Papers by Keyword: Accuracy

Abstract: The straightness movement error of the machine tools axis contributes significantly to the straightness of the workpiece machining feature. This paper focuses on the assessment study of CNC machine tools’ straightness geometric error for obtaining recommendation information to improve machine geometric accuracy. A research method by determining measurement parameters according to ISO 230 procedure, no-load measurement of straightness vertical-horizontal geometric error using a laser interferometer, collecting data, data analysis. Data analysis calculates positional straightness deviation, mean positional deviation, systematic positional deviation, repeatability, and accuracy of straightness movement for each machine axis, and generating error compensation values for improving machine geometric error. The travelled distance of the X, Y, and Z-axis CNC milling machine tested is about 1100 mm, 560 mm, and 520 mm. The assessment result shows mean deviation straightness horizontal of X, Y, and Z-axis is 4.14 μm, 3.41μm, and 0.95 μm. The mean deviation straightness vertical of X, Y, and Z-axis is 3.75 μm, 2.63 μm, and 2.30 μm. Finally, the assessment outcome is generating error compensation values of each axis. It could be recommendation information for setting back error compensation parameter on CNC controller, hence the mean deviation of straightness geometric error machine tools to be less than 1 μm.

Abstract: In recent years, the diffusion of additive manufacturing (AM) or 3D printing (3DP) techniques for polymers have been boosted by the expiration of earlier patents from the last century and the development of low-cost machines. Since these technologies become more widespread, there is a need to assess the capability and accuracy of low-cost machines in terms of dimensional and geometric tolerance. To this aim, this work proposes an innovative reference part for benchmarking layerwise processes that involve the curing of photopolymers. The geometry of the part is conceived to include several classical shapes that are easily measurable for defining the part accuracy in terms of ISO IT grades and GD&T values. Two replicas of the reference part were fabricated by stereolithography (SLA) and digital light processing (DLP) using two machines and related proprietary materials by Sharebot Company. The replicas were printed with a layer thickness of 50 μm for the DLP process and 100 μm for the SLA one. The results of dimensional measurements of the replicas, that were carried out using a Coordinate Measuring Machine (CMM), show that the geometric accuracy of the time-consuming DLP process is slightly better than that of stereolithography.

Abstract: The article presents the results of studies of the surfaces of parts processed by the contactless method of laser polishing. The results of technological surface treatment using a laser technological complex based on an ytterbium fibre laser with a power of 5 kW are presented. The results of studies of the surface roughness of the samples after laser treatment, including the non-uniform character due to the redistribution of the liquid metal melt over the surface, are shown. Requirements for metrological support of additive technology have been developed using the example of the process of laser remelting in order to improve quality and further automation.

Abstract: Despite years of supporting research, commercial use of the Single Point Incremental Forming process remains very limited. The promised flexibility and lack of specific tooling is contradicted by its highly complex deformation mechanics, resulting in a process that is easy to implement but where workpiece accuracy is very difficult to control. This paper looks at geometry compensation as a viable control strategy to increase the accuracy of produced workpieces. The input geometry of the process can be compensated using knowledge about the deformations occurring during production. The deviations between the nominal CAD geometry and the actual produced geometry can be calculated in a variety of different ways, thus directly influencing the compensation. Two different alignment methods and three deviation calculation methods are explained in detail. Six combined deviation calculation methods are used to generate compensated inputs, which are experimentally produced and compared to the uncompensated part. All different methods are able to noticeably improve the accuracy, with the production alignment and closest point deviation calculation achieving the best results

Abstract: The validation method for determination of chemical oxygen demand (COD) with indirect UV-Vis spectrometry have been done. This method enable to easily perform highly sensitive, considerably faster and easier, and minimize the use of digestion solution. This method is the development of standard method of COD determination by closed reflux using UV-Vis spectrometry so it requires the method validation stage. The validation is used to ensure linearity, limit of detection, limit of quantification, precision, and accuracy values in accordance with quality control. This study was also carried out to formulate the uncertainty calculation modeling of COD on water analysis. The result of validation method show that the calibration curve linearity is 0.9994 with the linear regression equation Y = 0.0003X + 0.0005. The method is able to have high sensitivity in measuring COD value with low concentrations with limit of detection and limit of quantitation of 9.78 and 32.59 mg O₂/L. Indirect UV-Vis spectrometry has high precision with relative standard deviation of 0.66% and high accuracy with the percentage of recovery of 91.35%. The uncertainty formulation model on determination of COD from the source of standard uncertainty of sample volume, calibration curves, and repeatability.

Abstract: This work indicates that the prediction of the geometric indicators of the quality of the machined surface in the design of technological operations for milling a profile surface of work-pieces with low rigidity is possible, on the basis of an analysis of the elastic displacements of the technological system elements, the flexural rigidity of the work-piece as a function of its initial dimensions, the locating chart and the physical and mechanical characteristics of the material being processed. The article describes the characteristics of the elements of the technological system for the profile milling of work-pieces of low rigidity; The analytical dependencies linking the elastic displacements of the work-piece during the processing of various wood species with elements of the milling mode and the design parameters of the mill are given. Extreme total elastic displacements of the technological system during the cutting process are determined. Mathematical models of the maximum geometric error of the machined surface, as a function of the work-piece's flexural rigidity and the spindle unit, are established. Based on the results of the analysis, recommendations for improving the accuracy of the product were developed.

Abstract: In this article the various methods of assessment of gas-thermal coating’s adhesion strength are considered. The methodology of carrying out the strength tests, using traditional methods of quantitative assessment of adhesive strength of a coating towards its basement, is reflected; the advantages and disadvantages of the represented methods are given. In the article, the theoretical justification of the mechanics of adhesive avulsion is given, and the imperfection of conic pins’ usage is shown. Aiming at increasing of the accuracy and quality of the strength tests of gas-thermal coatings, a modernised methodology, as well as the samples (а.с.1436025), related to detection of the adhesion strength, are suggested. The theoretical computation of the reasonableness of usage of ring cross section of the coating, resulted in the event of usage of the offered sample, is given. On the basis of theoretical computation, a defining formula of the adhesive strength is conducted. Comparison tests of adhesion strength with various sample’s designs are completed. The reasonableness and effectiveness of usage of the offered methodology in assessment of gas-thermal coating’s adhesion strength are proven.

Abstract: This paper provides a methodology for continuous computer support of technological quality assurance for assembly units based on automated subsystems to conduct a dimensional analysis for the main life cycle stages allowing technological, assembly and operational dimensional relations in machines construction to be analyzed.

Abstract: Incremental forming is a promising manufacturing process which allow the user to obtain sheet metal parts, in a flexible manner, without the use of a die. However, the industry is still reluctant to apply the process on an industrial scale. Several drawbacks of the process which hinder its industrial implementation are reviewed in the paper. Among them, the low accuracy of the parts and the low productivity of the process are considered. The lack of dedicated technological equipment and specific CAM software tools are also seen as major drawbacks. Moreover, the lack of any analytical tools to predict the plastic behaviour of the processed part and to predict the moment when it loses its integrity influences the adoption of incremental forming on a large scale. Aside of summarizing these drawbacks, the paper tries to develop a decision-making system, based upon fuzzy logic, for assessing the degree of industrial implementation of the incremental forming process, if certain conditions are met.

Abstract: In the article the strategy and algorithm of technological control of the process of bilateral abrasive processing of cylindrical bearing rollers are considered. The main variable control parameters of the process are the parameters of the angular position of the grinding wheels, the size of the removed allowance and the feed rate of the workpieces. As a result of complex theoretical and experimental research, control principles, criterial conditions, functional and parametric constraints are formulated. The solution of the problem of synthesis of control parameters is given. The effectiveness of the technological control is confirmed by production tests and is expressed in increasing the accuracy and productivity of processing rollers.