Positioning Error of Feed Axis Decouple-separating Modeling and Compensating Research for CNC Machine Tools

Due to the errors of the servo system and the errors of the ball screw drive system, the positioning errors inevitably occur in the process of CNC machine tools. The measurement of traditional equipment is limited by a fixed measurement radius and a single degree of freedom, which can only be measured within a fixed plane. In this paper, four different positioning errors of CNC machine tools are first measured at full scale by using J-DBB (a modified double ball bar with one spherical joint connecting two bars) method. The J-DBB device uses a three-degree-of-freedom spherical joint as a connecting part, which realizes that the measurement radius can be continuously changed, and the measurement space is a spatial sphere. First, the principle of the J-DBB method is briefly introduced. Next, four typical positioning errors of CNC machine tools are analyzed and examined, which contain the uniform contraction error of ball screw and linear grating, periodic error of the ball screw and linear grating, interference of measurement devices error, and opposite clearance error. In the end, the trajectories of the CNC machine tool spindle with a single positioning error are simulated by using the J-DBB method. The results reveal that this method can be used for the positioning error of machine tools, which helps to better understand the spatial distribution of CNC machine tool errors and provides guidance for the reasonable selection of working areas to improve the machining accuracy of parts.

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The Use of Response Surface Methodology to Optimize Parameter Adjustments in CNC Machine Tools

Mathematical Problems in Engineering ◽

10.1155/2014/797091 ◽

2014 ◽

Vol 2014 ◽

pp. 1-11 ◽

Cited By ~ 5

Author(s):

Shao-Hsien Chen ◽

Wern-Dare Jehng ◽

Yen-Sheng Chen

Keyword(s):

Regression Analysis ◽

Response Surface ◽

Machine Tools ◽

Cnc Machine Tools ◽

Contour Plot ◽

Machining Accuracy ◽

Analysis Method ◽

Cnc Machine ◽

Acceleration And Deceleration ◽

Feed Axis

This paper mainly covers a research intended to improve the circular accuracy of CNC machine tools and the adjustment and analysis of the main controller parameters applied to improve accuracy. In this study, controller analysis software was used to detect the adjustment status of the servo parameters of the feed axis. According to the FANUC parameter manual, the parameter address, frequency, response measurements, and the one-fourth corner acceleration and deceleration measurements of the machine tools were adjusted. The experimental design (DOE) was adopted in this study for taking circular measurements and engaging in the planning and selection of important parameter data. The Minitab R15 software was adopted to predict the experimental data analysis, while the seminormal probability map, Plato, and analysis of variance (ANOVA) were adopted to determine the impacts of the significant parameter factors and the interactions among them. Additionally, based on the response surface map and contour plot, the optimal values were obtained. In addition, comparison and verification were conducted through the Taguchi method, regression analysis to improved machining accuracy and efficiency. The unadjusted error was 7.8 μm; through the regression analysis method, the error was 5.8 μm and through the Taguchi analysis method, the error was 6.4 μm.

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Compensation System for Thermal Deformations of Ballscrews

Volume 3: Engineering Systems; Heat Transfer and Thermal Engineering; Materials and Tribology; Mechatronics; Robotics ◽

10.1115/esda2014-20469 ◽

2014 ◽

Cited By ~ 1

Author(s):

Michał Kowal ◽

Roman Staniek

Keyword(s):

Thermal Expansion ◽

Machine Tools ◽

Kinematic Chain ◽

Indirect Measurement ◽

Cnc Machine Tools ◽

Positioning Error ◽

Cnc Machine ◽

Measurement Systems ◽

Drive Systems ◽

Precise Machine

Accurate ballscrews are vital components of precise machine tool drive systems. As determined by direct measurement systems, the ballscrew positioning error has no bearing on the final positioning accuracy of the axis. For economical reasons, however, most machine tools are equipped with indirect measurement systems, in which errors stemming from thermal expansion of the ballscrew constitute approximately 60% of the kinematic chain error sum. Moreover, the currently observed boost in productivity of modern CNC machine tools leads to significant amplification of energy dispersal values in the nut-screw systems, due to the increased positioning velocity of the controlled axes. This, in turn, contributes to a rise of positioning error values through thermal expansion of the aforementioned ballscrews. This article deals with technological and constructional problems of screw lengthening compensation. It enumerates methods of thermal expansion-based error compensation as attained through utilization of indirect measurement systems. Finally, it presents experimental data indicating the possibility of effective screw lengthening compensation, thus proposing an alternative to the currently applied compensation systems.

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Influence of Resistant Forces on the Positioning Precision of Kinematic Feed Chains Used on CNC Machine Tools

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.657.495 ◽

2014 ◽

Vol 657 ◽

pp. 495-499

Author(s):

Marian Funaru ◽

Gheorghe Stan

Keyword(s):

Machine Tools ◽

Hydraulic System ◽

Check Valve ◽

Hydraulic Cylinder ◽

Cnc Machine Tools ◽

Cnc Machine ◽

Positioning Precision ◽

The Past ◽

Feed Axis ◽

Simulated Force

Many researches from the international literature and also those of the specialised companies from the machine tools domain, have focused in the past years on increasing the positioning precision and implicitly, the manufacturing precision of the numerically controlled machine tools. The results of these efforts have led to the elimination or compensation of different factors which affect the positioning precision of the kinematic feed chains. Nevertheless, the effects of some factors still find themselves in the positioning error of the kinematic feed chains, an important component of this error being represented by the cutting and friction force induced error (resistant errors). This paper presents a new method of experimental analysis for establishing the influence of resistant forces on the positioning precision of the kinematic feed axis. Due to the fact that measuring the positioning precision during the cutting process is difficult to achieve, the experiments were carried out using a simulated force. In order to simulate an axial force, a hydraulic system was adopted, composed of a hydraulic cylinder, a distributor valve and a check valve.

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