Application of the hottest laser interferometer in

The application of laser interferometer in the maintenance of CNC machine tools

a four axis machining center has a vibration fault of the machine tool in the processing process. Check the mechanical parts of the machine tool, confirm that the y-axis bearing is worn, replace the bearing, and the machine tool is normal. The original point and positioning accuracy of the machine tool are lost due to the replacement of the bearing of the machine tool. In order to restore the accuracy of the machine tool, the y-axis positioning accuracy of the machine tool is detected and compensated with a laser interferometer, so as to restore the accuracy of the machine tool

1. Troubleshooting

check the operation of the mechanical parts of each axis of the machine tool respectively, and it is found that the vibration sound is obvious when the Y axis moves. Check the y-axis transmission parts, find the wear of the angular contact bearing of the y-axis, find the specific cause of the failure, and deal with the machine tool failure

purchase and replace the bearing according to the bearing model, reassemble the bearing, connect the y-axis servo motor, and the machine tool can operate normally. However, due to the replacement of the y-axis bearing and the reassembly of the y-axis transmission parts of the machine tool, the origin and positioning accuracy of the Y-axis of the machine tool are lost. In order to restore the accuracy of the machine tool, the y-axis accuracy of the machine tool needs to be recalibrated. At present, laser interferometer is the best method to calibrate the positioning accuracy of machine tools. Therefore, this paper uses a laser interferometer to detect and compensate the y-axis accuracy of the machine tool and restore the accuracy of the machine tool

2. Accuracy recovery

due to the reassembly of the y-axis transmission parts of the machine tool, the y-axis origin needs to be reset. The specific steps are as follows:

(1) set the parameter 1815#4, Y-axis = 0, the absolute pulse encoder origin position

(2) set the parameter 1006 × 5, Y axis = 0, and the direction of returning to the reference point is positive

(3) shut down and restart the machine tool

(4) manually move the Y-axis of the machine tool to make the servo motor rotate for more than 1 revolution

(5) shut down and restart the machine tool

(6) select the mode to move the Y axis of the machine tool to the new origin position

(7) select the machine tool in MDI mode, set the parameter 1815 4, Y axis = 1

(1) install the laser interferometer

the detection equipment of the laser interferometer adopts the xl-80 laser head, linear measurement mirror, linear interferometer and wavelength compensation unit produced by rienshaw company and the corresponding test software. The specific installation and connection diagram is shown in Figure 1. ① Install the laser head. Install the xl-80 laser head horizontally on the tripod, connect the power supply, turn on the laser head and preheat for 5 minutes to make the laser stop stably: when the injection molding cycle is interrupted; ② Install XC compensation unit. Connect the material temperature sensor and air temperature sensor with XC compensation unit. ③ Install the measuring lens group. Install the linear reflector and linear interference mirror on the spindle and workbench of the machine tool, and align the laser. Adjust the position of xl-80 laser head and reflector so that the beam passes through the interference mirror and is reflected back by the reflector. Move the laser head, interference mirror and reflector so that the measuring beam and reference beam overlap in the middle of the optical target. Move along the Y axis within the coordinate travel range to ensure that the two beams of light remain overlapping. ④ Run the linearity test software. Connect the laser head and XC compensation unit to the computer, and then open the linearity test software

(2) setting of detection data

before detection, it is necessary to set the system parameters, mainly to determine the moving range, detection interval, detection times and detection points of the detection axis. The specific setting data are shown in Table 1

in addition to setting the detection data, in order to obtain better compensation accuracy, the pitch error compensation value and reverse clearance of the machine tool should be set to 0. Enter the system parameter interface of FANUC 0I MD NC system. The specific methods are as follows: ① put the system in "MDI" mode; ② Open the setting screen and set the "write parameter" to 1; ③ Set the parameter 8135#0 = 0 to confirm that the pitch compensation function has been turned on; ④ 3620 compensation reference point y axis = 218; ⑤ 3621 negative minimum point compensation number, Y-axis = 200; ⑥ 3622 positive maximum point compensation number, Y axis = 219; ⑦ 3623 compensation magnification, Y-axis = 1; ⑧ 3624 compensation interval, Y-axis = 30000; ⑨ Open the pitch error compensation table and clear the data in the range of 200-218; ⑩ 1851 reverse can achieve accurate arbitrary waveform control gap, Y-axis =0; Restart the machine tool

(3) write the detection program

write the machine tool detection program according to the data in Table 1. The program is as follows:

o1001; (main program)

n10 M98 P1 L3;//Call subroutine I and detect

n20 M30 for 3 times

O0001; (subroutine I)

n10 G90 G01 F2000

N20 Y5. 0;

N30 G4 X2. 0;

n40 pressure testing machine measurement precautions, fixture selection fixture selection common fatigue classifications are: spring fatigue testing machine, rubber fatigue testing machine, sucker rod fatigue testing machine, etc. Y0 is very critical

N50 G4 X4. 0;

N60 M98 P2 L17;//Call subroutine II

n70 y-5 0;

N80 G4 X2. 0;

N90 Y5. 0;

N100 G4 X4. 0

N110 M98 P3 L17;//Call subroutine III

n120 M99

O0002; (subroutine II)

n10 G91 y-30 0;

N20 G4 X4. 0;

N30 M99;

O0003; (sub process III)

n10 G91 y30 0;

N20 G4 X4. 0;

N30 M99;

(4) data acquisition

run the Y-axis of the machine tool to the origin → run Renishaw laser XL linear measurement software (the software setting value corresponds to table 1) → run the test program → conduct data acquisition and collect the data curve

2. 3 positioning accuracy compensation

analyze the collected data, set the compensation type as incremental value, convert the symbol into compensation value, and calculate the pitch error compensation data with software, as shown in Figure 3

according to the pitch compensation data in Figure 3, the specific steps are as follows:

(1) reverse clearance compensation. The reverse clearance of the y-axis is 0.001 mm. Set the reverse clearance compensation parameter 1851, and the value of Y axis is 1

(2) pitch error compensation. Open the system pitch error compensation table and input the compensation value in Figure 3. The specific data are shown in Table 2

2. 4 positioning accuracy verification

after Y-axis compensation of the machine tool, run the test program again to measure the positioning accuracy of the machine tool

and collect data

y-axis positioning accuracy is 0 002 958 mm, accuracy has been restored

3. Conclusion

during the maintenance of CNC machine tools, pay attention to the restoration of the accuracy of the machine tools after the mechanical faults of the machine tools are eliminated and the functions are restored, so as to ensure the working accuracy of the machine tools. Laser interferometer has the advantages of high measurement accuracy, stable data, simple operation and so on. It is especially suitable for the positioning accuracy detection and compensation of CNC machine tools. The y-axis positioning accuracy and reverse clearance of the machine tool are compensated by laser interferometer, and the positioning accuracy of the NC machine tool is effectively restored