Thermal deviation induced by ambient temperature changes and heat generated during machine operations influences the accuracy of machine tools. A thermal test is essential to evaluate the influence of thermal deviation. ISO 230-3 provides displacement sensor-based thermal tests for machine tools. This paper proposes a machining test that enables a user to visually, by the naked eye, observe the integrated thermal influence on the tool trajectory's displacement in the direction normal to the test piece surface from the length of the machined slots. The proposed test consists of the machining of the five surfaces to observe the thermal influence of the tool position with respect to the test piece in X-, Y- and Z-directions, as well as the position of two rotary axes with respect to the tool position. The advantages of the proposed test include that it requires no measuring instrument to quantitatively evaluate the thermal error in all directions. And since the thermal influence is evaluated by observing the position where the cutting tool leaves the test piece surface, where the cutting force is zero, the influence of the cutting force on the test results can be ignored. Thermal influences of a five-axis machine tool during the warm-up cycle are investigated by experiment to validate the feasibility of the proposed method. Results show that 150 min is needed for sufficient warm-up for the selected machine tool if permissible tolerance for thermal deviation is 2.5 um for all the errors.

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