Modeling and compensation method for the spindle's radial thermal drift error in a horizontal CNC lathe

Patent metadata

Field	Value
Publication number	US-10838392-B2
Application number	US-201716325984-A
Country	US
Kind code	B2
Filing date	Nov 6, 2017
Priority date	Nov 6, 2017
Publication date	Nov 17, 2020
Grant date	Nov 17, 2020

Abstract

The invention provides a method for modeling and compensating for the spindle's radial thermal drift error in a horizontal CNC lathe, which belongs to the field of error compensation technology of CNC machine tools. Firstly, the thermal drift error of two points in the radial direction of the spindle and the corresponding temperature of the key points are tested; then the thermal inclination angle of the spindle is obtained based on the thermal tilt deformation mechanism of the spindle, and the correlation between the thermal inclination angle and the temperature difference between the left and right sides of the spindle box is analyzed. According to the positive or negative thermal drift error of the two points that have been measured and the elongation or shortening of the spindle box on the left and right sides, the thermal deformation of the spindle is then classified and the thermal drift error model under various thermal deformation attitudes is then established. Then the influence of the size of the machine tool's structure on the prediction results of the model is analyzed. In real-time compensation, the thermal deformation attitude of the spindle is automatically judged according to the temperature of the key points, and the corresponding thermal drift error model is automatically selected to apply the compensation to the spindle. The method is used to distinguish the thermal deformation attitude of the spindle in a CNC lathe, and the thermal deformation mechanism is used to predict the radial thermal drift error of the spindle.

First claim

We claim:

1. The invention relates to a method for modeling and compensating for the spindle's radial thermal drift error in a horizontal CNC lathe, comprising:
measuring the radial thermal drift error and the temperature of the key points of the spindle of a CNC; lathe, said measuring the radial thermal drift error comprising:
testing the radial thermal drift error and temperature of the spindle of a CNC lathe; using two temperature sensors respectively to measure the temperatures T 1 and T 2 of both the left and right sides of the spindle box, using two displacement sensors to measure the error in the X direction of the two location points of the detecting check bar clamped by the spindle; during the test, heating the spindle by rotating the spindle at a certain speed for a few hours, and then stopping the spindle for a few hours to cool down, wherein the thermal error e i of the spindle in the vertical direction produces the thermal error component e i,x in the X direction, and the thermal errors e 1,x and e 2,x of the spindle in the X direction are calculated according to the following formula:
e 2,x =sin(α xdir )× e 2   (1)

e 1,x =sin(α xdir )× e 1   (2)

wherein in the above formula, α xdir is the tilt angle of the X axis of lathe, i=1 or 2, 1 indicates the right side and 2 indicates the left side;

analyzing between the thermal inclination and the temperature difference of the spindle, said analyzing comprising:
calculating the thermal dip angle of the spindle, after being heated, using the following formula:

φ
s

=

arctan
⁢

e

1
,
x

-

e

2
,
x

sin
⁢

⁢

(

α
xdir

)

×

L
snr

(
3
)

wherein in the above formula, φ s is the thermal dip angle of the spindle and L snr is the distance between the two error measuring points;
determining the relation diagram between the thermal dip φ s of the spindle and the difference of the two temperatures ΔT is then determined, ΔT=T 1 −T 2 ,
analyzing the similarity of the two curves; and
calculating the correlation between φ s and ΔT according to the following formula:

R
⁡

(

φ
s

,

Δ
⁢

⁢
T

)

=

Cov
⁡

(

φ
s

,

Δ
⁢

⁢
T

)

Cov
⁡

(

φ
s

,

φ
s

)

⁢

Cov
⁡

(

Δ
⁢

⁢
T

,

Δ
⁢

⁢
T

)

(
4
)

wherein in the above formula, R is the correlation matrix between φ s and ΔT, Cov (φ s , ΔT) is the covariance matrix between φ s and ΔT;

setting up the error models of the spindle's radial thermal drift under different thermal deformations, and setting up comprising:
according to the sign of the two error data points, e 1,x and e 2,x , and the extension or shortening of the spindle box on the left and right sides, dividing the

Assignees

• Univ Dalian Tech

Inventors

• Liu Kuo
• Wang Yongqing
• Liu Haibo
• Li Te
• Liu Haining
• Li Dawei

Classifications

• G05B2219/49219

  Compensation temperature, thermal displacement · CPC title

• B23Q11/14

  Methods or arrangements for maintaining a constant temperature in parts of machine tools · CPC title

• G05B19/404 Primary

  characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia (G05B19/19, G05B19/41 take precedence) · CPC title

• B23Q17/22

  for indicating or measuring existing or desired position of tool or work {(B23Q16/005 takes precedence)} · CPC title

• B23Q15/18

  Compensation of tool-deflection due to temperature or force · CPC title