3D nanometer features by ultra precision machining

Until now grating machines were mainly used to produce high-resolution mechanically divided gratings by scratching the structures in thin metal layers. Hereinafter, a new method is presented to produce echelette as well as echelle gratings on curved substrate surfaces. This is achieved with a modified planing procedure whereupon there are no limits to the maximum structure height.     

Helical surface creation by wire electrical discharge machining for micro tools

In mechanical micromachining, micro tooling is one of the key factors affecting the finished geometrical accuracy and surface quality. To overcome the serious tool wear caused by relatively longer micromachining time, micro tools are usually made of ultra-hard materials such as polycrystalline diamond (PCD) or cubic boron nitride (CBN). Wire Electrical discharge machining (WEDM) is a good choice for efficient fabrications of micro tools made of ultra-hard materials. Considering the traces of wire motions form ruled surfaces, in this paper, typical custom micro milling tools with helical surfaces are generated by ruled surfaces. The simulation shows that the selection of guide lines and generating lines for ruled surface is the key point relating to the final geometrical accuracy and machining efficiency in custom micro tool fabrications by WEDM. Based on the mathematical models built in this paper, overcut can be avoided in the process planning stage for complicated helical surfaces. Furthermore, wire locations can be created conveniently by the introduced mathematical models for post processing in dedicated CAM systems.     

Potentials of precision machining processes for the manufacture of micro forming molds

Molds for micro forming processes require specific functional surfaces to provide optimized tribological condition for forming processes. Such topographies with microscopic dimensions can for instance be generated by lithographical methods. However, a main disadvantage of these processes is their low flexibility, e.g. changing the structures to be generated causes extensive adaptations in the manufacturing process. Therefore, mechanical precision machining processes like micro milling, micro grinding and micro polishing are appropriate processes for the manufacture of micro molds of manifold shapes and with well suited micro topographies.     

Fabrication of microfluidic structures in quartz via micro machining technologies

Microfluidic channels have been created for quartz material using micromechanical manufacturing technologies such as micro laser machining, micro ultrasonic machining, and ultra-precision machining. Ultra-precision machining has been used to manufacture cross-junction channels 14 µm wide and 28 µm deep with a three-dimensional triangle cross-section. Micro laser machining has been used to manufacture U-shaped and -shaped microfluidic channels. Deep holes and microfluidic channels with a high slenderness ratio (width/depth) can be obtained by using micro ultrasonic machining technology. These three machining techniques are compared with respect to surface profiles and machining quality.

     

High aspect ratio micromolds for the electroplating of micro electro discharge machining tools

A new approach using micro systems technology for the fabrication of micro electro discharge machining tool electrodes using a combination of positive and negative photoresist fabricated with near UV-lithography as high aspect ratio micromolds was developed. Micromolds with heights varying from 200 to 650 μm and an aspect ratio of up to 26:1 were fabricated using SU-8?, a negative photoresist, as a micromold for the electrodeposition of the micro tool electrodes. Besides serving as a micromold, SU-8? is also used as an insulator to protect the sidewalls of the tool electrodes from corrosions. The fabrication of the SU-8? micromold was optimized to avoid cracks and delaminations. In the experiments, electrodes made of Cu, WCu, and CoFe were deposited into these High Aspect Ratio Micro Structure Technology (HARMST) micromolds. Furthermore, the process technique for electroplating in deep micromolds is discussed in this paper.     

Fabrication of high-aspect-ratio microscale Ta mold inserts with micro electrical discharge machining

We report fabrication of microscale Ta mold inserts by micro-electrical-discharge-machining (μEDM). Morphology, chemistry, and structure of the near-surface region of as-μEDMed Ta blanks have been characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. A TaC surface layer forms on as-μEDMed Ta surfaces. This altered surface layer was removed by electro-chemical-polishing. Further modification of Ta insert surfaces was accomplished by deposition of a conformal Ti-containing hydrogenated carbon coating. We demonstrate successful replication of high-aspect-ratio microscale structures in Al and Cu by compression molding with such surface-engineered Ta mold inserts.     

Fabrication of high-aspect-ratio electrode array by combining UV-LIGA with micro electro-discharge machining

In this paper, the combination of UV-LIGA with the Micro electro-discharge machining (Micro-EDM) process was investigated to fabricate high-aspect-ratio electrode array, and an easy and rapid process for fabricating ultra-thick SU-8 microstructures up to millimeter depth was described. First, the modified UV-LIGA process was used to fabricate the copper hole array, and then the hole array electrode was employed as a tool in the Micro-EDM process to fabricate the multiple-tipped electrodes. Electrode array of various shapes have been fabricated by this technique. The aspect ratio is up to 17.65.     

Fabrication of steel roller imprinting molds through adapting conventional planar micro fabrication tools

A soft lithography process has been developed to transfer a pattern directly from a flat PDMS stamp to a stainless steel cylindrical substrate using an SAM ink, without any need to physically attach the stamp to a roller. The process uses standard semiconductor wafer processing equipment, along with specially designed elements to adapt to the cylindrical substrates. The entire process can be applied to batch processing and thus can be directly applied to manufacturing. This technique was demonstrated by fabricating a steel herringbone journal bearing with a diameter of 1.5 mm. The HGJB is an important element which is used for high-speed rotating spindles of electro-mechanical systems such as hard disk drives, CD-Rom drives, and DVD drives in the consumer electronics industry. In this case, the pattern had a dimension of 85 microns and depth of 3 microns. Features as deep as ten microns and as narrow as two microns have been also demonstrated.     

Training ultra precision engineers for UK manufacturing industry

Ultra Precision Engineers are in demand in both UK and European manufacturing industries. Engineering Companies can address this skills shortage by training existing staff or recruiting new staff with the appropriate skills. Since companies are understandably reluctant to lose key staff for re-training, it is preferable to meet the shortfall by recruitment. This paper describes how UK engineering companies have worked in partnership with academia to design a postgraduate course in ultra precision technologies. The new Masters level course has come to fruition under the auspices of the integrated knowledge centre in Ultra Precision structured surfaces (UPS²), as a component of its Knowledge Transfer portfolio. The MSc in “Ultra Precision Technologies” is led by Cranfield University, with support from University College London and the University of Cambridge. The role of industrial partners is described, from course design to student placements for individual project work; and the lessons learned from the first four cohorts are discussed.     

Development of electrochemical micro machining for air-lubricated hydrodynamic bearings

 A specially-built EMM (Electrochemical Micro Machining)/PECM (Pulse Electrochemical Machining) cell, a electrode tool filled with non-conducting material, a electrolyte flow control system and a small & stable gap control unit are developed to achieve accurate dimensions of spindle recesses. Two electrolytes, aqueous sodium nitrate and aqueous sodium chloride are investigated in this study. The former electrolyte with few pits on the surface of workpiece has better machine-ability than the latter one with many pits on the surface of workpiece. It is easier to control the machining depth precisely with pulse electrical current than direct electrical current. This paper also presents an identification method for the machining depth by in-process analysis of applied electrical current and interelectrode gap size. The interelectrode gap characteristics, including pulse electrical current, effective volumetric electrochemical equivalent and electrolyte conductivity variations, are analyzed using the model and experimental results. Received: 5 July 2001/Accepted: 11 December 2001 This work was supported by Korea Research Foundation Grant (KRF-2001-041-E00095) Paper presented at the 12th Annual Symposium on Information Storage and Processing Systems, Santa Clara, CA, USA, 28–29 June, 2001.     

Fabrication of micro gear by micro powder injection molding

Micro components made from polymers can be easily processed but they may not be suitable for all applications. One example is where good mechanical properties are required. Thus, the fabrication of micro components from non-polymeric materials such as metals and ceramics is essential. In this paper, the fabrication of 316L stainless steel micro gear by micro powder injection molding is reported. The specifications of the green micro gear were: 10 teeth, module of 0.08, outer diameter of 1 mm and a length of 1 mm. Injection molding was conducted on a conventional injection molding machine with a small screw diameter of 14 mm. The green micro gear was well replicated. The debound micro gear retained its shape and the teeth were well defined. After sintering, the shape was also retained but with some surface irregularities. The process differences between μPIM and PIM, such as the use of smaller particle size and higher mold temperature are also highlighted.     

Fabrication of CVD diamond photoconductive detectors

We present an investigation on the fabrication of synthetic diamond based photon detectors. These devices are made by depositing small gap interdigitated contacts on polycrystalline diamond films grown by Microwave Plasma Enhanced Chemical Vapour Deposition. Gold interdigitated contacts were deposited on the typically rough surface of these films by using both wet etching and unconventional lift-off lithographic processes. These detectors were tested through X-ray irradiation in order to compare their potentialities in obtaining higher performance diamond photoconductive detectors. A better resolution was observed in samples obtained through the lift-off process. In particular for these samples the gap between electrodes could be kept very small and of the order of the grain size, giving higher response due the lower contribution of grain boundary effects.     

CAD of worms and their machining tools

To develop high-quality products, geometric modeling is needed in gear engineering to calculate the workpiece and tool geometry of worms, threads, or similar mechanical elements that can be described by helical or rotatory surfaces and that are to be generated by milling, grinding, or whirling. A survey will be given on the theoretical background, corresponding procedures, and illustrating examples of application concerning: (a) design of gear or worm profiles by means of curve primitives, their motion and manipulation; (b) calculation of conjugate gear profiles subjected to trochoidal motion; (c) calculation of arbitrary plane intersections of helicoids; and (d) calculation of the rotatory machining tool surface for a given worm and the inverse problem, including the solution of the undercut problem. Basic to the achieved integrated approach to CAD/CAM in this field is a discrete curve representation as sequence of points, tangent lines, and osculating circles providing higher geometrical information about curve and surface shape, which is also of high functional and economical importance for technological decisions.     

Fabrication of drive and guide components for micro motors

This paper provides a contribution to the technology and fabrication of functional components for micro motors based on an electromagnetic principle. The focus of this research is on components for the drive, guide and bearing for magnetic actuator systems. The technology and fabrication process of an electromagnetic guide is presented in detail. Its active principle is based upon repellent magnetic forces. Furthermore, the components of a linear variable reluctance micro motor are described. An improvement of driving forces has been achieved in comparison to the first prototype by determined optimizations. In addition, the weight of the traveller could be decreased. The fabrication of compact coil designs for the electromagnetic guide as well as the optimization of components for the reluctance motor are mainly attributed to the implementation of new fabrication technologies and new materials like inorganic insulation layers and electrodepositable photo resists.     

Parallel precision alignment of multiple micro components

Micro components are available in a variety of shapes sizing from 1 mm down to 0.01 mm. Today, their mass production is quite common using state of the art production technology. Micro spheres for example, are on the one hand available in lot sizes up to some thousands in a constant quality within micron accuracy. On the other hand they are quite commonly provided as bulk material with diameter variations of up to 10% in each lot size Brandau (Chem Ingenieur Tech 75:1741–1745, 2003). In both cases, the bulk micro components are usually arranged in incoherent batches which are packed in plastic bags or small jars for handling and shipping. The decollating of the single components for follow-up micro assembly processes is complicated by the well-known effects in micro handling such as dominating adhesion and friction forces (Petersen 2003). These effects limit the post processing of bulk micro components to manual work in order to sort and align the single micro components prior to their exposure to an automated assembly line. To enable a sophisticated and automated handling of the single micro components, automated sorting and alignment mechanisms are necessary to arrange the bulk micro components in a well defined pattern structure which is essential to realize an efficient automated micro assembly.     

Improving machining accuracy in precision line boring

There is an ever-growing demand for high precision machining to obtain increased accuracy and surface finish, as they are key factors in product quality and performance. Machining operations, in general, are associated with errors of varying magnitude originating from different sources. As a result, the sizes of the machined features usually deviate from their desired, nominal values. Identification of error sources, techniques of measurements (on/off line), and efficient strategies for their compensation are the steps required to minimize, and, in some cases eliminate process errors. This paper focuses on modeling and compensation of geometric errors in machining operations specific to the line boring process. It is part of an undergoing research project focused on design and development of an agile precision line boring station for machining of long bores. After a brief overview of sources of geometric errors and their components, a methodology for their calculation is introduced. In this regard, error equations reflecting the effects of machine tool geometric errors at the tool tip are derived. It is shown that these equations can be further simplified without significantly affecting computational accuracy of the results. This makes the approach more attractive for real-time applications. A set of experimental data obtained from a prototype of the machine is used to study the effectiveness of the proposed approach and the results are reported. The paper concludes with discussions and presentation of different methods and available tools for real time compensation of these errors.     

超精密伺服系统控制与应用

随着智能微纳器件和高性能数字系统的飞速发展,超精密伺服技术已逐步成为信息存储、精密成像、半导体装备等新兴行业的核心技术.本文从微纳操控领域的设计和控制问题着手,首先介绍了超精密伺服系统的设计及分析方法,进而阐述了超精密伺服系统对控制理论提出的诸多挑战.特别针对这类系统中广泛存在的模型不确定性及高阶未建模动态特性,非线性迟滞特性及执行机构饱和非线性,多源复杂干扰并存情况的抗干扰控制问题,以及面向复杂轨迹的高精度跟踪控制问题,给出了具有代表性的控制算法和应用实例.本文最后以高精度直写式真空蒸发系统为例,介绍了超精密伺服技术在现代精密仪器设备中的重要应用.     

Design and manufacturing of micro milling tools

The actual geometrical design of micro milling tools has been adopted from macro tools, assuming that the effects during the milling process are analogical. Experience has also proved that micro tools respond to influences in a very different way than macro tools do. So it is very important to achieve a comprehensive understanding of the entire process by taking a structural, mechanical and cutting technological approach to micro milling tools in order to be able to optimize them. Oftentimes, structural details such as the rake angle and the twist angle impede further miniaturization and are impossible to achieve with conventional manufacturing techniques. This paper deals with an alternative method to manufacture structural optimized milling tools, namely Electro Discharge Machining (EDM). The present state of research already puts the deficits of the currently available tools on display. Manufacturing tolerances of ±10 μm on a micro tool are insufficient to ensure constant cutting conditions for the commonly used lateral infeed or feed per tooth of a few micrometers. Sometimes, only one cutting edge is engaged, which results in increased wear, increased cutting forces, minor surface quality and a higher risk of milling cutter breakage. That is why a single-edged micro milling tool has been developed. It guarantees clear adjustment of the process parameters, feed per edge and lateral infeed. For that purpose, stability analyses of simple stylus geometries have been conducted by means of FEM simulations. Corresponding to the results of the simulation the geometry of this tool was optimized in several steps. The resulting tool with a diameter down to 30 μm was machined on the EDM-machine (Sarix SX 100) at the wbk—Institute of Production Science. Initial tests have been carried out and showed the ability of these tools to optimize cutting process.     

Fabrication of microchannels in single crystal diamond for microfluidic systems

A growth of single crystal diamond (SCD) microchannels on HPHT diamond substrate has been carried out successfully by a simple and novel method. Firstly, aluminum film was patterned on SCD diamond substrate surface by magnetron sputtering, photolithography and dry etching techniques. Secondly, the aluminum patterns were transferred onto diamond substrate via inductively coupled plasma etching to form grooves on diamond surface. Finally, microchannels were achieved by epitaxial lateral overgrowth of SCD on the surface of prepared substrate by microwave plasma chemical vapor deposition system. After that, fluorescent liquid was introduced to check hollowness of the microchannels. This work provides a simple and time saving method to fabricate SCD microchannels for microfluidic system, which offers a great potential for hard environment applications.