Papers by Keyword: Accuracy

Abstract: The basis of effective and efficient production are the measurements. Manufacturing processes should meet the accuracy requirements to produce fit products. Processes capabilities are determined (estimated) and managed by measurements and not at least the suitability of the products are also found by measurements. The measurement technique is considered as a factor associated with costs without taking part in the creation of added value. As a logical consequence is offered to reduce the measurements in order to reduce costs, according to the possibilities, but this leads to increasing of defects in production. This expensive and sometimes fatal consequences of this mentality are not reported. Processes and products are evaluated incorrectly. The number of errors and the expenses increase.

Abstract: Non-conventional manufacturing techniques are most widely used in industries in order to achieve high accuracy and desirable product quality. Therefore, the selection of an appropriate machining parameter has become a crucial job before starting the operation. Several optimization methods are available to resolve the upstairs situation. The current study explores a novel technique namely multi-objective optimization on the basis of ratio analysis (MOORA) to solve different multi-objective problems that are encountered in the real-time manufacturing industries. This study focuses on the application of MOORA method for solving some non-conventional machining processes that have multiple criteria problems. Wire-Electric Discharge Machining (WEDM), Plasma Arc Cutting (PAC), Electro Chemical Micro Machining (ECMM), Electro Chemical Machining (ECM), Abrasive Jet Machining (AJM), Abrasive Water Jet Machining (AWJM), Ultrasonic Machining (USM), Laser Beam Machining (LBM) and Laser cutting process are the major attentions in the current study. Total nine NTM multi-criteria problems which include selection of proper machining parameters have been studied. The optimal settings of input variables obtained by using MOORA method nearly tie with those derived by the earlier investigators.

Abstract: Nitride coatings were deposited by vacuum arc plasma, in an atmosphere of argon and nitrogen using different deposition conditions of part location and configuration, angle between plasma flow and processing surface. The coating thickness, part dimensions and surface roughness were measured before and after coating deposition. The type of part poor shape precision after coating deposition by vacuum arc plasma was defined. An impact of coating deposition by vacuum arc discharge on the part dimensional and form accuracy was revealed. The effect of parts location on dimensional and radial surfaces form accuracy was induced. The effect of coating surface polythickness on part dimensional and form accuracy for parts with different stiffness was defined. The impact of part location area and parts quantity on coating thickness, surface roughness, dimensional and form accuracy of part was revealed. The coating thickness distribution law, parts quality class and accuracy degree after vacuum ion plasma coating deposition were assigned.

Abstract: Micro lubrication pockets decrease the frictional losses and improve the wear resistance of lubricated machine elements. Depending on the application, the pocket dimension and the area density (ratio of the projected pocket area to the non-textured area) must be optimized. Otherwise, the lubrication pockets might increase friction and wear. Besides the determination of the optimized texture, the production process needs to manufacture the pockets with high reproducibility and accuracy, since each deviation of the texture might reduce the improvement of the tribological properties. The goal of this work is to develop a new forming setup capable of decreasing the influence of deviations in the material, of the tool or due to a process inaccuracy ́s. Therefore, a roller-coining process based on a pneumatic system was developed to keep the forming force and thus the pocket dimension constant. This setup was as well used to texture the roller, since the manufacturing of a prominent micro texture on a curved surface with high tolerances is a difficult task for other texturing methods. The experimental verification of the setup showed that by using the pneumatic setup the standard deviation of the pocket depth was reduced by an average factor of 1.9.

Abstract: Additive manufacturing processes and materials are described with respect to their ability to generate finished products. The accuracy of produced parts is seen as an important criterion for this technology to compete with subtractive or constant volume technologies. From the existing literature can be concluded process variation is high and part accuracy is not better then IT grade 9. The manufacturing process itself is complex and dependent on a number of machine, material and geometry parameters. A better understanding of the heat transfer within the product build environment will assist in the future to improve the process and therefore the resulting parts’ accuracy.

Abstract: Dimensional metrology plays an important role in the modern manufacturing technology. Accurate machining technology remains the main focus of global industry, where needs to permanent study for the purpose of improving. Coordinate metrology is an important inspection tool of dimension and geometrical surface form for machined work-piece to provide functionality in quality process. Several factors affect the accuracy and quality of manufactured parts when machined using circular pocket cycles on CNC machining centers. Such accuracy depends to a great extent on work-piece material, the cutting conditions; namely spindle speed, feed rate, depth of cut and the structure of the fixed cycle. The accuracy of dimensional and geometrical form plays a vital function on the required tolerance and fit of manufactured parts to be assembled.This paper studies the influence of those parameters on the accuracy and quality of milled pocket diameter with its roundness. Several specimens made of aluminum, copper and steel metals were pocket milled on a CNC using different cutting conditions. CMM was used to assess the errors in diameter and roundness measurements of machined parts. In despite of scientific advances in machining technology, however there are still clear deviations in the measurement results according to choice of the cutting condition, especially when change the type of work-piece material. Monitoring suitable validiation method for a typical manufacturing machining is achieved accurately. Moreover, expanded uncertainty in measurement has been estimated using statistical repeatability analysis and most effective experimental parameters.

Abstract: This article describes the process of designing and testing the accuracy of trajectory following for omnidirectional mobile robot Odin. It explains the relation between mobile robotic stair climbing system with shaped wheels and omnidirectional wheels, which are used together in a combined locomotive system. It is presented by the conception study only on account of realization of the simplified chassis with the omnidirectional wheels for testing mechanical parameters and the accuracy of the trajectory ride. The omnidirectional mobile robot Odin was built based on a simplified chassis with omnidirectional wheels and with the modular manipulator Schunk mounted on top. The article concludes with a description and comparison of the achieved results by testing the accuracy of the trajectory ride for the simplified chassis and for the omnidirectional mobile robot Odin.

Abstract: The paper presents a stage of the research concerning the development and improvement of a low cost small flexible coordinate measuring machine (CMM) that could be used in the future both in research and industry. Its main advantage could refer to the low cost (only about 30 ÷ 40% of the cost of a CMM in the category on the market, having similar dimensions) in conditions of high performance criteria. This could be possible due to the fact that they were implemented some recycled components in the construction of the robotic drive axes of the machine structure, low cost scanning devices and low cost mechanical systems for fixing and adapting the scanning devices. The research stage presented in the paper is essential for the later stages of research to develop an integrated concept: low-cost, flexibility, precision and efficiency, all criteria referring to a small portable scanning CMM, with possible application in any domain. Specifically, the described research stage refers to evaluate the implementation of some scanning systems, type non-contact low-cost and modern displacement transducers, on the principle of emission of LASER radiation, in terms of scanning accuracy. The reason is that currently these systems are used more and more in the CMMs construction.

Abstract: The development of low-cost desktop versions of three-dimensional (3D) printers has made these devices widely accessible for rapid prototyping and small-scale manufacturing in home and office settings. Many desktop 3D printers rely fused deposition modeling process, that it is based on heated thermoplastic filiform material that it is extrused through a nozzle and deposited afterwards onto a heated building platform. The extruding accuracy in part fabrication is subject to transmission machinery and filament diameter on one hand and the technological parameters that are used in the manufacturing process (raster angle, tool path, slice thickness, build orientation, deposition speed, building temperature, etc.) on the other hand. The presented work try to investigate by using the finite element method, how the building temperature in close connection with the material characteristics is influencing the accuracy of a test part that has been designed in order to callibrate an Desktop 3D Printer machine that has been originally designed and produced at the Technical University of Cluj-Napoca (TUC-N).

Abstract: Product and process conformance are determined by measurements that are taken by a measurement system. A clear understanding of the results of any measurement system requires an understanding of the possible errors within this system. Measurement system errors can be classified into two categories: accuracy and precision. The accuracy of a measurement system is usually broken into three components: bias, linearity and stability and the precision into repeatability and reproducibility. There are a number of procedures which are used, in the automotive and other industries to assess these statistical properties of any measurement system. Usually, companies use repeatability & reproducibility procedures but, according to a measurement systems analysis study, these may not be enough for a company that wants to meet current worldwide quality system standards. Lack of measurement equipment bias and linearity generally is not as predominant error as repeatability and reproducibility, nevertheless, it should be identified because each person that have direct responsibility for measurement evaluation, selection, and control must hand on experience in how to produce a bias and linearity study. A bias study examines the difference between the observed average of the measurements and a reference value. It answers the question “How accurate is my measurement equipment when compared to a master value ”. A linearity study tells one how accurate the measurements are through the expected range of the measurements. It answers the question “Does my measurement equipment have the same accuracy for all sizes of objects being measured ”. Determining the bias and linearity of the measuring equipments and understanding their impact on the measured values will contribute to the effectiveness of the measurement system. In this context, conception and method of bias and linearity analysis of measurement systems are introduced in this paper followed by a real world application done in a major local automotive company. The analysis had ensured consistency of measurements and provided evidence that the measurement system is functioning properly. Minitab software was used to study bias and linearity of the analyzed measurement system.