• Journal of the Korean Society for Precision Engineering
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• v.30 no.5
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• pp.507-512
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• 2013

This paper proposes a new model to compensate for errors of a five-axis machine tool. A matrix with error components, that is, an error matrix, is separated from the error synthesis model of a five-axis machine tool. Based on the kinematics and inversion of the error matrix which can be obtained not by using a numerical method, an error compensation model is established and used to calculate compensation values of joint variables. The proposed compensation model does not need numerical methods to find the compensation values from the error compensation model, which includes nonlinear equations. An experiment using a double ball-bar is implemented to verify the proposed model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.650-653
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• 2002

In this paper, a methodology to assess machine tool errors quickly is suggested using a touch probe and a cube array artifact. Parameterized error models derived are expressed of model coefficient vectors and backlash errors to be determined. To determine the unknown model coefficient vectors, a cube array artifact is proposed. Considering CMM measurement data of cube vertex coordinates. error vectors for all axes ate obtained and used to complete the error model. Some simulation results show that the suggested error model can follow the true values within 10$\mu\textrm{m}$. To verify the error model, a circular part with two concentric circles is measured and simulated. The results show that the differences between CMM and OMM radius errors are smaller than 15$\mu\textrm{m}$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.501-504
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• 2001

The use of error compensation techniques has been recognized as an effective way in the improvement of the accuracy of a machine tool. The laser measurement method for identifying position errors of machine tool has the disadvantages such as high cost, long calibration time and usage of volumetric error synthesis model. Accordingly, this paper deals with analysis of the position errors of a machine tool using ball bar test without using complicated error synthesis model. Statistical analysis method was adopted in this paper for deriving position errors using hemispherical helix ball bar test.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.48-53
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• 2010

5-axis CNC machining now is getting popular because it can deal with complex shapes such as impeller, turbine blade and propeller without additional equipment or process, proving a set of various tool orientations. CAM software related to 5-axis machining is being developed quickly so that users can take advantage of potential capacities of 5-axis machine tools. However, only a few researches can be found in the area of control strategy development for 5-axis machining. This paper proposes a 5-axis cross-coupling control system based on a novel tool orientation error model. The proposed tool orientation error model provides accurate information on the tool orientation error in real time, which in turn enables directly controlling the tool orientation accuracy. The proposed control system also employs a contour error model to calculate the contour error and reflect it in the control as well. The accuracy of the proposed tool orientation error model is verified and the performance of the 5-axis cross-coupling control system in terms of both contouring and tool orientation accuracy is evaluated through computer simulations compared with existing 5-axis control systems.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.3 s.96
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• pp.215-221
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• 1999

The object of the thermal error compensation system in machine tools is improving the accuracy of a machine tool through real time error compensation. The accuracy of the machine tool totally depends on the accuracy of thermal error model. A thermal error model can be obtained by appropriate combination of temperature variables. The proposed method for optimal variable selection in the thermal error model is based on correlation grouping and successive regression analysis. Collinearity matter is improved with the correlation grouping and the judgment function which minimizes residual mean square is used. The linear model is more robust against measurement noises than an engineering judgement model that includes the higher order terms of variables. The proposed method is more effective for the applications in real time error compensation because of the reduction in computational time, sufficient model accuracy, and the robustness.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.1
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• pp.1-6
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• 2014

This paper describes a method of estimating and evaluating the volumetric errors of multi-axis machine tools. The estimation method is based on a generic model that was developed from conventional kinematic error models for the geometric and thermal errors to help predict the volumetric error easily in various configurations. To demonstrate the advantages of the model, an application in the early stages of a five-axis machine tool design is presented as an example. The model was experimentally evaluated for a four-axis machine tool by using the data from ISO230-6 and R-test measurements to compare the estimated and measured volumetric errors.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.577-578
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• 2009

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.367-372
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• 2000

Accuracy of a machined component is determined by the relative motion between the cutting tool and the workpiece. One of the important factors which affects the accuracy of this relative motion is the geometric error of machine tools. In this study, geometric error is modeled using form shaping motion of machine tool, where a form shaping function is derived from the homogeneous transformation matrix. Geometric errors are measured by laser interferometer. After that, the local positioning error can be estimated from the form shaping model and geometric error data base. From this information, we can remodel the part by shifting the design surface to the amount of positional error. By generating tool path to the redesigned surface, we can reduce the machining error.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.3
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• pp.28-34
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• 1999

The objective of this study is to estimate and to compensate far the volumetric error of a workpiece influenced by the geometric error of a machine tool. In this paper, the volumetric error is defined and the error synthesis model is presented. Then, the volumetric error of workpiece is calculated and compared through the simulation, and a new tool-path is generated to compensate for the error in the post-processor of CAM system using the error synthesis model. By this method, the error is compensated without modification or replacement of a machine tool being in use.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.1003-1006
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• 2002

In machining free-form curves with a machine tool equipped with parallel device, improving contouring accuracy is very important. In this paper, we present contouring control algorithm far parallel machine tool. The relation between the error in Joint space and the error in catesian space is evaluated, and we estimate contouring error vector which efficiently determines the variable gains for the cross coupled control. To show the validity of the algorithm, the contouring control is simulated for free form contour trajectory in cubic parallel machine tool model.