JPH0515427Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the structure of a laser processing head used in a carbon dioxide laser processing machine or the like.

[Conventional technology]

FIG. 2 is a sectional view of a processing head of a conventional carbon dioxide laser processing machine. To briefly explain the structure of the processing head, a main body with a built-in condenser lens (ZnSe) is attached to the tip of the beam introduction tube through which the carbon dioxide laser beam passes. A condensing lens mount to which a condensing lens is fixed is inserted into the main body, a cooling water passage is provided in the main body near the mount, the tip of the main body is shaped like a nozzle, and assist gas is supplied to the nozzle base. A port for introducing the light is provided to prevent contamination of the surface of the condenser lens.

These laser processing heads are designed to focus a laser beam that has passed through a beam introduction tube using a condensing lens to form a focal point on the surface of the workpiece. When processing is repeated, spatter, dust in the atmosphere, oil, and other contaminants adhere to the lens surface, increasing the absorption rate of laser light and raising the temperature of the lens. In the laser processing head shown in Figure 2, the lens is cooled with cooling water, but as the contamination progresses, this cooling becomes insufficient, leading to destruction of the surface coating of the condenser lens or even destruction of the lens itself. For this reason, condensing lenses are cleaned regularly to remove dirt, maintain lens performance, and prevent lens damage.

However, since there was no way to accurately determine whether the lens was dirty during use, the appropriate cleaning interval was not known, and the cleaning frequency was usually set excessively, wasting effort and resulting in damage to the coating film. There was a problem that it caused premature damage. In addition, the cleaning frequency was low and sometimes caused damage to the lens surface.

[Problem that the invention attempts to solve]

The present invention eliminates the drawbacks of conventional laser processing heads and is equipped with a detection means that accurately detects the temperature rise of the condenser lens, making it possible to use a laser that can accurately detect the degree of contamination of the condenser lens. The aim is to provide a processing head.

[Means for solving problems]

The present invention provides a laser processing head that has a condensing lens built into the end of a beam introduction tube and a nozzle whose tip is narrowed close to the diameter of the beam. This laser processing head is characterized in that a radiation thermometer is attached through the beam introduction tube to detect the temperature rise of the condensing lens by sensing radiation in the 20 to 30 μm band from the laser beam.

FIG. 1 is a sectional view of a laser processing head that is a specific example of the present invention. FIG. 1 shows an example in which a radiation thermometer is used as a means for detecting a temperature rise in a condensing lens, and is an improvement on the laser processing head shown in FIG. 3 described above. That is, a radiation thermometer is provided so as to penetrate the side wall of the beam introduction tube, so that the temperature of the surface of the condenser lens can be detected.

Further, when the degree of contamination of the condensing lens exceeds a certain limit and cleaning becomes necessary, an alarm can be issued by activating a sound or light notification means in conjunction with the temperature rise.

The laser beam is not limited to CO ₂ laser, but can also be applied to CO laser and other lasers.

[Effect]

Output using the laser processing head shown in Figure 1
While cutting an S45C steel plate using a 3KW CO ₂ laser, we measured the degree of contamination of the condenser lens and the temperature rise. As a result, the relationship between the degree of contamination and the temperature rise was as shown in FIG.

In other words, the degree of contamination that causes surface damage is:
It was 0.8 or more, and the temperature increase at that time was 6°C.

As a result, it was found that as the condensing lens is used, the temperature will rise if dirt adheres to it, but if the lens is removed and cleaned at an increased temperature of 4 to 5 degrees Celsius, no laser damage will occur and the life of the lens will be extended. Therefore, we measured the temperature rise of the lens commensurate with each laser output, laser irradiation time, etc., and cleaned the lens before damage occurred.

By employing a radiation thermometer as a means for detecting the temperature rise of the condensing lens, the lens surface temperature is measured by directly sensing the radiation, so the measurement accuracy is high and the responsiveness is good. In particular, when using a radiation thermometer that is sensitive to radiation in the 20 to 30 μm band,
Filters the 10.6μm reflected light from the lens surface of the carbon dioxide laser beam and the reflected light that passes through the condenser lens, is reflected by the workpiece, etc., and then enters the condenser lens again (only 20 to 30μm is transmitted).
The condenser lens (ZnSe) is excluded from the measurement target due to
By measuring only radiation in the wavelength range of 20 μm or more that does not pass through, it is possible to accurately measure the temperature on the surface of the condenser lens.

Note that radiation with long wavelengths of 30 μm or more has very low energy, so it does not drop into the measurement, and if wavelengths of 20 μm or less are detected, the absolute accuracy will be affected by the back side of the lens.

Comparing the absolute accuracy of temperature rise detection means used in laser processing heads, when using a radiation thermometer that is sensitive to wavelengths of 20 to 30 μm, the accuracy is ±5°C, whereas when using a radiation thermometer that is sensitive to wavelengths of 30 μm or less, it is ±5°C. When used, the temperature was ±20°C.

[Effect of idea]

By adopting the above configuration, the present invention can accurately detect the degree of contamination of the lens, accurately grasp the cleaning period, and maintain the cleaning frequency at an appropriate level, thereby reducing the effort required for cleaning. We were able to reduce this and significantly extend the life of the lens.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a laser processing head according to an embodiment of the present invention, FIG. 2 is a sectional view of a conventional device, and FIG. 3 is a graph showing the relationship between the degree of lens contamination and temperature rise.

Claims (1)

[Scope of utility model registration request] In a laser processing head that has a condensing lens built into the end of the beam introduction tube and a nozzle whose tip is narrowed close to the diameter of the beam, the condensing lens is
Made of ZnSe or GaAs, 20
A laser processing head characterized in that a radiation thermometer that detects a temperature rise in a condensing lens by sensing radiation in the ~30 μm band is attached through a beam introduction tube.