Papers by Keyword: Geometric Error

Abstract: Computer numerical control (CNC) machine tool plays an extremely significant role in any manufacturing industry due to its automation and high accuracy. Keeping the CNC machine tool at its highest performance to meet the demand of high accuracy machining is always significant. To maintain the accuracy of a machine tool over the time, it is important to measure and compensate the geometric error, one of the main error source of machine tool, especially when the machine get old. There are totally 21 geometrical errors in a 3-axis machine tool including three translational errors and three rotational errors for each axis and three perpendicular error (Squareness) within three axes of the machine. This paper presents an economical and simple method for measuring the geometric error of a 3-axis CNC machine tool based on the machining of actual samples. Three samples for each axis will be machined following a design cutting path. The samples will then be measured using a coordinate measuring machine (CMM). The collect data will be used for estimating the geometric errors. The volumetric errors will be then computed and verified through machining of 3D geometries.

Abstract: The geometrical interpretation of the transformation of cylindrical milling of products into profile milling by shaping cutters with a convex and concave cutting profile is considered. A mathematical model of geometric errors of profile surfaces processed with tools with the specified cutting profiles is developed. On the basis of the model and the results of its analysis, scientifically based recommendations for designing a technological operation for profile milling of products have been developed. When processing a product with a contoured cutter with a concave profile, it is recommended to calculate the geometric errors formed in the transverse plane of the shaping cutter, and when machining with a shaping cutter with a convex cutting profile - in the planes of both its ends. The calculated values of the above geometric errors should be compared with the values limited by the work drawing of the product. The implementation of these recommendations will reduce the labor costs for experimental research and control operations associated with ensuring a given geometric accuracy of products.

Abstract: The increase of the quality in a productive process allows reduction of costs besides adding value to the product. When manufacturing a product within the tolerances specified in the design it is possible to obtain a correct operation of this product, ensuring the minimum time of use and with a lower risk of early failure. In this sense, machines and equipments involved in the manufacturing and inspection processes must also maintain an acceptable quality of operation by knowing the errors present in the machine structure through the calibration, such as errors due to lack of orthogonality between the axes, caused by inaccurate assemblies. The calibration errors in these machines allow elaborate error compensation plans and thus improve the rate of flawless products in production. The objective of this paper was to identify the influence of errors due to a lack of orthogonality in a bridge type coordinate measuring machine (CMM) through calibration and mathematical modeling of errors. Error calibration is performed with a linear displacement transducer, a granite square and a set support brackets for the granite square. By means of the calibration data and the mathematical modeling of the orthogonality deviation an influence of the measured deviation on the "X" and "Y" directions of the CMM is obtained. The error due to the lack of orthogonality between the "X" and "Y" axes of the CMM was approximately 8.9558 negative arcoseg; in this way, it is evidenced that the angle formed between these axes is 89.9975°. Through this study it can be concluded that orthogonality deviation in the main plane of the machine produces negative components for the axes "X" and "Y", with higher influence on the points collected as it away from machine scales, making greater the error intensity on the results of measurements made at positions farthest from the "X" and "Y" scales.

Abstract: The article establishes the analytical relationships linking the geometric parameters of the shaping cutters. A mathematical model describing the geometrical errors caused by the discrete process of product profile milling with shaping cutters was developed. It was specified based on the model that the distribution of errors on the surface treated with cylindrical and shaping cutters is significantly different. It is found that the errors due to the kinematics of the cylindrical milling process, are constant at value irrespectively of the considered cross section of the cutting tooth, and the errors after the milling significantly differ in the distance function of considered transverse plane from its geometric center. The maximum error occurs in the local longitudinal planes of the product, the profile of which is located at the maximum distance from the mounting technological base of product's surface. The plane of the product, where the maximum geometrical errors are formed during the profile milling is called limiting surface. The design of technological process is performed in the product profile geometry, formed in this plane. The rule of spacious arrangement location of the limiting surface of the product according to its drawing. Using the limiting surface in the design of the operation of profile milling with shaping cutters significantly reduces the duration of the design procedure and eliminates the cost of production on experimental studies related to ensuring the geometric accuracy of products at the initial stage of their production.

Abstract: In view of defects-"chew cutting" generated by the five-axis nc machine tool in the process of machining the S sample, the machine tool motion error model is established based on multi-body system theory. After that,combining sensitivity analysis theory with the research of machine tool processing defect causes.Then find out the main error terms which take great responsibility of machining defects and optimize related motion components,to meet accuracy requirements before leaving the factory.

Abstract: In this paper, a new method is presented for the identification of machine tool component errors. Firstly, the Non-Uniform Rational B-spline (NURBS) is established to represent the geometric component errors. The individual geometric errors of the motion parts are measured by laser interferometer. Then, the volumetric error for a machine tool with three motion parts is modeled based on the screw theory. Finally, the simulations and experiments are conducted to confirm the validity of the proposed method.

Abstract: Cutting force is the major factor which causes machine tool geometric error, for the sake of finding the relationship between cutting force and the machine tool geometric error, this paper established a model to simulate and analysis, Mastered the situation of stress distribution of various points on the machine and the regularity of internal stress and strain distribution; designed experiments for the precise measurement, and obtained the actual data of machine geometric error. the data matches the results of the simulative analysis. the results has a certain referential value to optimize the design of machine tool, the geometric error modeling and make the realization of software compensation, etc.

Abstract: To bring a new technological revolution, CNC technology and machines give the birth of a new era of control and production. The rapid development of CNC has considerably advanced the precision and ultra-precision machining technology to improve a new level and great attention. From error prevention and compensation, researches of the CNC machines precision at home and abroad were introduced. Key reasons for error compensation hardly use in the domestic widely were pointed out. Finally, the necessity and main contents of error compensation technology were presented according to the actual situation of enterprises.

Abstract: Antenna is an important and valuable component in industry. In order to protect it, the radome is adopted. As the non-uniform thickness of radome affects the performance of the antenna, in order to maintain the performance of antenna, it is necessary to have a dedicated device to detect the radome, thus the detection machine tool is used. The accuracy is the key point of the detection machine tool, so in this paper, its error model and measurement are presented. By the pitch compensation, the accuracy is enhanced, which achieves the desired value.

Abstract: The relationship between the installment and machining errors and the follower displacement error for a translating roller follower plate cam was studied. The formulae of the follower displacement error were derived. These expressions can be used to calculate the follower displacement error. The follower displacement error of a translating roller follower cam system is closely related to the cam geometric error and offset distance error. By taking the values and signs of the cam geometric error and offset distance error properly, we can minimize the roller follower displacement error and design the high precision translating roller follower plate cam