Method of cutting pyrographite

FIELD: physics; lasers.

SUBSTANCE: present invention pertains to laser technology, particularly to the method of cutting pyrographite using laser, and can be used in instrument making, and mainly in electronics. Laser radiation with central mode TEM00 is focused on the material. The focus of the beam is directed on the surface of the material, while keeping the density of the incident power within the 106-107 W/cm2 range. The work piece is moved at speed ranging from 1 to 3 mm/s. The cutting process parameters are determined by the expression , where K is the coupling factor of parameters, chosen from the condition 7·10-5≤K≤12·10-5; f is the repetition frequency of the laser radiation, τ is the pulse duration of the laser radiation, d is the diameter of the spot of focused laser radiation, and h is the thickness of the work piece. A laser with yttrium aluminium garnet active element, with controlled distribution of power in the section of the beam is used.

EFFECT: high quality of cutting material with a smaller heat affected zone during optimum process modes.

2 cl, 1 ex

 

The present invention relates to laser technology, in particular to methods of laser cutting of materials in the manufacture selenocentric products that can be used in the field of instrumentation, mainly in electronic engineering.

The known method of cutting pyrographite, according to which in the manufacture of a grid of pyrographite punches holes "sand blasting" through a mask or by using a beam CO2laser [1]. Mesh made in such a way, is a single leaf, used in a powerful tetrode. About using pyrographite as a material for the manufacture of fine-grained grids with high transparency used in LBO, klystrons, etc. currently no data available.

Known methods of laser machining of composite materials in the manufacture selenocentric products,

In the laser machining of composite materials [2], taken as a prototype, as a source of continuous laser radiation used CO2laser, as well as the mode composition of radiation using an integrated fashion SO01. The focus of the beam is directed to the inside of the material on the distance from the surface within 1/2-5/8 thickness. The radiation power is maintained in the range of 500-700 watts. The speed of movement of the beam is in the range of 0.8-2.5 cm/is. This allows to obtain a high quality cut on the top and bottom surfaces of the material with minimal heat affected zone.

The scheme of the method involves cutting the thickened material. This method is not applicable to conduct cutting thin sheets of pyrographite.

The basis of the invention is to develop a method of laser cutting of thin pyrographite, which would ensure high quality of cutting material with a reduced heat-affected zone at optimal conditions of the process.

The problem is solved as follows. In the method of cutting pyrographite, including the impact on the material of the focused laser radiation, as the mode composition of the radiation used Central fashion SO00and the focus of the beam directed to the surface of the material, while maintaining the power density of the incident radiation 106-107W/cm2the speed of movement of the workpiece 1-3 mm/s, while the technological cutting parameters determined in accordance with the expression, where K is the coupling coefficient between the parameters selected from conditions 7·10-5≤≤12·10-5;

f is the repetition frequency of the laser radiation;

τ - pulse duration of the laser radiation; d is the spot diameter of the focused laser beam;/p>

h - thickness of the workpiece.

In addition, when cutting using the laser light from the active element YAG garnet with controlled power distribution over the cross section of the beam.

The advantage of the proposed technical solution is that the focusing of the beam on the surface of the material with the proposed modulem composition of radiation in the optimization of process parameters, the optimal radiation power and speed of movement of the workpiece will provide end-to-end cutting thin pyrographite with minimal heat-affected zone and the roughness of the contour cut within ±20 microns.

When the Central fashion polarization of the radiation intensity distribution in it is concentrated in the center of the beam, which allows to obtain the power density of the incident radiation 106-107W/cm2necessary for the implementation of process quality cutting pyrographite. When laser radiation with a pulse width varying in the range 10-9-10-3C. in the heat-affected zone created region of the stress state of the material, which in the operation of the devices of pyrographite can lead to fracture of the material: the development of cracks, running radially from the center of impact of the laser radiation, the stratification of material destruction in the area the cat is who influence up to the drop-ring material the respective rings stresses. Minimum stresses are characterized by the modes in which these parameters, f is the repetition frequency of the laser radiation; τ - pulse duration of the laser radiation; d is the spot diameter of the focused laser beam; and h is the thickness of the workpiece associated with the expression, where K is the coupling coefficient between the parameters is selected from conditions 7·10-5≤≤12·10-5. When exposed to pyrographic laser radiation with a pulse duration of about 10-6-10-3with the reduction in power density of the incident radiation <106W/cm2and increasing the speed of movement of the workpiece above 3 mm/s, i.e. when the value of K>12·10-5the quality of cut is undergoing significant deterioration. If the value of K<7·10-5it is necessary to use a large power density of the incident radiation to achieve high-quality cutting, which leads to the complexity of the design.

Example. Studies were conducted on samples from pyrographite thickness of 150 μm. Cutting was carried out along a curved trajectory in the form of an ellipse with semi-axes 2 and 4 mm in the specified rectangle 2×4 mm2.

As the source of pulsed radiation served as a solid-state laser active element YAG garnet with controlled distribution is the group of the power of the radiation beam. As the optimal mode structure when processing pyrographite with the aid of laser radiation is the Central fashion polarization - SO00. The result is a high-quality cuts for optimization of technological modes (coupling coefficient was in the range of 7·10-5≤≤12·10-5when the power density of the incident radiation 106-107W/cm2and the velocity of the blanks from 1 to 3 mm/s

Held laser cutting pulse solid-state laser active element YAG garnet spherical grid with a diameter of 10 mm cathode-grid node from thin pyrographite. The thickness of pyrographite 150 μm. Available spherical the workpiece with the deflection of the sphere of 1.9 mm was placed in the fixture placed on the coordinate table. Was carried out by cutting the mesh with the control program focused laser beam in air. The cutting parameters were chosen such that the coupling coefficientbetween the repetition frequency f and pulse duration τ a laser beam, the spot diameter d of the focused laser beam, the thickness h of the workpiece, was in the range of 7·10-5≤≤12·10-5. Maintained while the power density of the incident radiation 106-107W/cm2speed per the placement of the workpiece in the range from 1 to 3 mm/s Got a spherical grid with a thick jumper 300±15 microns.

The proposed method dimensional processing pyrographite when used will allow you to:

- conduct qualitative dimension processing pyrographite along a curved path in an automated mode,

- to reduce the cost of manufacture of a grid of pyrographite by reducing energy consumption, reduction of manufacturing time of each grid,

the proposed grid will improve the geometrical characteristics of the flow of electrons to create high-quality low-noise TWT with high performance characteristics.

Sources of information

1. Application 2276681, France. MCI H01j 1/46. La grille pour unetube / G.Pierre, B.Gilles; Thomson-CSF (France). No. 7422686; claimed 28.06.74; publ. 23.01.76.

2. Patent No. 2219029, Russia. IPC WC 26/38. Method of machining composite material / Pastushenko, Iagurav, Apotheke; Institute of materials of Khabarovsk scientific center of the far Eastern branch of RAS (Russia). - Declared 10.06.2002; date of beginning of validity of the patent 10.06.2002; publ. 20.12.2003.

1. Method of cutting pyrographite, including the impact on the preparation of the focused laser radiation, characterized in that as the mode composition of the radiation used Central fashion SO00and the focus of the radiation directed onto the surface of the workpiece support is th the power density of the incident radiation 10 6-107W/cm2and the workpiece is moved with a speed of from 1 to 3 mm/s, thus define the technological parameters of cutting in accordance with the expression, where K is the coupling coefficient between the parameters selected from conditions 7·10-5≤≤12·10-5; f is the pulse frequency of the laser radiation; τ - pulse duration of the laser radiation; d is the spot diameter of the focused laser beam; and h is the thickness of the workpiece.

2. The method according to claim 1, characterized in that use radiation solid-state laser active element YAG garnet with controlled power distribution of the radiation beam.



 

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