Method of laser labeling surface of metal or alloy

FIELD: machine building.

SUBSTANCE: invention refers to method of laser labelling surface of metal or its alloy and can be implemented in machine building, jewellery industry and medicine. The method consists in preliminary plotting a calibration curve of dependence of depth of marking surface of a sample of specified metal or its alloy by means of effect of specific power of radiation incoming on surface. By means of a computer there is generated a protective digital code, where specific depth of marking and specific power of laser radiation correspond to each digit. A mark visible by a naked eye is applied on the marked surface of metal or its alloy by means of laser radiation transferred along marked surface; this mark corresponds to alpha-numeric or graphical information. A protective digital code in form of sequence of recesses invisible to a naked eye is applied on the produced surface visible to a naked eye; this code is marked by laser radiation of specific power chosen from the said calibrating curve.

EFFECT: high level of protection and simplified process.

8 cl, 5 dwg, 1 tbl, 1 ex

 

The invention relates to a method of applying information or verification code on the surface of metal products, which are coated with an alphanumeric or graphic information exposure to laser radiation. The inventive method can find application in various industries, including engineering, as well as in jewelry and medical fields.

When applying a vector or bitmap image by using laser marking on the surface of metal products, the image consists of a set of lines of different lengths. The depth of these lines determines the image contrast and, in practice, is selected based on the objectives of the subsequent perception of the observer marked. Usually, the contrast is chosen in such a way as to provide surveillance of the applied marking the naked eye.

Known method of applying a verification marking securities or media (see PCT application no WO 2009003588, IPC B41M 3/14, published, 08.01.2009), comprising coating the surface of modified laser radiation substrate, performing at least one of the holes in the product in a region overlapping with the substrate and modification of the substrate directed laser radiation.

The known method is applicable only for labeling products having a small thickness and, in addition, technologically complex, as it requires a pre-coating the substrate with the help of special equipment.

A known method of applying invisible to the naked eye markings on the surface of the product (see patent FR No. 2755902, IPC B41M 3/14, published 05.22.1998), including the effects of directed laser light on the surface for applying a specified image. The parameters of the marking radiation are selected in such a manner as to cause the modification of only the first surface atomic layer of the material marked product, which is invisible to the naked eye, but is also due to the effect of luminescence in the rays of the excimer laser.

The known method is technologically difficult to check for invisible marking requires sophisticated equipment, but also limits the potential for further use of marked product as the mechanical impact can ruin caused by way of the label.

A known method of applying on the subject of subsurface marking (see patent RU No. 2124988, IPC B41M 5/24 published 20.01.1999), including direction on the surface of the object beam of laser radiation to which the material of the object, essentially opaque, and the energy of the beam absorbed by the surface of the object sufficient for the education of localized stresses in the object, in pixels, spaced from the said surface, without the formation of any appreciable change in the surface, and localized voltage formed so usually invisible to the naked eye, but can become visible in polarized light.

The known method eliminates the possibility of simultaneous mechanical or laser engraving the surface of the object in a decorative or industrial purposes, as in this case, the sub-surface marking can be broken.

There is a method of marking the surface of the products and materials (see international application no WO 2008093006, IPC B41M 5/24, B23K 26/00, published 07.08.2008), coinciding with the proposed technical solution for the greatest number of significant features and adopted for the prototype. In a known manner on the surface of metal, plastic or ceramic products carry out the drawing of characters, one of which is visible and the other invisible, to the naked eye. Signs contain coded information. For forming a visible mark is used inkjet printer, and the invisible beam of pulsed laser radiation, characterized by a pulse duration of not more than 10 picoseconds. The application of marks is as follows. Using a computer to generate protective digital code. This code contains in the ormatio about the serial number or other characteristics of the marked product, for example, the date marking the batch number of the product. Randomly choose a region of the surface of the marked product for applying an invisible sign. Then in the selected area using a beam of laser radiation is applied an invisible sign, representing a two-dimensional barcode containing a predetermined digital code. Drawing an invisible sign shall exercise one of two options. In the first variant uses a series of pulses of laser radiation. Move the laser beam relative to the surface of the product in accordance with the graphical topology of two-dimensional barcode using a system of rotating mirrors. In the second variant uses one monoenoic laser radiation, and in the optical path marking system type spatial modulator beam matrix type, which is managed by a computer modulates the beam in accordance with the topology of two-dimensional barcode. When applying an invisible sign choose the energy density of the laser radiation in such a way as to carry out the erosion of the material with the characteristic size (diameter) of not more than 50 μm and a depth of not more than 5 μm. Due to this condition is achieved the indistinguishability of the mark to the naked eye. Then, on the surface of the product in areas not affected by l is Zernovo radiation, using an inkjet printer put a visible mark. This symbol also represents the two-dimensional bar code and contains information relative location invisible to the naked eye mark on the surface of the product.

The main disadvantage of the prototype method is the complexity of its technical implementation, requiring the simultaneous use of a laser marking system and an inkjet printer. It should also be noted that the known method involves, first, the interaction of laser radiation with the material of the product, which is the erosion of the surface to a depth of not more than 5 μm, secondly, labeling using an inkjet printer, which, of course, reduces wear as visible to the naked eye, and visible signs done by the method of the prototype.

The task of the invention was to provide such a method of marking the surface of the metal or its alloy, which would ensure the application in one process wear marks, one of which is a sign, visible to the naked eye, and the other protective digital code, invisible to the naked eye.

The problem is solved in that a method of laser marking the surface of the metal or alloy includes a preview build of gruberova the Noah curve depth marking of the sample surface of a given metal or alloy from the power density incident on the surface of the radiation under monotonic increase of the power density on the value of 1 j/(cm 2·) to the amount at which are marked on the surface of the drops of the melt. Then carry out the generation of protective digital code using a computer, where each number corresponds to a certain depth marks and the power density of the laser radiation, certain of the above-mentioned calibration curve, and the difference between the maximum and minimum depth marking selected experimentally so that the difference of depths was not observed with the naked eye (not more than 100 microns). After that put on the marked surface of the metal or its alloy by laser light is moved relative to the surface are marked, visible to the naked eye sign, representing an alphanumeric or graphical information with a minimum size of an individual element is not less than 20 μm. On the surface visible to the naked eye sign cause the protective digital code in the form invisible to the naked eye of a sequence of recesses with a linear size of not more than 100 μm and a depth corresponding to the specified number of protective digital code, the laser radiation is selected by the aforementioned calibration curve specific power.

Moving the laser relative to the surface of the metal or its alloy can be maintained under continuous laser light or pulse from the teachings of the laser, for example, with a pulse duration of 5 NS to 100 μs.

Moving the laser relative to the surface of the metal or its alloy can maintain a speed of 0.1-20000 mm/S.

Moving the laser relative to the surface of the metal or its alloy can be maintained for a given program, for example, by progressive scanning, referred to the surface.

Application of visible and invisible marks can be carried out consecutively or within one pass of the beam of laser radiation.

The visible sign may contain information about the chemical composition of the alloy product.

It is important to note that when exposed to laser radiation with a power density on the value of 1 j/(cm2·C), removing the metal or alloy in the area of impact of the beam occurs in the evaporative mode. When the threshold value of the power density of the incident radiation, are marked on the surface will form droplets of the melt, so as the removal of material will occur in evaporative mode, with the additional removal of the molten metal or alloy by vapor pressure.

When constructing a calibration curve, experimentally determine the following parameters marking: minimum thickness and depth of the line, observed with the naked eye, the cat heaven for the average human eye is 20 μm; the largest possible difference between the maximum and minimum depth marks and the maximum linear dimension of the recesses along the marked lines, which are not observed, the average naked eye and can be 100 microns.

The inventive method is illustrated in the drawing, where:

figure 1 shows a picture of the main labeling observed with the naked eye;

figure 2 shows a perspective view of the main plot marking depth H, is depicted in figure 1;

figure 3 shows a section along the longitudinal axis of the schematic representation of the main marking with indistinguishable to the naked eye additional protective marking a digital code, each number of which has a different depth h1-h6and a constant length L;

figure 4 shows a top view of the marking is shown in figure 3;

figure 5 the table below shows parameters of laser radiation to obtain four different depth values;

figure 6 shows a photograph of the surface on which is formed the visible and invisible to the naked eye image.

The inventive method of laser marking the surface of the metal or its alloy is as follows. Since the physical properties of various metals and alloys, the geometric characteristics of the marked product can significantly distinguish the Xia, the pre-build a calibration curve according to the depth of marking the surface of the sample of a given metal or alloy from the power density incident on the surface of the radiation under monotonic increase of the power density on the value of 1 j/(cm2·) to the amount at which are marked on the surface of the drops of the melt. Then carry out the generation of protective digital code using a computer, where each number corresponds to a certain depth marks and the power density of the laser radiation, certain of the above-mentioned calibration curve, and the difference between the maximum and minimum depth marking does not exceed 100 microns. Protective digital code written in a particular number system. The radix may be selected arbitrarily, but the possibility of its use needs to be checked. Due to the physical processes accompanying the laser marking may "swimming" adjacent to each other of the recesses. This imposes certain restrictions on the ability of the proposed method. First, the maximum depth of additional marking protective digital code may not exceed the thickness D of the product. Secondly, the process of ablation (removal) of material limits the relative size of the additional marking, i.e. the value of CH is bin h 1h2, ... h6length L (see figure 3). Therefore, previously conducted test marking, which establish minimum possible values of hi, (hi=D·i/(2·A), where D is the thickness of the product, And - the radix code, i=1, 2...(A) and L, choose numbering system applied protective digital code. If each of the recesses obtained during the test marks, cannot be separated from the next in depth, you should choose a smaller value and repeat the test labeling. To read protective digital code can be applied visual observation with a microscope of the type LOMO METAM. After that put on the marked surface 1 of metal or its alloy (see figure 1, figure 2) the laser light is moved relative to the surface are marked 1, visible to the naked eye mark 2 depth N=10-100 μm, representing an alphanumeric or graphical information with a minimum size of an individual element is not less than 20 μm. The obtained surface 3 visible to the naked eye mark 2 is applied protective digital code in the form invisible to the naked eye sequence of the recess 4 (see figure 3, figure 4) with a linear size of not more than 100 μm and a depth of hicorresponding to the specified number of protective digital code. Security code causing the laser radiation is selected by the aforementioned calibration curve specific power. To read the verification code conduct depth measurement markings along the edges of the entire image. Example marking protective digital code encoded sequence of numbers "1221304289" is shown in figure 3. Modern laser systems installation type "Biomarker allow you to mark a very thin lines of different depths: for example, a thickness of 30 μm, a depth of 10 to 50 μm. Observation with the naked eye marking constant thickness of about 20-30 μm, it is possible, and the supervision of the marking of variable depth of 10-50 μm is on the threshold sensitivity of the human eye. The observation of variable depth markings made in such a setup, thus, will be indistinguishable to the naked eye.

Example. Was made marking polished plate of size 10×8×0.5 mm, material - gold 585.

Visible to the naked eye the picture - the image of a female head and figures "585". Invisible to the naked eye pattern is a sequence of numbers "03 21 110 21 120"that the numeral system with base 4 means the date the marking "03 02 2009" and serial number "24". Labeling was performed on a universal installation precision laser marking and engraving on the basis of Nd:YAG laser with diode pumping "Biomarker" produced by LLC "Laser Center. Move the s of the laser beam relative to the surface of the product was carried out using a two-axis scanner-based actuators G325DT GSI Lumonics. The duration of monopulse laser radiation was 35 NS, the modulation frequency is 18 kHz, the energy monopulse measured with a pyroelectric sensor Ophir D-25, 0.5 MJ. Previously, using a sample of material was constructed calibration curve according to the depth of marking the surface of the sample given alloy from the power density incident on the surface of the radiation. It was also found that the line width of 30 μm and a depth of 20 μm are observed with the naked eye; a possible difference between the maximum and minimum depth marks and the maximum linear dimension of the recesses along the marked lines, which are not observed with the naked eye, 50 μm and 100 μm, respectively. Next, using the obtained experimental data and calibration curve was plotted visible and undetectable to the naked eye marks on the surface of the plate, under the action of laser radiation of appropriate power. The parameters of laser radiation to obtain four different depth values shown in the table on figure 5. Changing the value of the power density of the laser radiation was achieved through variations in the speed of movement of the beam of radiation in the range of 10-50 mm/sec. As a result of exposure to laser radiation on the surface of the formed aggregate image is of Ajani, visible and invisible to the naked eye (6).

1. The method of marking the surface of the metal or alloy, including preliminary construction of the calibration curve according to the depth of marking the surface of the sample of a given metal or alloy from the power density incident on the surface of the radiation under monotonic increase of the mentioned power density on the value of 1 j/(cm2·) to the amount at which are marked on the surface of the drops of melt generation protective digital code using a computer, where each number corresponds to a certain depth marks and the power density of the laser radiation, certain of the above-mentioned calibration curve, and the difference between the maximum and minimum depth marking does not exceed 100 μm, the drawing are marked on the surface of the metal or its alloy visible to the naked eye sign, representing an alphanumeric or graphical information with a minimum size of an individual element is not less than 20 μm, the laser radiation, which move relative to the marked surface, and coating the surface obtained visible to the naked eye of the protective sign of the digital code in the form invisible to the naked eye sequence recesses with linear razmerama more than 100 μm and a depth, corresponding to the specified number of protective digital code, the laser radiation is selected by the aforementioned calibration curve specific power.

2. The method according to claim 1, characterized in that the movement of the laser radiation relative to the surface of the metal or its alloy is carried out at continuous laser radiation.

3. The method according to claim 1, characterized in that the movement of the laser radiation relative to the surface of the metal or its alloy is carried out at a pulse laser light with a pulse duration of 5 NS to 100 μs.

4. The method according to claim 1, characterized in that the movement of the laser radiation relative to the surface of the metal or alloy of lead with a speed of 0.1-20000 mm/S.

5. The method according to claim 1, characterized in that the movement of the laser radiation relative to the surface of the metal or its alloy is carried out by progressive scanning, referred to the surface.

6. The method according to claim 1, characterized in that the application visible to the naked eye sign and protective digital code carried out consistently.

7. The method according to claim 1, characterized in that the application visible to the naked eye sign and protective digital code carried out during one passage of the laser radiation.

8. The method according to claim 1, characterized in that the visible sign contains information on the chemical the composition of the alloy product.



 

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