JPS6036358B2 - Laser processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a laser processing apparatus that irradiates a workpiece with a laser beam to perform processes such as welding, cutting, and heat treatment on the workpiece.

A conventionally known laser processing device is shown in FIG.

In the figure, 1 is the laser oscillator, 2 is the laser beam emitted from the laser oscillator 1, and 3 is the condenser (parabolic mirror).
, 4 is a workpiece, 5 is a power meter that measures the output of the laser beam, and 6 is a laser power control device that feeds back the laser power signal sent from the power meter 5 to the laser oscillator 1. . Next, the operation will be explained.

First, a laser beam 2 emitted from a laser oscillator 1 is shielded by a power meter 5 provided in its path, and the output is measured. The laser power control device 6 is the power meter 5
The laser oscillator 1 is controlled according to the measured output and adjusted to a predetermined laser power. Thereafter, the power meter 5 is removed from the beam path as shown by the dotted line, and the laser beam 2 is focused to a predetermined spot size by the condenser 3 and irradiated onto the surface of the workpiece 4. Energy absorbed by the surface of the workpiece 4 is converted into thermal energy, and the workpiece 4 is welded, cut, or heat-treated. Furthermore, after the processing is completed, the path of the laser beam 2 is again blocked by the power meter 5 and the laser output is measured to confirm the laser output used for processing. However, the beam energy Pa actually absorbed by the workpiece 4 is expressed by the beam output P emitted from the laser oscillator 1, the optical energy EM lost as thermal energy in the condenser 3, and the workpiece 4. reflected light energy E
This is the remainder after subtracting R.

That is, the beam energy actually absorbed by the workpiece Pa=
P-(EM+ER), and especially when processing metals with high reflectance such as copper and aluminum, ER becomes large and Pa is 10% or less of P. Furthermore, when processing a metal that evaporates easily, such as magnesium, as the processing time becomes longer, impurities are deposited on the surface of the condenser 3 and the reflectance decreases, resulting in an increase in EM. However, in the conventional apparatus, only the laser output P emitted from the laser oscillator 1 is measured, and P is multiplied by the reflectance of a general material, and P is taken as the absorbed energy of the workpiece. However, the reflectance does not correspond sufficiently with the reflectance of the surface of the workpiece 4 that is actually irradiated with the laser beam, and as a result, the surface condition of the workpiece 4 may be uneven and the reflectance may change, or the If the reflectance changes greatly depending on the shape of the object 4, the beam output of the laser oscillator 1 cannot be controlled in response to changes in the object 4 during processing, which may cause non-uniformity or defects in the processed product. It was the cause of this. In particular, this problem is unavoidable in processes that do not melt the surface, such as surface heat treatment of steel, and in cutting metal plates. Further, as shown in FIG. 2, after irradiating the workpiece with a laser beam, the workpiece 4 is placed in pure water 8 in a container 7 made of a heat insulating material.
There is also a method of making the temperature distribution of the pure water 8 uniform, then measuring the temperature rise of the pure water 8 with a thermometer 9, and calculating the laser output absorbed by the workpiece 4 from this measurement value. Object 4 - It is not possible to measure the laser energy actually absorbed by the workpiece 4 because it is not possible to measure it while the laser beam is irradiating it, and if the laser irradiation time becomes long, most of the absorbed energy is dissipated. There were some problems, such as not being able to do it.

This invention was made in order to eliminate the drawbacks of the conventional device as described above. A beam splitter with a known amount of transmission is installed in the path of the laser beam, and the beam is reflected from the deflection surface of the beam splitter. A calorimeter is provided to measure the energy of the laser beam, and the calorimeter measures the amount of heat taken away by the laser beam by the condenser, and the laser beam reflected from the surface of the workpiece.
A reflected beam absorption device that absorbs all of the laser beam is installed, and these devices, including a beam splitter, calorimeter, and reflected beam absorption device, detect the true laser beam power absorbed by the workpiece during processing. By controlling the laser power to a predetermined value based on the detected value, a laser processing apparatus is provided which can process a workpiece having an uneven surface condition without producing unevenness or defects.

An embodiment of the present invention shown in FIG. 3 will be described below.

In the figure, the same reference numerals as in FIG. 1 indicate the same or equivalent parts, 7 is a beam splitter whose division (reflectance: transmittance) of the laser beam is known, and 8 is a beam splitter 7.
This is a cone-shaped calorimeter that absorbs the laser beam reflected from the deflection surface of the cone 9. The inner surface of the cone 9 is coated with an absorber such as oxide, and the outer surface of the cone 9 is equipped with a water-cooled tube 10. The water cooling pipe 1 is covered with a heat insulating material 11. In addition, a thermoelectric body 12 such as copper-constantan is set at the inlet and outlet of the water cooling pipe 10, and a thermoelectric body 12 is set at the inlet and outlet of the water cooling pipe 10.
2 is connected to a differential amplifier 13a, which measures the amount of laser beam absorbed by the cone calorimeter 8 from the temperature difference between the water temperature at the inlet and the water temperature at the outlet, and the measured laser beam amount is sent to the differential amplifier as a signal PM. 13a to the Caesar power control device 6. 14 is a reflected beam absorber that absorbs the laser beam reflected from the surface of the workpiece 4, the inner surface of which is coated with an absorber such as an oxide film or phosphate, and the outer surface of which is provided with a water-cooled tube 10. Furthermore, the entire structure is covered with a heat insulating material 11 to reduce the influence of external temperature changes.

In addition, a thermoelectric body 12 is installed at the inlet and outlet of the water pipe 10,
Further, the thermoelectric body 12 is connected to a differential amplifier 13b, which measures the amount of laser beam absorbed by the reflected beam absorber 14 from the temperature difference between the water temperature at the inlet and the water temperature at the outlet, and the measured value is sent as a signal LR to the differential amplifier 13b. It is then transmitted to the Caesar power control device 6. 15 is a calorimeter provided in contact with the condenser 3, and thermoelectric bodies are installed at the inlet and outlet of the water-cooled tube 10 to transfer the amount of laser beam that is thermally lost by the condenser 3 to the condenser 3. 12, and the measured value is transmitted to the laser power control device 6 as a signal LM by the differential amplifier 13c.

The laser power control device 6 includes each differential amplifier 13
It receives signals PM, LR, and LM transmitted from the laser oscillator 1, and feeds these signals back to the laser oscillator 1 to set a predetermined output. In such a mechanism, a laser beam 2 emitted from a laser oscillator 1 is passed through a beam splitter 7 whose splitting ratio (reflectance:transmittance) is known (transmittance f%).
pass through.

On the other hand, the amount of the reflected beam of the laser beam 2 reflected from the deflection surface of the beam splitter 7 is detected by a cone-shaped calorimeter 8, and the detected amount is transmitted as a signal PM from the differential amplifier 13a to the laser power controller 6. . The laser beam that has passed through the beam splitter 7 is focused by the condenser 3 into a predetermined spot size. Here, the amount of laser beam lost as heat in the condenser 3 is
The amount of laser beam lost as heat is detected by the calorimeter 15 in contact with the condenser 3, and the detected amount is transmitted to the laser power control device 6 from the differential amplifier 13c as a signal LM. Furthermore, the laser beam focused by the condenser 3 passes through a hole or slit provided in a part of the reflected beam absorber 14 and is irradiated onto the workpiece 4 inside the reflected beam absorber 14 . The laser beam reflected from the surface of the workpiece 4 is transmitted to the reflected beam absorber 14.
It is converted into heat by the inner absorber. Therefore, the amount of reflected beam is measured as the amount of heat, and the signal L is output from the differential amplifier 13b.
It is transmitted as R to the laser power control device 6. With the above device, the true power P absorbed by the workpiece 4 is
a becomes Pa=(-goa)-LM-LRI-stroke m,
PM is measured by a cone calorimeter 8, the transmittance f of the beam splitter 7 is known, LM is measured by the calorimeter 10, and LR is measured by a reflected beam absorber and transmitted to the laser power controller 6. Therefore, the true laser power Pa absorbed by the workpiece 4
can be measured.

In addition, the laser power control device 6 uses these signals PM,
The laser transmitter 1 is controlled so that the laser power Pa actually absorbed by the workpiece 4 from LM and LR is set to a predetermined value, and the output P=(half) is adjusted. In the above embodiment, a device for measuring the amount of reflected beam from the beam splitter, a device for measuring the amount of laser beam reflected from the workpiece, and a device for measuring the amount of laser beam lost in the condenser are used. In this method, running water was used as a detection element for absorbed laser energy, and the temperature rise was measured with a thermocouple.However, as a detection element for absorbed laser energy, a temperature detector using thermoelectromotive force such as a metal wire, thermistor, or thermopile was used. You may.

As described above, the present invention measures the power of the laser beam reflected from the deflection surface of a beam splitter whose laser beam is known, and also measures the amount of heat loss of the laser beam by the condenser and the amount of heat reflected from the surface of the workpiece. Since the amount of each laser beam is measured and the laser power of the laser oscillator is controlled according to these measured values, the laser power actually absorbed by the workpiece is always constant, regardless of the surface condition of the workpiece. It is automatically set to a predetermined value and the workpiece is processed uniformly and without defects.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing a conventional laser processing device, Fig. 2 is a sectional view showing another conventional embodiment for measuring laser power absorbed by a workpiece, and Fig. 3 is an embodiment of the present invention. It is a block diagram which shows an example. In the figure, 1 is a laser oscillator, 2 is a laser beam, and 3 is a laser oscillator.
is a concentrator, 6 is a laser power controller, 7 is a beam splitter, 8 is a cone-shaped calorimeter, 9 is a cone, 1
11 is a heat insulator, 12 is a thermoelectric body, 13 is a differential amplifier, 14 is a reflected beam absorber, and 15 is a calorimeter. Note that the same reference numerals in the figures indicate the same or corresponding parts. Figure 3 Figure 1 Figure 2

Claims (1)

[Claims] 1. In a laser processing device that processes a workpiece by focusing a laser beam emitted from a laser oscillator using a condenser and irradiating it onto the surface of a workpiece, the laser beam is a beam splitter that reflects a portion of the laser beam, a first measurement device that measures the output of the laser beam reflected by the beam splitter, and a second measurement device that measures the energy loss of the laser beam in the condenser. a third measuring device that measures the amount of laser beam reflected from the surface of the workpiece; and controlling the laser output of the laser oscillator according to the outputs of the first, second, and third measuring devices. A laser processing device characterized by comprising a control device.