Thermally induced errors on machine tools are one of the most important error sources in precision machining. Up to 75% of the overall geometrical errors on workpieces are caused by thermal errors of the machine tool [1]. The work presented in this paper deals with the differences in the thermal behavior of machine tools for dry or wet cutting. It is shown, that the thermal error is enlarged on the machine tool under investigation with cutting fluid. Large differences can also be seen if the cutting fluid is used for a dynamic changing load case. Here, the cutting fluid has a “damping” effect on certain thermal resonance frequency of the machine tool. It is discussed how cutting fluid is influencing the chosen machining strategies for precise workpieces.

This paper presents the results of detailed thermal analysis of a 5-axis machine tool with focus on the rotary axes. The rotary axes are characterized regarding their position and orientation errors as a function of the underlying thermal load, contributing significantly to the overall accuracy. A physical model is presented, which allows the simulation of the thermal behavior of the rotary axes based on the power input to the drives of the rotary axes and the heat conduction in a swiveling rotary table unit and convection into environment. This enables an external online-compensation of thermal errors. The compensation model is verified and validated.

Thermally induced errors are responsible for up to 75% of the geometric errors on a workpiece. The demand for 5-axis machine tools is still increasing, but in the focus of thermal research there are only the influences of spindles, linear axes and the envionmental temperature change. In this article, a procedure for characterizing the thermal behaviour of rotary axes of five axes machine tools is described. Infrared camera records visualize the change of the temperature field in the machine tool structure due to underlying load cycles. Thermocouple measurements are carried out to receive detailed temperature data. They show phenomena which are typically for fast rotating axes. Displacement measurements with the measurement system R-Test enable a phenomenological modelling which can be used to predict the thermal behaviour of a rotatory axis. This can be used for a significant reduction of the total thermal error of a machine tool, and therefor to an increased accuracy.

Thermally induced errors of machine tools cause up to 75% of the geometric errors on workpieces. Research carried out in the last decades focused on influences by the environment, spindles and linear axes. With the increasing demand for five-axis machining, the rotary/swivelling axis units have to be checked and compensated for thermal errors. The R-test set-up is a proper measuring device to characterise these errors. This paper introduces a compensation approach to reduce up to 85% of the thermally induced location errors of rotary/swivelling axis units based on internal NC signals, like power supplied to drives.

Zusammenfassung Thermische Einflüsse sind für bis zu 75% der geometrischen Fehler auf Werkstücken verantwortlich. Obwohl die Nachfrage für 5-achsige Werkzeugmaschinen immer weiter steigt, stehen bis jetzt die thermischen Einflüsse von Spindeln, Linearachsen und der Umgebungstemperatur im Mittelpunkt der Forschung. Dieser Beitrag beschreibt eine Prozedur zur Charakterisierung des thermischen Verhaltens von Dreh-/Schwenkachsen von 5-achsigen Werkzeugmaschinen. Infrarotkameraaufnahmen visualisieren die Änderungen des Temperaturfeldes in der Maschinenstruktur aufgrund ausgeführter Achsbewegungen. Messungen mit Thermoelementen liefern detaillierte Temperaturdaten und zeigen spezielle Phänomene, wie sie vor allem bei schnell drehenden Rundachsen auftreten. Verlagerungsmessungen mit dem Messsystem R-Test ermöglichen zusammen mit einer phänomenologischen Modellierung die Vorhersage des thermischen Verhaltens von Rundachsen, was zu einer Reduktion des thermischen Fehlers der Maschine und somit zu einer erhöhten Bearbeitungsgenauigkeit genutzt werden kann.

Up to now, research of the thermo-mechanical deformations was focused on the environment, the spindle, the bed and the linear axes of machine tools. The thermal behavior of rotary and swiveling axes was not studied in the same detail, but they are getting more important due to the increasing requirements for 5-axis machine tools. This paper deals with the comparison of a physical and a phenomenological simulation model for a model-based compensation of thermal errors of rotary axes.

Square pyramid and conical test-pieces have been machined. Disadvantages of square pyramid in respect to conical test-piece have been shown. Following the proposal of Bossoni [1], ISO presents a test-piece for simultaneous, 5-axis movement in ISO/DIS 10791-7 [4] without specifying the exact position and orientation of the test-piece. Therefore in this paper, test-pieces milled at four different positions on a 5-axis machining center are analyzed and the results are compared with kinematic simulations. It is shown by simulation and machining, that the accuracy of the test-pieces depends not only on the geometric characteristics of the machine tool, but also on the position and orientation of the test-piece.

Thermal errors of machine tools are one of the major sources of inaccuracy. Therefore, the reduction of temperature induced deviations or the compensation of the resulting tool center point (TCP) errors have been of strong interest to the manufacturing industry for a couple of years. Up to now, the observation of the environment, the main spindle, the linear axes and the machine bed were in the focus of research, but with the rising demand for 5-axis machine tools and the increasing requirements regarding their accuracy, the analysis of the thermal behavior of rotary axes becomes more and more important. This paper gives an overview of corresponding thermal measurements of machine tools. The thermal behavior of rotary and swiveling axes is analyzed in detail. A simulation model and an approach for a phenomenological compensation of the TCP error are introduced and verified by measurements.

Up to 80% of all deviations on machine tools are caused by thermal effects [1]. To investigate the influence of thermal caused location errors of rotating and swiveling axes, different measurement set-ups (e.g. R-test) are examined. Thermal errors caused by rotary axes are compared to thermal errors caused by the environment, linear axes and spindles. It is shown that rotary axes can have a significant share in the total thermal distortions of 5-axis machine tools.