidal grid change with the variation of the FTS machining condition.Wetting properties of UV-moulded surface were evaluated,the best contact angle was measured to be 120.5° on the sinusoidal grid surface with profile wavelength of 350 μm and peak-to-valley amplitude of about 16 μm.     

Modelling tool wear in cemented-carbide machining alloy 718

Tool wear is a problem in turning of nickel-based superalloys, and it is thus of great importance to understand and quantitatively predict tool wear and tool life. In this paper, an empirical tool wear model has been implemented in a commercial finite element (FE) code to predict tool wear. The tool geometry is incrementally updated in the FE chip formation simulation in order to capture the continuous evolution of wear profile as pressure, temperature and relative velocities adapt to the change in geometry. Different friction and wear models have been analysed, as well as their impact on the predicted wear profile assessed. Analyses have shown that a more advanced friction model than Coulomb friction is necessary in order to get accurate wear predictions, by drastically improving the accuracy in predicting velocity, thus having a dramatic impact on the simulated wear profile. Excellent experimental agreement was achieved in wear simulation of cemented carbide tool machining alloy 718.     

Spindle rotary position estimation for fast tool servo trajectory generation

In diamond turning of non-rotationally symmetric surfaces, fast tool servo (FTS) trajectory is generated in real time based on the spindle rotation angle. Essentially, a digital rotary encoder updates its output (samples the spindle angle) at fixed rotary angle interval. In time domain, the encoder sampling frequency is different from that of the FTS control computer. Without proper spindle position estimation, this asynchronous nature between the encoder spatial sampling and the computer temporal sampling can cause significant amount of aliasing noise in the generated trajectory. In this paper, we first analyze this aliasing phenomenon using discrete-time signal processing theories. Based on this analysis, a spindle rotary position estimator is designed to improve both accuracy and resolution of the spindle angle feedback. Its effectiveness and the associated trajectory generation are experimentally verified in diamond turning of sinusoidal surfaces with ultra-FTS.     

Influence of tool vibration on machining performance in electrochemical micro-machining of copper

Electrochemical micro-machining (EMM) appears to be promising as a future micro-machining technique since in many areas of applications, it offers several advantages, including biomedical and MEMS applications. A suitable micro-tool vibration system has been developed, which consists of tool-holding unit, micro-tool vibrating unit, etc. The developed system was used successfully to control material removal rate (MRR) and machining accuracy to meet the micro-machining requirements. Micro-holes have been produced on thin copper workpiece by EMM with stainless-steel micro-tool. Experiments have been carried out to investigate the most effective values of process parameters such as micro-tool vibration frequency, amplitude and electrolyte concentration for producing micro-hole with high accuracy and appreciable amount of MRR. From the experimental results and SEM micrographs, it is evident that the introduction of micro-tool vibration improves EMM performance characteristics. Lower electrolyte concentration in the range of 15–20 g/l reduces stray current effects. Hertz (Hz) range of tool vibration frequency improves the removal of sludge and precipitates from very small interelectrode gap. The 150–200 Hz range of tool vibration frequency can be recommended for EMM, which provides a better electrochemical machining in the narrow end gap. Compared to kHz range, Hz range micro-tool's vibration improves the MRR and accuracy in EMM.     

纯铜表面激光熔覆铜合金涂层的组织及耐磨性

采用光学显微镜、扫描电镜、X射线衍射及能谱分析对纯铜表面送粉激光熔覆制备的铜合金涂层进行了分析.结果表明,涂层与基体为冶金结合,无气孔、裂纹等缺陷,涂层稀释率极低,铜合金涂层在凝固过程中通过液相分离形成大量均匀弥散分布的细小球形分离相、富含铜的固溶体和少量大块分离相聚集体;细小分离相的平均直径小于5μm,分离相由富含Fe、Co、Mo的多元金属硅化物组成.富含铜固溶体的硬度为280 HV0.1,大块分离相聚集体的硬度为510 HV0.1.磨损试验结果表明,激光熔覆涂层的耐磨性较纯铜基体有显著提高.     

A fast tool servo design for precision turning of shafts on conventional CNC lathes

A technique for precision turning of shafts on conventional CNC turning centers is presented. The shaft is semi-turned on a conventional CNC lathe. The precision finish turning operation is delivered by a piezoelectric based fast tool servo which is mounted on the same CNC lathe's turret. The precision tool tip motion is delivered by a proposed sliding mode controller which is robust to changes in the cutting process and hysteresis in the piezo actuator. Sliding mode controller is also quick to compensate the cutting force disturbances, and keeps the tool tip at the desired location within the displacement measurement sensor resolution (±0.1 μm). The fast tool servo system is packaged in a PC, and its effectiveness is demonstrated on a bearing location turning.     

高强高导纳米复合材料CuCrZr/AlN的组织与性能

采用粉末冶金方法制备高强高导铜合金基纳米复合材料（CuCrZr／AlN），用TEM、SEM等方法研究不同工艺条件如温度、压力、复压压力及复烧温度对复合材料组织与性能的影响。结果表明：烧结后的试样密度随压力、烧结温度的升高而增大，复压复烧后致密度达98％：试样抗弯强度随密度的增大而增大，复压复烧后，试样最大抗弯强度达到417MPa；600MPa复压950℃复烧试样的软化温度大于600℃；烧结温度为950和900℃，相对应的晶粒尺寸分别是0．26-0．44μm和0．1-0．21μm；材料的电导率随着密度的增大而增大，复压复烧后可以达到62％（IACS）。     

Micro patterning on curved surface with a fast tool servo system for micro milling process

Demand for generating functional micro patterns on a curved surface such as molds has increased in various industrial sectors. In order to meet the demand, it is important to develop advanced micro machining technology to generate curved form and fine patterns, simultaneously and efficiently. This paper presents a newly developed machining system equipped with a fast tool servo mechanism for milling process driven by a giant magnetostrictive actuator and evaluation of its basic machining performance. The results confirmed that the developed system has capability to position the end mill precisely during machining and to generate patterned curved surface.     

紫铜表面激光熔覆镍基合金的组织与性能

利用激光熔覆技术在紫铜表面制备镍基合金涂层。采用SEM、XRD、EDS、显微维氏硬度计进行组织结构和硬度分析,并测试了紫铜基体、镍基熔覆层的耐冲蚀磨损性能。结果表明:激光熔覆层与铜基体形成冶金结合,组织致密、晶粒细小、无裂纹、孔隙、夹杂等缺陷,熔覆层内具有等轴晶、树枝晶及平面晶等不同结构,并有Cr、Ni、B等强化相颗粒。当冲蚀角为60°时紫铜基体和熔覆层的质量损失率都比较大,随着冲蚀时间的增加,熔覆层质量损失率比紫铜的质量损失率要低得多,激光熔覆层的耐磨性比基体组织的耐磨性提高了近3倍,激光熔覆层的耐冲蚀磨损性能得到明显提高。     

半固态挤压铸造铜合金组织和力学性能研究

以半固态ZCuSn10P1铜合金为研究对象,自主设计了1套1模4件挤压模具并进行了半固态挤压铸造成形实验,研究了成形比压和挤压速率对半固态ZCuSn10P1铜合金挤压铸造组织和性能的影响规律。结果表明:当成形比压由180 MPa增加到250 MPa时,半固态铜合金平均晶粒直径逐渐减小,由89.25μm减小至77.96μm,液相率由36.7%减少至22.3%,抗拉强度由318 MPa增加至387 MPa,提高了21.70%,延伸率由4.2%降至2.8%;当挤压速率由11 mm/s增加至15 mm/s时,固相晶粒圆整度由1.54减小至1.32,此时抗拉强度由368 MPa增加至387 MPa,提高了5.16%,延伸率由3.3%降低至2.8%。     

Three-axial cutting force measurement in micro/nano-cutting by utilizing a fast tool servo with a smart tool holder

Cutting force is a significant indicator for in-process monitoring of cutting status. Although dynamometers are widely used in cutting force measurement, they are not suitable for nano-cutting due to insufficient sensitivities and low integrating possibilities. This paper presents a smart tool holder composed by piezoelectric ceramics and a flexible hinge, which could be integrated with a fast tool servo (FTS), for three-axial cutting force measurements in micro/nano-cutting. An algorithm was developed for enabling its quasi-static force measurement. Experiments were performed to verify the capabilities of cutting force measurement, demonstrating a high measurement sensitivity for indicating the micro/nano-cutting status.     

Monel合金/Cu爆炸复合棒界面的微观组织和力学性能

利用爆炸复合的方法成功制备了Monel合金/Cu双金属复合棒材.借助金相显微镜(OM)、扫描电子显微镜(SEM)、能谱分析(EDS)和压剪分离测试,探讨了不同工艺条件下Monel/Cu爆炸复合界面的微观组织和力学性能.结果表明,随着爆炸比的增加,结合界面逐渐由平直状过渡到波状;在铜基体晶粒内的形变孪晶数量随爆炸比的增加而增加;界面局部存在少量熔区,熔区内存在细小的柱状晶;复合界面中没有发生扩散,但经过热处理后其界面观察到了扩散.剪切断裂发生在铜侧而非界面处,表明界面结合强度高于铜基体.     

Fabrication of free-form surfaces using a long-stroke fast tool servo and corrective figuring with on-machine measurement

Fabrication of free-form surfaces that are frequently demanded for the construction of optical imaging systems is described. To obtain a tool motion with large amplitude and high bandwidth, a novel long-stroke fast tool servo is proposed and installed on the Z-axis of a diamond turning machine as an additional synchronized axis. In addition, a special on-machine measurement device is used to measure the optical parameters of the machined surface and to compensate for the residual form of errors that are commonly produced in the diamond turning process. Actual machining test results show that the proposed procedures are capable of generating the copper free-form mirrors of 50 mm diameter to a form accuracy of 0.15 μm in peak-to-valley value error.     

半固态挤压铸造ZCuSn10铜合金的组织演变

对ZCu Sn10铜合金坯料进行液态浇注和半固态挤压成形,通过组织演变的分析,研究不同工艺对ZCu Sn10铜合金半固态挤压液固协同流动性的影响。结果表明,不同工艺对ZCu Sn10铜合金挤压组织液固协同流动性影响不同,在930℃保温40 min挤压速率为12 mm/s可获得固液协同流动较好的挤压成形件组织。相同挤压工艺条件,半固态挤压成形件各个位置组织差异较大。近冲头位置保持初始半固态组织;试样中部位置为固液两相共存的半固态组织、固相颗粒圆整度较高;试样最前端的微观组织中以液相为主,固液两相分布均匀性较差。     

镁合金微弧氧化涂层上化学镀铜层的显微组织和导电性（英文）

为了赋予镁合金微弧氧化(MAO)涂层以导电特性,对MAO涂层进行化学镀铜处理。通过测试镀层的显微组织、耐蚀性和导电性,研究镀覆温度和络合剂浓度对化学镀铜层性能的影响。结果表明,最优镀覆温度为60℃,最佳络合剂浓度为30 g/L。在此条件下,可获得完整、致密的镀层。分析镀层在镁合金MAO涂层上的形成机制,提出镀覆过程的三阶段模型。镀后试样的表面方阻在经历第三阶段后降低至0.03Ω/。通过化学镀铜,MAO样品在未明显降低耐蚀性的同时获得了良好的导电性。     

Feed-forward control of fast tool servo for real-time correction of spindle error in diamond turning of flat surfaces

A fast tool servo is designed and tested to obtain sub-micrometre form accuracy in diamond turning of flat surfaces. The thermal growth spindle error is compensated for real time using a fast tool servo driven by a piezoelectric actuator along with a capacitive displacement sensor. To overcome the inherent non-linearity of the piezoelectric actuator, Proportional Integral (PI) feedback control with a notch filter is implemented. Besides, feed-forward control based on a simple feed-forward predictor is added to achieve better tracking performance. Actual machining data are discussed in detail to prove that the proposed fast tool servo is capable of fabricating flat aluminum specimens of 100 mm in diameter to a form accuracy of 0.10 μm in peak-to-valley error value.     

点焊电极纳米复合材料(CuCrZr/AlN)组织性能分析

用机械合金化、粉末冶金方法制备铜铬锆合金基纳米复合材料(CuCrZr/AlN)点焊电极.采用透射电镜TEM,扫描电镜能谱SEM等方法表征纳米复合材料的组织性能.结果表明,纳米复合材料的电导率随AlN含量的增加而降低;纳米复合材料的热导率随AlN含量的增加而降低;纳米复合材料的软化温度随AlN含量的增加而提高,当AlN含量为0.4%(质量分数)时,纳米复合材料的软化温度为900℃左右;综合考虑各项性能,当AlN含量为0.2%(质量分数)时,纳米复合材料有较好的综合性能适合做点焊电极.