Software Error Compensation Research Articles

Error correction technique for numerical control machine tools based on the simplex method

The objective of this research is to develop a novel correction mechanism to reduce the fluctuation range of tools in numerical control (NC) machining. Error compensation is an effective method to improve the machining accuracy of a machine tool. If the difference between two adjacent compensation data is too large, the fluctuation range of the tool will increase, which will seriously affect the surface quality of the machined parts in mechanical machining. The methodology used in compensation data processing is a simplex method of linear programming. This method reduces the fluctuation range of the tool and optimizes the tool path. The important aspect of software error compensation is to modify the initial compensation data by using an iterative method, and then the corrected tool path data are converted into actual compensated NC codes by using a postprocessor, which is implemented on the compensation module to ensure a smooth running path of the tool. The generated, calibrated, and amended NC codes were immediately fed to the machine tool controller. This technique was verified by using repeated measurements. The results of the experiments demonstrate efficient compensation and significant improvement in the machining accuracy of the NC machine tool.

Measurement and compensation of machine tool geometry error based on Abbe principle

The error measurement of numerically controlled machine tools is fundamental to error compensation. The installation position of measurement equipment has a significant influence on the measurement accuracy. Accurate measurement should satisfy the requirement that five factors are on the same line, or the Abbe error will result in measurement data inaccuracy. In this study, the reasons for the Abbe offset are analysed. The measuring equipment and measured object are adjusted so that the Abbe arm length is reduced to zero. When the measurement system is limited by the object condition, the compensation methods for these errors are provided. The system error is significantly decreased by software error compensation according to the error model based on the Abbe principle. The experimental results demonstrate that the machine tool accuracy is improved significantly. Therefore, the proposed compensation method is effective in compensating for the geometric error of the machine tool.

Laser Interferometer Based Measurement for Positioning Error Compensation in Cartesian Multi-Axis Systems

Accuracy is one of the most important key indices to evaluate multi-axis systems’ (MAS’s) characteristics and performances. The accuracy of MAS’s such as machine tools, measuring machines and robots is adversely affected by various error sources, including geometric imperfections, thermal deformations, load effects, and dynamic disturbances. The increasing demand for higher dimensional accuracy in various industrial applications has created the need to develop cost-effective methods for enhancing the overall performance of these mechanisms. Improving the accuracy of a MAS by upgrading the physical structure would lead to an exponential increase in manufacturing costs without totally eliminating geometrical deviations and thermal deformations of MAS components. Hence, the idea of reducing MAS’s error by a software-based alternative approach to provide real-time prediction and correction of geometric and thermally induced errors is considered a strategic step toward achieving the full potential of the MAS. This paper presents a structured approach designed to improve the accuracy of Cartesian MAS’s through software error compensation. Four steps are required to develop and implement this approach: (i) measurement of error components using a multidimensional laser interferometer system, (ii) tridimensional volumetric error mapping using rigid body kinematics, (iii) volumetric error prediction via an artificial neural network model, and finally (iv) implementation of the on-line error compensation. An illustrative example using a bridge type coordinate measuring machine is presented.

Research on Thermal Errors Compensation Techniques in Machining Center’s On-Line Inspection Software

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.

The Integration and Innovation Design of Single Chip Computer and NC Machine Tool Control

Against to the problem of widely used of software error compensation, raises error compensation device to instead of PC to realize erro r compensation. And introduces multi-body system relating to error compensation, represents the feasibility and implementation techniques of software error compensation using SCM. This program will show great values in the field of CNC.

The Design of New-Type Digital Readout Device by Inductosyn

The paper introduces the operation principle and system structure of intelligence digital readout system by inductosyn. The system adopts integrated subdivision circuit on the basis of AD2S90 and QA740210 and is controlled by MCU. It adopts phase demodulation mode, with functions of multipoint preset, power-fail protect, absolute origin setting, software error compensation, LCD display and so on, except simple PLC function and standard RS485 communication interface.

On-machine volumetric-error measurement and compensation methods for micro machine tools

The CNC micro machine tool is an essential of the micro machining process for manufacturing miniature high-tech products. A software-based error compensation method based on measured volumetric errors that can pre-compensate cutting path can further enhance a machine’s accuracy without increasing its manufacturing cost. Considering the limited workspace of a micro machine tool and the instrument cost, an on-machine and vision-based measurement method integrating machine vision method with use of 3 COMs and homogeneous transformation method was proposed in this study. Sensitivity analysis was conducted to analyze the influence of the CMOS pixel error to the measurement accuracy. To improve the machining accuracy, the measured errors were directly compensated to the machining trajectory with use of an error compensation method that consists of an element-free error interpolation scheme and a recursive software error compensation scheme. Experiments on a toggle-type micro machine tool were conducted to verify the effectiveness of the proposed methods. The results have shown that the feasibility and effectiveness of the proposed methods. The tracking errors of the machine was further improved from (x = 7.9 μm, y = 4.1 μm) to (x = 5 μm, y = 3.7 μm).

Error Modeling and Iterative Algorithm for Compensation Instructions of Five-Axes NC Machine Tools Based on the Multi-Body System Theory

The machining accuracy of NC machine can be improved significantly through the error compensation. The kernels of (multi-body system)MBS theories are that the number arrays of low-order body are used to describe the topological structures which are taken to generalize and refine MBS, and the characteristic matrix are employed to represent the relative positions and gestures between any two bodies in MBS. Based on the theory of rigid body dynamics and homogeneous coordinate transformation techniques, the space error model of five-axis gantry NC machine can be established, the modified NC instructions can be obtained and it prepares well ready for the software error compensation and the practical application. Gyratory motion of five-axis NC machine will generate the coupling of translational motion, so it is different from the three-axis NC machine in the process of error compensation and we need to decoupling.

A Method for Measuring the Systematic Errors of CNC-Machine Tools

The method used for measurement and calibration of machine tool errors should be general and efficient. With this method, the machine tool status can be completely identified and its accuracy can be enhanced by software error compensation. The point compensation method can be used as a means for modifying the nominal tool path and on-machine inspection where the machine tool is used as a coordinate measuring machine. The validity of the error calibration method proposed in this' paper was shown using a vertical 3-axis CNC machine with a laser interferometer and a ball bar technique.

Positioning Error Compensation for Machining Center Based on Spline Interpolation

Related to the machining precision, especially for the middle and low end machining center, the positioning error is often considered as a major factor, which can be traditionally decreased by the pitch compensation function integrated in the CNC system. However, the function is just founded on that all of positioning errors remain constant in the machining process, and it is difficulty to meet the compensation needs in different machining condition. At the same time, it involves a mass of parameters that need professional manual correction. Therefore, the software error compensation method is put forward. Firstly, based on cubic spline interpolation, the error compensation model is designed through the processing of positioning error which is collected by the laser interferometer. Secondly, with the characteristics of G codes, the database is established for error compensation, which can effectively correct different machining G codes with enough error information. Finally, by the experiment and accuracy evaluation, results show that after the positioning error of machining center is compensated by the presented scheme, its precision is improved obviously.

Geometric error compensation software system for CNC machine tools based on NC program reconstructing

It has been proved that error compensation is an effective approach to improve machining accuracy of a machine tool cost efficiently. In this paper, the framework of an error compensation software system, which can realize software error compensation via numerical control (NC) programs reconstructing, is investigated. And the algorithms relating to error prediction are discussed in detail, such as positioning movement error compensation, linear interpolation movement, and circular interpolation movement error compensation. To realize the error compensation, NC program is reconstructed according to the predicted errors during virtual machining before it is fed to the actual machining. Two controlled machining experiments were carried out. The results show that error compensation methods via reconstructing NC programs can improve the movement accuracy of a computer numerical control CNC machine tool obviously.

Reconstructing NC Program-Based Geometrical Error Compensation for Heavy-Duty NC Machine Tool

Heavy-duty NC machine tool is difficult and costly to evidently improve their precision via manufacturing technology only. It is proved being an effective approach to improve machine tool manufacturing precision based on software error compensation. In this paper, an error compensation algorithm based on reconstructing NC program is discussed. Following comprehensive discussion on basic algorithm of positioning error compensation in detail, linear interpolation and circular interpolation movement error compensation algorithm are further sketched in brief. To decrease the machining error, NC program is reconstructed before actual machining. The experiment results show that error compensation methods based on reconstructing NC program can improve profile accuracy of heavy-duty NC machine tools obviously.

D-optimal design of artifacts used in-machine software error compensation

A methodology for the design of artifacts used in software error compensation of rapid prototyping (RP) machines is presented. In software error compensation, an artifact is frequently utilized for measuring parametric errors of the machine axes. In the past, different artifacts have been used and designed in an ad hoc way. To date, no method is available to evaluate the design of an artifact based on its effect on the precision of the fitted models estimated using the artifact. This paper proposes a method to evaluate and improve the design of an artifact using design of experiments (DOE) techniques and numerical optimization. As demonstrated by the results, a D-optimality criterion optimized using simulated annealing techniques can be used to evaluate and improve the design of an artifact so that the components of the volumetric error are predicted more precisely, with the benefit of better error compensation over repeated use of the error models. Although in this paper the concept is only demonstrated for the SLA 250 RP machine, it can be applied to the design of any artifact used for machine error compensation.

A kinematics and experimental analysis of form error compensation in ultra-precision machining

Ultra-precision machining has drawn much attention and the error compensation is an essential issue for improving the accuracy of the machining process. However, the analysis of kinematics errors on the surface generation in ultra-precision machining has received relatively little attention. Ultra-precision machine can be represented as a multi-body system. Based on the theory of multi-body system, a kinematics model of two-axis ultra-precision machining system has been developed in the present study. Hence, a software error compensation method is incorporated which is carried out by modifying the idea tool path in the NC program. The modified NC program takes into account the kinematics error factors and so the actual tool path generation can be compensated for the kinematics errors on the machining of the surface of the workpiece. To verify the theoretical kinematics model and the error compensation method, a series of machining experiments have been conducted and the experimental results indicate that better surface quality was achieved with the implementation of the proposed compensation method.

Error compensation for fused deposition modeling (FDM) machine by correcting slice files

PurposeThe purpose of this research is to extend the previous approach to software error compensation to fused deposition modeling (FDM) machines and explores the approach to apply compensation by correcting slice files.Design/methodology/approachIn addition to applying the stereolithography (STL) file‐based compensation method from earlier research; a new approach using the slice file format to apply compensation is presented. Under this approach, the confounded effects of all errors in a FDM machine are mapped into a “virtual” parametric machine error model. A 3D artifact is built on the FDM machine and differences between its actual and nominal dimensions are used to estimate the coefficients of the error functions. A slice file compensation method is developed and tested on two types of parts as a means for further improving the error compensation for feature form error improvement. STL file compensation is also applied to a specific FDM 3000 machine and the results are compared with those of a specific SLA 250 machine.FindingsThe two compensation methods are compared. Although, the slice file compensation method theoretically allows higher compensation resolution, the actual machine control resolution of the FDM machine can be a limitation which makes the difference between STL compensation and slice file compensation indistinguishable. However, as the control resolution is increased, this method will make it possible to provide a higher degree of compensation.Originality/valueCompensation method applied to slice file format is developed for FDM machines and its limitations are explored. Based on the experimental study, dimensional accuracy of parts is considerably improved by the software error compensation approach.

Software compensation of rapid prototyping machines

This paper addresses accuracy improvement of rapid prototyping (RP) machines by parametric error modeling and software error compensation. This approach is inspired by the techniques developed over the years for the parametric evaluation of coordinate measuring machines (CMM) and machine tool systems. The confounded effects of all errors in a RP machine are mapped into a “virtual” parametric machine error model. A generic artifact is built on the RP machine and measured by a master CMM. Measurement results are then used to develop a machine error function and error compensation is applied to the files which drive the build tool. The method is applied to three test parts and the results show a significant improvement in dimensional accuracy of built parts.

Assessing geometrical errors of multi-axis machines by three-dimensional length measurements

In this paper a method is presented for assessing geometrical errors of multi-axis machines based on volumetric three-dimensional length measurements. A universal machine error model is proposed since a large variety of machine configurations exists. Such models can be used for software error compensation techniques in order to improve the machine’s positioning behaviour as well as for diagnostic purposes. Length measurements are chosen for the measurement of the positioning errors of a multi-axis machine because these measurements can be executed in a short period of time in a relatively simple way combined with a high accuracy. In order to get comparable results for the geometrical errors as measured with conventional techniques, i.e., laser interferometry, the design of the measurement setup as well as the formulation of the machine error model (including parameter correlation effects) appeared to be of major importance and are subject of this paper.

L∞ Parameter estimates for volumetric error in models of machine tools

Software error compensation is becoming an increasingly important aspect of numerically controlled machine tools. Currently, the error models are identified using the least-squares criterion. This criterion does not necessarily reflect the evaluation criteria of a machine's performance. In this paper, we develop a method for identifying the error model of a machine tool using a Chebyshev norm. The model parameter identification procedure becomes a linear program, and the resulting error models minimize the maximum error of the machine across its workspace thus affording strict on the errors produced by the machine.

Fast calibration and modeling of thermally-induced machine tool errors in real machining

Calibration and modeling of thermally induced errors is a critical part of enhancing machine accuracy by software error compensation. In most applications, parametric thermal errors of a machine tool are calibrated and modeled individually by air-cutting experiments. Calibrating thermal errors individually is time-consuming and may neglect thermal interaction among thermal sources. The accuracy of the air-cutting model in real machining is also questionable. In this report, thermal errors of multiple machine axes in real cutting were calibrated simultaneously by a quick set-up measurement system consisting of on-machine probes and artifacts. Characteristics of thermal errors in real cutting under different cutting conditions, cutting paths and workpiece materials were investigated. It was found that thermal errors in real machining were distinct from those in air cutting.

A study of thermally induced machine tool errors in real cutting conditions

A thermal error model for software error compensation is usually established from air cutting experiments. The accuracy of the air cutting model in real machining applications is often questioned. In this research the characteristics of thermal errors in real cutting conditions are studied. An analysis based on a regression error model and an artificial neural network-based error model are studied and compared for free air cutting and real cutting conditions. The result shows that the prediction accuracy of the air cutting model is unacceptable in real cutting applications. This is because the cutting load and the cutting coolant applications produce significant thermal effects not taken into account by the air cutting approach. In some cases the predicted result of an air cutting model may go in the opposite direction to the actual error in real cutting. On the other hand, the hybrid model derived from air cutting and real cutting data gives a satisfactory prediction for real cutting conditions.