Pcjn Nick Rosielle

Design of a High-precision 3D-Coordinate Measuring Machine

Abstract In Precision Engineering components are getting smaller and tolerances become tighter, so demands for accuracy are increasing. To improve the precision of Coordinate Measuring Machines (CMMs) we designed an alternative high precision 3D-CMM with measuring uncertainty beneath 0.1 μm in a measuring volume of 1 dm 3 . The machine design is based on the Abbe and Bryan principle, thus smaller measuring errors are feasible with less effort on software compensation. Application of a light and stiff construction, compensated air bearings and well-positioned linear motors result in high stiffness and favourable dynamic behaviour. A statically determined design, extensive use of aluminium and mechanical thermal length compensation make the machine less sensitive to temperature changes. To prevent mechanical disturbances an active vibration isolation system was designed. This paper focuses on machine design aspects showing analytical- and experimental results and design synthesis.

Design of a kinematic coupling for precision applications

To machine a complex precision product, several tools are needed. These tools are placed on a tool turret. A tool must return several times to its original position. To attain a very high repeatability between the upper part and the base of the tool turret mounted on a precision lathe, it is preferable that the parts of the tool turret are statically determined in their contacts. This is attained by using a kinematic coupling. To attain the required stiffness this coupling is provided with a preload of 1.5 · 103 N. The machining forces are typically less than 1 Newton. A special kinematic coupling, consisting of grooves and balls, was designed, made, and tested. By providing the grooves with self-adjusting surfaces, hysteresis is reduced to less than one-tenth of a micrometer. Maximum stiffness is aimed at by using cemented carbide, a material with a high admissible stress, at the contact points. Experiments show that this kinematic coupling, under a preload of 1.5 · 103 N, has a static stiffness of more than 1 · 108 N/m in every direction and a repeatability better than one-tenth of a micrometer.

An elastically guided machine axis with nanometer repeatability

This paper focuses on the on the design and calibration of an elastically guided vertical axis that will be applied in a small high precision 3D Coordinate Measuring Machine aiming a volumetric uncertainty of 25 nm. The design part of this paper discusses the principles of this system, the compensation of the stiffness of the vertical axis in the direction of motion, the weight compensation method and the design and performance of the axis precision drive system, a Lorentz actuator. In the metrology part of this paper the calibration methods to determine the linearity as well as motion straightness and axis rotation errors are discussed. Finally first calibration results of this axis show nanometer repeatability of the probing point over the 4 mm stroke of this axis. The causes of the short-term variations with a bandwidth of about ± 10 nm are under investigation. Error compensation may reduce the residual error of the probing point to the nanometer level.

Design of a set-up for high-accuracy 3D PTV measurements in turbulent pipe flow

Turbulent flows are often encountered in common practice, usually at high Reynolds number. The development of Lagrangian stochastic models of these flows requires knowledge of Lagrangian statistics. To study the Lagrangian statistics of turbulent pipe flow, a dedicated 3D particle tracking velocimetry set-up has been designed. In this paper, design parameters, selection criteria and solutions are discussed. The measurement accuracies are studied in detail. Typical 3D particle tracking velocimetry results for turbulent pipe flow are compared and found to be in good agreement with direct numerical simulations.

Deformable mirrors: design fundamentals for force actuation of continuous facesheets

Adaptive Optics is established as essential technology in current and future ground based (extremely) large telescopes to compensate for atmospheric turbulence. Deformable mirrors for astronomic purposes have a high number of actuators (> 10k), a relatively large stroke (> 10μm) on a small spacing (< 10mm) and a high control bandwidth (> 100Hz). The availability of piezoelectric ceramics as an actuator principle has driven the development of many adaptive deformable mirrors towards inappropriately stiff displacement actuation. This, while the use of force actuation supersedes piezos in performance and longevity while being less costly per channel by a factor of 10-20. This paper presents a model which is independent of the actuator type used for actuation of continuous facesheet deformable mirrors, to study the design parameters such as: actuator spacing & coupling, influence function, peak-valley stroke, dynamical behavior: global & local, etc. The model is validated using finite element simulations and its parameters are used to derive design fundamentals for optimization.

An advanced ceramic optical diamond turning machine : design and prototype development,

A new high precision optical diamond turning machine was designed and developed with all ceramic slides, having submicrometer accuracy and mirror surface quality. In view of improving repeatability, basic fundamentals like kinematic design, the Rule of Abbe, high stiffness structural loop design, hardware compensation of thermal expansion, force compensation and (thermal) symmetry were built in throughout the machine. The vertical axis machine tool with aerostatic slides and linear direct drives differs significantly from conventional lathes in design at the component level as well as in material utilisation. This paper focuses on machine design aspects showing analytical and experimental results and design synthesis.

Design of an E-ELT M1 segment measurement machine with nanometer accuracy

The baseline design of the European Extremely Large Telescope features a telescope with a 39-meter-class primary mirror (M1), consisting of 798 hexagonal segments. A measurement machine design is presented based on a non-contact single-point scanning technique, capable of measuring the form error of each segment with nanometer uncertainty, fast, and with low operational costs. The implementation of a tactile precision probe eliminates the need for the CMM in the earlier segment manufacturing process. Preliminary assessment show nanometer-level uncertainty after calibration.

Improving Maneuverability and Tactile Feedback in Medical Catheters by Optimizing the Valve Toward Minimal Friction

A new extended hemostasis valve for sheaths is presented, with minimized stick-slip behavior to be used in (heart) catheterization procedures during long interventions (3–6 h). The invented extension to this existing sheath bypasses the silicone rubber sealing (hemostasis valve) and replaces it with a dedicated seal with the two functions separated: (1) sealing around the catheter being used and (2) closing the sheath when the catheter is removed (valve function). Measurements have been performed on the current and the invented seals, showing that the axial friction force is reduced, with a factor of 6.4, from 1.4 N to 0.22 N. DOI: 10.1115/1.3054389

Design and calibration of an elastically guided CMM axis with nanometer repeatability

This paper focuses on the on the design and calibration of an elastically guided vertical axis that will be applied in a small high precision 3D Coordinate Measuring Machine aiming a volumetric uncertainty of 25 nm. The design part of this paper discusses the principles of this system, the compensation of the stiffness of the vertical axis in the direction of motion, the weight compensation method and the design and performance of the axis precision drive system, a Lorentz actuator. In the metrology part of this paper the calibration methods to determine the linearity as well as motion straightness and axis rotation errors are discussed. Finally first calibration results of this axis show nanometer repeatability of the probing point over the 4 mm stroke of this axis. The causes of the short-term variations with a bandwidth of about ± 10 nm are under investigation. Error compensation may reduce the residual error of the probing point to the nanometer level.