Research On Distribution Of CNC Machining Accuracy

With the development of science and technology, the mechanical product quality requirements more and more high. The NC machining technology for its high accuracy, easy control, high flexibility, has become the mainstream of the development of machinery manufacturing industry compared to the traditional machining technology. Mechanical products quality is closely related with the manufacturing quality of the mechanical parts of products. Higher accuracy and surface quality can be obtained in CNC machining. Different surfaces have different cutting methods. Therefore, it is important significance how to be cutting, which ensure part quality, increase productivity and reduce labor costs, This dissertation focuses on on several aspects of the application of CNC machine tools such as CNC turning, CNC milling, CNC grinding, EDM wire cutting and CNC boring-milling machining center cutting machine parts, and then choose several methods to measure precision of specific items. Data processing method of range analysis and test plan based on the orthogonal test was proposed and carried out. Machining tolerance was obstained in the numerical control cutting workpieces. Distribution law was realized. This thesis put stress on the following aspects:(1) According to machining method and characteristics, machining precision of the CNC turning, CNC milling, CNC grinding, CNC wire cutting and CNC curve grinding and processing center milling were analyzed in theory and reviewed in this paper. Distribution and trends related to CNC machining precision were also discussed. This paper also expounded the distribution of the different characteristics the of CNC machining accuracy and non-CNC machining precision and studied problems and significance of CNC machining precision distribution. The influence factors of the CNC machining accuracy distribution were determined and the CNC machining accuracy distribution of relevant specific content and methods of the study were put forward.(2) According to the relative objectives with the accuracy distribution of the CNC processing, the experimental plans are proposed with respect to turning, milling, grinding, wire-electrode cutting and curve grinding. The desired equipments and measurements are prepared, and the workpieces are pre-machined for the planned samples. The methods of the range analysis and others are used to deal with the measured data, which can deeply show the distribution tendency of the processing accuracy. It ensures that the reliability of the conclusions while decreasing the experimental times and balancing the distribution of the measured points.(3) The accuracy and surface roughness of CNC machining parts in experiments were detected and programming for data processing. The experimental samples accuracy are obtained from a large number of experiments based on the CNC machining accuracy distribution system. For different dimensional accuracy, shape accuracy, positional accuracy, a variety of different testing instruments and methods were used in a large number of detection and analysis. The Matlab data processing distribution pattern and its implementation technology were studied. The automatic drawing machining precision distribution curve was realized. The goodness-of-fit test of normal distribution was discussed.(4) The rule of distribution of dimensional accuracy, position accuracy and shape accuracy of six kinds of NC machining methods were researched systematically. The distributions and trends presented of a variety of CNC machining precision were obtained by the statistical analysis and mathematical statistics, variance analysis method, a single factor test, orthogonal test and MATLAB calculation methods. Some influencing factors and causes of the CNC machining precision were analyzed and valuable conclusions for process application were acquired.(5) Investigation and analysis of three-dimensional profile and distribution rules of surface roughness were conducted about machined surface of CNC machining. Three-dimensional surface profiles and surface roughness values of the workpieces were measured. Differences of surface roughness distributions of six CNC machining methods were obtained by the height probability density distributions, and the correlations of their influencing factors were found out.(6) Three kinds of comparative analysis on precision machining distribution included CNC turning and CNC grinding, EDM wire cutting and CNC profile grinding, CNC milling and CNC machining center were conducted preliminarily. The same or similar of three test pieces were machined variably and the distribution of machining precision were analyzed based on comparative test results. Data of the samples obtained showed that characteristic parameter changes about the distribution of machining precision. They provide the basis for reasonable choice of the CNC machining processing.Finally, conclusions are drawn and experimental study is mainly on NC machining distribution of precision under the premise of workpiece material and The cutting tool material. conducive factors of the workpiece quality are analysed, and then the biggest impact are found, so that the actual production error is objectively controled and compensated...