Geometric Accuracy, Volumetric Accuracy and Compensation of CNC Machine Tools

The production of geometrically and dimensionally defined workpieces is what the user expects from a machine tool. Deviations from these prescribed dimensions and geometry are due to machine inaccuracies. Therefore, it was necessary to develop tests and tests on the properties and parameters of machine tools that can detect these. Every new machine tool undergoes these tests.How to perform and evaluate these tests is determined and recommended primarily by standards and regulations. When testing the properties of machines, it is not only about knowing and knowing how to measure machines, but also how I can analyze and apply the obtained results. Is it necessary to do a mechanical intervention of the machine or is it enough to compensate the software

A novel haptic model and environment for maxillofacial surgical operation planning and manipulation

This paper presents a practical method and a new haptic model to support manipulations of bones and their segments during the planning of a surgical operation in a virtual environment using a haptic interface. To perform an effective dental surgery it is important to have all the operation related information of the patient available beforehand in order to plan the operation and avoid any complications. A haptic interface with a virtual and accurate patient model to support the planning of bone cuts is therefore critical, useful and necessary for the surgeons. The system proposed uses DICOM images taken from a digital tomography scanner and creates a mesh model of the filtered skull, from which the jaw bone can be isolated for further use. A novel solution for cutting the bones has been developed and it uses the haptic tool to determine and define the bone-cutting plane in the bone, and this new approach creates three new meshes of the original model. Using this approach the computational power is optimized and a real time feedback can be achieved during all bone manipulations. During the movement of the mesh cutting, a novel friction profile is predefined in the haptical system to simulate the force feedback feel of different densities in the bone

Traceability of on-machine tool measurement: a review

Nowadays, errors during the manufacturing process of high value components are not acceptable in driving industries such as energy and transportation. Sectors such as aerospace, automotive, shipbuilding, nuclear power, large science facilities or wind power need complex and accurate components that demand close measurements and fast feedback into their manufacturing processes. New measuring technologies are already available in machine tools, including integrated touch probes and fast interface capabilities. They provide the possibility to measure the workpiece in-machine during or after its manufacture, maintaining the original setup of the workpiece and avoiding the manufacturing process from being interrupted to transport the workpiece to a measuring position. However, the traceability of the measurement process on a machine tool is not ensured yet and measurement data is still not fully reliable enough for process control or product validation. The scientific objective is to determine the uncertainty on a machine tool measurement and, therefore, convert it into a machine integrated traceable measuring process. For that purpose, an error budget should consider error sources such as the machine tools, components under measurement and the interactions between both of them. This paper reviews all those uncertainty sources, being mainly focused on those related to the machine tool, either on the process of geometric error assessment of the machine or on the technology employed to probe the measurand

A Novel Geometric Theory of On-Machine Tool Measurement and Practical, Optimal Approaches to Highly Accurate and Efficient On-Machine Measurement

Modern industry trends to smart machining that improves productivity at a low cost. The kernel technology of intelligent manufacturing is the automatic on-machine measurement (OMM). When applying OMM technology to computer numerical control (CNC) machines, in-situ measurement takes place in the machining environment without the need of unloading the tool and the part. However, adverse measurement environment, limitations on the efficiency of data capturing and processing, and diversified measured objects render efficient and accurate OMM very difficult. Holistic solutions are needed to advance OMM technology and therefore many scientific topics are involved. This work primarily focuses on geometric modeling of the on-machine cutting tool measurement and kinematic modeling for the calibration process of both the probe and the machine. On-machine cutting tool measurement often takes place on a laser tool setter. However, the geometry principles of the gauging mechanisms of laser tool setters are complicated and had not been studied before. This dissertation modeled such a gauging mechanism and presented virtual simulations of the measurement processes on laser tool setters based on geometry principles. The virtual simulations can predict and compensate the measurement errors, allowing for accurate tool setter calibration processes in practical situations. For cutting tool measurement, the tool length characteristic curve for measurement of round-insert mills is discovered. The derivation of the tool length characteristic curve was carried out by modeling the geometries of tool length measurement processes on a laser tool setter. Based on this characteristic curve, an accurate and efficient approach to measuring lengths of mills with round inserts and bottom cutting edge wear is proposed. Current techniques for probe calibration and machine calibration assume the impractical situations where either the machine is accurate or the location of the probe is accurately known. To address these drawbacks, the actual kinematic model of a six-axis belt grinding CNC machine with a customized add-on probe is built in this dissertation. Using this model along with a specially designed artifact can facilitate the simultaneous calibration of the probe position and the machine geometry error

Manufacturing Metrology

Metrology is the science of measurement, which can be divided into three overlapping activities: (1) the definition of units of measurement, (2) the realization of units of measurement, and (3) the traceability of measurement units. Manufacturing metrology originally implicates the measurement of components and inputs for a manufacturing process to assure they are within specification requirements. It can also be extended to indicate the performance measurement of manufacturing equipment. This Special Issue covers papers revealing novel measurement methodologies and instrumentations for manufacturing metrology from the conventional industry to the frontier of the advanced hi-tech industry. Twenty-five papers are included in this Special Issue. These published papers can be categorized into four main groups, as follows: Length measurement: covering new designs, from micro/nanogap measurement with laser triangulation sensors and laser interferometers to very-long-distance, newly developed mode-locked femtosecond lasers. Surface profile and form measurements: covering technologies with new confocal sensors and imagine sensors: in situ and on-machine measurements. Angle measurements: these include a new 2D precision level design, a review of angle measurement with mode-locked femtosecond lasers, and multi-axis machine tool squareness measurement. Other laboratory systems: these include a water cooling temperature control system and a computer-aided inspection framework for CMM performance evaluation

Traceable onboard metrology for machine tools and large-scale systems

Esta tesis doctoral persigue la mejora de las funcionalidades de las máquinas herramienta para la fabricación de componentes de alto valor añadido. En concreto, la tesis se centra en mejorar la precisión de las máquinas herramienta en todo su volumen de trabajo y en desarrollar el conocimiento para realizar la medición por coordenadas trazable con este medio productivo. En realidad, la tecnología para realizar mediciones en máquina herramienta ya está disponible, como son los palpadores de contacto y los softwares de medición, sin embargo, hay varios factores que limitan la trazabilidad de la medición realizada en condiciones de taller, que no permiten emplear estas medidas para controlar el proceso de fabricación o validar la pieza en la propia máquina-herramienta, asegurando un proceso de fabricación de cero-defectos. Aquí, se propone el empleo del documento técnico ISO 15530-3 para piezas de tamaño medio. Para las piezas de gran tamaño se presenta una nueva metodología basada en la guía VDI 2617-11, que no está limitada por el empleo de una pieza patrón para caracterizar el error sistemático de la medición por coordenadas en la máquina-herramienta. De esta forma, se propone una calibración previa de la máquina-herramienta mediante una solución de multilateración integrada en máquina, que se traduce en la automatización del proceso de verificación y permite reducir el tiempo y la incertidumbre de medida. En paralelo, con el conocimiento generado en la integración de esta solución en la máquina-herramienta, se propone un nuevo procedimiento para la caracterización de la precisión de apunte del telescopio LSST en todo su rango de trabajo. Este nuevo procedimiento presenta una solución automática e integrada con tecnología láser tracker para aplicaciones de gran tamaño donde la precisión del sistema es un requerimiento clave para su buen funcionamiento.<br /

ESDA2008-59473 HIGH STIFFNESS CLOSED-FORM KINEMATIC STRUCTURAL DESIGN OF A LOW- COST 4/5-AXIS MICRO/MESO-SCALE INVERTED HIGH-SPEED MACHINING CENTER

ABSTRACT The demand for miniaturized components is increasing in various industries, such as the biomedical, consumer electronics, optics and defense-related industries. The production of the micro/meso-scale components and parts in these industries is typically undertaken using MEMS-type photolithographic production techniques that have limitations in the materials and geometries that can be produced. However, numerous research efforts during the course of the last five to ten years have developed micro-scale EDM processes, microlaser processes and micro-machining operations. In particular, the micro-machining processes have been demonstrated to provide a credible solution to the production of micro/mesoscale parts with complexes geometries in a broad range of materials. The development of mMTs is growing with the rapidly increasing demand for tighter tolerances. Traditionally, mMTs have been developed based on horizontal or vertical Cartesian co-ordinate machine tool structures. However, as the need for increased process flexibility and productivity is continuously being driven higher, there is a need to develop higher degree of freedom machining systems, including 4-axis and 5-axis machining centers. In this paper, the design of a low-cost, high-precision, high-speed 4/5-axis micro/meso machining center is presented as a cost-competitive alternative to existing open-form kinematics precision machining centers. A key departure from traditional machine tool design approach that has been adopted in this design is the utilization of closedform kinematic structural design to create a high-stiffness, lowcost machine tool base. In addition, the lower thermal mass of the mMT base enhances rapid thermal washout in the structure and significantly reduces the thermal gradients in the structure. Consequently the thermal errors present in the structure are limited and simply and adequately handled using existing error compensation strategies. Initial results from an analytical and numerical investigation of the thermo-mechanical response of an innovative, kinematically closed-form inverted micromachining center are presented. A coarse resolution parametric study was undertaken to evaluate the preferred preferred design space for maximum stiffness and minimum thermal distortion in low-cost, high precision, high-speed micro-machining centers. In addition, in order to facilitate part loading and unloading operations will be considered as a key design characteristic. A key result of this study has been the identification of a preferred design space for kinematic form selection, material selection and structural design options for increased rigidity, reduced thermal error and reduced production costs for flexible 4/5-axis micro/meso-scale machining centers. The proposed mMT design achieves a 3X increase in rigidity over a comparable tradition kinematically open horizontal mMT system INTRODUCTION The demand for miniaturized components is increasing in various industries, such as the biomedical, consumer electronics, optics and defense-related industries. The production of the micro/meso-scale components and parts in these industries is typically undertaken using MEMS-type photolithographic production techniques that have limitations in the materials and geometries that can be produced. However, numerous research efforts during the course of the last five to ten years have developed micro-scale EDM processes, micro-laser processes and micro-machining operations. In particular, the micro-machining processes have been demonstrated to provide a credible solution to the production of micro/meso-scale parts with complexe geometries in a broad range of materials. The development of mMTs is growing with the rapidly increasing demand for tighter tolerances. While the pace of development of mMT technology has accelerated during the recent past, the remaining limiting factors for micro-mechanical machining are the miniaturization of the components, tools, and processe

DEVELOPMENT OF EXPERIMENTAL FACILITIES FOR INVESTIGATIONS OF VORTEX MACHINING

This dissertation presents work done in investigation of a novel polishing process called Vortex Machining. Vortex Machining uses an oscillating probe to induce vortices in a polishing slurry above a workpiece, thereby removing material in regions measuring micrometers laterally. The probe features a high-aspect ratio geometry that enables it to reach into (and potentially polish) complex geometries such as small holes and deep channels. The probe can also be used for force and displacement feedback, providing potential for in situ measurement. Throughout this research two test facilities have been developed; a low-power facility utilizing a 7 ?m diameter probe oscillating at 32.7 kHz with amplitudes in the tens of micrometers, and a high-power facility utilizing a 500 µm diameter probe oscillating at several kHz with amplitudes of several hundred micrometers. The facilities control probe position to 0.5 µm, slurry depth to 10 µm, and probe phase to 2.5°; and have demonstrated machining capabilities used in preliminary studies of the process. Analysis software was developed to characterize process footprints. While substantial variability in footprints is observed, material removal rates of the order 10-8 and 10-4 mm3·hr-1 have been measured on silicon. Surface finish values of footprints are typically sub-nanometer and thus comparable to traditional polishing