RU2753066C1 - Optical head for laser cutting - Google Patents

Abstract

FIELD: processing materials.

SUBSTANCE: invention relates to the field of processing materials with a laser beam, and in particular to an optical head for laser cutting. The optical head contains an outer fixed body (1) and an inner movable body (3). A focusing lens (5) is rigidly fixed on the inner movable body, ensuring that its cylindrical surface is based on the cylindrical surface of the inner movable body (3). The nozzle (6) body is rigidly fixed to the inner surface of the outer stationary body (1), a sealed closed cavity (10) is formed between the nozzle (6) body and the outer stationary body (1), communicated with the active gas supply channel (9) and through holes (8) in the nozzle (6) body. The closed cavity (10) is formed by an annular plate (7) that encloses the nozzle (6) body around the circumference, and the nozzle (6) protrusion. The nozzle (6) body is cylindrical. A capacitive sensor (17) is installed in the lower part of the outer stationary body (1) to determine the distance between the nozzle (6) exit and the cut metal (18). The removable nozzle (17) is made narrowing-expanding.

EFFECT: optical head provides a minimum cutting width and minimum surface roughness, as well as a minimum heat-affected zone by setting the focal length and, accordingly, the diameter of the focal spot, depending on the thickness of the metal being cut.

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Description

The invention relates to the field of processing materials with a laser beam, namely, laser cutting and drilling holes.

Known optical head for laser cutting of sheet metal (patent RU No. 151792, IPC B23K 26/38, published on 20.04.2015), in which the unit for moving the focusing system along the optical axis relative to the telescopic system is made in the form of two cylinders interconnected by a threaded connection of different diameter with the ability to move relative to each other along the optical axis, while the focusing system is installed on the side of the free end of the cylinder of a smaller diameter, and the telescopic system is installed on the side of the free end of the second cylinder of a larger diameter, and the unit for simultaneous movement along the optical axis of the focusing and telescopic systems is made in the form of a cylinder with a thread on the outer surface, while on the inner surface of the optical head housing there is a thread corresponding to the thread of the specified cylinder, and the cylinder itself is rigidly fixed on the outer side of the cylinder with the focusing system of the unit for moving the focusing systems along the optical axis relative to the telescopic system. However, the known device does not provide sufficient precision in material processing and has a complex structure.

Known optical head for laser processing (patent RU No. 34427, IPC B23K26 / 00, B23K26 / 02, B23K26 / 03, published 10.12.2003). containing a device for outputting laser radiation from an optical fiber, a rotary interference mirror, a telescopic system consisting of a negative component and a positive component, a focusing system, a visual observation system including a video camera optically coupled with a rotary interference mirror with a focusing system, and a monitor. To control the radiation between the device for outputting laser radiation and the focusing system, one of the optical elements of the telescopic system (for example, an optical element) is installed with the ability to move along its optical axis. The radiation output device, rotary interference mirror, telescopic system, focusing system, visual observation system are located in a single housing. However, the known device has a complex structure.

Known optical laser head (patent RU No. 2578885, IPC B23K26 / 14, published 03/27/2016), containing external and internal gas nozzles with channels for supplying active and protective gases, installed concentrically and with a gap, a focusing lens placed in the internal nozzle, and through holes formed on the side surface of the inner nozzle. The inner nozzle is made like a Laval nozzle, and the focusing lens is placed in the inner nozzle with the provision of basing its cylindrical surface along the cylindrical surface of the inner nozzle with the ability to move along the axis, while the channel for supplying the active gas to the inner nozzle is located between the focusing lens and the Laval nozzle, and the through holes in the inner nozzle are located above the lens. The optical laser head is equipped with locks with the ability to limit the movement of the focusing lens along the axis, located below the through holes and above the lower channel for supplying the process gas. However, the known device does not provide sufficient accuracy in material processing due to piston movement of the nozzle, change of specialized optical heads for performing various technological operations (cutting, welding, drilling holes). This leads to a loss of time, low accuracy and equipment downtime during its retooling.

Known laser optical head (patent RU No. 2641213, IPC B23K 26/14, published on January 16, 2018), patent holder KNITU-KAI, where the inner movable body with a nozzle is installed in a fixed outer body with the ability to move by means of a gear transmission made in the form of a toothed rack mounted on the inner casing, and a pinion shaft mounted on a bracket fixed on the outer stationary casing and connected to an electric drive, and a capacitive sensor is installed in the lower part of the outer stationary casing for setting and controlling the size between the nozzle exit and the workpiece, and on at the nozzle outlet there is a removable nozzle with a converging-expanding channel at the outlet. However, the laser optical head performs three operations on one head. At the same time, it does not provide sufficient accuracy of laser processing when changing processing operations (cutting, welding, punching holes), the complexity of control when changing operations.

Known laser optical head (patent RU No. 2727392, IPC B23K 26/14, published on January 16, 2018), patent holder KNITU-KAI, the closest in technical essence and taken as a prototype, where the nozzle body is cylindrical, with two annular plates for overlapping channels for supplying active and protective gases during movement, while on the outer end surfaces of the annular plates there are sealing cuffs with a smooth surface, and between the outer stationary body and the inner movable body there are restraining rings, the removable nozzle is made tapering, the removable nozzle is made narrowing expanding, the cuffs are made of a compacted structure with composite linings that ensure optimal sliding, a capacitive sensor is installed in the lower part of the outer stationary body to determine the distance between the cylindrical nozzle cut and the workpiece. However, the laser optical head does not provide sufficient accuracy within the target depth and does not provide sufficient laser cut depth.

The technical problem to be solved by the claimed invention is the creation of an optical head for use in laser cutting and drilling of holes with high technological performance.

The technical result to be achieved by the present invention is to increase the purity and accuracy of processing, increase the depth of the laser cut by adjusting the diameter of the focal spot, reduce energy consumption, simplify equipment, and increase the reliability of the structure.

The technical result is achieved by the fact that in the optical head for laser cutting, containing an outer stationary body with a channel for supplying an active gas, inside the stationary body concentrically and with a gap there is an inner movable body, a focusing lens, a nozzle, on the side surface of which through holes are made, and at its exit there is a removable attachment, new is that the focusing lens is rigidly fixed in the inner movable body with the provision of basing its cylindrical surface on the cylindrical surface of the inner movable body, the nozzle body is rigidly fixed to the inner surface of the outer stationary body,Between the nozzle body and the outer stationary body, a sealed closed cavity is formed, connected with the active gas supply channel and through holes in the nozzle.

The nozzle body is cylindrical.

A capacitive sensor is installed in the lower part of the outer stationary body to determine the distance between the nozzle exit and the workpiece.

The detachable nozzle is made of narrowing-expanding.

Figure 1 shows a longitudinal section of an optical head for laser cutting in the cutting and drilling mode.

Figure 2 shows view A (Figure 1).

Figure 3 shows an enlarged view of position 15 (Fig. 1) of the removable nozzle.

Figure 4 shows a photograph of a sample of duralumin alloy D16 with a thickness of 3.5 mm with parameters of pulsed laser cutting with laser power P = 4000 W, cutting speed Vc = 0.05 m / s, pulse frequency n = 5000 Hz, pulse duration τi = 60 ms, pause duration τp = 40 ms, deepening of the focal spot into the material ∆f = -1.5 mm, distance from the nozzle exit to the metal surface s = 0.5 mm, process gas pressure - air p = 1.5 MPa, where shows the transition from the heat-affected zone to the base metal after pulsed laser cutting.

The optical head for laser cutting contains an external stationary body 1, which is equipped with a cover 2 (figure 1). Inside the outer stationary body 1 there is an inner movable body 3 with the ability to move (Fig. 1) using a mechanical or electrical drive 4 (Fig. 1). Focusing lens 5 is rigidly fixed in the inner movable housing 3 with the provision of basing its cylindrical surface along the cylindrical surface of the inner movable body 3. To the inner surface of the outer stationary body 1, the nozzle body 6, made cylindrical, is rigidly fixed. The body of the nozzle 6 is rigidly fixed either by welding, or made as a whole product. Through holes 8 are made on the side surface of the nozzle body 6 (Fig. 1). The stationary body 1 has a channel 9 for supplying an active gas - oxygen into a closed cavity 10. Closed cavity 10, formed by an annular plate 7 located below the channel 9, and the protrusion of the nozzle body 6 communicates with the oxygen supply channel 9 and through holes 8. Closed cavity 10 is made sealed and equipped with sealing collars 11 for snug fit to the inner wall of the outer stationary body 1, which protects against oxygen ingress into the laser cut zone 12. In the cutting or drilling mode, the axes of the through holes 8 are perpendicular to the axis of the laser beam. At the ends of the protrusions of the inner movable body 3, sliding cuffs 13 with a sealed structure and composite sealed gaskets are inserted, providing a snug fit to the inner surface of the outer stationary body 1 and smooth movement of the inner movable body 3.

Figure 1 shows the position of the inner movable body 3 at a minimum focal distance to the cut metal 18, corresponding to the maximum thickness of the cut metal 18 to 40 mm. The sealing collars 11 ensure the tightness of the closed cavity 10, therefore, there is 100% supply of active gas from the channel 9 to the closed cavity 10 and to the through holes 8, respectively.

The movement of the inner movable body 3 is fixed by the stop rings 14 to the stop (Fig. 1).

During cutting or drilling holes, the movement of the inner movable body 3 with the focusing lens 5 adjusts the focal length and, accordingly, the set the diameter of the focal spot (Fig. 1). Active gas, oxygen, is supplied to the closed cavity 10 through channel 9. In cutting modes and drilling holes, a converging-expanding removable nozzle 15 is attached to the nozzle body 6 (Fig. 1), which for cutting metals with a thickness of 1 mm to 40 mm has a diameter in a narrow section of 0.5 ± 0.02 mm and an expansion angle 15 ° (Fig. 7). Figure 2 shows an enlarged view A (Fig. 1) of a converging-expanding removable nozzle 15 in the mode of cutting and drilling metal holes with a thickness of 1 mm to 40 mm. For fastening the converting-expanding removable nozzle with 15 metric screws M2 mm (Fig. 1) there is a key hole 16 (Fig. 5). In the area of the laser cut 12 (Fig. 1) through the focusing lens 5, the nozzle body 6 and the removable nozzle 15, a laser beam enters with oxygen.

On the outer stationary body 1, a capacitive sensor 17 is rigidly fixed (Fig. 1) to determine the distance between the nozzle 6 and the cut metal 18, which is mounted on the bracket 19 in the lower part of the outer stationary body 1, which ensures the operability of the optical head .

Figure 4 shows the structure of a defect-free transition from the heat-affected zone of a pulsed laser cut to the base metal. The sample shows a uniform dendritic structure without cracks, no intercrystalline inclusions, no scratches, no sagging. The minimum width of the heat-affected zone indicates the optimal parameters for pulse cutting. The impulse cutting mode is optimal as a confirmation of the technical result.

The optical head for laser cutting works as follows.

When cutting metals with a thickness of 1 mm to 40 mm, the focal length and the diameter of the focal spot are set depending on the thickness of the metal being cut 18 and on the type of metal by moving the inner movable body 3 with a focusing lens 5. For part thicknesses from 5 mm to 40 mm corresponds to the minimum focal length, which is determined by the experimental method (Fig. 1). Moving the inner movable body 3 adjusts the focal length and the diameter of the focal spot, respectively. A converging-expanding removable nozzle 15 is installed at the outlet of the nozzle 6. To achieve the smallest diameter of the focal spot when cutting large thicknesses or drilling holes, the inner movable body 3 is moved downward by a mechanical or electric drive 4 until it stops by the stop rings 14. Then a laser beam is supplied with certain modes into the optical head. The laser beam passes through the focusing lens 5. The axes of the through holes 8 are perpendicular to the axis of the laser beam. An active gas - oxygen is supplied to the closed cavity 10 through the channel 9, which passes through the through holes 8 of the nozzle 6 and, together with the laser beam through the focusing lens 5, enters the laser beam coaxially into the laser cut zone 12 (Fig. 1). The laser beam and oxygen pass through a converging-expanding removable nozzle 15, in which the flow rate of the gas jet is supersonic, which will simultaneously clean the material processing site from slags and improve the processing quality. A supersonic jet blown into the laser cut zone 12 through a converging-expanding nozzle 15 removes the resulting metal melt from a narrow laser cut 12 (minimum cutting width b = 0.1-0.3 mm minimum surface roughness Rz = 1.075 μm)) with high efficiency, which allows the mode of cutting metals of large thicknesses up to 40 mm at a high cutting speed, which will generally lead to an increase in the quality of laser cutting and an increase in the depth of laser cut 12 workpieces 18.

To achieve the largest diameter of the focal spot when cutting small thicknesses or drilling holes in parts of small thicknesses, the inner movable body 3 is moved upwards by a mechanical or electric drive 4 up to the stop with stop rings 14. For thicknesses from 1 mm to 5 mm, the maximum focal length corresponds to determined by a similar method (Fig. 1). Subsequent actions are carried out similarly to the previous ones for large thicknesses.

In the mode of drilling holes in metals, the process is similar to the mode of laser cutting of metals, but in addition, a high power of laser radiation is required.

As a result of experiments carried out at PJSC "KAI-Laser", the following indicators were obtained: the roughness of the cut surface on titanium alloys for thicknesses from 1 mm to 40 mm not higher than 2 ... 4 microns, on stainless and high-alloy steels not exceeding 10 ... 28 microns at cutting width 0.1 ... 0.35 mm, the depth of the heat-affected zone is not more than 0.2 mm. Adjustable modes - power, speed, duration and frequency of pulses affect the quality of the cut: cutting width b, surface roughness Rz and the width of the heat-affected zone.

Technological characteristics of "Optical head for laser cutting":

Process gas pressure, MPa up to 2.5 Process gas overpressure focusing optics, MPa no more than 0.02 Laser power, kW 0.1 ... 30 Aperture angle of laser radiation, ° C 2 ... 30

According to the experimental data, the process gas consumption is saved by 60%.

The optical head for laser cutting will allow cutting and drilling holes in metals from 1 mm to 40 mm thick with high processing purity and high accuracy. The depth of the laser cut is determined by the focal length and the diameter of the focal spot, respectively, which is set by the movement of the inner movable body 3 with the focusing lens 5. In addition, the proposed design will reduce energy consumption, simplify equipment, increase the reliability of the structure and ensure high productivity due to optimal cutting modes.

Claims (4)

1. Optical head for laser cutting, containing an outer stationary body with a channel for supplying an active gas, an inner movable body located concentrically and with a gap inside the stationary body, a focusing lens and a nozzle, on the side surface of which through holes are made, and a removable attachment, characterized in that the focusing lens is rigidly fixed in the inner movable body with the provision of basing its cylindrical surface along the cylindrical surface of the inner movable body, and the nozzle body is rigidly fixed to the inner surface of the outer stationary body, while Between the nozzle body and the outer stationary body, a sealed closed cavity is formed, connected with the active gas supply channel and through holes in the nozzle. 2. The optical head according to claim 1, characterized in that the nozzle body is cylindrical. 3. The optical head according to claim 1, characterized in that a capacitive sensor is installed in the lower part of the outer fixed body to determine the distance between the nozzle exit and the cut metal. 4. Optical head according to claim 1, characterized in that the removable attachment is made converging-expanding.

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