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A novel concept for improving machine dynamic performance was developed and realised, a virtual metrology frame, for a small size CNC machine with flexible frame. Its implementation in a simplified linear motion system shows a reduction in the magnitude of the first resonance in the plant frequency response function by 12 dB. Realising the concept required developing a real -time accelerometer-based measurement technique. It shows a low sensor noise σ=30 nm with optimal phase delay of

The Cranfield University Precision Engineering Institute team has created a unique plasma figuring capability to correct large optical surfaces at atmospheric pressure. In the context of ever increasing dimensions of optical components, there is a need for improving the robustness and securing the performance of our Plasma Delivery System (PDS). The current PDS is based on an inductive output L type RF circuit, Inductively Coupled Plasma (ICP) torch and computer numerically controlled (CNC) motion system. The combination of optical component surface areas and the nature of the sub-aperture plasma tool lead to significant processing duration. This atmospheric pressure processing environment is more cost-effective than vacuum chamber based ones which are often used by competitors. However it requires deep awareness and fine understanding of technologies used. Based on the knowledge acquired for the past eight years, we have created a smart control system for our unique PDS that equips a machine called Helios1200. This novel control system aims at securing the process determinism and assisting the machine operator by tuning some key electrical components of the RF network and monitoring some processing parameters. Furthermore, specific assistance is provided during the different phases of the plasma processing. This paper describes the main design aspects.

To satisfy the worldwide demand for large ultra-precision optical surfaces, a fast process chain - grinding, polishing and plasma figuring- has been established by the Precision Engineering Institute at Cranfield University. The focus of Cranfield Plasma Figuring team is the creation of next generation of highly collimated energy beam for plasma figuring. Currently, plasma figuring has the capability to shorten processing duration for the correction of metre-scale optical surfaces. High form accuracy can be achieved (e.g. 2.5 hours and 31 nm RMS for 400mm diameter surface). However, it is known that Mid Spatial Frequency (MSF) surface errors are induced when the plasma figuring process is carried out. The work discussed in this paper deals with the characterisation of highly collimated plasma jets delivered by the Inductively Coupled Plasma (ICP) torches. Also a computational fluid dynamics (CFD) model is introduced. This model is used to assess the behaviour of the plasma jet within the best known processing condition. Finally temperature measurement experiments were performed to determine the energy dissipated values that characterise best the ICP torch coil and its De-Laval nozzle.

The following study is realised within the frame of the PACMAN project: a study on Particle Accelerator Components Metrology and Alignment to the Nanometre scale, which is a Marie Curie program supported by the European commission and hosted by CERN (European Organisation for Nuclear Research). The aim of this program is to develop and build a pre-alignment bench on which each component is aligned to the required level in one single step using a stretched wire. During the operation, the centre of the stretched wire is aligned with the magnetic axis of the magnet. Then, the position of the wire is measured to the highest possible accuracy using a 3D Coordinate Measuring Machine (CMM) Leitz PMM-C Infinity from HEXAGON Metrology. The research described in this paper is two-fold: on one hand we apply a strong magnetic field to the head of the CMM and evaluate its influence on the measurement accuracy; on the other hand we measure the position

L’étude suivante est réalisée dans le cadre du projet PACMAN (a study on Particle Accelerator Components Metrology and Alignment to the Nanometre scale) : une étude sur la métrologie et l’alignement à l’échelle nanométrique des composants d’un accélérateur de particules. C’est un programme Marie Curie supporté par la Commission Européenne et hébergé par le CERN. Le but de ce programme est de faire travailler en équipe de jeunes chercheurs sur le développement d’un banc de pré-alignement pour l’accélérateur linéaire CLIC (Compact Linear Collider). Sur ce banc, chaque composant sera aligné au niveau requis en une seule opération basée sur l’utilisation d’un fil tendu. Pendant cette opération, le fil matérialisera les axes magnétiques et électriques des composants, c’est-à-dire qu’il sera à la position théorique du faisceau de particules. Puis il servira de référence et la position de son axe sera mesurée avec autant de précision que possible par une machine de mesure tridimensionnelle. La recherche présentée dans ce papier est en deux parties : la première vise à présenter les propriétés du fil nécessaires au projet qui ont été mesurées, tandis que différents capteurs potentiels pour le banc final se trouvent dans la seconde.

We discuss the creation of an Integrated Knowledge Centre, a unique collaboration between academia and industry, which is delivering to UK industry 'disruptive' technologies based on ultra precision engineering. The partners include Cranfield University, the University of Cambridge, University College London, and the OpTIC Technium. This paper concentrates on the development of Knowledge Transfer systems and the successful implementation of processes for the delivery of postgraduate taught courses, short courses for industry, and distance learning packages. In order to retain competitive advantage, UK precision engineering industry requires a regular supply of technically proficient and organizationally prepared graduates. This paper explains the approach taken by Cranfield University and its partners to increase the size of the pool of postgraduate precision engineers and to enhance the skills of industrially based engineers. The approach involves the design of a multi-level system, which draws on increased connectivity between the University, UK Engineering companies, and the student. The main vehicle for providing the technical training is the postgraduate Masters degree in "Ultra Precision Technologies". We explain how this course has been designed for broad appeal, whilst incorporating world class technical teaching and an external focus on the needs of participating companies.

A Coriolis mass flow meter (CMFM) measures the rate of fluid flow from the effect of forces induced by the Coriolis effect on a vibrating tube. This work considers scaling a CMFM to measure small mass flow rates. The effect of the tube dimensions on the measured response, the pressure drop and the resonance frequency is analysed. It is shown that these properties cannot be tuned independently by scaling the tube's dimensions, posing a fundamental limit on the performance of a small flow CMFM.

The fields of astronomy science have presented significant precision engineering challenges. Numerous solutions for these fields of science have achieved unprecedented levels of accuracy, sensitivity and sheer scale. Notwithstanding of their importance to science understanding, many of these precision engineering developments have become key enabling technologies for wealth generation and other human well-being issues. This paper provides a brief historical overview of astronomy instruments. Later, details of critical precision engineering developments that supported the establishment of leading European astronomical instruments are illustrated. Finally, significant precision engineering demands to enable future sciences programmes are introduced.

Recently established the Helios 1200 (RaptTM ) is a unique facility designed for the figuring of large optical surfaces [1]. It combines a CNC machine tool with a reactive atom plasma (RAP) process. This provides a unique rapid surface figuring capability with tool size and tool path motion flexibility. RAP is a proven technology for processing silicon based optical materials [2]. The aim with this technique is to achieve figuring correction of metre size optical components in 10 hours - a much reduced process time compared to the 100 hours currently needed. This paper focuses on key technical tasks to achieve a cost-effective figuring method using RAP. Classically a figuring process is carried out iteratively by analyzing surface figure error and removing material using an optimum tool path algorithm. In this work, the material removal is achieved by decomposing the compound SF6 in a plasma jet to obtain free fluorine radicals which etch away silicon based material. In this paper, measurements of the specific material removal rate and footprint of the plume over a range of substrate temperatures are presented. Then the authors present a base-line process for the neutral removal of material over a large area. Various tool path algorithms are investigated some of which include time-dwell adaptation based on substrate temperature. Finally, the issue of heat transfer is discussed, and both experimental and finite element analysis results are presented. The processed surfaces are analyzed using coherence probe and phase-shifting interferometers for surface morphology and 3D surface form respectively. Surface roughness (Sq) is reported within the 2-3 nanometre range on fused silica and surface flatness is within the +/-50 nanometre range after 0.5 micrometre deep material neutral removal (Typical processed area: 70x200millimetre).