CERES :: Browsing by Author "Morantz, Paul"

Browsing by Author "Morantz, Paul"

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Open Access
An accelerometer based-feedback technique for improving dynamic performance of a machine tool
(European Society for Precision Engineering and Nanotechnology, 2016-06-30) Abir, Jonathan; Morantz, Paul; Longo, Stefano; Shore, Paul
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 <70 μs.
Open Access
Active magnetic bearing for ultra precision flexible electronics production system
(Cranfield University, 2015-12) Tantau, Mathias; Shore, Paul; Morantz, Paul
Roll-to-roll printing on continuous plastic films could enable the production of flexible electronics at high speed and low cost, but the granularity of feature sizes is limited by the system accuracy. Technologies such as gravure printing and nanoimprint lithography demand a level of rotary motion precision that cannot be achieved with rolling element bearings. Manufacturing tolerances of the rotating parts, thermal drift and process forces in combination with structural compliance add up to additional error motions. In this master by research an active magnetic bearing (AMB) solution is designed for a new, super-sized roll-to-roll flexible electronics production machine, which was so far based on hydrostatic bearings. The magnetic bearing could actively compensate the accumulated synchronous error and maintain high accuracy under all conditions. However, the asynchronous error of a conventional AMB with the required size and power is a problem. In order to reduce the relatively high positioning uncertainty of active magnetic bearings an innovative radial position measurement based on linear, incremental encoders with optical conversion principle is proposed. A commercial encoder scanning head faces a round scale with concentric, coplanar lines on its face. By counting these lines the radial position can be measured. Because such a scale is not readily available, it is made by micro-machining. In experiments, different machining methods are compared. Then a magnetic bearing is built to demonstrate the efficacy of the proposed sensor. As a result, the best measurement noise is 3.5nm at 10kHz and a position uncertainty of approximately 0.25µm has been achieved for the magnetic bearing. These promising results are especially interesting for applications with high precision requirements at low speed of rotation.
Open Access
Advanced Bearing System for Ultra Precision Plastic Electronics Production Systems
(Cranfield University, 2014-09) Zhao, Gang; Shore, Paul; Morantz, Paul
The aims of this MSc research project are to investigate the application of aluminium for the main components of an ultra-precision spindle defined for use in R2R production systems and to produce a reel to reel rotary aluminium hydrostatic bearing system of high accuracy to meet the demand of manufacturing the flexible displays with an effective production capability for this special kind of film-based product. The original concept design was already finished to manufacture the bearing components and the objective of this project was to test the functionality of this new hydrostatic bearing system. Firstly, theoretical were performed to work out the output responses, including temperature rise, flow rate, load capacity etc., of the hydrostatic bearing system under different input design parameters, including supply pressure, fluid viscosity, the rotational speed etc. Then ANSYS software was used to build a FEA model to simulate the actual working conditions of the hydrostatic bearing system and to obtain the theoretical output parameters, especially the deflection conditions of the bearing shaft. Finally the experimental validation tests were conducted to verify the actual output responses to check correlation with the modelled results.
Open Access
Advances in optical surface figuring by reactive atom plasma (RAP)
(Cranfield University, 2012-10) Castelli, Marco; Shore, Paul; Morantz, Paul
In this thesis, the research and development of a novel rapid figuring procedure for large ultra-precise optics by Reactive Atom Plasma technology is reported. The hypothesis proved in this research is that a metre scale surface with a form accuracy of ~1 μm PV can be figure corrected to 20 – 30 nm RMS in ten hours. This reduces the processing time by a factor ten with respect to state-of-the-art techniques like Ion Beam Figuring. The need for large scale ultra-precise optics has seen enormous growth in the last decade due to large scale international research programmes. A bottleneck in production is seen in the final figure correction stage. State-of-the-art processes capable of compliance with requisites of form accuracy of one part in 108 (CNC polishing, Magneto-Rheological Finishing and Ion Beam Figuring) have failed to meet the time and cost frame targets of the new optics market. Reactive Atom Plasma (RAP) is a means of plasma chemical etching that makes use of a Radio Frequency Inductively Coupled Plasma (ICP) torch operating at atmospheric pressure. It constitutes an ideal figuring alternative, combining the advantages of a non-contact tool with very high material removal rates and nanometre level repeatability. Despite the rapid figuring potential of this process, research preceding the work presented in this manuscript had made little progress towards design and implementation of a procedure for metre-class optics. The experimental work performed in this PhD project was conducted on Helios 1200, a unique large-scale RAP figuring facility at Cranfield University. Characterisation experiments were carried out on ULE and fused silica surfaces to determine optimum process parameters. Here, the influence of power, surface distance, tool speed and surface temperature was investigated. Subsequently, raster-scanning tests were performed to build an understanding on spaced multiple passes ... [cont.].
Open Access
A basis for the representation, manufacturing tool path generation and scanning measurement of smooth freeform surfaces
(2017-02) Morantz, Paul; Shore, Paul
Freeform surfaces find wide application, particularly in optics, from unique single-surface science programmes to mobile phone lenses manufactured in billions. This thesis presents research into the mathematical and algorithmic basis for the generation and measurement of smooth freeform surfaces. Two globally significant cases are reported: 1) research in this thesis created prototype segments for the world’s largest telescope; 2) research in this thesis made surfaces underpinning the redefinition of one of the seven SI base units – the kelvin - and also what will be the newly (and permanently) defined value for the Boltzmann constant. Theresearchdemonstratestwounderlyingphilosophiesofprecisionengineering, the critical roles of determinism and of precision measurement in precise manufacturing. The thesis presents methods, and reports their implementation, for the manufacture of freeform surfaces through a comprehensive strategy for tool path generation using minimum axis-count ultra-precision machine tools. In the context of freeform surface machining, the advantages of deterministic motion performance of three-axis machines are brought to bear through a novel treatment of the mathematics of variable contact point geometry. This is applied to ultra-precision diamond turning and ultra-precision large optics grinding with the Cranfield Box machine. New techniques in freeform surface representation, tool path generation, freeform tool shape representation and error compensation are presented. A comprehensive technique for very high spatial resolution CMM areal scanning of freeform surfaces is presented, with a new treatment of contact error removal, achieving interferometer-equivalent surface representation, with 1,000,000+ points and sub-200 nm rms noise without the use of any low-pass filtering.
Open Access
Characterisation and measurement to the sub-micron scale of a reference wire position
(EDP Sciences, 2015-09-21) Sanz, Claude; Cherif, Ahmed; Mainaud-Durand, Hélène; Morantz, Paul; Shore, Paul
Open Access
Current trends and future of sequential micro-machining processes on a single machine tool
(Elsevier, 2017-04-18) Chavoshi, S. Z.; Goel, Saurav; Morantz, Paul
A sequential micro-machining process chain is described as the machining strategy whereby two or more micro-machining techniques are implemented in sequence on same or different machine tools. This is in contrast to hybrid micro-machining where two standalone machining technologies are integrated together. A recent surge of interest is geared towards building sequential micro-machining capabilities on a single machine tool to avoid realignment and registration errors between processes. One of the major advantages of performing sequential micro-machining on a single machine tool is that it suppresses repositioning errors so enabling much higher levels of accuracy (and thereby tighter tolerances), reduced rejection of machined components, and lower production time; all of these would be otherwise unachievable. Thus, multifunctional micro-machining centres are attracting global interest. Clearly, the necessity of developing reconfigurable, precise and flexible manufacturing is a key driver to this trend. This review aims to provide a critical insight into the recent trends and new classification of sequential micro-machining processes with a special focus on evaluation of such capabilities built on a single machine tool and further potentials. The machining capabilities, advantages and opportunities in the area of sequential micro-machining techniques are evaluated thoroughly and the directions for future work are highlighted.
Open Access
Dynamic Analysis of Aerostatic Guideway and FEA Model Development
(Cranfield University, 2009-12) Lim, Chee Wang; Shore, Paul; Morantz, Paul
A dynamically optimal design is essential for a motion system to perform high speed operation without compromising its accuracy, settling time and vibration specification. Good design practice which accounts for dynamic characteristics in the modelling of a motion system warrants higher performance precision machines and cuts down redevelopment effort to ‘patch’ inherent shortcoming of the machine dynamics. This research aimed to accurately describe the non-linear dynamics of a non-mechanical contact aerostatic guideway system in order to achieve an accurate FEA model of the design stage. The single axis aerostatic guideway is comprised of several machine in¬terfaces that impact the dynamic behaviour of the guideway. Modelling each air bear¬ing pad by a single stiffness element is not adequate to predict the guideway modal behaviour accurately. The aerostatic guideway has been broken down into several key machine interface elements. In-depth investigation of the air film and the air bearing mounting mechanism was carried out. A dedicated air film test rig was designed and built to acquire insight of the air film dynamic characteristics. It is observed that the mounting mechanism of the air bearing constitutes to a signifi-cant dynamic effect to the entire air bearing setup. Based on the findings of the mount-ing mechanism’s stiffness properties, a method was developed to estimate ‘true’ air gap heights which cannot be easily assessed and measured directly in most aerostatic guideway carriages. The estimation method enables a more rigorous FE model of the aerostatic guideway system. The comprehensive dynamic analysis methodology pro-posed in this research greatly increases the confidence and accuracy of the aerostatic guideway’s FE model.
Open Access
Evaluation of the performance variation of porous air pads on discontinuous surfaces
(Elsevier, 2019-10-31) Sanz, Claude; Morantz, Paul; Lunt, Alexander J. G.; Shore, Paul; Chérif, Ahmed; Schneider, Jürgen; Mainaud-Durand, Hélène; Steffens, Norbert
A new high accuracy position measurement system has been developed. It measures the position of a 0.1 mm diameter copper-beryllium wire that informs alignment of energy beams in advanced particle accelerators. This new measurement system employs air pads to provide precision and friction free rotation of a sensor. To enable the measuring system to be positioned over the wire, a slot is required in the measuring device rotor. To optimise the design of this measuring system it was necessary to understand the performance of the air pads as they pass over the gaps (slots) in the rotor. This paper describes modelling and experiments that were performed to gain understanding of air pad performance when encountering such a surface gap. Particularly, an analytical model of the variation of load of a 20 mm × 40 mm porous air pad during the passing of a 1.5 mm wide slotted surface. Subsequent experimentation revealed that the general behaviour of the load variation had been captured effectively. The results of this analysis reveal that air pads of this size can reliably pass above an opening of this size with about 14% reduction in force. The results and the methodology presented in this paper can be used as an effective basis for future designs and studies
Open Access
Fast figuring of large optics by reactive atom plasma
(2012-09-13T00:00:00Z) Castelli, Marco; Jourdain, Renaud; Morantz, Paul; Shore, Paul; Ramón, Navarro; Colin, R. Cunningham and Eric Prieto.
The next generation of ground-based astronomical observatories will require fabrication and maintenance of extremely large segmented mirrors tens of meters in diameter. At present, the large production of segments required by projects like E-ELT and TMT poses time frames and costs feasibility questions. This is principally due to a bottleneck stage in the optical fabrication chain: the final figuring step. State-of-the-art figure correction techniques, so far, have failed to meet the needs of the astronomical community for mass production of large, ultra-precise optical surfaces. In this context, Reactive Atom Plasma (RAP) is proposed as a candidate figuring process that combines nanometer level accuracy with high material removal rates. RAP is a form of plasma enhanced chemical etching at atmospheric pressure based on Inductively Coupled Plasma technology. The rapid figuring capability of the RAP process has already been proven on medium sized optical surfaces made of silicon based materials. In this paper, the figure correction of a 3 meters radius of curvature, 400 mm diameter spherical ULE mirror is presented. This work demonstrates the large scale figuring capability of the Reactive Atom Plasma process. The figuring is carried out by applying an in-house developed procedure that promotes rapid convergence. A 2.3 μm p-v initial figure error is removed within three iterations, for a total processing time of 2.5 hours. The same surface is then re-polished and the residual error corrected again down to& lambda;/20 nm rms. These results highlight the possibility of figuring a metre-class mirror in about ten hours.
Open Access
Form measurement of a 0.1 mm diameter wire with a chromatic confocal sensor, with associated uncertainty evaluation
(IOP Publishing, 2018-06-07) Sanz, Claude; Giusca, Claudiu; Morantz, Paul; Marin, Antonio; Chérif, Ahmed; Schneider, Jürgen; Mainaud-Durand, Hélène; Shore, Paul; Steffens, Norbert
The accurate characterisation of a copper–beryllium wire with a diameter of 0.1 mm is one of the steps to increase the precision of future accelerators' pre-alignment. Novelties in measuring the wire properties were found in order to overcome the difficulties brought by its small size. This paper focuses on an implementation of a chromatic-confocal sensor leading to a sub-micrometric uncertainty on the form measurements. Hence, this text reveals a high-accuracy metrology technique applicable to objects with small diameters: it details the methodology, describes a validation by comparison with a reference and specifies the uncertainty budget of this technique.
Open Access
Grinding metre scale mirror segments for the E-ELT ground based telescope
(Technische Rundschau, Hallwag Publishers; 1999, 2011-04-21T00:00:00Z) Comley, Paul; Morantz, Paul; Shore, Paul; Tonnellier, Xavier
The next generation of ground based telescopes require many hundreds of metre scale off-axis mirrors. In this paper the grinding of a 1.45m scale Zerodur® mirror segment for the European Extremely Large Telescope (E-ELT) is introduced. Employing an R-theta grinding mode with a multi stage grinding process material removal rates of up to 187.5mm3/s are achieved, whilst typically removing up to 1mm depth of material in total. Results show a RMS form error of <1μm, with subsurface damage <10μm, and a production cycle time under 2
Open Access
A method for assessing measurement precision and stability of optical probes
(European Society for Precision Engineering and Nanotechnology, 2016-06-30) Norman, James; Tonnellier, Xavier; Morantz, Paul
The current strategy for measuring non-specular metre-scale surfaces – for instance segmented freeform optics post-grinding – in the mid- frequency bandwidths (S-filter), involves the use of contact probe based systems where measurement precision is a limiting factor. Equivalent non-contact optical probes claim accuracies up to an order of magnitude higher and could therefore improve current measurement systems. Chromatic confocal probes measure the distance to a surface using the principle of axial chromatic dispersion. The stability of a CHRocodile SE 300 μm probe was shown to be 200 ± 20 nm over an eight hour measurement period. A probe holder should be designed with a low thermal expansion material in order to thermally insulate the probe measurement for further investigation. The accuracy of the probe was assessed at the extremes of its measurement range. The maximum deviation over a 5 μm displacement was measured to be 85 nm. The entire measuring range should be investigated.
Open Access
Micro-scale finishing of the surface and form of a Ti-6Al-4V lightweight rotor obtained by laser powder bed fusion used for air bearing
(Elsevier, 2018-07-26) Sanz, Claude; Gerard, Romain; Morantz, Paul; Chérif, Ahmed; Shore, Paul; Mainaud-Durand, Hélène; Lunt, Alexander J. G.
The European Organisation for Nuclear Research, CERN, is in the process of designing and testing parts for the next generation of linear accelerators. In order to operate the experiments, the pre-alignment precision of the components of the two opposing accelerating complexes has placed increased demands on part tolerances, which are now approaching the micrometre. In order to meet these demanding requirements, improvements are necessary to the build processes, machining parameters and post-manufacture characterisation stages. One of the most promising methods for the production of these parts is Laser Powder Bed Fusion, and as such, this paper focuses on the manufacture of the lightweight air bearing rotor component and the micro-scale tolerance machining required by this part. The results demonstrate that despite being able to initially machine the part to a form tolerance approaching 2 μm, subsequent notch cutting and the release of residual stresses from the part obtained by Laser Powder Bed Fusion induces an 18 μm part misalignment which is larger than the tolerance limits of 5 μm required for operation. This demonstrates that further minimisation and understanding of the residual stresses induced during machining are required to facilitate the effective manufacture of high precision components of this type.
Open Access
Microwaves enable activated plasma figuring for ultra-precision fabrication of optics
(European Society for Precision Engineering and Nanotechnology, 2016-06-30) Bennett, Adam; Jourdain, Renaud; Kirby, Paul; MacKay, P.; Shore, Paul; Nicholls, John R.; Morantz, Paul
Activated plasma figuring using microwaves aims at providing highly efficient activated energy beams for rapid fabrication of optics. The chemical nature of this type of energy beam leads to targeting silicon-based materials. Furthermore this technology is proposed to address the needs of ultra-precision optical components. In this paper, we present a novel ADTEC microwavegenerated plasma torch design which is operated at atmospheric pressure. In this study, the plasma torch is fed with either argon or helium carrier gas. However this novel design for Plasma Figuring is targeted at local surface correction of crystal quartz which is a material of great interest for optical systems, such as acousto-optic devices. Also this novel design is targeted at reducing midspatial frequency errors such as waviness, ripple errors and residual sub-aperture tool footprints. These are responsible for the scattering of light at small angles, resulting in optical hazing effects, photonic energy loss and pixel cross-talk. Also the results of a preliminary investigation using Optical Emission Spectroscopy (OES) are reported and discussed. These results show the operat ing range when the main processing parameters are changed: microwave forward power values, gas flow rates and the types of gasses.
Open Access
New potential for the Leitz Infinity Coordinate Measuring Machine
(Euspen, 2015-06-01) Sanz, Claude; Cherif, Ahmed; Mainaud-Durand, Hélène; Schneider, Jürgen; Steffens, Norbert; Morantz, Paul; Shore, Paul
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
Open Access
A novel accelerometer based feedback concept for improving machine dynamic performance
(Elsevier, 2016-11-10) Abir, Jonathan; Morantz, Paul; Longo, Stefano; Shore, Paul
Small size ultra-precision Computer Numerical Control (CNC) machines require high dynamic performance. Flexible frame phenomena can limit the machine dynamic performance, particularly in small size machines. A novel accelerometer based feedback concept for improving machine dynamic performance was developed and realised, a virtual metrology frame. It expends the limited techniques for improving dynamic performance of a small size machine by measuring the flexible frame displacement, and feeding it into the controller. The concept was implemented in a simplified linear motion system, and showed a 12dB reduction in the magnitude of the first resonance in the plant frequency response function. This allowed improving the servo bandwidth by 58% based on a PID controller. A new technique for real-time dynamic displacement measurements using accelerometer was developed. It shows a low sensor noise σ<30 nm; thus, accelerometers are used as a displacement sensor in a control system.
Open Access
Numerical and experimental modal analysis applied to an optical test system designed for the form measurements of metre-scale optics
(Hindawi Publishing, 2018-11-04) Golano, P. G.; Zanotti Fragonara, Luca; Morantz, Paul; Jourdain, Renaud
The work focuses on the structural design and performances of a unique optical test system (OTS) used for measuring metre-scale optical surfaces. The investigation was carried out through a modal analysis. Two sets of results are presented. Both modal analysis of the entire OTS and transmissibility function related to its use as an optical system are carried out and analysed. The OTS is used for the measurements of the form accuracy at nanometre level of metre-scale concave surfaces. The OTS is a four and half-metre-tall mechanical structure made of bolted aluminium profiles, two structural platens, two dedicated precision positioning supports, a test piece, and a state-of-the-art laser interferometer. The OTS was numerically modelled and fully instrumented with triaxial accelerometers. The results of the modal analysis highlight the natural modes of the entire OTS. Both numerical and experimental methods are designed. The investigation methods are iterative. Indeed, a preliminary numerical model is created using finite element analysis (FEA). FEA results enable the determination of the dynamic range and suitable locations of accelerometers that are mounted onto the OTS for the experimental validation of the FEA model and further to carry out the transmissibility study. Natural frequencies, damping ratios, and mode shape values are obtained and scrutinized. These results are used for refining the FEA model. In fact, the lack of symmetry and the use of feet are identified as the key design feature that affects the OTS. The correlation between experimental and numerical results is within five percent for the first four modes. The results of the transmissibility study highlight the specific natural modes that influence the OTS measurement capability. Overall, the study enables to guide engineers and researchers towards a robust design using a validated and methodical approach.
Open Access
Optimized estimator for real-time dynamic displacement measurement using accelerometers
(Elsevier, 2016-07-30) Abir, Jonathan; Longo, Stefano; Morantz, Paul; Shore, Paul
This paper presents a method for optimizing the performance of a real-time, long term, and accurate accelerometer based displacement measurement technique, with no physical reference point. The technique was applied in a system for measuring machine frame displacement. The optimizer has three objectives with the aim to minimize phase delay, gain error and sensor noise. A multi-objective genetic algorithm was used to find Pareto optimal estimator parameters. The estimator is a combination of a high pass filter and a double integrator. In order to reduce the gain and phase errors two approaches have been used: zero placement and pole-zero placement. These approaches were analysed based on noise measurement at 0g-motion and compared. Only the pole-zero placement approach met the requirements for phase delay, gain error, and sensor noise. Two validation experiments were carried out with a Pareto optimal estimator. First, long term measurements at 0g-motion with the experimental setup were carried out, which showed displacement error of 27.6 ± 2.3 nm. Second, comparisons between the estimated and laser interferometer displacement measurements of the vibrating frame were conducted. The results showed a discrepancy lower than 2 dB at the required bandwidth.
Open Access
Position sensor for active magnetic bearing with commercial linear optical encoders
(Elsevier, 2021-05-19) Tantau, Mathias; Morantz, Paul; Shore, Paul
Active magnetic bearings are used in a number of applications but their disadvantage is the high asynchronous error due to sensor noise amplification. In this paper a new radial position sensor for active magnetic bearings (AMB) based on linear optical encoders is presented. A commercial encoder scanning head faces a round scale with concentric, coplanar lines on its face. Because such a scale is not readily available, it is made by high precision micro machining and different options are compared. In experiments a measurement noise of 3.5 nm at 10 kHz bandwidth is achieved. In addition, a magnetic bearing is built to demonstrate the sensor in closed-loop.