Corrective polishing of complex ceramics geometries

High quality surfaces in terms of low roughness and high form accuracy are achieved by polishing as the essential finishing step. Polishing of brittle materials is an established process in science and industry. However, the machining is limited to planar or spherical geometries. The objective of this paper is to present first results to overcome this limitations indicated by processing advanced ceramics.In order to finish complex surfaces, a technological transfer of known parameters and conditions of 2-dimensional to zonal polishing is undertaken. To shorten the development of stable and reproducible processes the knowledge and understanding of the complex interactions of the 2-dimensional process is used. The applicability of these conditions is evaluated by extensive research on the zonal polishing setup. The used machine tool is capable of adjusting significant process factors, such as free controlled force and heterodyne velocity profiles. By use of a small tool the material removal is only affecting a zonal area of a complex surface. Based on preliminary investigations concerning the material removal function the scientific insight on zonal processes is extended. This first approach will be used for corrective polishing of zonal form deviations.     

Damage-free tribochemical polishing of diamond at room temperature: a finishing technology

Polished surfaces are characterized by a geometric shape and a surface finish, the latter being defined by surface roughness (smoothness) and subsurface damage. In general, mechanically polished surfaces have a high geometric precision and are optically smooth, but they are subjected to surface and subsurface damage. Tribochemical polishing gives smooth surfaces and damage-free subsurfaces, but the surface geometric precision is often poor at the submicron level. Diamond is the hardest material known, and the standard polishing technique for such hard materials is mechanical polishing, causing surface and subsurface damage. In this paper a novel method of tribochemical polishing of natural and synthetic monocrystalline diamond at room temperature is described, which gives very smooth surfaces of, at least, (100) planes, free from surface and subsurface damage within the instrumental detection limits. Such diamond surfaces are van der Waals bondable to other materials. With this novel technology only low material removal rates can be achieved. Therefore, it is mostly adapted as a finishing technique. The described polishing technology can be applied to other (hard) materials as well.     

一种大型复杂构件加工新模式及新装备探讨

大型复杂构件是航空航天、能源、船舶等领域装备的核心结构件，此类构件通常具有尺寸大、形状复杂、刚性弱等特点。传统“分体离线加工-在线检测”模式存在工艺不稳定、过程复杂、柔性差、周期长等问题，以龙门式多轴数控机床加工为代表的“包容式”加工模式，难以适应大型复杂构件的高效高质量加工制造需求。提出一种基于移动式和吸附式机器人的多机协同原位加工新模式，通过多机器人系统自主寻位、精确定位加工与加工质量原位检测，实现大型复杂构件多安装面并行铣削、制孔与打磨等作业。多机器人系统包括移动式混联机器人、吸附式并联机器人、移动式串联铣削机器人、移动式双臂加工机器人和移动式打磨机器人。构建多机协同原位加工模式，需要揭示多机器人协同原位加工行为与大型弱刚性结构件质量控制的交互机理，面临着本体、测量、工艺和集成四个方面的挑战，需要设计高灵活、高刚度的移动式和吸附式加工机器人，解决移动机器人自主准确寻位和超大结构件原位高精检测难题，攻克加工变形误差在线补偿和振动抑制技术，通过集成实现多机协同高效高精加工，为大型复杂构件的高效高质量制造提供创新技术及装备，并实现此类构件制造核心技术及装备自主可控。     

Using a Nd:YAG laser and six axes robot to cut zinc-coated steel

Zinc-coated steel sheets are important materials in the automobile and home appliance industries. Currently, lasers are the preferred tools for metal cutting because of their good cutting quality, flexibility and excellent features and results, as compared to traditional tools. The solid-state Nd:YAG laser has successfully replaced the gaseous CO₂ laser for metal cutting; its small size and short wavelength makes it suitable for cutting bright and metal-coated materials, as well as being able to be transmitted via optical fibers and robots to cut complicated three dimensional and curved shapes. In this work, the Nd:YAG laser is used to cut 1 mm zinc coated steel sheets. We demonstrate the effects of different cutting parameters such as laser power, cutting speed, different gas types and pressures, and focus position on the cutting quality characteristics of attached dross, kerf width and cut surface roughness. Using a six axes robot, cutting speed was limited to 6 m/min because of the noticeable vibration at higher speeds. Results showed that the cutting surfaces achieved were very sharp and smooth. In cutting, Nd:YAG required less power and attained higher speeds than the published results of a CO₂ laser, which makes Nd:YAG an economical alternative to cut zinc and metal-coated materials. In addition, laser cutting using robots provided efficient and consistent cutting quality, especially in the case of 3D and countered cutting. Apart from using low speed, robots proved to be more economical than costly, specially designed CNC tables.     

Review on mechanism and process of surface polishing using lasers

Laser polishing is a technology of smoothening the surface of various materials with highly intense laser beams. When these beams impact on the material surface to be polished, the surface starts to be melted due to the high temperature. The melted material is then relocated from the ‘peaks to valleys’ under the multidirectional action of surface tension. By varying the process parameters such as beam intensity, energy density, spot diameter, and feed rate, different rates of surface roughness can be achieved. High precision polishing of surfaces can be done using laser process. Currently, laser polishing has extended its applications from photonics to molds as well as bio-medical sectors. Conventional polishing techniques have many drawbacks such as less capability of polishing freeform surfaces, environmental pollution, long processing time, and health hazards for the operators. Laser polishing on the other hand eliminates all the mentioned drawbacks and comes as a promising technology that can be relied for smoothening of initial topography of the surfaces irrespective of the complexity of the surface. Majority of the researchers performed laser polishing on materials such as steel, titanium, and its alloys because of its low cost and reliability. This article gives a detailed overview of the laser polishing mechanism by explaining various process parameters briefly to get a better understanding about the entire polishing process. The advantages and applications are also explained clearly to have a good knowledge about the importance of laser polishing in the future.     

Signal analysis and real-time monitoring for wafer polishing processes using the ch computing environment

There are several processes used in the silicon wafer fabrication industry to achieve the planarity necessary for photolithography requirements. Polishing is one of the important processes which influence surface roughness in the manufacturing of silicon wafers. As the level of a silicon wafer surface directly affects device line-width capability, process latitude, yield, and throughput in the fabrication of microchips, it is necessary for it to have an ultra precision surface and flatness. The surface roughness in wafer polishing is affected by many process parameters. To decrease the surface roughness of the wafer, controlling the polishing parameters is very important. Above all, a real-time monitoring technology of the polishing parameters is necessary for the control. In this study, parameters affecting the surface roughness of the silicon wafer are measured in real-time. In addition comparing the predicted value is done according to the process parameters using the artificial neural network. Through these results, we conduct research on the efficient parameters of silicon wafer polishing. Required programs are developed using the Ch computing environment.     

软体机器人研究现状综述

软体机器人由柔韧性材料制成,可在大范围内任意改变自身形状、尺寸在侦察、探测、救援及医疗等领域都有广阔的应用前景。综述软体机器人结构类型、驱动方式、物理建模技术和加工制造方法等问题。其结构模仿生物的静水骨骼结构和肌肉性静水骨骼结构,采用形状记忆合金、气动、电活性聚合物等物理驱动方式或将化学能转化为机械能的化学驱动方式。软体机器人建模困难,主要采用试验分析或使用超冗余度机器人建模方法近似研究。制造中的问题包括柔性本体制造、柔性致动器制造以及可伸展电路的制造,采用形状沉积、激光压印、智能微结构等新型制造工艺。软体机器人是一种全新的机器人,对它的研究刚刚起步,涉及材料科学、化学、微机电、液压、控制等多学科,从材料、设计、加工、传感到控制、使用均存在着一系列问题需要继续研究。     

模具光整加工技术新进展

从工艺——机械抛光、特种抛光、复合抛光，自动化——数控机床、机器人、知识库、测量，“一次过加工技术”——高频窄脉冲和展成电解加工、混粉电火花镜面加工、高速铣加工三方面对现有的模具抛光技术进行了较为详细的介绍，分析了各自的特点、适用场合及某些技术关键。     

Novel hybrid robot and its processes for precision polishing of freeform surfaces

Freeform surfaces have important applications in various industrial fields. However, achieving a high level surface finish on freeform surfaces using polishing is always a challenging task. Hybrid robots are promising alternatives to conventional computer numerical control (CNC) machines and industrial robots for ultra-precision machining. Herein, we present a novel custom-built hybrid robot for freeform polishing. After the laboratory prototype was successfully developed, its automation for a specific freeform surface was a major obstacle preventing its application. This critical issue was addressed by presenting a process to deal with tedious robot programming. Random tool path planning was performed in the task space, and hybrid robot motion planning was conducted in the joint space. By integrating the process flows, a robot programming toolkit was developed to directly output the control program for a specific robot controller. An illustrative example with a freeform surface is provided to verify the functionality of the developed hybrid robot and the proposed control processes, and the corresponding experimental results verify their effectiveness.     

X射线—极紫外光学中的超精密加工及其应用

短波光学技术的发展对高精密超光滑表面提出了严格要求。在X射线—极紫外光学中,光学元件表面粗糙度均方根值必须达到埃量级。制造这样表面的超精加工包括切割、研磨和抛光等工艺过程。本文介绍一种制造X射线望远镜中非球面镜的复制方法。     

X射线—极紫外光学中的超精密加工及其应用

短波光学技术的发展对高精密超光滑表面提出了严格要求。在X射线—极紫外光学中,光学元件表面粗糙度均方根值必须达到埃量级。制造这样表面的超精加工包括切割、研磨和抛光等工艺过程。本文介绍一种制造X射线望远镜中非球面镜的复制方法。     

研磨抛光表面微孔织构的形成

由于表面织构可以改善机械零部件的摩擦磨损特性,延长其使用寿命,本文基于研磨抛光方法开发了一种表面微孔快速成型技术。该技术的特点是微孔成型过程与抛光过程同步进行。选取载荷为0.023 2 MPa、研磨液浓度为9%、研磨速度为2.09m/s以及研磨粒径为0.5μm作为考察条件,研究了微孔在金属表面的形成机理,证明了表面微孔是由于研磨颗粒在表面预制微缺陷处做涡旋运动,同时工件的自转使研磨颗粒在360°方向上依次磨削微缺陷壁面而形成的。利用该技术所形成的微孔周边为圆弧过度,无其他织构技术所形成的凸起和毛刺,因此无需进行抛光后处理。利用该方法在一定的织构条件下可以形成次生孔,从而进一步增加工件的比表面积。另外,选取合适的研磨时间在适当的织构条件还可以在工件表面形成微米及亚微米孔,为减少类金刚石(DLC)薄膜内应力和提高界面结合强度提供了新的思路。研究显示研磨抛光表面微孔织构技术具有设备简单、效率高、适合大面积,多种材料织构等特点。     

软体磨具新技术

零件曲表面的磨光,抛光技术是精密加工技术领域的难题,传统的磨具难以直接对不规则的曲面进行加工。作者研究的软磨具,是一种体内均匀含磨料的新型高分子复合材料、磨料和抛光粉为加工要素,聚氨酯基网链状高分子材料为连接剂并为抛光要素。新型软磨具为三维柔软的弹性体,能适应任意曲率的零件（金属或非金属）表面的磨光和抛光要求。本文包括新型软磨具的生成理论,制造技术和曲面零件抛光的工艺性能试验研究。     

A survey of climbing robots: Locomotion and adhesion

Climbing robots are robotic systems to move over 2D or complex 3D environments such as walls, ceilings, roofs, and geometric structures and to conduct various tasks. They will not only replace human workers for carrying out risky tasks in hazardous environments, but also increase operational efficiency by eliminating the costly erection of scaffolding and staffing costs. Climbing robots have special characteristics and the ability to adhere to different types of 2D or 3D surfaces, move around, and carry appropriate tools and sensors to work, while self-sustaining their bodies. Therefore, the most significant criterion for designing a climbing robot is to equip it with an appropriate locomotive and adhesion mechanism for adapting to the given environmental requirements. In this paper, a classification of climbing robots and proper examples with a brief outline are presented with considerations of the locomotive and adhesion mechanisms. Also, a list of climbing robots is provided with respect to fields of application that range from cleaning tasks in the construction industry to human care systems in the biomedical service industry.     

An advisory system for the analysis and design of deformable beam-type multi-body systems

Multi-body systems can be used to model mechanisms, robots and many other mechanical assemblies. When these devices are subjected to high-speed and high accuracy requirements, their elastic behavior will merit thorough investigation. The finite element analysis and design of deformable multi-body systems is a very complex, iterative process requiring a high level of expertise and engineering intuition. This paper presents an advisory system developed to help a designer with the key parameters through the analysis, design, and validation processes. The related knowledge such as to determine the optimum parameters for mesh, time step, type of analysis, type of element, the numerical integration scheme and the corresponding parameters, and the design considerations such as material selection method, and geometric synthesis algorithm are also documented.     

Review of manufacturing processes for soft biomimetic robots

This paper reviews various processes for manufacturing new type of robots termed “soft biomimetic robots.” Most robots are made of rigid metallic materials. But in recent years, various biomimetic robots based on soft materials and compliant parts have been developed. New manufacturing processes are required to fabricate these types of robots, and the processes include Shape Deposition Manufacturing (SDM) and Smart Composite Microstructures (SCM). Since the design of robots are limited by the available material and manufacturing processes, it is important to develop new manufacturing processes that will enable development of novel soft biomimetic robots. In this paper, various manufacturing processes which can be applied to soft robot fabrication are summarized, and features of those processes are described. Processes are divided into three categories; soft robot body fabrication, actuators for soft robots and stretchable electronics. This review provides a guideline for selecting manufacturing processes for soft robots and developing new processes that will enable new type of robots to be designed.     

Investigations on the automatic precision polishing of curved surfaces using a five-axis machining centre

Polishing is usually indispensable process when better surface roughness is required for the parts such as injection mold. However, polishing process is often performed by manual operations. In this paper, an automatic polishing method for the metal parts with curved surfaces is proposed based on a machining centre. In order to realize the control of contact force, the relationship between the displacement of polishing disk and the force impacted on the polished part is first established. Then, within the contact zone between the polishing disk and the polished part, a pressure distribution model is derived for planar and curved surface polishing according to the specific process parameters. On this basis, the model of removal depth distribution along the vertical direction of feed is built for each polishing pass, and thus a suitable stepover size is further obtained so as to reduce the fluctuations of remove depth to most extent. Finally, an effective planning algorithm of cutter location data in polishing is proposed for a given CNC machine tools, and validation experiments are performed on planar and curved parts. The results show that the proposed automatic polishing scheme is able of achieving a mirror effect surface and keep a good global uniformity, at the same time it improves the polishing efficiency and realizes the integration with milling process.     

一种中小口径非球面元件数控抛光技术

基于自主设计研制的FSGJ-3型非球面数控加工中心,针对口径φ108 mm凸非球面透镜(曲率半径R＝318 mm,k=－3),研究了非球面粗抛光工艺、精抛光工艺、抛光设备、磨料以及相关工艺参数,提出了规范的中小口径非球面加工的工艺方法和新型轮式抛光技术,实现了中小口径非球面元件的数控快速精密铣磨成型,且保证了光学零件具有较高的面形精度。抛光后元件面形精度达到0.306 λ(PV)、0.028λ(RMS) (λ=0.632 8μm)。满足了在光学系统中使用非球面零件,明显改善像质,提高光学特性,减少光学零件数目,从而简化系统结构,减小系统体积,减轻系统质量的目的。     

Theoretical and experimental investigation of surface generation in swing precess bonnet polishing of complex three-dimensional structured surfaces

Three-dimensional structured surfaces (3D-structured surfaces) possessing specially designed functional textures are widely used in the development of advanced products. This paper presents a novel swing precess bonnet polishing (SPBP) method for generating complex 3D-structured surfaces which is accomplished by the combination of specific polishing tool orientation and tool path. The SPBP method is a sub-aperture finishing process in which the polishing spindle is swung around the normal direction of the target surface within the scope of swing angle while moving around the center of the bonnet. This is quite different from the ‘single precess’ and ‘continuous precessing’ polishing regime, in which the precess angle is constant. The technological merits of the SPBP were realized through a series of polishing experiments. The results show that the generation of complex 3D-structured surfaces is affected by many factors which include point spacing, track spacing, swing speed, swing angle, head speed, tool pressure, tool radius, feed rate, polishing depth, polishing cloth, polishing strategies, polishing slurry, etc. To better understand and determine the surface generation of complex 3D-structured surfaces by the SPBP method, a multi-scale material removal model and hence a surface generation model have been built for characterizing the tool influence function and predicting the 3D-structured surface generation in SPBP based on the study of contact mechanics, kinematics theory, abrasive wear mechanism, and the convolution of the tool influence function and dwell time map along the swing precess polishing tool path. The predicted results agree reasonably well with the experimental results.     

Surface integrity of silicon wafers in ultra precision machining

Silicon wafers are the most extensively used material for integrated circuit (IC) substrates. Before taking the form of a wafer, a single crystal silicon ingot must go through a series of machining processes, including slicing, lapping, surface grinding, edge profiling, and polishing. A key requirement of the processes is to produce extremely flat surfaces on work pieces up to 350 mm in diameter. A total thickness variation (TTV) of less than 15 μm is strictly demanded by the industry for an 0.18 μm IC process. Furthermore, the surfaces should be smooth (R_a<10 nm) and have minimum subsurface damage (<10 μm) before the final etching and polishing. The end product should have crack-free mirror surfaces with a micro-roughness less than 1.8 Å. In this paper, experiments are conducted to investigate the effects of various parameters on the subsurface damage of ground silicon wafers.