RU2086376C1 - Method of laser machining of surface of materials - Google Patents

Abstract

FIELD: laser machining of various materials (metals, wood, bones, leather, plastics) and articles made from them by industry, modification of surface structures of optical materials. SUBSTANCE: area of machined surface is divided into surface elements with linear dimensions

, where d is diameter of laser radiation beam focussed machined surface. Focused laser radiation beam is moved over these surface element with area

over coordinates X and Y with rates determined from relationships v_x= mP/Δq_iyb v_y= nP/Δq_iya where v_x, v_y are rates of movement of focused beam over surface element over coordinates X and Y correspondingly; a, b are linear dimensions of machined surface over coordinates X and Y correspondingly; n, m are numbers of surface elements over coordinates x and Y correspondingly; P is power of laser radiation in focal spot on machined surface; Δq_iy is energy absorbed by surface elements specified by distribution of energy g(x, y) over area of machined surface. EFFECT: provision for possibility of formation of relief pattern of specified configuration or image with preset contrast / specified distribution of change of surface properties under action of laser radiation on surface of machined material or article/.

Description

 The invention relates to laser technology and can be used for various materials (metal, wood, bone, leather, plastic) and products from them in industry, as well as for modifying the surface structure of optical materials.

A known method of laser surface treatment of materials and a device for its implementation consists in synchronous movement in two coordinates with speeds V ₁ and V ₂ combined, focused and equalized in size in the processing plane of the beams of a technological laser of the infrared spectrum and a laser of the visible spectrum and scanning the zone processing in the plane optically conjugated with the processing plane relative to a fixed hole of size l, with l≅0,1d, where d is the size of the processing zone beam of the visible range of the spectrum with a speed of V ₃ , with V ₃ <V ₁ , V ₂ [A.S. N 1635017, CL B 23 K 26/04, BI N 10 1990

 The reasons that impede the achievement of the required technical result include the absence of restrictions on the speed of movement of the focused laser beam along the surface to be treated and, therefore, the absence of restrictions on the duration of exposure to a specific section of the surface to be treated, leading to a specific change in the properties of the surface to be treated in accordance with a given distribution of changes properties over the entire surface of the treated surface, which will not allow to form on the surface to be worked is a relief pattern of a given configuration or an image with a given contrast.

There is a known method of drilling holes and a device for its implementation consisting in the fact that the area of the holes is divided into a series of concentric circles, the sizes of the two closest of which differ by the step size not exceeding the diameter of the laser radiation focused on the surface of the beam, and the focused beam is successively moved along concentric circles with a constant linear speed on each of them, starting either from the center or from the outer radius of the hole [A.S. N 1750900 A1, CL B 23 K 26/00, 07/30/92 g]
This method in its technical essence is closest to the claimed one and is therefore selected by the authors for the prototype.

 The reasons that impede the achievement of the technical result when using the prototype method include, as well as the analogue method, the absence of restrictions on the speed of movement of the focused laser beam along the treated surface.

 The invention consists in the following. For forming on the surface of the processed material or product a relief pattern of a given configuration or image with a given contrast (for example, with varying degrees of blackening or lightening), i.e. Given the distribution of changes in surface properties under the action of laser radiation, it is necessary to create a method that allows for a specific change in the surface properties of a particular area of the processed surface.

 The given distribution of changes in surface properties under the action of laser radiation, i.e. a specific change in the properties for each particular area of the treated surface with the same laser radiation power in the exposure zone equal to the diameter of the focal spot and isotropy of the surface properties of the processed material can be achieved by changing the duration of exposure Δτ on this particular area or, which is the same by changing the speed moving the laser beam over the areas of the treated surface.

 If the optical (reflection and absorption coefficient) and other (thermal conductivity, density, thermal diffusivity, etc.) surface properties of the processed material are anisotropic (for example, nonuniform in density), one should strive to reduce the exposure duration, i.e. to increase the speed of movement and radiation power, at which the heterogeneity of the properties affects the result of the impact to a lesser extent.

где a, b линейные размеры обрабатываемой поверхности в координатах X и Y соответственно, n, m число элементарных участков на обрабатываемой поверхности по координатам X и Y соответственно, со скоростью пропорциональной поглощаемой поверхностью этих элементарных участков энергии Δq_ij приводящей к конкретному изменению свойств поверхности на каждом конкретном участке, может быть сформировано заданное распределение изменения свойств поверхности.Thus, when processing the surface of a material or product with a focused beam of laser radiation, which is moved along elementary surface sections with an area

where a, b are the linear dimensions of the treated surface in the X and Y coordinates, respectively, n, m are the number of elementary sections on the treated surface in the X and Y coordinates, respectively, with a speed proportional to the absorbed surface of these elementary sections of energy Δq _ij leading to a specific change in the surface properties on each specific site, can be formed a predetermined distribution of changes in surface properties.

где d диаметр сфокусированного на поверхность обработки пучка лазерного излучения по этим площадкам с площадью

по координатам X и Y определяют из соотношений:

где V_x, V_y скорости перемещения сфокусированного пучка лазерного излучения по элементарным площадкам по координатам X и Y соответственно;
a, b линейные размеры обрабатываемой поверхности по координатам X и Y соответственно;
n, m число элементарных площадок по координатам X и Y соответственно;
P мощность лазерного излучения в фокальном пятне на обрабатываемой поверхности;
Δq_ij энергия, поглощенная элементарной площадкой, задаваемая распределением энергии q(x, y) по площади обрабатываемой поверхности.The specified technical result in the implementation of the proposed method is achieved by the fact that in the laser surface treatment method, the surface area to be treated is divided into elementary areas with linear dimensions

where d is the diameter of the laser beam focused on the processing surface along these areas with an area

the coordinates X and Y are determined from the relations:

where V _x , V _{y the} velocity of the focused laser beam along the elementary areas along the coordinates X and Y, respectively;
a, b linear dimensions of the machined surface in the coordinates X and Y, respectively;
n, m are the number of elementary sites along the coordinates X and Y, respectively;
P the power of the laser radiation in the focal spot on the treated surface;
Δq _{ij is the} energy absorbed by the elementary area, defined by the distribution of energy q (x, y) over the area of the treated surface.

Скорость перемещения по элементарным площадкам с площадью

при любой траектории движения (которую чаще всего выбирают из условия минимизации энергетических затрат при обработке) сфокусированного пучка определяются из условия поглощения конкретной элементарной площадкой энергии Δq_ij необходимой для конкретного изменения свойств поверхности в соответствии с заданным распределением энергии q(x, y) по площади обрабатываемой поверхности, создающим это заданное распределение изменения свойств, т.е.To create a given distribution of changes in surface properties during laser processing, the linear dimensions of a particular section of the processed surface of the elementary site into which the processed surface is divided when determining the trajectory and speed of the laser beam focused on the surface are limited by the diameter of this focused beam, i.e.

The speed of movement on elementary sites with an area

for any trajectory of movement (which is most often chosen from the condition of minimizing energy costs during processing), the focused beam is determined from the condition that the energy Δq _ij necessary for a specific change in surface properties is absorbed by a particular elementary area in accordance with a given energy distribution q (x, y) over the area processed surface creating this predetermined distribution of changes in properties, i.e.

где

длительность воздействия сфокусированного пучка лазерного излучения на конкретную площадку при данной мощности P в фокальном пятне на обрабатываемой поверхности.

Where

the duration of the effect of a focused laser beam on a specific site at a given power P in the focal spot on the treated surface.

 The radiation power in the focal spot on the treated surface is determined by the material of the product, the uniformity of its properties.

 The power limitation is the degree of destruction of the material. A limitation on the speed of movement of the focused laser beam is the inertia of specific actuators - scanners and, although to a lesser extent, the speed of the computer that controls the movement of the beam.

 For example, when processing wood and plywood, a power of 10 W is used. When processing glass, a short-term exposure, i.e. high speeds of beam movement both at relatively low powers, where the relief pattern is formed due to the collision of small glass particles with the processing surface, and at powers of 50-60 W, where the relief pattern is formed due to the evaporation of the glass. Such an exposure regime may be accompanied by whitening or darkening of the exposure zone due to crystallization or redistribution of impurities.

 Processing of metal surfaces can also be carried out in two modes with a relatively low power (up to 10 W), where the pattern on the surface is formed due to structural transformations without material destruction and in the energy-intensive mode of evaporation at a power of up to 100 watts.

 The formation of a relief pattern on the skin and plastic is carried out at relatively low power exposure up to 10 watts. The power limit, as in the case of a tree, is chosen experimentally.

 The analysis of the prior art cited by the applicant, including a search by patents and scientific and technical sources of information, made it possible to establish that the applicant has not found a method characterized by features identical to all the essential features of the proposed method, and a set of distinctive essential features has been identified with respect to the technical result.

 Therefore, the claimed method meets the requirement of novelty.

 To carry out the correspondence of the proposed method to the requirements of the inventive step, an additional search was carried out for known solutions to identify signs that create distinctive features of the prototype of the claimed invention.

 The result of this search shows that the inventive method does not follow for a specialist explicitly from the prior art.

The drawing shows a diagram of a device for implementing the proposed method (Fig. 1). This device should contain the following basic elements:
I. A radiation source (1) with a power supply (2) a continuous technological laser designed for thermal exposure of the processed material in the processing plane (12). CO ₂ laser (λ10.6 μm) or YAG laser (l1.06 μm);
II. forming an optical system comprising a shutter (3), scanners (4) with a power and amplification unit (8) and a focusing system (5);
III. IBM-PC / XI type computer control system (9) for controlling scanners (4) and shutter (3);
IV. a process laser radiation visualization system consisting of a visible spectrum laser, for example, a He-Ne laser with l0.63 μm (6), an optical system (7), rotary mirrors (10) and (11) and a forming lens (5).

 The device operates as follows. The radiation from the process laser (1) passes through an open electromechanical shutter (3), is reflected from the scanner mirrors (4) and is focused by the lens (5) in the processing plane (12). Scanning of a focused laser beam along a given path with a given speed in the processing plane is carried out by the scanner mirrors (4) controlled by the control system (9).

 To visualize the size of the impact zone and determine its spatial location in the processing plane, He-Ne laser radiation (6) is used, which is combined with rotary mirrors (10) and (11) with the radiation from the technological laser. The optical system (7) together with the focusing system (5) serves to change the size of the beam cross section of the visible range of the spectrum in the processing plane.

As an example, illustrating the operation of the device and explaining the essence of the method, we consider an example of forming a relief pattern of complex shape with an area of 25 cm ² on a quartz glass plate.

с линейными размерами

где d диаметр сфокусированного в плоскость обработки пучка лазерного излучения, для данного конкретного устройства d приблизительно 100 мкм. Для каждой элементарной площадки ΔS_ij задаем глубину рельефа H_ij, отсчитывая ее от поверхности пластины, т.е. H_min=0 уровень поверхности.We break the surface area of the picture into a number of elementary areas

with linear dimensions

where d is the diameter of the laser beam focused onto the processing plane, for this particular device d is approximately 100 microns. For each elementary site ΔS _{ij, we} set the relief depth H _ij , counting it from the plate surface, i.e. H _min = 0 surface level.

The depth range H _min -H _{max of the} relief pattern for quartz glass of approximately 2 mm can be achieved with certain fixed values of the radiation power in the focal spot on the treated surface, for example, P ₁ , P ₂ , P ₃ , P ₄ , P ₅ <10 Tue

 According to the dependences Η = f (Δτ) where Δτ is the exposure duration constructed on the basis of experimental data for fixed values of the radiation power P, the dependences H = f (v) are determined (Fig. 2).

When choosing the radiation power P from a number of possible values, preference is given to the option that provides maximum processing productivity (use of high speeds) and maximum use of the entire range of permissible speeds for this scanner. For the dependencies shown in FIG. 2, the option with power P ₃ described by curve 3 meets these requirements.

Scanner control providing for each elementary site DS _ij speed V _ij , i.e. the depth of the relief H _ij is carried out by the control system.

 Thus, the above information confirms the possibility of implementing the method in the totality that is set forth in the independent claim.

 Therefore, the claimed invention meets the requirement of industrial applicability.

Claims (1)

The method of laser surface treatment of materials, which consists in the fact that the processed surface is divided in one coordinate into elementary areas, the linear size of which in the direction of partition is equal to the diameter of the laser beam focused on the processing surface and move this beam over the resulting areas, characterized in that it is additionally carried out partition into elementary areas along the second coordinate with a linear partition size equal to the linear size of the partition along the first coordinate, and ck grow moving laser beam focused on an area element with an area

the coordinates X and Y are determined from the relations

where v _x , v _{y the} velocity of the focused laser beam along the coordinates X and Y, respectively;
a, b linear dimensions of the machined surface in the coordinates X and Y, respectively;
m, n is the number of elementary sites along the coordinates X and Y, respectively;
P the power of the laser radiation in the focal spot on the treated surface,
Δq _ij is the energy absorbed by the elementary platform ΔS _ij , defined by the distribution of energy q (X, Y) over the area of the treated surface.

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