Main shaft thermal error compensation method

Abstract

The invention discloses a main shaft thermal error compensation method, and belongs to the field of machine tool machining, the main shaft is driven to rotate for preset time, the temperature T of a bearing in the preset time period is collected through a temperature sensor, and main shaft thermal error data E in the preset time period is collected through a displacement sensor; correcting the original temperature data T to obtain a temperature correction value Tc, performing linear regression analysis on the main shaft thermal error data E and the processed temperature Tc to obtain a compensation coefficient k, calculating a thermal error compensation value according to the compensation coefficient k, and taking the minimum compensated thermal error E2 as a target to obtain values of a weighting coefficient alpha and a time interval delta t; and the position of the main shaft is adjusted according to the thermal error compensation value D, so that the thermal error is reduced to a greater extent, and the surface quality of a machined workpiece is improved.

Description

Technical Field

[0001] This invention relates to the field of machine tools, and in particular to a method for compensating for spindle thermal errors. Background Technology

[0002] When the spindle rotates at high speed, bearing friction generates heat. Due to thermal deformation, the spindle system produces machining errors, accounting for 40%-70% of the total error, which is a core limiting factor for the accuracy of high-speed precision machine tools. To reduce machining errors, machining compensation is performed on the spindle.

[0003] Existing spindle thermal compensation methods typically compensate directly based on the collected temperature. Since the temperature data is unprocessed, the compensation is greatly affected by abnormal temperature fluctuations, resulting in poor stability and the inability to guarantee the surface quality of the workpiece. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a spindle thermal error compensation method with high compensation accuracy.

[0005] One of the objectives of this invention is achieved through the following technical solution: Data acquisition: Drive the spindle to rotate for a preset time, first make the spindle rotate and heat up to a steady state, then stop rotating and cool down to a steady state. The temperature T of the bearing is collected by the temperature sensor within the preset time period, and the thermal error data E of the spindle is collected by the displacement sensor within the preset time period. The thermal error data E includes the heating stage and the cooling stage. Data processing: The CNC system updates the real-time temperature value according to the set time interval Δt. Each time the real-time temperature is updated, the original temperature data T is corrected to obtain the temperature correction value Tc. Based on the real-time temperature value Ti+1 and the existing temperature processing value Tci in the system, Tci+1 is calculated and stored. Tci+1=αTci+(1-α)(Ti+1-Tci), where Tci is the i-th original temperature data and α is the weighting coefficient. Predicting the compensated thermal error: Perform linear regression analysis on the spindle thermal error data E and the processed temperature Tc to obtain the compensation coefficient k. Calculate the thermal error compensation value D=k*Tc based on the compensation coefficient k. The compensated thermal error E2=D+E. Weighting coefficient calculation: With the goal of minimizing the compensated thermal error E2, the values ​​of the weighting coefficient α and the time interval Δt are obtained; Spindle compensation: Adjust the spindle position according to the thermal error compensation value D.

[0006] Furthermore, in the data acquisition step, the temperature T is a dataset extracted according to time interval Δt.

[0007] Furthermore, in the spindle compensation step, the thermal error compensation value is refreshed at intervals of Δt, and the spindle position is adjusted according to the latest thermal error compensation value.

[0008] Furthermore, the weighting coefficient α ranges from 0.001 to 0.02, and the time Δt ranges from 1 to 10 seconds.

[0009] Furthermore, in the data acquisition step, the temperature acquired by the temperature sensor is the temperature of the front bearing.

[0010] Furthermore, in the data acquisition step, the displacement sensor is an eddy current displacement sensor.

[0011] Furthermore, in the data processing step, the temperature correction value resolution is 0.001 degrees, and the spindle position adjustment amount is limited to 0.1~0.2μm each time the temperature adjustment compensation value is refreshed.

[0012] Compared to existing technologies, the spindle thermal error compensation method of this invention involves driving the spindle to rotate for a preset time, collecting the bearing temperature T within the preset time period using a temperature sensor, and collecting the spindle thermal error data E within the preset time period using a displacement sensor. The original temperature data T is corrected to obtain a temperature correction value Tc. Linear regression analysis is performed on the spindle thermal error data E and the processed temperature Tc to obtain a compensation coefficient k. The thermal error compensation value is calculated based on the compensation coefficient k, with the goal of minimizing the compensated thermal error E2, resulting in the values ​​of the weighting coefficient α and the time interval Δt. The spindle position is adjusted based on the thermal error compensation value D, thereby further reducing the thermal error and improving the surface quality of the machined workpiece. Attached Figure Description

[0013] Figure 1 This is a flowchart of the spindle thermal error compensation method of the present invention; Figure 2 The main spindle thermal error versus temperature curve; Figure 3 This is an error curve diagram before and after compensation by the spindle thermal error compensation method of the present invention. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or it can be fixed through another intermediate component. When a component is said to be "connected to" another component, it can be directly connected to the other component or it may be fixed through another intermediate component. When a component is said to be "set on" another component, it can be set directly on the other component or it may be set through another intermediate component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0017] Please see Figure 1 The present invention provides a spindle thermal error compensation method, comprising the following steps: Data acquisition: Drive the spindle to rotate for a preset time, first make the spindle rotate and heat up to a steady state, then stop rotating and cool down to a steady state. The temperature T of the bearing is collected by the temperature sensor within the preset time period, and the thermal error data E of the spindle is collected by the displacement sensor within the preset time period. The thermal error data E includes the heating stage and the cooling stage. Data processing: The CNC system updates the real-time temperature value according to the set time interval Δt. Each time the real-time temperature is updated, the original temperature data T is corrected to obtain the temperature correction value Tc. Based on the real-time temperature value Ti+1 and the existing temperature processing value Tci in the system, Tci+1 is calculated and stored. Tci+1=αTci+(1-α)(Ti+1-Tci), where Tci is the i-th original temperature data and α is the weighting coefficient. Predicting the compensated thermal error: Perform linear regression analysis on the spindle thermal error data E and the processed temperature Tc to obtain the compensation coefficient k. Calculate the thermal error compensation value D=k*Tc based on the compensation coefficient k. The compensated thermal error E2=D+E. Weighting coefficient calculation: With the goal of minimizing the compensated thermal error E2, the values ​​of the weighting coefficient α and the time interval Δt are obtained; Spindle compensation: Adjust the spindle position according to the thermal error compensation value D.

[0018] In the data acquisition step, temperature T is the dataset extracted according to time intervals Δt. Time Δt ranges from 1 to 10 seconds. The temperature acquired by the temperature sensor is the temperature of the front bearing. The displacement sensor is an eddy current displacement sensor.

[0019] In the data processing step, the processed temperature resolution is 0.001 degrees.

[0020] In the weighted coefficient calculation step, the compensated thermal error E2 is 0.0005mm-0.005mm.

[0021] In the spindle compensation step, compensation is performed through the CNC system PLC program. A timer is set to control the on / off state, and the temperature is read, processed, and the compensation value is refreshed at regular intervals Δt. The spindle position is adjusted based on the latest thermal error compensation value. To improve the stability of the compensation value, frequent refreshes are avoided; the time interval is typically set to 1-10 seconds, and the weighting coefficient α ranges from 0.001 to 0.02. Each time the temperature compensation value is refreshed and adjusted, the spindle position adjustment is limited to 0.1-0.2 μm.

[0022] like Figure 2 As shown, the original temperature curve in the prior art exhibits abnormal fluctuations and a resolution of only 0.1 degrees, affecting the compensation effect. This application processes the temperature data, resulting in a smoother curve and improved resolution to 0.001 degrees. Previously, the error lagged behind temperature changes, exhibiting poor correlation. Through data processing, the patterns of temperature and error changes become more consistent, improving the correlation between temperature and error.

[0023] like Figure 3 As shown, the compensation procedure in the prior art results in an error of 0.025 mm after compensation, with an error fluctuation of 0.003 mm. The compensation procedure in this case results in an error of 0.012 mm after compensation, with an error fluctuation of only 0.001 mm, which can reduce thermal errors to a greater extent and improve the surface quality of the processed workpiece.

[0024] Compared to existing technologies, the spindle thermal error compensation method of this invention involves driving the spindle to rotate for a preset time, collecting the bearing temperature T within the preset time period using a temperature sensor, and collecting the spindle thermal error data E within the preset time period using a displacement sensor. The original temperature data T is corrected to obtain a temperature correction value Tc. Linear regression analysis is performed on the spindle thermal error data E and the processed temperature Tc to obtain a compensation coefficient k. The thermal error compensation value is calculated based on the compensation coefficient k, with the goal of minimizing the compensated thermal error E2, resulting in the values ​​of the weighting coefficient α and the time interval Δt. The spindle position is adjusted based on the thermal error compensation value D, thereby further reducing the thermal error and improving the surface quality of the machined workpiece.

[0025] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These are all equivalent modifications and improvements made to the above embodiments based on the essential technology of the present invention, and all of these fall within the protection scope of the present invention.

Claims

1. A method for compensating for spindle thermal errors, characterized in that, Includes the following steps: Data acquisition: Drive the spindle to rotate for a preset time, first make the spindle rotate and heat up to a steady state, then stop rotating and cool down to a steady state. The temperature T of the bearing is collected by the temperature sensor within the preset time period, and the thermal error data E of the spindle is collected by the displacement sensor within the preset time period. The thermal error data E includes the heating stage and the cooling stage. Data processing: The CNC system updates the real-time temperature value according to the set time interval Δt. Each time the real-time temperature is updated, the original temperature data T is corrected to obtain the temperature correction value Tc. Based on the real-time temperature value Ti+1 and the existing temperature processing value Tci in the system, Tci+1 is calculated and stored. Tci+1=αTci+(1-α)(Ti+1-Tci), where Tci is the i-th original temperature data and α is the weighting coefficient. Predicting the compensated thermal error: Perform linear regression analysis on the spindle thermal error data E and the processed temperature Tc to obtain the compensation coefficient k. Calculate the thermal error compensation value D=k*Tc based on the compensation coefficient k. The compensated thermal error E2=D+E. Weighting coefficient calculation: With the goal of minimizing the compensated thermal error E2, the values ​​of the weighting coefficient α and the time interval Δt are obtained; Spindle compensation: Adjust the spindle position according to the thermal error compensation value D.

2. The spindle thermal error compensation method according to claim 1, characterized in that: In the data acquisition step, the temperature T is the dataset extracted according to the time interval Δt.

3. The spindle thermal error compensation method according to claim 2, characterized in that: In the spindle compensation step, the thermal error compensation value is refreshed at intervals of Δt, and the spindle position is adjusted according to the latest thermal error compensation value.

4. The spindle thermal error compensation method according to claim 3, characterized in that: The weighting coefficient α ranges from 0.001 to 0.02, and the time Δt ranges from 1 to 10 seconds.

5. The spindle thermal error compensation method according to claim 1, characterized in that: In the data acquisition step, the temperature collected by the temperature sensor is the temperature of the front bearing.

6. The spindle thermal error compensation method according to claim 1, characterized in that: In the data acquisition step, the displacement sensor is an eddy current displacement sensor.

7. The spindle thermal error compensation method according to claim 1, characterized in that: In the data processing step, the temperature correction value has a resolution of 0.001 degrees, and the spindle position adjustment is limited to 0.1~0.2μm each time the temperature adjustment compensation value is refreshed.

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