JPH07132437A - Ball screw thermal displacement correcting method - Google Patents

Abstract

PURPOSE:To correct the Thermal displacement of a ball screw always with the correct correction value of thermal displacement correction quantity of the ball screw by inputting the correction quantity, obtained by catching the temperature change of a ball screw every moment in correspondence with the actual operating state of the ball screw, into the memory of a numerical control device for rewriting. CONSTITUTION:The cumulative accuracy measurement at the standard temperature of a ball screw 2, the cumulative accuracy measurement to the optional temperature of the ball screw 2, and the correction quantity to difference temperature between the standard temperature and oiptional temperature are obtained to determine the degree of change, and the correction quantity corresponding to a change rate to the difference temperature from the standard temperature is determined every specified temperature change by measuring the temperature of cooling air A passing at least in the ball screw 2 upon the subsequent start of operation. The pitch error data of a numerical control device is successively rewritten by this correction quantity to execute the thermal displacement correction always with the correct value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting thermal displacement of a ball screw of a machine tool or the like, which is an improved method of correcting temperature by the temperature difference from room temperature.

[0002]

2. Description of the Related Art Conventionally, as a method for correcting thermal displacement of a ball screw of a machine tool or the like, the one disclosed in Japanese Patent Laid-Open No. 63-256336 is provided. However, since the change in thermal displacement of the ball screw is considered to change with time,
Although the temperature changes greatly depending on the actual operating conditions of the ball screw irrespective of time, the correction coefficient and the correction amount are constantly stored in the memory of the NC controller according to the time-controlled thermal displacement correction amount of the ball screw. However, there is a drawback that the correction control is performed with a correction value having an error with respect to the correct thermal displacement correction amount of the ball screw.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to solve the above-mentioned problems of the prior art, and to grasp the temperature change momentarily according to the actual operating condition of the ball screw. The correction coefficient and the correction amount are stored in the memory of the NC controller and rewritten, and the thermal displacement correction of the ball screw is always performed with the correct correction value of the thermal displacement correction amount of the ball screw.

[0004]

The concrete means of the present invention is as follows.
Cumulative accuracy measurement at standard temperature of the ball screw, cumulative accuracy measurement at arbitrary temperature of the ball screw, and correction amount for the difference in temperature between the standard temperature and arbitrary temperature are obtained to determine the degree of change, At the start of operation, at least the temperature of the cooling air passing through the ball screw is measured to determine a correction amount corresponding to the change rate with respect to the temperature difference from the standard temperature for each predetermined temperature change. This is a method for correcting thermal displacement of a ball screw, which is characterized in that error data is rewritten at any time and the thermal displacement of the ball screw is always corrected with a correct correction value.

[0005]

According to the present invention, the ball screw is cooled corresponding to the actual operating condition of the ball screw in a machine tool and the temperature change of the cooling air is accurately grasped moment by moment.
The correction coefficient and the correction amount are put in the memory of the NC control device and rewritten. Then, the thermal displacement correction of the ball screw can always be executed with the correct correction value of the thermal displacement correction amount of the ball screw.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below. Figure 1
2 is a schematic front view showing a thermal displacement correction system for a ball screw of a machine tool according to the present invention, and FIG. 2 is a thermal displacement tendency diagram of the ball screw according to the present invention. FIG. 3 is a flow chart showing a method for correcting thermal displacement of a ball screw of a machine tool according to the present invention.

In FIG. 1, reference numeral 1 denotes a bed of a machine tool or the like, and a moving body T arranged on the upper surface of the moving body T has a nut 5 on the rear surface screwed onto a ball screw 2 and a servo motor M mounted on one end of the ball screw 2. To move left and right. Both ends of the ball screw 2 are supported by bearings 3 and 4, and the rotational force of the servomotor M is smoothly received and transmitted to the moving body T. Although not shown, the moving body T is supported by a sliding surface and moves smoothly. A machine tool having three axes orthogonal to each other has three sets of the moving bodies T.

Next, the drive system of the servomotor M is NC
The control device 10 includes a driver D that drives the servo motor M by a movement control command issued from the control device 10, and an encoder E that detects a rotation amount of the servo motor M and feeds back to the NC control device 10.

The present invention is provided for the drive system of the servomotor M. Since the temperature of the ball screw 2 is indirectly and accurately measured, the temperature of the nut 5 screwed into the ball screw is adjusted. The sensor S1 is provided. Then, the temperature sensor S2 for measuring the body temperature is attached to a portion of the body 1 such as the bed 1 where the temperature change is small (for indirectly measuring the room temperature). Further, a temperature sensor S3 for the cooling air A passing through the ball screw is provided on the outlet side to measure the temperature of the ball screw.

Information from the three temperature sensors S1, S2 and S3 is input to the arithmetic processing section C. As shown in FIG. 2, the arithmetic processing unit C is a ball screw standard (reference).
Cumulative accuracy measurement (measured value) at temperature, cumulative accuracy measurement (measured value) for arbitrary temperature of ball screw (temperature difference of 1 ° C), and correction amount for the difference between standard temperature and arbitrary temperature Determine the degree of change. Then, when the operation is started, the correction amount corresponding to the rate of change with respect to the temperature difference from the standard temperature is determined by measuring the temperature of the nut screwed on the ball screw 2 for each predetermined temperature change. The pitch error data of the NC control device 10 is rewritten according to this correction amount at any time, and the thermal displacement correction of the ball screw is always executed with a correct correction value.

Next, a method of correcting thermal displacement of a ball screw according to the present invention will be described with reference to FIGS. First, prior to the start of operation
"Measurement of cumulative accuracy at standard temperature of ball screw" (A)
"Accurate accuracy measurement for arbitrary temperature of ball screw (every 1 ° C in temperature difference)" (a), "Calculate correction amount for difference in temperature between standard temperature and arbitrary temperature" (c), and "For difference in temperature" Determine the degree of change ”(d). Then, when the operation is started, "nut temperature measurement and cooling air temperature measurement" (f) is performed to measure the temperature of the ball screw 2, and, for example, the temperature difference between the standard temperature and the arbitrary temperature Determine the correction amount according to the rate of change with respect to temperature "(ki). Then, based on this correction amount, the NC controller 10 "rewrites the pitch error data as needed" (K), so that the thermal displacement correction of the ball screw can always be executed with a correct correction value.

Based on the information from the three temperature sensors S1, S2 and S3, the arithmetic processing section C measures the cumulative accuracy at the standard (reference) temperature of the ball screw (actual measurement value) and the arbitrary temperature (temperature difference) of the ball screw. Accurately determine the degree of change by obtaining the temperature such as cumulative accuracy measurement (measured value) for each 1 ° C. with high accuracy. In particular, since the thermal displacement correction method is performed after cooling the ball screw to suppress the thermal displacement to the minimum, highly accurate correction is possible.

Needless to say, the present invention is not limited to the above-described embodiments, and design changes can be made within the scope of the invention. For example, the number of axes of the machine tool does not matter.

[0014]

According to the present invention, the cumulative accuracy measurement of the ball screw at the standard temperature, the cumulative accuracy measurement of the ball screw at an arbitrary temperature, and the correction amount for the temperature difference between the standard temperature and the arbitrary temperature are obtained and the change thereof is calculated. The degree is determined, and at the start of operation thereafter, the correction amount corresponding to the rate of change with respect to the temperature difference from the standard temperature is determined for each predetermined temperature change by measuring the temperature of the bearing member group engaged with the ball screw. The pitch error data of the NC controller is rewritten to the correction amount as needed, and the thermal displacement correction of the ball screw is always executed with the correct correction value, so that the temperature change of the environment or the temperature change of the machine is drastic like machine tools. In the above, the effect of the optimum action that can assure the precise feeding of the moving body with high accuracy can be obtained.

In particular, since the thermal displacement correction method is carried out after the ball screw is cooled to suppress its thermal displacement to a minimum, highly accurate correction is possible, and this accurate correction amount is NC. It is possible to obtain the effect that the thermal displacement correction of the ball screw can always be performed with the correct correction value of the correct thermal displacement correction amount of the ball screw by putting it in the memory of the control device and rewriting.

[Brief description of drawings]

FIG. 1 is a schematic front view showing a thermal displacement correction system for a ball screw of a machine tool according to the present invention.

FIG. 2 is a thermal displacement tendency diagram of the ball screw according to the present invention.

FIG. 3 is a flowchart showing a method for correcting thermal displacement of a ball screw of a machine tool according to the present invention.

[Explanation of symbols]

 1 bed 2 ball screw 3,4 bearing 5 nut 10 NC control device 11 memory A cooling air C arithmetic processing unit T moving body M servo motor S1, S2, S3, S4 temperature sensor

Claims (1)

[Claims] 1. A cumulative precision measurement of a ball screw at a standard temperature, a cumulative precision measurement of a ball screw at an arbitrary temperature, and a correction amount for a temperature difference between the standard temperature and the arbitrary temperature is obtained to determine the degree of change. However, at the start of operation thereafter, at least the correction amount corresponding to the change rate with respect to the difference in temperature from the standard temperature is determined for each predetermined temperature change by measuring the temperature of the cooling air passing through the ball screw. A method for correcting thermal displacement of a ball screw, characterized in that the pitch error data of the NC control device is rewritten at any time, and the thermal displacement of the ball screw is always corrected with a correct correction value.