A hybrid process for complex-shaped parts electroforming

We present new interaction and visualization paradigms relying on free form surfaces for studying and exploring human anatomy. We propose an interface for building three-dimensional anatomical scenes incorporating 3D anatomical organ models, freely orientated slices and free form surfaces extracted from the Visible Human dataset. Compared with planar slices, free form surfaces allow to follow curved anatomic structures such as the aorta tree or the pelvis. In the present paper, we describe in detail 3D interaction techniques for creating free form surfaces. The interactive placement of surface boundary curves relies on the combination of an interactive slice navigator and of a 3D visualization interface integrated within a single java applet. Surface boundary curve control points are placed with the mouse at the desired locations within the selected slices. The corresponding boundary curves are displayed in the 3D visualization interface as fat 3D cubic spline curves, which provide immediate feedback. Boundary curves may be easily duplicated, translated and modified. The specified boundary curves are interpolated by Coons patches, yielding a perfectly smooth surface. That surface may be visualized in combination with semi-transparent organ models. It may also be flattened and shown in a separate window. The presented application is available online as a Java applet (http://visiblehuman.epfl.ch).

The elastic response of a vacancy in a semi-infinite fcc copper lattice containing a free surface is calculated by using a new multiscale Green's function method. The method treats the lattice distortion near the vacancy at the atomistic level and the free surface at the macroscopic continuum level in the same formalism. The lattice is modeled using the lattice statics Green's function that fully accounts for the discrete atomistic structure of the lattice and can model a large crystallite containing a million atoms without excessive CPU effort. The method is especially useful for modeling the elastic response of nanocrystals containing point defects in which surfaces and interfaces play important roles. The method bridges the length scales seamlessly by relating the microscopic lattice distortion near a point defect to measurable macroscopic parameters of the solid such as the strain and the displacement field at a free surface. Using the interatomic potential derived by Cleri and Rosato, the lattice distortion, relaxation energy, and relaxation volume due to a vacancy are calculated in an otherwise perfect copper lattice for a million-atom model containing a free (100) surface. The calculated value of the relaxation volume is in excellent agreement with the observed value. Numerical results are also presented for the strain and the displacement fields at the free surface due to a vacancy and the interaction energy between a vacancy and the free surface in anisotropic semi-infinite copper.

For the manufacturing of molds and dies a considerable high amount of manufacturing costs and time are allocated into finishing procedures (grinding, lapping and polishing). As current automated finishing techniques are almost not applicable on parts with free form surfaces and function relevant edges, as commonly found in molds and dies, the finishing of these tools has to be done predominantly manually. This paper shows a robot assisted fine machining approach developed at Fraunhofer IPT, with which it was possible to grind, lap and polish free form surfaces. High gloss surface qualities with an Ra value of 15 nm and an Rt of 0,4 μm could be achieved.

Constructing smooth freeform surfaces of arbitrary topology with higher order continuity is one of the most fundamental problems in shape and solid modeling. This paper articulates a novel method to construct C∞ smooth surfaces with negative Euler numbers based on hyperbolic geometry and discrete curvature flow. According to Riemann uniformization theorem, every surface with negative Euler number has a unique conformal Riemannian metric, which induces Gaussian curvature of --1 everywhere. Hence, the surface admits hyperbolic geometry. Such uniformization metric can be computed using the discrete curvature flow method: hyperbolic Ricci flow. Consequently, the basis function for each control point can be naturally defined over a hyperbolic disk, and through the use of partition-of-unity, we build a freeform surface directly over hyperbolic domains while having C∞ property. The use of radial, exponential basis functions gives rise to a true meshless method for modeling freeform surfaces with greatest flexibilities, without worrying about control point connectivity. Our algorithm is general for arbitrary surfaces with negative Euler characteristic. Furthermore, it is C∞ continuous everywhere across the entire hyperbolic domain without singularities. Our experimental results demonstrate the efficiency and efficacy of the proposed new approach for shape and solid modeling.

With the advent of techniques devised for the mass production of optical components made with surfaces of arbitrary form (also known as free form surfaces) in the last years, a parallel development of measuring systems adapted for these new kind of surfaces constitutes a real necessity for the industry. Profilometry is one of the preferred methods for the assessment of the quality of a surface, and is widely employed in the optical fabrication industry for the quality control of its products. In this work, we present the design, development and assembly of a new profilometer with five axis of movement, specifically suited to the measurement of medium size (up to 150 mm of diameter) free-form optical surfaces with sub-micrometer accuracy and low measuring times. The apparatus is formed by three X, Y, Z linear motorized positioners plus and additional angular and a tilt positioner employed to locate accurately the surface to be measured and the probe which can be a mechanical or an optical one, being optical one a confocal sensor based on chromatic aberration. Both optical and mechanical probes guarantee an accuracy lower than the micrometer in the determination of the surface height, thus ensuring an accuracy in the surface curvatures of the order of 0.01 D or better. An original calibration procedure based on the measurement of a precision sphere has been developed in order to correct the perpendicularity error between the axes of the linear positioners. To reduce the measuring time of the profilometer, a custom electronics, based on an Arduino™ controller, have been designed and produced in order to synchronize the five motorized positioners and the optical and mechanical probes so that a medium size surface (around 10 cm of diameter) with a dynamic range in curvatures of around 10 D, can be measured in less than 300 seconds (using three axes) keeping the resolution in height and curvature in the figures mentioned above.

Interaction of divalent cations with basal planes and edge surfaces of phyllosilicate minerals: Muscovite and talc

When machining a free-form surface automatically and digitally, especially in the case of sophisticated surface shapes, it is very difficult to control the surface quality, and thus sophisticated surfaces are usually polished using manual labor. Over the past few years, there has been little attention to the calculation of material removal depth models and construction of theoretical roughness models considering the influence of the curvature radius. Bonnet polishing can be automatically adapted to polish complex free-form surfaces. This paper explores key problems related to forecasting surface quality with respect to bonnet polishing of free-form surfaces. First, for the convex and planar sub-regions, this paper deduces the relationship expressing the maximum pressure distribution and the curvature radius, and presents a computational expression for material removal depth, taking into consideration the influence of the curvature radius. An expression is also deduced for the dwell time relationship between the adjacent processing points according to the experimental results pertaining to the material removal depth. From this, a theoretical roughness model is constructed that relates the bonnet curvature radius and the workpiece curvature radius. The validity of the experiments is summarized in the conclusion. The research findings provide a basic theory for the prediction of surface quality that can be automatically adapted to a free-form surface shape in bonnet polishing.

Efficient optimal design of smooth optical freeform surfaces using ray targeting

Optics with free form surface can be achieve special imaging effects and reduce component amounts in optical systems. However, it is difficulty to fabricate high accuracy, damage-free optical surface with free form surfaces by conventional method. Atmospheric plasma machining is a non-contact chemical processing method which can fabricate optics without damaged layer. Numerical controlled atmospheric pressure plasma machining (NC-APPM) method is proposed to machine optical free form surfaces. A new atmospheric pressure plasma jet generator was designed to get Gaussian rotational symmetry removal spot and the spot maximum diameter is 1.5mm. Base on dwelling time algorithm, a sinusoidal wave structure, the pitch 2mm and the amplitude 500 nm, is fabricated on a pre-polished flat silica quartz surface using three-axis numerically controlled machine made by ourselves. The result shows that the amplitude error is 59 nm compare to the expectation value surfaces using numerical controlled atmospheric plasma machining method.

The data volume of Web3D representation based on polygon meshes is so large that transferring practical data fast is a difficult problem. This paper proposes 3D object structure, a new framework for a compact 3D representation with high quality surface shape. By utilizing a free form surface technique, qualified surfaces are transferred with limited amount of data size and rendered. 3D graphic structure can be regarded as both polygon meshes and free form surfaces. Therefore, it can be easily integrated to existing Web3D data formats, for example VRML & XML. The 3D object’s structure also enables modeling free form surface shapes intuitively with polygon modeling like operations. In this paper, we propose and verify an algorithm on representation of 3D objects using X3D.

In this paper a simultaneous engineering approach is introduced to cope with the complex and elaborative engineering design process for bifurcated sheet metal products. The design process comprises product design, sheet blank design, and tool design. Free form surfaces derived from mathematical optimization processes are the starting point for product, tool, and sheet blank design. Part design is strongly connected and references to the underlying free form surface. For the 3D-CAD models a modeling concept is introduced where free form surfaces are referenced from an external source. A workflow to manage the design process and to deal with possible changes and iterations during product development is also developed and presented.

An off-axis three-mirror detection system with a large field of view is designed in order to improve the space target detection capability. The optical system is a Cook-TMA with the focal length of 127mm, the F number of 2, the field angle of 25° × 25° and the spectral range of 400-700nm. The primary mirror and the tertiary mirror of the off-axis three mirror system are all designed by free form surfaces: the primary mirror is characterized by Zernike polynomial and the tertiary mirror is described by XY polynomial. At the same time, we analyze the related characteristics of Zernike polynomial and XY polynomial. The results show that the free form surfaces have great advantages in improving the field of view and the imaging quality of the off-axis optical system. The system has high energy concentration and good imaging quality, which can capture and track the target in a wide range is suitable for wide area target monitoring.

In the continuous casting process, the surface quality of the steel is as important as its productivity. The surface quality is mostly decided in the molten metal flow during the initial solidification stage, which progresses at the free surface of the molten steel. To improve the surface quality, this flow must be controlled. M‐EMS generates a time‐varying electromagnetic force, which helps to control the shape of the free surface. In this paper, we evaluate the possibility of controlling the flow at the free surface by MHD calculations. The results show a slight possibility for the flow at the free surface to be controlled. Although the free surface variation in a pulsed EMC process, which controls the shape of the free surface using the time‐varying electromagnetic force component, depends on electromagnetic force, the time‐varying component in the M‐EMS depends on the velocity of the molten metal. Since there is a first‐order lag between the electromagnetic force and this velocity, free surface variation in M‐EMS does not linearly depend on the time‐varying electromagnetic component. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(3): 62–68, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21167

In the continuous casting process, surface quality of steel is as important as its productivity. The surface quality is mostly decided in the molten metal flow during initial solidification stage, which progresses at the free surface of the molten steel. To improve the surface quality, this flow must be controlled. M-EMS generates the time-varying electromagnetic force, which helps to control the shape of the free surface. In this paper, we evaluate the possibility of controlling the flow at the free surface by the MHD calculations. The result showed a little possibility of the flow at the free surface being controlled. Though the free surface variation in a pulsed EMC process, which controls the shape of the free surface using the time-varying electromagnetic force component, depends on electromagnetic force, the time-varying component in the M-EMS is decided by the velocity of the molten metal. Since there is a first-order lag between the electromagnetic force and this velocity, free surface variation in M-EMS does not linearly depend on the time-varying electromagnetic component.

Freeform surface has been widely applied to various optical components which require a surface quality with submicrometer form accuracy and nanometric surface finish. Currently the achievement of such ultra-precision surface quality relies largely on the skills and experience of the operator based on a trial-and-error approach, which is a time consuming and expensive process. Ultra-precision raster milling is an enabling technology to generate freeform surfaces with the optical surface quality without any subsequent processing. This paper presents the fundamental knowledge about ultra-precision raster milling, including the cutting mechanism, cutting strategies, cutting path plans, tool path generation and hence a slide motion error model has been established to predict the form error generation. A series of experimental studies have been undertaken and the prediction results were found to agree well with the measured values.