Details of a Researcher - Beaucamp, Anthony

Papers - Beaucamp, Anthony

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Development of a new computer aided manufacturing system for variable pitch screws fabrication

Nabeta Y., Jain S., Beaucamp A., Takeuchi Y.

Journal of the Korean Society for Precision Engineering 37 ( 3 ) 195 - 200 2020.03

ISSN 12259071

The study focused on the development of the CAM system restricted to the fabrication of variable pitch screws by using turning centers. To develop the dedicated CAM system at a low cost, open source programming language was used as much as possible. A commercially available 3D-CAD system was used to model variable pitch screws. The edge data of the variable pitch screw was extracted from 3D-CAD data of the variable pitch screw, and then a number of the edge data were copied by the amount of feed in the longitudinal direction of the screw to make a cutter path. The successive cutter path was repeatedly generated by reducing the size of the edge data. The advantage of this method of generating the cutter path is very simple and easy to use, compared with the conventional CAM systems. During the cutter path generation, the system can detect the collision between the cutting tool and the workpiece. As a result, the validity of the developed CAM system for variable pitch screws fabrication was confirmed from several examples of the cutter path generation.

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Effect of polymer relaxation in automated micro polishing

Soufian Ben Achour, Wule Zhu, Giuliano Bissacco, Anthony Beaucamp, Leonardo De Chiffre

AIP Conference Proceedings 2205 2020.01

Accepted, ISSN 0094243X

© 2020 Author(s). Micro polishing is a process used when a fine surface quality is desired. In optics, it represents the key process to achieve low surface roughness and form error required for optics application. Automated micro polishing with polymer-based tools requires a better understanding of the interaction between tool and workpiece than conventional polishing, and an important phenomenon that has to be taken into account is polymer relaxation. Stress relaxation is due to the non-linear viscoelastic behaviour of polymers. This relaxation is a time-dependent phenomenon that causes a decrease in stress, although the strain is kept constant. In this work, the effect of polymer stress relaxation on polishing is studied. While this effect can be neglected in conventional polishing, it becomes an essential and dominant factor in micro polishing. Characterization tests are conducted on a very common extruded polyurethane (LP-66) used in polishing. Subsequently, bonnet polishing using a spherical tool with a diameter of 1 mm is performed for 8 minutes on a nickel sample. Due to relaxation, the induced stress on the tool decreases during polishing, causing a reduction in the polishing pressure. This implies a reduction in the material removal rate in accordance with Preston's law. Experimental results are in accordance with the physical phenomenon. The polymer relaxation characteristics can be used to compensate the tool path to achieve uniform removal along the polished surface.

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Investigation of critical material removal transitions in compliant machining of brittle ceramics

Wu Le Zhu, Beaucamp Anthony

Materials and Design 185 108258-1 - 108258-13 2020.01

Accepted, ISSN 02641275

© 2019 The Authors Compliant machining processes, such as bonnet polishing, can be used on hard and brittle ceramic materials such as alumina and silicon carbide, to produce ultra-precise surfaces with sub-micron form accuracy and nanometric surface roughness. However, a comprehensive understanding of the removal mechanism in such process is lacking. In this paper, an analytical model is proposed that is based on the existence of “three zones” in compliant machining process, namely elastic recovery, plastic removal and brittle fracture. The inherent relationships of the three critical pressures with actual pressure, due to compression of the elastic bonnet tool and asperity effect, are established and analyzed in association with different material removal behaviors. Analysis indicates that pad asperity plays an important role in material removal and that lower material hardness combined with higher tensile strength contributes to enlarged plastic removal zone, and thus higher manufacturability. Removal footprints and polishing tests were then generated to verify accurate prediction of the material removal rate under different conditions and demonstrate effectiveness of the proposed model.

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静電気力と超音波振動を用いたナノブラスト研磨用砥粒粒径均一化に関する研究

森有花, Beaucamp Anthony, 松原厚

精密工学会学術講演会講演論文集 (公益社団法人精密工学会) 2020 153 - 154 2020

ナノ粒子を用いた超微細ブラストの研究を行っている．自然状態ではナノ粒子は凝集粒子を形成し，その粒径のばらつきは精密仕上げに要求される砥粒の粒径分布より大きい．本研究では，粒子間の付着力を上回る外力を加えることで凝集粒子の平均径と分布幅を小さくする方法を提案する．有限要素解析と実験により，超音波振動と静電力を同時に印加すると粒径分布が改善するとわかったが，凝集粒子は完全には分離しなかった．

Elucidation of levitation principle in float polishing method

Nagai Kotaro, Beaucamp Anthony, Matsubara Atsushi, Namba Yoshiharu, Suzuki Hirofumi

Proceedings of JSPE Semestrial Meeting (The Japan Society for Precision Engineering) 2020 157 - 158 2020

Machining conditions in float polishing method have been determined empirically and there is a need to elucidate the levitation principle of the workpiece and to propose a theoretical method to determine the machining conditions. In this research, the levitation quantity of the workpiece was measured by the displacement sensor and found to be about 4 µm. The order of this value agreed with the prediction in the literature. From the FEM simulation of the thin film fluid based on the Reynolds equation, it was predicted that the pressure distribution under the workpiece was non-uniform and cavitation was generated.

Deterministic polishing of micro geometries

Soufian Ben Achour, Giuliano Bissacco, Anthony Beaucamp, Leonardo De Chiffre

CIRP Annals (Elsevier USA) 69 ( 1 ) 305 - 308 2020

ISSN 00078506

Ultraprecision polishing of miniature components and features with small curvature radii is limited by surface accessibility, availability of suitable tools and the capability to control material removal with sufficient spatial resolution. This paper presents the development of an approach for the application of nearly deterministic micro polishing using miniature tools with 400 μm radius. To enable implementation of the proposed approach, the effect of tool wear and polymer relaxation on the control of local contact pressure is characterized and compensation of tool wear along the tool path is introduced. The process is experimentally validated by application to features in nickel phosphor with lateral dimensions down to 2 mm, yielding roughness down to less than Sa 1 nm and profile accuracy better than 10 nm P-V.

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Non-Newtonian fluid based contactless sub-aperture polishing

Wu-Le Zhu, Anthony Beaucamp

CIRP Annals (Elsevier USA) 69 ( 1 ) 293 - 296 2020

ISSN 00078506

Compliant polishing (e.g. bonnet polishing) is widely used to finish freeform surfaces. However, direct pad/surface contact often causes scratches or embedding of abrasives, especially on metal moulds. Here, the use of non-Newtonian fluid (polymer and starch) to enable contactless polishing without need for a polishing pad is reported. Modelling and analysis are conducted to reveal the influence of fluid rheology on the material removal mechanism. Using #6000 grit alumina, Gaussian shaped removal footprints can be obtained, with a completely scratch-free roughness of 3.9 nm Ra on Nickel, in contrast with 70.3 nm Ra obtained by general water based bonnet polishing.

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Feed-rate scheduling by optimization of bulk removal

Mizoue Yuichi, Beaucamp Anthony, Matsubara Atsushi

Proceedings of JSPE Semestrial Meeting (The Japan Society for Precision Engineering) 2020 159 - 160 2020

The scheduling of feed-rate is an important procedure in CNC finishing of high-precision optical surfaces. Since the polishing process is described as the convolution operation between a tool influence function and a dwell-time map, deconvolution operation gives an optimal dwell-time map. However, physical achievability of the obtained dwell-time map is not considered. This research elucidates the effect of the bulk removal, a constant removal layer across the surface, on the convolution process in spatial domain and time domain. Based on this investigation, we propose a theory that has the potential to analytically adjust dwell-time, feed-rate, and acceleration without compromising the surface accuracy, and to predict the total machining time as a function of the bulk removal.

Zernike mapping of optimum dwell time in deterministic fabrication of freeform optics

Wule Zhu, Anthony Beaucamp

Optics Express 27 ( 20 ) 28692 - 28706 2019.09

Accepted

© 2019 Optical Society of America. In optics fabrication technologies such as computer controlled optical surfacing (CCOS), accurate computation of the dwell time map plays an essential role in the deterministic performance of the fabrication process. However, it is still difficult for existing methods to derive smooth dwell time maps that reduce dynamic stressing on the machine especially at the aperture edge region, while retaining fine correction capability on freeform optics. To answer these challenges, we propose a new method based on Zernike decomposition and improved differential evolution optimization of the dwell time map, which can be applied to time-dependent optics fabrication processes such as fluid jet machining. Simulations and experiments based on a bi-sinusoidal freeform design were carried out to assess the feasibility of the proposed methodology. With appropriate fluid jet pressure, a bi-sinusoidal optical surface with demanding form error target of sub-100 nm in peak-to-valley was achieved, showing a remarkable improvement on the state-of-the-art, while keeping a good average surface roughness of 2.6 nm Ra on the optical glass.

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Theoretical and experimental investigation of material removal mechanism in compliant shape adaptive grinding process

Wu Le Zhu, Yue Yang, Hao Nan Li, Dragos Axinte, Anthony Beaucamp

International Journal of Machine Tools and Manufacture (ELSEVIER SCI LTD) 142 76 - 97 2019.07

Accepted, ISSN 08906955

© 2019 Elsevier Ltd Modeling of grinding process, especially the grinding forces, has been studied extensively. Most previous work concerns the conventional grinding process using a rigid wheel, where the forces are generally based on the preset depth of grinding. However, for compliant grinding such as Shape Adaptive Grinding (SAG) that adopts an elastic tool covered with abrasive pellets, the penetration depth of individual abrasive grains is not simply equal to the preset value. As elastic contact occurs between the tool and workpiece, previous models are not able to estimate the material removal mechanism. Besides, the progressive transitions in grain-workpiece interaction for compliant cutting tools have not been reported yet. To fill these gaps and to offer a fundamental understanding of the compliant grinding process, we propose in this study a new multi-scale model spanning from macroscopic tool-workpiece contact to microscopic grain-workpiece interaction in the unique conditions of using a compliant grinding tool, i.e. SAG tool. Based on the spring-grain model and considering the stochastic nature of grain size and wear flat area, the static penetration and dynamic removal of individual grain can be predicted. Particularly, the removal mechanism is clarified with a new consideration of the transition between rubbing, plowing and cutting stages for each individual grain of the compliant tool. Experiments including scratch tests and removal footprints were carried out, and the high consistency with theoretical predictions validates the proposed model. Finally, considering the progressive abrasive wear in grinding, in-process wear compensation was conducted to enable consistent material removal on aspheric steel molds. The proposed method is not only meaningful to reveal the mechanism of SAG process, but also offers a new foundation for studying other compliant grinding processes in future.

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Ultra-precision finishing of low expansion ceramics by compliant abrasive technologies: A comparative study

Wu Le Zhu, Anthony Beaucamp

Ceramics International (ELSEVIER SCI LTD) 45 ( 9 ) 11527 - 11538 2019.06

Accepted, ISSN 02728842

© 2019 Advanced ceramics have many attractive features such as high stability and wear resistance that find broad applications in various fields, e.g. optics, aerospace, etc. However, the accompanying difficult-to-machine property with complex geometry brings great challenges to the commonly used laser machining and rigid wheel based grinding in industry. To achieve optical surface quality with surface roughness below 10 nm Ra, three promising ultra-precision compliant machining technologies using adaptive elastic tools are presented in this paper, including bonnet polishing, compliant pitch polishing and shape adaptive grinding with fine grain size. A comparative study was conducted by machining three different low thermal expansion ceramics while continuously increasing attack angle, spindle speed and tool offset across rectangular regions. Material removal rate (MRR) and surface roughness (Ra) with respect to different process conditions are compared. With sufficient data, the processing ability using above three compliant machining technologies is summarized based on the MRR-Ra plots for different ceramics. In addition, microscopic observation and X-ray diffraction analysis are conducted to characterize differences in material behavior.

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Title advances in optical fabrication for astronomy

David D. Walker, Guoyu Yu, Hongyu Li, Brian W. Myer, Anthony T. Beaucamp, Yoshiharu Namba, Lunzhe Wu

Monthly Notices of the Royal Astronomical Society (OXFORD UNIV PRESS) 485 ( 2 ) 2071 - 2082 2019.02

Accepted, ISSN 00358711

© The Author(s) 2018. The fabrication of precision optical surfaces has undergone a revolution in recent years. The first purpose of this paper is to present case studies of novel optical designs not previously published, that utilize complex, or 'freeform', surfaces. These designs are described both for their own merits, and as pointers towards the types of adventurous designs for ground or space-based astronomy that might now be envisaged. The potential benefits are enhanced optical performance in more compact, lower mass, and rugged packages. Such designs would, until recently, have been impossible to fabricate, and so we also describe some of the recent technical advances that have materially changed this position.

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走査型原子間力顕微鏡を用いた単粒子研磨加工実験と準連続体解析の比較

永井孝太郎, Anthony Beaucamp, 松原厚

精密工学会学術講演会講演論文集 (公益社団法人精密工学会) 2019 54 - 55 2019

本研究では，走査型原子間力顕微鏡を用いて，ナノスケールでの単純押し込み実験と，単粒子による研磨加工の模擬実験を行った．また，準連続体解析と実験結果を比較することで，解析法の妥当性を検証した．その結果，単純押し込み実験においては，解析結果が実験結果と一致することがわかった．一方，単粒子研磨加工実験では，金属短針の摩耗という実験における問題点が明らかとなった．

Model of material removal in vibratory finishing, based on Preston's law and discrete element method

Yusuke Makiuchi, F. Hashimoto, Anthony Beaucamp

CIRP Annals (ELSEVIER SCIENCE BV) 68 ( 1 ) 365 - 368 2019

Accepted, ISSN 00078506

© 2019 Vibratory finishing is widely used in mass-finishing of components. However, it is difficult to guarantee shape accuracy and predict surface roughness evolution. Here, a material removal model is proposed that is based on Preston's law and statistical overlapping of particle trajectories computed by Discrete Element Method (DEM). After validating DEM motion by particle image velocimetry and rope experiment, the occupancy ratio is studied as function of media type and mixing. Predictions of removal volume and surface roughness agree with experimental results within 12% on average, making this simulation method a very practical tool that reduces the need for extensive trial runs and barrel reloading.

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Centrifugal and hydroplaning phenomena in high-speed polishing

Wu Le Zhu, Soufian Ben Achour, Anthony Beaucamp

CIRP Annals (ELSEVIER SCIENCE BV) 68 ( 1 ) 369 - 372 2019

Accepted, ISSN 00078506

© 2019 Super fine polishing with compliant tools can achieve nanoscale roughness, but has limited productivity due to low material removal rate (MRR). Increased spindle speed in high-speed polishing (HSP) might increase MRR, but significant challenges appear above 10,000 rpm because of centrifugal deformation of the tool and pad lifting due to hydroplaning phenomenon. Here, a tool offset compensation strategy is proposed for centrifugal deformation and novel pad patterning design that mitigates hydroplaning. Through this new approach, linear increase in MRR for spindle speed up to 24,000 rpm is demonstrated. This work lays the foundation for future developments of HSP in fabrication of ultraprecision optics.

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Abrasive processes for micro parts and structures

J. C. Aurich, Benjamin Kirsch, Dinesh Setti, Dragos Axinte, Anthony Beaucamp, Paul Butler-Smith, Hitomi Yamaguchi

CIRP Annals 68 ( 2 ) 653 - 676 2019

Accepted, ISSN 00078506

© 2019 The demand for miniaturized products and functionalized parts is increasing, and many such products are made of hard and brittle materials machined by abrasive processes. The first part of this keynote paper is dedicated to a discussion of micro parts and micro structures machined – at least in part – by abrasive processes, followed by a discussion of the associated abrasive processes. The strengths and limitations of these processes, among which include dicing, micro grinding, micro abrasive blasting, and vibration and magnet field assisted finishing are discussed. The paper concludes with a discussion of future trends in the field.

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Theoretical study of path adaptability based on surface form error distribution in fluid jet polishing

Yanjun Han, Lei Zhang, Cheng Fan, Wule Zhu, Anthony Beaucamp

Applied Sciences (Switzerland) (MDPI) 8 ( 10 ) 1814 2018.10

Accepted, ISSN 2076-3417

© 2018 by the authors. In the technology of computer-controlled optical surfacing (CCOS), the convergence of surface form error has a close relationship with the distribution of surface form error, the calculation of dwell time, tool influence function (TIF) and path planning. The distribution of surface form error directly reflects the difference in bulk material removal depth across a to-be-polished surface in subsequent corrective polishing. In this paper, the effect of path spacing and bulk material removal depth on the residual error have been deeply investigated based on basic simulation experiments excluding the interference factors in the actual polishing process. With the relationship among the critical evaluation parameters of the residual error (root-mean-square (RMS) and peak-to-valley (PV)), the path spacing and bulk material removal depth are mathematically characterized by the proposed RMS and PV maps, respectively. Moreover, a variable pitch path self-planning strategy based on the distribution of surface form error is proposed to optimize the residual error distribution. In the proposed strategy, the influence of different bulk material removal depths caused by the distribution of surface form error on residual error is compensated by fine adjustment of the path spacing according to the obtained path spacing optimization models. The simulated experimental results demonstrate that the residual error optimization strategy proposed in this paper can significantly optimize the overall residual error distribution without compromising the convergence speed. The optimized residual error distribution obtained in sub-regions of the polished surface is more uniform than that without optimization and is almost unaffected by the distribution of parent surface form error.

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Process mechanism in ultrasonic cavitation assisted fluid jet polishing

Anthony Beaucamp, Tomoya Katsuura, Kie Takata

CIRP Annals (ELSEVIER SCIENCE BV) 67 ( 1 ) 361 - 364 2018.01

Accepted, ISSN 00078506

© 2018 Material removal rate in fluid jet polishing is significantly enhanced when ultrasonic cavitation bubbles are introduced at the nozzle outlet. In this paper, two theories are put forward to explain the process mechanism: a micro-scale hypothesis in which the surface is micro-jetted by collapsing bubbles, and a macro-scale hypothesis in which vibration of the fluid in the impingement region increases abrasive particle erosive action. Experimental investigation suggests the higher likelihood of the macro-scale phenomenon, and a material removal model is proposed accordingly. Process footprints simulated by this model were found to agree well with experimental measurements.

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Research on edge-control methods in CNC polishing

Guoyu Yu, David Walker, Hongyu Li, Xiao Zheng, Anthony Beaucamp

Journal of the European Optical Society (EUROPEAN OPTICAL SOC) 13 ( 1 ) 24 2017.12

Accepted, ISSN 1990-2573

© 2017, The Author(s). Background: We have developed edge-control for the Precessions TM process suitable for fast fabrication of large mirror segments, and other applications sensitive to edge mis-figure. This has been applied to processing of European extremely large telescope (E-ELT) prototype mirror-segments, meeting the specification on maximum edge mis-figure. However we have observed residuals that have proved impossible to correct with this approach, being in part the legacy of asymmetries in the input edge-profiles. Methods: We have therefore compared different proposed methods experimentally and theoretically and report here on a new edge-rectification step, which operates locally on edges, does not disturb the completed bulk area. Results: A new toolpath has been developed and experiments have been carried out to demonstrate that local edge rectification can be carried out. Conclusions: With this method, the residue error on edges can be removed separately and has potential to reduce total process time.

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Automated finishing of organ models created by 3D printing

Yoshihide Tamaki, Kohji Niwa, Anthony Beaucamp, Yoshimi Takeuchi

Proceedings of the 9th International Conference on Leading Edge Manufacturing in 21st Century, LEM 2017 2017.11

Accepted

In recent years, transparent resin organ models created by 3D printing have found application in the medical fields. The inside of the organ model contains diseased parts, blood vessels and so on, but they cannot be seen due to the layered appearance of printed surfaces. To address this issue, an automated system was developed using an industrial robot to replace the manual polishing currently needed. The automated system consists of three aspects: fixturing of the organ model, polishing tool path generation and polishing process conditions. From polishing experiments on a relatively simple shape, it was found that the system has the potential to deliver transparent surfaces on complex resin organ models.

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