Dissertationen zum Thema „Volumetric compensation“

This work is focused on the software compensation of the geometric and volumetric errors. In the thesis there are descripted the measuring instruments suitable for measuring geometric and volumetric errors of the machine tool. In addition, there are described control systems and selected software compensations currently used in the machine tools. In the experimental part of the thesis there is briefly described the machining machine where the experiment was performed. Detailed procedures for using the used measuring instruments are also described. The aim of this thesis is to determine the influence of the size of the compensated volume on the geometric and volumetric precision of the machine tool.

This diploma thesis describes the procedures of individual electronic compensations for CNC machines used to increase the accuracy of machines. This part is followed by the determining tolerance of the measuring and the influence of individual electronic compensations based on measured data using touch probe and calibrated standards according to VDA 5 norm.

This diploma thesis describes realization and testing on-the-fly measurement using tracking interferometer. This measurement enables to achieve higher amount of measured points and decrease time of machine tool calibration. Calibration and verification values of machine parameters, as well as time of measurement and other details of this method are compared with results of conventional method called trigger. To evaluate the quality of volumetric compensation created from calibration values, we use verification measurement of circular interpolation.

This diploma thesis deals with the influence of electronic compensation on accuracy of the measurement using the touch probe. The theoretical part concerns touch probes, specifically their classification, principles of working and applications. This part also includes devices used later in the experiment, particularly double ballbar, laser interferometer and LaserTRACER. The Practical part describes an experiment, demonstrating the correlation between the accuracy improvement of the touch probe and the electronic compensation’s level. All measurements were executed in accordance with the norm VDA 5 and were evaluated by the Matlab software. The graphs of reliance tolerance of capability of measurement on the length of the benchmark. At the end of this diploma thesis there are partial conclusions deduced. The deduction is based on generated graphs. The partial conclusions synoptically compare the influence of individual machine´s configurations on the accuracy of the touch probe.

As Máquinas de Medir a Três Coordenadas (MM3Cs) desde sua criação evoluíram sensivelmente, entretanto poucas foram as modificações estruturais observadas. Hoje, para fabricantes de máquinas destacarem-se no mercado, são necessários grandes investimentos na busca de novos materiais estruturais e no desenvolvimento de programas computacionais cada vez mais versáteis. O sistema eletrônico e os programas computacionais utilizados durante as medições são inacessíveis e rígidos. Estes aplicativos normalmente não podem ser analisados nem modificados pelo usuário. São exemplos clássicos desta rigidez as características préestabelecidas pelo programa, ou métodos de ajustes utilizados na definição das grandezas. Este trabalho tem por objetivo exibir a interface eletrônica e computacional que quebra essa rigidez e permite a aquisição dos sinais das escalas da MM3C, possibilitando o desenvolvimento de novos aplicativos computacionais. O sistema foi aplicado em uma MM3C do tipo Ponte Móvel. Foi desenvolvido um programa computacional, MaqMed 2000, que utiliza os valores dos pontos coordenadas capturados no volume de trabalho da MM3C, e faz a compensação das coordenadas dos pontos utilizados, através das equações do Modelo Reduzido de Sintetização de Erros (MRSE). A avaliação da compatibilidade do dispositivo construído foi feita através do MaqMed 2000 em situações práticas. Foram tomados pontos no perfil de artefatos-padrão e os pontos ajustados através de duas rotinas, uma com e outra sem compensação dos erros. Os artefatos foram medidos em várias posições no volume da MM3C e averiguada a proximidade entre os resultados compensados e os não compensados, ao valor calibrado do artefato. O sistema desenvolvido permitiu compensar os erros em até 98% para compensação bidimensional e 87% para tridimensional.
Since the advent Coordinate Measuring Machines (CMMs) have improved substantially. However, only a small number of structural modifications were observed. Nowadays, considerable capital expenditure is needed to keep CMM builders competitive. Most important research fields concern structural material and production of more flexible and versatile software. The electronic system and the software used during measurement with CMM are rigid and inaccessible and no user modification is permitted. Typical examples are the predetermined software features and curve fitting methods used on the magnitudes definition process. This research aims to exhibit an interface that copes with the system stiffness and enables signal acquisition from the scales of the CMM, allowing the development of new types softwares. The proposed system was implemented on a moving bridge type CMM. A program that uses the values of the coordinate points obtained from the CMM work volume was created. The software MaqMed 2000 performs the compensation of the coordinates of the used points by means of synthesized errors equations. Evaluation of the performance of the built device was carried out using MaqMed 2000 in practical situations. Data sets were collected along the profile of artefacts and fitted by means of two routines, one with error compensation and the other not compensated. Artefacts were measured in several locations in the whole volume of the CMM. The proximity between the compensated and noncompensated results with respect to the calibrated artefact value was examined. The developed system allowed for error compensation of 98% for bi-dimensional compensation and 87% for tri-dimensional compensation.

碩士
國立臺灣大學
機械工程學研究所
102
In the modern metrological technology, traditional coordinate measuring machines (CMM) is not able to satisfy the required precision and accuracy in micro/nano scale. Therefore, NTU Metrology Lab developed a Micro coordinate measuring machine (Micro-CMM) with high precision. This research presents the combination of industrial techniques, including an Abbe free XY Co-planar stage, Z-axis ram, scanning probe and high-resolution sensors. Based on these parts, the goal of this research is to improve Micro-CMM, which contains Laser wavelength error and volumetric error. For the wavelength part, this research designs a wavelength compensator by transmission grating and temperature sensor, and calibrates the real wavelength under temperature variation. Besides, this research builds a volumetric model, verified by experiments of Abbe error, perpendicular error, flatness error and mirror error. By this volumetric error model, the performance of Micro-CMM will be promoted well. This research also improves the method of the fabrication process of optical fiber tip ball. By this method, the fiber is heated to melting point and extruded before forming the tip ball. The result tip ball diameter is around 50μm, and it’s much better than commercial products. Finally, apply the Micro-CMM to measure different parts with various functions, such as small lens and commercial camera model.

Machine tools produce positioning errors due to thermal and structural deformations of the structural elements, geometric errors due to inaccuracies in the manufacturing and assembly of their components, and computer numerical control errors caused by the bandwidth of their servo drives. This thesis presents the measurement, modeling and compensation of geometric errors of three axis machine tools in order to simulate and improve their volumetric accuracy in virtual environment. The geometric accuracy of each axis is measured using a laser interferometer. The displacement, pitch, yaw and backlash errors of each axis element are measured and mapped to the machine coordinates using rigid body kinematic transformations of the system. The identified errors are curve fitted to the position of each drive in the machine coordinates. The algorithm allows prediction of relative positioning error between the tool and workpiece within the working volume of the machine tool, or pre-compensates the errors by adding the estimated positioning errors to Numerical Control (NC) program in Virtual Environment before the machining takes place. The prediction and compensation of geometric errors are experimentally demonstrated on a three axis, vertical CNC machining center. Standard ISO geometric profiles, a circle and a diamond, slot milled on the machine. The machined profiles are measured using a coordinate measuring machine, and the lengths and offsets from the command profiles are estimated from the measurements. The measurement results and the predicted geometric errors are compared. The contributions of CNC and tool deflections to the total errors are estimated, and the remaining errors are correlated to geometric errors of the machine tool. Although, it was not possible to account all the machine tool errors, the proposed prediction and correction method in virtual environment improved the compensation of geometric errors significantly. The overall model is integrated to UBC Manufacturing Automation Laboratory's Virtual CNC system for use in industry.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1990.
Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (147-153).

碩士
國立臺灣大學
機械工程學研究所
104
The position feedback control of NC machine tool controllers mostly employs displacement sensor (such as optical scale or encoder) as a single sensor system. Distance between axis of sensor and axis of cutting could lead to massive enlargement of the positioning error of each axis which is known as the Abbe principle. The movement of linear stage inherently has position and orientation errors in six degree of freedom, which are three linear errors (positioning error, horizontal straightness and vertical straightness) and three rotational angles (pitch, yaw and roll). As a result, Abbe error is considered to be the major cause for volumetric error of machine tool. In this study, a multi-sensor feed-back compensation system which consists of three angular sensors and NC controller is developed to greatly enhance the machine tool accuracy by detecting angular errors in real-time and corresponding Abbe offsets so as to compensate for the Abbe errors dynamically. It can also be embedded in NC controllers to improve the accuracy of machine tool. In the measurement system, autocollimator and roll are deployed to monitor the angular errors of machine tool by constantly converting the measuring signals into Pc-based controller(with embedded volumetric error model) Experiments show that the positioning error of an investigated NC machine tool Fis mainly affected by Abbe error. With the proposed volumetric error compensation system, the positioning accuracy can be significantly improved by more than 80%.

碩士
國立臺北科技大學
機電整合研究所
102
There are many factors, such as straightness of guild way, flatness, pitch error, backlash of three axes, to affect the machining accuracy of CNC machines. Nowadays, CNC machines are only compensated three errors : 、 、 by the manufacturers ignoring other errors causing inefficient compensation. An equipment using for volumetric error compensation on CNC machines usually cost a lot. For improving those defects, the study use iterative learning control software compensation to increase the adaptability on CNC machines and low cost. The process of compensation would get the pitch errors from error tables by using interpolation rule first, and compensate the processing commands. After first step’s compensation, use the iterative learning control to find the compensating commands in the limited running times that would cause the minimum volumetric errors. Setting two simulations test the effect of the compensation software. The simulation 1 is testing about the influence of points, and the convergence of the volumetric errors is 88.8% compared with the original. Simulation 2 is imitating the spiral moving process by using the compensation software, and the convergence of the volumetric errors is 82.6%. After knowing the result of simulation, try three kinds of cutting tests and analyze the variation of the data. The cutting test 3 shows that the volumetric error compensation software is working and at least makes the error compensate 12.99%, at most makes the error compensate 98.9%. Results of those simulations and cutting tests indicate that the volumetric errors can be significantly reduced by applying the compensation software.

碩士
國立成功大學
機械工程學系
106
The purpose of this study is to improve the machining precision and processing efficiency in the milling process of thin workpieces. In the case of thin workpieces, elastic deformation is the main problem causing volumetric errors during milling. To solve this problem, the tool path is modified to compensate for volumetric error. First, the cutting forces generated during the milling process can be predicted from a cutting force model. Second, in order to analyze the elastic deformation of a workpiece, feature points are chosen on the workpiece, and the predicted cutting forces are set as the load on these feature points in ANSYS to conduct a static analysis. Then, the workpiece deformation data is used to build a deformation matrix in order to generate a new tool path that enables volumetric error compensation. This modified tool path is generated as a CL (cutter location) file. Finally, CAM (computer aided manufacturing) software is used to convert the modified CL file into NC code, so milling experiments can be conducted. In this study, the cutting forces during the milling process are measured using a sensory tool holder. To use the cutting force data from a sensory tool holder to do an analysis, data coordinate transformation between the tool and workpiece is necessary. Moreover, in order to establish a process that can allow users to quickly and easily obtain the compensation tool path necessary to conduct a milling experiment, three main program interfaces are built using MATLAB software. Three programs are used to calculate the cutting constants, to predict the cutting force, and to generate the compensation tool path, respectively. Finally, for demonstration and verification, a thin workpiece machining example was made, including a tool path simulation in NX CAM software and practical machining on a CNC milling machine. The results of the thin workpiece milling experiment proved the approach presented in this study successfully improved machining precision and processing efficiency at the same time.

碩士
國立成功大學
機械工程學系碩博士班
101
Multi-axis machine tools are used for machining of complex workpieces with high precision, such as medical and aerospace parts, some of which are thin workpieces with low structural rigidity. On account of avoiding elastic deformation of thin workpieces caused by multi-axis machining, most engineers in the past must repeat test and measurement in the process planning stage for the optimal material removal within precision requirement. If an analysis and compensation system for volumetric errors of thin workpieces can be established, it will provide for users with complex process planning to improve the efficiency of processing for thin workpieces. In this research, a cutting force simulation program is used for calculating the cutting force during machining process of thin workpieces, and then finite element software is applied for analyzing the deformation of thin workpieces under static condition. Taking MATLAB for formula fitting, the error matrix can be calculated, and then the cutting path can be modified. Finally through the form shaping function, the NC code with compensation can be generated by postprocessing. In order to evaluate the compensated results, the modified cutting paths are simulated by Vericut software, and the unloading process of thin workpieces after virtual processing is simulated by the finite element software, thus, the volumetric errors with modified cutting path can be generated. Through the evaluation system, the users can obtain the result to check if the precision of the workpiece meet the requirements or not, and regard the evaluation result as the basis for process planning. In this thesis, a system has been constructed for analyzing the volumetric errors of thin workpieces and compensate it. It can be applied for the process planning of multi-axis machining with thin workpiece. The system makes great improvements not only on the efficiency of the overall manufacturing process but also on the precision of the product.

碩士
中原大學
機械工程研究所
100
Non-MEMS micro machining technology has been regarded as one of the key technologies for the development of precision industry. However, very less research efforts had been devoted in developing volumetric error measurement method and synchronous movement error calibration. Due to the workspace constraints of a micro machine tool, the current measurement methods used in industry cannot be applied. With use of image identification/tracking, coordinate transformation, sensitivity analysis, and error identification/compensation, the on-machine micro error measurement, calibration, and compensation methods with use of image capture system and control information were developed in this study. The methods provide 4 main functions: (1) volumetric error measurement, (2)volumetric error compensation, (3) internet-based remote control and automatic measurement (4) contouring/tracking error inspection. The methods can be used before the machining process to improve the machining accuracy, such as: (1) off-line cutting path error compensation, (2) synchronous movement error calibration. In addition to develop the methods and systems, sensitivity analysis was made. Micro machining experiments were conducted on a micro machine tool to verify the feasibility and reliability of the developed system.

碩士
中原大學
機械工程研究所
97
Non-MEMS micro machining technology has been regarded as one of the key technologies for the development of precision industry. However, difficulties in positioiung the micro cutter and in measuring the volumetric errors of a micro machine tool restrict the implementation of this technology to industry. An on-mahcine error measurement and compensation system that can accurately position a micro tool and meausure/compensate volumretric errors of a mcro machine tool was developed in this study. Sensitivity analysis was also adopted to analyze the influences of major error sources on the measurement accuracy. With using 3 COMSs, Power Law Method, Canny Edge Metho, and image projection method were adopted to develop the function of micro tool positioning. The initial positioning error of a micro tool can be inspected by the system and compensated through executing a NC program generated by the NC-code writing unit. With Canny Edge Method, Homogeneous Transformation Method, Element Free method, and use of the resolution targets, the volumetric error measurement method was developed and used to measure the volumetric errors at nodal points for Element Free Method. With integration of Element Free Method, the recursive error compensation algorithm, and the NC-code identifying and writing unit, the machining trajectory errors can be predicted and compensated. Experiments were conducted to verify the effectiveness of the developed system. The experimental have shown that the system can effectively improve the maching accuracy of a micro machine tool.

Il est généralement admis que la vision joue un rôle prépondérant dans la formation des représentations spatiales. Qu’advient-il alors lorsqu’un individu est atteint de cécité? Dans le premier volet de cette thèse, les habiletés spatiales des personnes aveugles ont été examinées à l’aide de différentes tâches et comparées à celles de personnes voyantes effectuant les mêmes tâches avec les yeux bandés. Dans une première étude, les capacités de rotation mentale ont été évaluées à l’aide d’une épreuve d’orientation topographique tactile. Les résultats obtenus montrent que les personnes aveugles parviennent généralement à développer des capacités de rotation mentale similaires à celles de personnes voyantes et ce, malgré l’absence d’information de nature visuelle. Dans une seconde étude, nous avons utilisé différentes tâches spatiales nécessitant l’utilisation de la locomotion. Les résultats obtenus montrent que les personnes aveugles font preuve d’habiletés supérieures à celles de voyants lorsqu’elles doivent apprendre de nouveaux trajets dans un labyrinthe. Elles parviennent également à mieux reconnaître une maquette représentant un environnement exploré précédemment. Ainsi, l’absence de vision ne semble pas entraver de manière significative la formation de concepts spatiaux. Le second volet de cette thèse s’inscrit dans la lignée des études sur la plasticité cérébrale chez les personnes aveugles. Dans le cas présent, nous nous sommes intéressés à l’hippocampe, une structure profonde du lobe temporal dont le rôle au plan spatial a été établi par de nombreuses études animales ainsi que par des études cliniques chez l’humain incluant l’imagerie cérébrale. L’hippocampe joue un rôle particulièrement important dans la navigation spatiale. De plus, des changements structuraux de l’hippocampe ont été documentés en relation avec l’expérience des individus. Par exemple, l’étude de Maguire et al. (2000) a mis en évidence de telles modifications structurelles de l’hippocampe chez des chauffeurs de taxi. À l’instar de ces derniers, les personnes aveugles doivent emmagasiner de nombreuses informations au sujet de leur environnement puisqu’elles ne peuvent bénéficier de la vision pour mettre à jour les informations sur celui-ci, sur leur position dans l’espace et sur la position des objets se trouvant hors de leur portée. Nous avons montré, pour la première fois, une augmentation du volume des hippocampes chez les personnes aveugles en comparaison avec les personnes voyantes. De plus, cette augmentation de volume était positivement corrélée à la performance à une tâche d’apprentissage de trajets. Les résultats présentés dans cette thèse permettent d’appuyer les études antérieures qui soutiennent que les personnes aveugles parviennent à compenser leur déficit et à développer des habiletés spatiales comparables, voire supérieures, à celles de personnes voyantes. Ils permettent également d’apporter un éclairage nouveau sur le concept de plasticité cérébrale présent chez cette population en montrant pour la première fois un lien entre le volume de l’hippocampe et les habiletés spatiales chez les personnes aveugles.
It is well known that the visual modality plays a key role in the development of spatial representations. Hence, one may wonder how complex spatial abilities develop and how the brain is able to adapt in the absence of this modality. In order to answer such questions we investigated the spatial abilities and cerebral plasticity of both early and late blind individuals in comparison to sighted blindfolded individuals. The first experiment was designed to assess mental rotation abilities. A tactile topographical orientation task was used. The results show that blind individuals are able to develop mental rotation abilities similar to those of sighted ones. In the second experiment, we used different spatial tasks requiring the use of locomotion and wayfinding. Results show that blind individuals are better than their sighted counterparts at learning new routes in a maze. They also perform better when having to recognize a small-scale model representing a real-size spatial layout they had previously explored. Thus, the absence of vision does not appear to significantly impede the formation of spatial concepts. The second part of this thesis is in line with studies on brain plasticity in blind individuals. We measured morphological changes in the hippocampus, a medial structure of the temporal lobe. Animal lesion-based and human brain imaging studies have shown that the hippocampus plays an important role in the processing of spatial information and in spatial navigation. Furthermore, structural changes in the hippocampus have been documented in relation to the ‘spatial’ experience of individuals. For instance, Maguire and colleagues (2000) have shown structural differences in the hippocampus of well-trained taxi drivers in comparison to individuals without extensive spatial training. Like taxi drivers, blind individuals require extensive storage of information regarding their environment. This is essentially because they cannot rely on visual cues to create a representation of the spatial organization of their environment, nor can they continuously visually update their position in space and the spatial coordinates of objects outside of their reach. Here we show for the first time an increase in the volume of the hippocampus in blind compared to sighted individuals. Moreover, this increase in hippocampal volume was positively correlated with performance on the route-learning task described above. Overall, the results not only support previous findings showing that blind individuals can develop spatial abilities similar or superior to those of sighted individuals, but also shed light on the concept of brain plasticity by showing for the fist time a correlation between hippocampal volume and spatial abilities in the blind.