RU2394780C1 - Method of laser pulsed shaping of solid non-metal materials - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: proposed method consists in that pulsed laser beam is directed to processed material to cause destruction in focusing points. Note that pulsed laser radiation is used with wavelength in or out of transparency range of processed material. Sequential removal of material is performed by focusing laser beam on processed material surface. Note here that sequential material layer removal is performed by producing group of hollows with variable coefficient of overlapping between separate layers in the range of 0.1 to 0.9. Then sequential step-by-step removal of next layer is performed, also with variable coefficient of overlapping between separate layers in the range of 0.2 to 0.95. In using pulsed laser radiation with wavelength in transparency range of processed material, sequential step-by-step material removal is performed by focusing laser beam at processed material inlet or outlet surface with respect to laser beam propagation direction.

EFFECT: expanded performances due to step-by-step removal of material from processed product surface.

2 cl, 12 dwg, 10 ex

Description

The invention relates to methods of processing materials, in particular to methods of forming and cutting solid non-metallic materials. The invention can be used in industry for shaping and cutting, obtaining parts of complex spatial shapes, engraving and marking various solid non-metallic materials, mainly various types of glass and ceramics.

The known process of laser scribing and destruction of thin glass sheets coated with a coating. It is carried out by directing the laser beam from a pulsed KrF laser, the wavelength of which is strongly absorbed by the glass, focusing the laser radiation on the surface of the material or in its thickness and forming a defect at the focusing point (US patent No. 5961852, B23K 26/00, publ. 5.10.1999 )

The disadvantage of this method is that it allows you to separate only thin sheet materials with a thickness of up to several hundred micrometers. In this case, the separation paths of the material are severely limited in geometric configurations.

A known method of processing glass and other brittle non-metallic materials under the action of thermoelastic stresses resulting from heating of the surface layer by laser radiation to a temperature not exceeding the softening temperature of the material, subsequent local cooling of the heating zone, while the rate of relative movement of the beam, material and the local cooling zone heating is selected from the conditions of formation in the material of a non-through separating crack (RF patent No. 2024441, С03В 33/02, publ. 15.12.1994).

The disadvantage of this method is that it, like the previously mentioned method, allows only the direct separation of sheet materials and does not allow for any other type of processing. At the same time, only sheet materials with a thickness of up to 10 mm can be subject to guaranteed quality separation.

Closest to the claimed is a method of cutting transparent non-metallic materials by directing the laser beam from a pulsed laser, focusing the laser radiation on the surface of the sample or in its thickness and forming a defect at the focusing point, and then applying mechanical force to the surface of the sample, characterized in that they use pulsed laser radiation with a wavelength lying in the transparency region of the material, a pulse duration of 10-100 ps and an energy in the pulse sufficient to produce a breakdown in the focus area, then the size of the defect is determined and defects are formed at the points of the sample spaced apart by a distance determined by 50% overlapping of the defects up to twice the distance between the defects (RF patent No. 2226183, С03В 33/00, publ. March 27, 2004).

The disadvantage of this method is the need for mechanical bending forces, which does not allow to obtain complex separation paths. Also, the method does not allow for any other processing, except for the separation of sheet materials.

The present invention is based on the task of expanding the technological capabilities of the process of laser pulsed processing of solid non-metallic materials by creating a method of laser pulsed shaping of solid non-metallic materials, including glass and ceramics, which will ensure sequential discrete removal of material from the surface of the workpiece.

The problem is solved in that in the method of laser pulsed shaping of solid non-metallic materials, pulsed laser radiation with energy in a pulse, which ensures the formation of optical breakdown in the focus area, is directed from the pulsed laser to the material being processed and damage is formed at the focusing points, using pulsed laser radiation with a wavelength, lying or not lying in the transparency region of the processed material, and carry out sequential discrete removal of material Ala in the form of a separate layer by focusing the laser beam on the surface of the processed material and forming a group of holes with a variable overlap coefficient, determined in the range from 0.1 to 0.9, then on the treated surface of the material carry out sequential discrete removal of the next separate layer of material, with a variable the coefficient of overlap between the individual layers, determined in the range from 0.2 to 0.95. When using pulsed laser radiation with a wavelength lying in the transparency region of the processed material, sequential discrete removal of the material is carried out by focusing the laser beam on the output or input surface of the processed material in relation to the direction of propagation of the laser beam.

Figure 1 shows a diagram of the formation of a single hole on the surface of the processed material. Figure 2 - scheme of sequential discrete material removal. Figure 3 is a diagram showing the limitation of surface formation. 4 is a processing diagram of a transparent material used for laser radiation by focusing the laser beam on the output surface of the workpiece. Figure 5 - holes of various shapes carved in sheet glass brand M1. 6 is a diagram of cutting a rectangular hole in sheet glass. 7 is a combined hole cut out in sheet glass of the brand M1. Fig. 8 is a combined hole cut out in M1 sheet glass. Fig.9 - screw M3 with countersunk head, cut from sheet glass brand M1. Figure 10 - marking the surface of the sheet glass of the brand M1.

The process of laser pulse shaping of the surface of the processed material is as follows (figure 1). Under the influence of a laser beam 1 focused on the surface of the processed material 2, a laser spark is formed due to optical breakdown of the surface of the material. Moreover, for a transparent material, the breakdown threshold of the surface is much lower than the breakdown threshold in its volume, since the surface of the material, as a rule, concentrates stresses, defects, and inhomogeneities.

The result of exposure to a laser pulse is a hole 3 of depth h and a transverse dimension d, which is formed due to a single removal of the material. When sequentially forming on the surface of the processed material a group of such holes at a distance S _H from each other, a sequential discrete removal of material occurs in the form of a separate layer. Then on the treated surface carry out sequential discrete removal of the next layer of material, etc. with the distance between the individual layers S _V (figure 2), thereby providing controlled shaping of the surface of the processed material. The described layer-by-layer removal of material allows to obtain surfaces of complex shape and their combinations.

The indicated distance between the wells S _H is selected for reasons that the adjacent adjacent wells in a separate layer are overlapped relative to each other. The overlap of the holes in the layer is determined as follows: let p be the relative overlap of neighboring wells, then the overlap coefficient K _H , defined as the ratio of the relative overlap p to the transverse size of the hole d, is taken from 0.1 to 0.9, depending on the type processed material and formed geometric elements. In this case, the overlap coefficient K _H can vary within a separate layer for various geometric elements being formed (corner sections, rounding sections of small radii (less than 0.3 mm), joint sections of various geometric elements).

The distance between the individual layers S _V is chosen for reasons that the adjacent layers being created are overlapped relative to each other. The overlap coefficient between the individual layers K _V is determined similarly to the overlap coefficient K _H : let p be the relative overlap of adjacent layers, then the overlap coefficient K _V , defined as the ratio of the relative overlap p to the depth of an individual hole h, is taken from 0.2 to 0, 95, depending on the type of material being processed and the formed geometric elements (corner sections, rounding sections of small radii (less than 0.3 mm), joint sections of various geometric elements).

At the same time, to ensure optimal sequential discrete removal of material, each group of holes in the next layer is shifted relative to the group of holes in the previous layer, so as to provide a "checkerboard pattern" of the relative positions of the holes in adjacent layers. For example, if a group of holes in the first layer is formed with the parameter S _H = 0.03 mm, then the group of holes in the second layer must be shifted relative to the first group by S _H / 2.

Since the focused laser beam has the form of a converging cone, when immersed at a certain depth of the caustic of the focused beam relative to the surface of the processed material 2, part of the focused beam 1 is blocked by the edges of the processed surface (Fig. 3). Thus, the vertical walls of the resulting surface as a result of such shaping will have a slope α≈arctg (D / 2F), where D is the diameter of the laser beam before focusing, F is the focal length of the lens used. Therefore, such a process diagram of laser pulsed shaping of solid non-metallic materials is suitable for separating sheet material, the edges of which do not have strict vertical requirements, or for shaping operations that do not require vertical walls with an angle of inclination less than the specified α. In this case, the separation of sheet materials can be carried out along any trajectories and without the need for mechanical forces.

Also, for transparent materials used for laser radiation, a processing scheme is used, which consists in sequential discrete removal of material by focusing the laser beam on the output surface of the processed material with respect to the direction of propagation of the laser beam (Fig. 4). The indicated scheme provides that the focusing of the laser beam 1 is on the opposite side of the processed material 2. In this case, the nature of the formation of the holes is similar to that given above, except that the threshold of optical breakdown of the output face of the processed material is lower than the input one due to interference of the incident wave with reflected.

This approach presents a number of conditions: the material must be transparent to laser radiation; the entrance surface must be polished; the presence of inhomogeneities and swirls in the volume of the material can lead to deviation of the focused laser beam, as a result of which the processing process can be unstable. At the same time, such a scheme of the shaping process allows one to form strictly vertical surfaces, i.e. surfaces parallel to the direction of propagation of the laser beam, which in turn allows, for example, to form narrow and at the same time deep holes in the processed material.

Since the surface of the processed materials, such as glass and ceramics, has defects and inhomogeneities, to ensure regular optical breakdown of the material surface, it is necessary to use pulsed laser radiation with energy in a pulse, which ensures stable formation of optical breakdown in the focus area.

When performing sequential discrete removal of material by focusing the laser beam on the output surface of the processed material, it is also necessary to take into account the absorption of laser radiation in the volume of material. For example, when cutting a through hole in a K8 optical glass product with a thickness of 100 mm, it is necessary to maintain a constant overlap coefficient K _V and K _H in the processing depth, since during the initial processing of the output surface of the specified product, part of the radiation (approximately 2-3%) will be absorbed. Thus, the assigned parameters S _V and S _H when processing the output face of the specified product must also be reduced by 2-3%, and then when approaching the input face, increase to the assigned values in a linear relationship. This circumstance is important when processing transparent sheet material of large thickness (> 100 mm) and when processing products from materials with a low transmittance (less than 0.9).

Examples of the method

All the above examples were performed using a pulsed Nd: AIG laser operating in the Q-switched mode at a wavelength of 1.06 μm with the central mode extracted using an aperture diaphragm, with a pulse duration of 15 ns and a pulse energy of 20 mJ. The focal length of the focusing lens is 56 mm.

The sheet glass of the M1 brand according to GOST 111-2001, the glass metal of the ST-50-1 brand according to the OST 11-054.263-79 and the optical glass of the K8 brand according to GOST 3514-94 were subjected to processing.

Examples 1, 2. Cut out two holes in the sheet glass with a thickness of 4 mm: rectangular (1 × 3 mm) and elliptical (1 × 3 mm) (figure 5). The laser beam was focused on the output surface of the processed material. The main value of the overlap coefficient K _{H was} taken to be 0.5, and to ensure separation in the corner sections and rounding sections with small radii, an additional overlap coefficient K _{ND of} 0.6 was used. In particular, the overlap coefficient K _{ND was} used in corner sections of 0.2 × 0.2 mm in size when cutting a rectangular hole and in rounding sections with a radius of 0.25 mm when cutting an elliptical hole. The distance between adjacent wells within an individual layer S _H was 0.024 and 0.03 mm for K _ND and K _H, respectively. The overlap coefficient between adjacent layers K _V was 0.6; the distance between adjacent layers S _V was 0.05 mm.

The thickness of the removed layer of material 5 to ensure complete separation of the workpiece 2 in the data and the following examples of the method, was taken 0.06 mm, which allowed the inner detachable part of the product 4 to be freely removed (Fig.6).

Example 3. Cut a rectangular hole 1 × 2 mm in the plate of glass, a thickness of 1 mm Processing parameters: K _H = 0.8, K _ND = 0.85, K _V = 0.7, S _H = 0.01 mm, S _ND = 0.0075 mm, S _V = 0.02 mm. The laser beam was focused on the input surface of the processed material.

Example 5. Received a combined hole (Fig.7), consisting of a cylindrical part with a diameter of 4 mm, turning into a square part with a side of 2 mm Cutting was made from sheet glass 3 mm thick.

Processing Parameters:

- cylindrical part: K _H = 0.5, K _V = 0.5, S _H = 0.03 mm, S _V = 0.05 mm;

- square part: K _H = 0.5, K _ND = 0.6, K _V = 0.5, K _VD = 0.7, S _H = 0.03 mm, S _ND = 0.024 mm, S _V = 0 , 05 mm, S _VD = 0.03 mm.

The laser beam was focused on the output surface of the processed material. The processing process consisted of two stages: 1) complete removal of the cylindrical part; 2) cutting out part of a hole of square section. When cutting a hole of a square section at the junction with an already cut part of a circular section, additional overlap coefficients K _ND and K _{VD were used} .

Example 6. Received a combined hole of sheet glass with a thickness of 4 mm, consisting of a cylindrical part with a diameter of 2.5 mm, turning into a conical part with an angle of convergence of the cone of 60 degrees (Fig. 8).

Processing Parameters:

- cylindrical part: K _H = 0.5, K _ND = 0.6, K _V = 0.5, K _VD = 0.7, S _H = 0.03 mm, S _ND = 0.024 mm, S _V = 0 , 05 mm, S _VD = 0.03 mm;

- conical part: K _H = 0.5, K _ND = 0.6, K _V = 0.5, K _VD = 0.7, S _H = 0.03 mm, S _ND = 0.024 mm, S _V = 0 , 05 mm, S _VD = 0.03 mm.

The laser beam was focused on the output surface of the processed material.

Example 8. The received part is a M3 screw with countersunk head according to GOST 17475-80 (Fig. 9). Processing parameters: K _H = 0.5, K _ND = 0.6, K _V = 0.5, K _VD = 0.7, S _H = 0.03 mm, S _ND = 0.024 mm, S _V = 0, 05 mm, S _VD = 0.03 mm.

Example 9. A through hole of 1 × 1 mm in size was obtained in optical glass of the K8 grade 25 mm thick. Processing parameters: K _H = 0.6, K _ND = 0.7, K _V = 0.5, S _N = 0.025 mm, S _ND = 0.02 mm, S _V = 0.05 mm. The laser beam was focused on the output surface of the processed material.

Example 10. Marking the surface of the sheet glass (figure 10). The inscription of the marking “FKhPiT” was carried out in the form of a relief with a depth of 1.5 mm. Processing parameters: K _H = 0.5, K _ND = 0.6, K _V = 0.5, K _VD = 0.7, S _H = 0.03 mm, S _ND = 0.024 mm, S _V = 0, 05 mm, S _VD = 0.03 mm. The laser beam was focused on the input surface of the processed material.

Claims (2)

1. The method of laser pulsed shaping of solid non-metallic materials, which consists in the fact that pulsed laser radiation with energy in a pulse, which provides the formation of optical breakdown in the focus area, is directed from a pulsed laser to the processed material and form fractures at the focal points, characterized in that they are used pulsed laser radiation with a wavelength lying or not lying in the transparency region of the processed material, and carry out sequential discrete removal of the mother In the form of a separate layer by focusing the laser beam on the surface of the processed material and the formation of a group of holes with a variable overlap coefficient, determined in the range from 0.1 to 0.9, then on the treated surface carry out sequential discrete removal of the next separate layer of material with a variable overlap coefficient between the individual layers, defined in the range from 0.2 to 0.95. 2. The method according to claim 1, characterized in that when using pulsed laser radiation with a wavelength lying in the transparency region of the processed material, sequential discrete removal of the material is carried out by focusing the laser beam on the output or input surface of the processed material in relation to the direction of laser propagation ray.

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