Papers by Keyword: Error Compensation

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: The development of additive manufacturing requires the improvement of 3D printers to increase accuracy and productivity. Delta kinematics 3D printers have advantages over traditional sequential kinematics 3D printers. The main advantage is the high travel speed due to the parallel movement of the platform from three pairs of arms. Another advantage is the relatively low cost due to the small number of structural components. However, delta 3D printers have received limited use. The main reason is the low positioning accuracy of the end effector. Errors in the manufacture and assembly of components of a parallel drive mechanism add up geometrically and cause an error in the position of the end effector. These formulas can be applied to a 3D printer as well. However, well-known studies consider deterministic models. Therefore, the analysis is performed for limiting size errors. The purpose of this article is to simulate the effect of statistical errors in displacements and arm lengths on the positioning errors of a platform with the end effector. The article effectively complements the field of error analysis research and provides theoretical advice on error compensation for delta 3D printer.

Abstract: Aiming at the error compensation problem for rectangular window, this paper presents a method of compensation for rectangular window based on NURBS (Non-Uniform Rational B-Splines) reconstruction. In the method, the machining surface is digitally obtained by means of on-machine measurement. The measured data are divided into four regions and different error compensation schemes are used for different regions. The adaptive compensation of the machining error calculated based on NURBS reconstruction theory is achieved by modifying the coordinates of the tool point in the cutter location file. The automation of error calculation and compensation is implemented by software development based on Visual Studio 2012. At the end of the paper, a compensating tool path is emulated in VERICUT. The results show our method is feasible.

Abstract: This paper investigates the software error compensation in CNC machining centers On-line inspecting system. Based on Windows 2000 operating system, compensation software is developed. It investigates modeling errors. The software can compensate probe errors, thermal and geometric errors. The software system is tested on MAKINO upright CNC machining centers, and the results verify the effectiveness of the method.

Abstract: Based on Windows operating system, the software of NC machine’s On-line inspection has been developed, the key technology in software development: Set up the comprehensive error model of the inspection system, probe error treatment technology, communication etc. Utilize this software to turn into the procedure of measuring automatically, and can compensate to probe error, the geometric error and thermal error of the machine, have improved the precision and efficiency.

Abstract: Aiming at the traditional measurement methods and equipment cannot meet the accurate measurement problems of complex inner surface geometry parameters. This paper proposes combining the laser displacement sensors, rotary encoders and machine control system to build the measurement system. This system overcomes the traditional contact measurement of the low efficiency, low velocity, low accuracy, and realizes measuring slender and long inner surface. Through analysis and processing of the acquisition of point cloud data, draw a cross-sectional contour of the workpiece to achieve a precise measurement of the internal surface.

Abstract: The paper is aim to design a control system fitting for fixed length cutting of industrial pipe. Electromechanical principles and methods of the system are elaborated in the paper. The system applies PLC which built-in electronic CAM to creates electronic CAM curve according to pipe chase cutting control’s requirements and the motion parameters’ calculation, so as to achieve the function of a synchronized motion in the cutting point that between the cutting platform and the pipes. A relatively static cutting is realized. There is no wearing and relative sliding in this system, furthermore, the processing precision and efficiency of the system are high, so it has a broad application prospect.

Abstract: A new method compensating geometric error components of a four-axis horizontal machine tool is presented in this paper. Homogeneous transformation matrices (HTMS) and error conversion are integrated in the compensation strategy. A mathematical model which contains 29 geometric error components is established based on HTMS and the errors in X, Y and Z directions are obtained through calculation. The errors in three directions are compensated by shifting the corresponding axis. But the configuration of this machine tool is X-axis, Z-axis, B-axis, C-axis without Y-axis, so the errors in X, Y and Z directions need to be converted into X, Z and C directions which is different from the traditional machine tools. The errors after conversion are used to compensation directly. This approach is significant for the error modeling and compensation which is an easy and efficient way to improve the precision of the four-axis machine tools.

Abstract: Spool valves are the main elements in electro-hydro servo valves. Hydraulic measurement is an important method for spool valve’s null cutting measuring process. Because of the flow pattern transition, the discharge coefficient is a variable. This phenomenon causes errors if we assume the discharge coefficient is a constant as we always do. In this paper, the variable discharge coefficient is considered to the submerged discharge equation, and the flow pattern error is defined. For improving the precision of overlap values measurements, a compensation method of flow pattern error is presented in this paper.

Abstract: In precision robotic applications, inaccuracy in workpiece geometry has been a common problem to the precise processing of the workpiece. Due to manufacturing defects and workpiece deformation, the actual geometry of the workpiece deviates from its nominal 3D CAD model which is defined as model error. For many of the existing industrial robotic applications today, the robot path for processing the workpiece is planned based on the nominal 3D CAD model of the workpiece. Hence, the model error of the workpiece leads to error in the robot path planning eventually inducing inaccurate processing. To enhance the accuracy of the robot in processing the workpiece, a framework for in-situ model error compensation has been proposed. Prior to the processing of each workpiece, the proposed technique employs 3D optical laser scanning technology to capture the actual 3D model of the workpiece and compares it with the nominal model to establish the model errors. The nominal path of the robot initially created based on the nominal CAD model is then modified according to the model error. Thus, this step performs the in-situ model error compensation making the robotic task adaptive to the actual workpiece geometry. Experiments have been conducted to verify the proposed framework and an accuracy of up to 30 micrometers has been achieved in model error identification and compensation. The proposed technique can be employed in applications such as high precision robotic tasks, where accuracy of task execution is an important factor.