WO2017043460A1

WO2017043460A1 - Laser processing method and laser processing device for minimizing incidence of self-burning

Info

Publication number: WO2017043460A1
Application number: PCT/JP2016/076072
Authority: WO
Inventors: 明彦杉山; 市川　智也; 真梨奈齋藤
Original assignee: 株式会社アマダホールディングス
Priority date: 2015-09-08
Filing date: 2016-09-06
Publication date: 2017-03-16
Also published as: JP6190855B2; JP2017051965A

Abstract

Provided is a laser processing method in which laser light having a wavelength in the 1 μm band is used, wherein a workpiece can be cut with consistent quality by minimizing the incidence of self-burning. A laser processing method in which a plate-shaped workpiece W is processed by cutting using laser light 9 having a wavelength in the 1 μm band, wherein: the position of the focal point 11 of the laser light 9 during processing of the workpiece by cutting is positioned between the center CL of the workpiece W in the plate thickness direction of the workpiece W and the end surface WU of the workpiece W on the trailing side in the direction in which the laser light 9 advances, which is the optical axis direction of the laser light 9; and the workpiece W is machined by cutting, using the laser light 9 having the focal point at the position of the focal point 11.

Description

Laser processing method and laser processing apparatus for suppressing occurrence of self-burning

The present invention relates to a laser processing method and a laser processing apparatus, and more particularly to a laser processing method and a laser processing apparatus that control laser light when laser processing is performed on a workpiece.

In the conventional laser cutting, as shown in FIG. 13, the energy density is increased by condensing the laser beam 303 into a spot size (condensed diameter) of 100 μm to 1000 μm using a condensing lens 301, and metal (soft steel). A portion of the plate (workpiece) 305 is instantaneously melted, and cutting is performed while removing the molten metal with an auxiliary gas (not shown in FIG. 13) as an assist gas.

Also, for thick steel plates, oxygen is used as an assist gas, and the plate thickness band, which is difficult to cut by laser power alone, is cut by the heat of oxidation reaction. Further, in the processing of mild steel sheets by cutting using oxygen, the focal position 307 is in a defocused state after being adjusted to an optically appropriate condensing diameter (the focal position 307 is positioned above the upper surface of the workpiece 305). In general, it is common sense to use a method of processing in a state where

Here, for example, Patent Document 1 can be listed as a conventional technical document.

Japanese Patent Laid-Open No. 6-155063

By the way, laser light with a wavelength of 1 μm band such as DDL (Direct Diode Laser) or fiber laser has a very high power intensity distribution near the center of the beam as compared with a CO2 laser (see FIG. 14B) (FIG. 14). (Refer to (a)), since the light absorptance with respect to the metal (work) is very high compared with the light of 10 μm band such as CO2 laser, the mild steel plate (work) using oxygen as an assist gas. In cutting, when the focused spot size of the laser beam optimal for cutting is irradiated, the cutting width (kerf width) on the upper surface of the material (workpiece) becomes too large, making kerf control difficult and excessive combustion (self There is a problem that cutting with stable quality is very difficult, such as causing burning.

Therefore, the present invention can cut a workpiece with stable quality by suppressing the occurrence of self-burning in the laser beam machining method and laser machining apparatus using a laser beam having a wavelength of 1 μm. An object is to provide a laser processing method and a laser processing apparatus.

According to one aspect of the present invention, there is provided a laser processing method for cutting a plate-shaped workpiece using a laser beam having a wavelength of 1 μm, and the focal point of the laser beam when the workpiece is cut. Is positioned between the center of the workpiece in the plate thickness direction of the workpiece and the end surface of the workpiece on the rear side in the traveling direction of the laser beam in the optical axis direction of the laser beam; There is provided a laser processing method including cutting the workpiece using the laser beam having a focal point at the focal position.

Preferably, in the laser processing method, the workpiece is a thick plate and is made of iron, steel, an iron alloy, or a material that generates heat by an oxidation reaction, and the cutting processing by the workpiece includes oxygen. Assist gas is sprayed from the small-diameter nozzle toward the workpiece, and the inner diameter of the small-diameter nozzle is not less than 0.6 mm and not more than 15% of the thickness of the workpiece. ing.

Preferably, in the laser processing method, the workpiece is a thick plate and is made of iron, steel, an iron alloy, or a material that generates heat by an oxidation reaction, and the cutting processing by the workpiece includes oxygen. Assist gas is sprayed from the small-diameter nozzle toward the workpiece, and when the workpiece is cut, the assist gas is placed inside the holes and grooves formed by the cutting. Spray.

Preferably, in the laser processing method, when the workpiece is pierced before the cutting processing, the position of the focal point of the laser beam when the piercing processing is performed in the plate thickness direction of the workpiece. , Between the center of the workpiece and the end surface of the workpiece in the optical axis direction of the laser beam and on the front side in the traveling direction of the laser beam, or in the optical axis direction of the laser beam and traveling of the laser beam Between the end surface of the workpiece on the front side in the direction and a position near the end surface of the workpiece on the front side in the traveling direction of the laser beam and slightly separated from the end surface of the workpiece on the front side in the traveling direction of the laser beam. .

According to another aspect of the present invention, a laser processing head that emits laser light having a wavelength of 1 μm toward a plate-shaped workpiece and is capable of changing a focal position of the laser light, and the workpiece is installed. When the workpiece installed on the workpiece installed section and the workpiece installed on the workpiece installed section are cut, the position of the focal point of the laser beam emitted from the laser machining head in the thickness direction of the workpiece, A laser including a control unit that controls the laser processing head so as to be positioned between the center of the workpiece and an end surface of the workpiece that is in the optical axis direction of the laser beam and is behind the laser beam traveling direction. A processing apparatus is provided.

Preferably, in the laser processing apparatus, when the workpiece is a thick plate and is made of iron, steel, an iron alloy, or a material that generates heat by an oxidation reaction, the cutting process with the workpiece is performed using oxygen. It is comprised so that it may be made using the assist gas sprayed toward the said workpiece | work from a small diameter nozzle, The internal diameter of the said small diameter nozzle is 0.6 mm or more, and the value of 15% or less of the plate | board thickness of the said workpiece | work It has become.

Preferably, in the laser processing apparatus, when the workpiece is a thick plate and is made of iron, steel, an iron alloy, or a material that generates heat by an oxidation reaction, the cutting process with the workpiece is performed using oxygen. A hole or a groove formed by using an assist gas sprayed from a small-diameter nozzle toward the workpiece, and when the workpiece is cut by the workpiece, the assist gas is formed by the cutting processing. It is configured to spray inside.

Preferably, in the laser processing apparatus, when the control unit performs piercing processing on the workpiece before performing the cutting processing, the position of the focal point of the laser light emitted from the laser processing head is determined. In the plate thickness direction of the workpiece, it is between the center of the workpiece and the end surface of the workpiece in the optical axis direction of the laser beam and on the front side in the traveling direction of the laser beam, or in the optical axis direction of the laser beam. The end surface of the workpiece on the front side in the traveling direction of the laser beam, and the position near the end surface of the workpiece on the front side in the traveling direction of the laser beam and slightly separated from the end surface of the workpiece on the front side in the traveling direction of the laser beam The laser processing head is controlled so as to be positioned between the two.

According to the present invention, in a laser beam machining method and a laser beam machining apparatus using a laser beam having a wavelength of 1 μm, it is possible to cut a workpiece with stable quality by suppressing the occurrence of self-burning. There is an effect.

It is a figure which shows schematic structure of the laser processing apparatus which concerns on embodiment of this invention. It is a figure which shows the laser beam which passed the condensing lens of the laser processing apparatus which concerns on embodiment of this invention. (A) is a figure which shows the state when cut | disconnecting a workpiece | work in an in-focus area with the laser processing apparatus which concerns on embodiment of this invention, (b) is the laser processing apparatus which concerns on embodiment of this invention. It is a figure which shows the state when carrying out the cutting process of the workpiece | work in a defocus area. (A) is a figure which shows schematically the case where assist gas is supplied with the conventional nozzle, (b) is the case where assist gas is supplied with the small diameter nozzle of the laser processing apparatus which concerns on embodiment of this invention. It is a figure shown roughly. It is a figure which shows roughly the state which is cutting the workpiece | work with the laser beam machine apparatus which concerns on embodiment of this invention. (A) is a figure which shows roughly the state which is cutting the workpiece | work in the state which made the focal position of the laser beam correspond to the upper surface (surface) of a workpiece | work with the laser processing apparatus which concerns on embodiment of this invention. Yes, (b) schematically shows a state in which the workpiece is cut and processed in a state where the focal position of the laser beam coincides with the center of the thickness of the workpiece in the laser processing apparatus according to the embodiment of the present invention. FIG. (A) shows the focus position and the collection of laser light when a small-diameter nozzle of the laser processing apparatus according to the embodiment of the present invention is used to cut a workpiece having a thickness of 12 mm while changing the focus position. It is a figure which shows the relationship between an optical diameter and the possibility of a process (good or bad of a process), (b) is a figure which shows the form of the processed surface of the workpiece | work in case a process is favorable. (A) is a figure which shows the form of the cutting groove formed by performing a cutting process to the workpiece | work of thickness 12mm with the laser processing apparatus which concerns on embodiment of this invention, (b) is embodiment of this invention. It is a figure which shows the presence or absence of generation | occurrence | production of the self-burning in the case where the workpiece is cut in the in-focus area and the workpiece is cut in the defocus area. (A) is a state of occurrence of self-burning when a single workpiece is cut in a defocus area by a laser processing apparatus according to an embodiment of the present invention to cut out 10 triangular products or semi-finished products. (B) is an enlarged view of one product or semi-finished product in which self-burning has occurred, and (c) is a diagram showing a processing failure state of what is shown in (b). . (A) is a state of occurrence of self-burning when a single workpiece is cut in an in-focus area by a laser processing apparatus according to an embodiment of the present invention and 10 triangular products or semi-finished products are cut out. (B) is an enlarged view of one product or semi-finished product in which self-burning has not occurred. In the laser processing apparatus which concerns on embodiment of this invention, it is a figure which shows the range which can be cut in the relationship between a laser output and a processing speed. It is a figure which shows the state of the process surface of a cutting process in the case of changing the focus position and processing speed of a laser beam with the laser processing apparatus which concerns on embodiment of this invention. It is a figure which shows the conventional laser processing. (A) is a figure which shows the profile of a fiber laser, (b) is a figure which shows the profile of CO2 laser.

As shown in FIG. 1 and the like, the laser processing apparatus 1 according to the embodiment of the present invention is configured to include a laser processing head 3, a workpiece setting unit 5 (see FIG. 5), and a control unit 7.

The laser processing head 3 emits laser light 9 having a wavelength of 1 μm (for example, 0.7 μm to 1.2 μm) toward a thick plate workpiece W installed in the workpiece installation unit 5 (FIG. 5). See also). As the laser beam 9, for example, a laser beam of a fiber laser, DDL (direct focusing semiconductor laser) or YAG laser can be listed. In the laser processing head 3, the position of the focal point (condensing point) 11 of the laser light 9 can be changed (changed and adjusted).

The laser processing apparatus 1 is further provided with an oscillator 13 and a process fiber 15. The laser light 9 oscillated by the oscillator 13 passes through the process fiber 15 and passes through the process fiber 15. The light is emitted toward the laser processing head 3 from the emission end 17 provided at the end.

The laser processing head 3 includes a casing 23 that includes a cylindrical main body 19 and a nozzle 21, a collimation lens 25, and a condenser lens 27. The collimation lens 25 is provided in the cylindrical main body 19 above the cylindrical main body 19, and the condensing lens 27 is provided in the cylindrical main body 19 below the cylindrical main body 19. Is provided. The nozzle 21 is provided at the lower end of the cylindrical main body 19.

An assist gas supply unit 36 is provided below the cylindrical main body 19, and an assist gas (for example, an assist gas containing a large amount of oxygen) 37 is supplied from the assist gas supply unit 36 into the nozzle 21.

The laser beam 9 emitted from the emission end 17 passes through the collimation lens 25 and the condenser lens 27 in this order, and is emitted downward, for example, from the opening 29 at the end (lower end) of the nozzle 21. Then, the workpiece W installed in the workpiece installation unit 5 is irradiated and laser processing (piercing processing and cutting processing) is performed on the workpiece W. Note that the optical axis of the laser beam 9 emitted from the emission end 17 and applied to the workpiece W extends, for example, in the vertical direction.

Further, the laser light 9 emitted from the emission end 17 is converted into a substantially parallel light beam by passing through the collimation lens 25, and then becomes convergent light by passing through the condenser lens 27.

When laser processing is performed on the workpiece W, the assist gas 37 supplied into the nozzle 21 is supplied (sprayed) toward the workpiece W from the opening 29 at the end of the nozzle 21.

The condensing lens 27 is provided integrally with the housing 23, but the collimation lens 25 is movable and positionable in a direction approaching or separating from the condensing lens 27 (housing 23). It can be moved and positioned with respect to the vertical direction). Thereby, the position of the focal point 11 of the laser light 9 (the distance LZ between the lower end of the nozzle 21 and the focal point 11 in the vertical direction) can be changed (change adjustment).

In addition to or in addition to making the collimation lens 25 movable and positionable in the vertical direction with respect to the housing 23, the condenser lens 27 is made movable and positionable in the vertical direction with respect to the housing 23. The position of the focal point 11 of the laser light 9 may be changed (change adjustment).

The workpiece setting unit 5 is provided, for example, on the lower side of the laser processing head 3, and the plate-like workpiece W installed (placed) on the workpiece setting unit 5 has a thickness direction of the workpiece W in the vertical direction. It has become. In addition, the laser processing head 3 can be moved and positioned relatively in the horizontal direction with respect to the workpiece W installed in the workpiece setting section 5, and can be moved and positioned in the vertical direction. A predetermined interval is provided in the vertical direction between the workpiece W installed in the section 5 and the laser processing head 3.

In the above description, the position of the focal point 11 is changed (change adjustment) by changing the positions of the collimation lens 25 and the condensing lens 27 of the laser processing head 3, but the collimation lens 25 and the condensing lens 27 are changed. Instead of or in addition to changing the position, the position of the focal point 11 may be changed (change adjustment) by changing the height position of the laser processing head 3 with respect to the workpiece setting unit 5. When the position of the focal point 11 is changed only by changing the height position of the laser processing head 3 with respect to the workpiece setting unit 5, the distance (in the height direction) between the lower end of the nozzle 21 of the laser processing head 3 and the focal point 11 is changed. The distance LZ does not change, but the distance between the lower end of the nozzle 21 of the laser processing head 3 and the workpiece placement unit 5 changes.

The control unit 7 includes a memory 31 and a CPU 33, and appropriately changes the position of the focal point 11 of the laser light 9 emitted from the laser processing head 3 according to an operation program stored in advance in the memory 31. For example, the operation of the laser processing apparatus 1 is controlled.

That is, when cutting the workpiece W, the control unit 7 controls the laser machining head 3 to change the position of the focal point 11 of the laser beam 9 emitted from the laser machining head 3 in the thickness direction of the workpiece W. (For example, in the vertical direction) the center (plate thickness center) CL of the workpiece W and the end surface (the laser processing head 3) of the workpiece W in the extending direction of the optical axis of the laser beam and on the rear side in the laser beam traveling direction. Opposite end face; bottom face) Located between WU. Here, the end surface of the work on the rear side in the traveling direction of the laser light means the end surface of the work on the side where the laser light passes through the work and is emitted from the work.

In the above control, the position of the focal point 11 of the laser light 9 may be coincident with the center CL of the workpiece W, but it is desirable that the position is higher than the lower surface WU of the workpiece W.

In addition, when the control unit 7 performs piercing on the workpiece W using the laser beam 9 before cutting, the control unit 7 determines the position of the focal point 11 of the laser beam 9 emitted from the laser processing head 3 as the plate of the workpiece W. In the thickness direction (vertical direction), between the center CL of the workpiece W and the end surface (upper surface) of the workpiece W in the optical axis direction of the laser beam 9 and in the forward direction of the laser beam 9, or the laser beam 9 The laser processing head 3 is positioned so as to be positioned between the end surface (upper surface) of the workpiece in the optical axis direction and the front side of the traveling direction of the laser light 9 and a location near the upper surface and slightly away from the upper surface. Control. Here, the end face of the workpiece on the front side in the traveling direction of the laser beam means the end surface of the workpiece on the side where the laser beam enters the workpiece.

Here, the in-focus area and the de-focus area will be described with reference to FIG. 2. The in-focus area is located above the focal point 11 of the laser light 9 that has passed through the condenser lens 27 (on the laser processing head 3 side). The area below the focal point 11 (on the side opposite to the laser processing head 3) is the defocus area.

In FIG. 6A, since the focal point 11 is positioned on the upper surface of the workpiece W, the workpiece W is cut in the defocus area. In FIG. 6B, since the focal point 11 is located at the center CL of the workpiece W (a plane located at the center in the thickness direction) CL, the workpiece 11 is cut into the workpiece W in the in-focus area above the center CL. Machining is performed, and the work W is cut in the defocus area below the center CL.

In the laser processing of the workpiece W, the workpiece W is pierced with the laser beam 9 and then moved relative to the laser processing head 3 starting from the through hole formed by the piercing processing. The workpiece W is cut with the laser light 9, and a product or semi-finished product having a predetermined shape is cut out from the workpiece W.

Work W is made of, for example, mild steel. When laser processing is performed on the workpiece W, an assist gas 37 composed of substantially oxygen is blown from the nozzle (small diameter nozzle) 21 toward the workpiece W.

At this time, when performing laser processing (piercing processing or cutting processing) on the workpiece W, the inner diameter of the small-diameter nozzle 21 is 0 in order to suppress the occurrence of self-burning in the workpiece W due to an oxidation reaction occurring in a wide range. .6 mm or more and 15% or less of the thickness of the workpiece W. Note that the plate thickness of the workpiece W is a thick plate as a workpiece to be processed by laser processing, and is, for example, in the range of 6 mm to 18 mm (may be 4 mm to 22 mm).

A frustoconical through-hole 35 is formed in the center of the small-diameter nozzle 21, and the small-diameter end of the frustoconical through-hole 35 (the upper surface having a small diameter on the truncated cone; the opening 29) is on the workpiece W side (lower side). The large-diameter end of the frustoconical through hole 35 (the large-diameter lower surface of the truncated cone) is located on the opposite side (upper side) of the workpiece W. The laser beam 9 is shaped like a truncated cone of the nozzle 21 so that the optical axis of the laser beam 9 and the central axis of the frustoconical through hole 35 coincide with each other (extend in the vertical direction). The through-hole 35 is emitted from the small-diameter opening 29 of the truncated cone-shaped through-hole 35 toward the workpiece W.

The inner diameter (opening diameter) of the small-diameter nozzle 21 is the inner diameter of the through-hole 35 at the small-diameter end (opening 29) of the frustoconical through-hole 35. The assist gas 37 supplied to the small-diameter nozzle 21 is blown downward toward the workpiece W from the circular opening 29 of the frustoconical through hole 35.

Since the through hole 35 of the small diameter nozzle 21 is formed in a truncated cone shape, the through hole 35 of the small diameter nozzle 21 is gradually throttled downward (approaching the workpiece W), and the assist gas 37 The gas flow blown out from, for example, flows downward and is difficult to diffuse outside (the upper surface of the workpiece W), and the diameter of the gas flow on the upper surface of the workpiece W is smaller than the kerf width formed on the workpiece W. It has become.

The supply amount of the assist gas 37 can be changed as appropriate according to the thickness of the workpiece W. Moreover, the pressure of the assist gas 37 (the supply pressure of the assist gas 37 to the small-diameter nozzle 21 or the pressure of the assist gas 37 in the opening 29 of the small-diameter nozzle 21) may be a gauge pressure. 0.05 MPa to 0.10 MPa.

As the material of the work W, iron, carbon steel, an iron alloy, or a material that generates heat by an oxidation reaction and promotes piercing or cutting by other than mild steel can be listed.

Further, in order to suppress the occurrence of self-burning in the workpiece W due to the occurrence of the oxidation reaction in a wide range, when laser processing (for example, cutting processing) is performed on the workpiece W, the assist gas 37 is used for laser processing (for example, cutting processing). ) May be configured to be sprayed into the hole or groove formed.

Furthermore, when laser processing is performed on the workpiece W, the surface of the workpiece W is sprayed by spraying the assist gas 37 on the inside of the holes and grooves formed by the laser processing (side surfaces of the holes and grooves; cut surfaces by laser processing). The assist gas 37 may not be directly blown onto the (upper surface) (the assist gas 37 blown from the small diameter nozzle 21 may not directly reach the surface of the workpiece W).

By the way, when a Laval nozzle is adopted as the small diameter nozzle 21 and the workpiece W is subjected to laser machining, the assist gas 37 may be blown into a hole or groove formed by laser machining at supersonic speed.

Next, the operation of the laser processing apparatus 1 will be described.

As an initial state, the workpiece W is placed on the workpiece placement unit 5, and the laser machining head 3 is positioned at a predetermined position (laser machining start position) with respect to the workpiece W placed on the workpiece placement unit 5. It shall be.

In the initial state, the laser beam 9 is irradiated from the laser processing head 3 toward the workpiece W, and the assist gas (oxygen) 37 is blown to perform laser processing (piercing processing) on the workpiece W. At this time, the focal point (condensing point) 11 of the laser beam 9 is positioned between the upper surface of the workpiece W and the center CL of the workpiece W in the plate thickness direction (vertical direction) of the workpiece W. 9 (focusing point) 11 is located above the upper surface of the workpiece W and in the vicinity of the upper surface of the workpiece W (a position where an energy density capable of melting the workpiece W can be obtained). Further, the focal point (condensing point) 11 of the laser beam 9 may be positioned between the center CL of the workpiece W and the lower surface WU of the workpiece W in the plate thickness direction (vertical direction) of the workpiece W. .

After the workpiece W is pierced, the workpiece W is cut relative to the laser machining head 3 with the through-hole formed by the piercing as a starting point, so that the workpiece W is cut and processed. Cut out products and semi-finished products from the shape. Also at this time, the focal point 11 of the laser light 9 is located between the center CL of the workpiece W and the lower surface WU of the workpiece W in the plate thickness direction (vertical direction) of the workpiece W.

In addition, when the cutting process is started from the end of the workpiece W, the cutting process may be performed without piercing the workpiece W.

Further, the workpiece W is melted by irradiating the workpiece W with the laser light 9 and the melted metal is removed by injecting the assist gas 37. Further, by using oxygen as the assist gas 37, it is possible to process a thick workpiece (a workpiece having a thickness of about 6 mm to 18 mm) W that generates heat of oxidation reaction and is difficult to cut with only laser output.

According to the laser processing apparatus 1, the position of the focal point 11 of the laser light 9 is positioned between the center CL of the workpiece W and the lower surface WU of the workpiece W in the plate thickness direction of the workpiece W. Therefore, the heat input to the workpiece W is reduced, the occurrence of self-burning in the workpiece W is suppressed, and the workpiece W can be cut with stable quality.

This will be described in more detail with reference to FIG. FIG. 3A shows an aspect corresponding to the above-described operation. In FIG. 3A, the focal point 11 of the laser light 9 is located on the lower end side of the workpiece W. The mode shown in FIG. 3B shows a comparative example. In FIG. 3B, the focal point 11 of the laser light 9 is located above the upper surface of the workpiece W. What is indicated by a broken line L <b> 1 in FIG. 3 is the wavefront of the laser light 9.

In FIG. 3A, the wavefront L1 of the laser beam 9 narrows downward at the workpiece W (convex upwards; the wavefront L1 is formed by a part of a spherical surface, and the center of this spherical surface is It is located below the wavefront L1). Thereby, the component (vector component in the traveling direction of the laser beam 9) 42 at the wavefront L1 of the laser beam 9 is orthogonal to the X direction (horizontal direction; side surface 39 of the hole or groove formed in the workpiece W). ) And the Z direction (vertical direction), the X-direction component 41 becomes inward, multiple reflection of the laser light 9 hardly occurs, and the amount of heat input to the side surface (cut surface) 39 decreases. The occurrence of self-burning is suppressed. The component 43 in the Z direction is from top to bottom.

On the other hand, in FIG. 3B, the wavefront L1 of the laser light 9 spreads downward at the workpiece W (projects downward; the wavefront L1 is formed as a part of a spherical surface, The center of this spherical surface is located above the wavefront L1). Thereby, when the component 42 in the wavefront L1 of the laser beam 9 is decomposed into the X direction and the Z direction, the component 41 in the X direction becomes outward, and multiple reflection of the laser beam 9 is likely to occur. ) The amount of heat input to 39 increases, and self-burning tends to occur.

Moreover, according to the laser processing apparatus 1, since the laser processing is performed using the assist gas 37 sprayed from the small diameter nozzle 21 toward the workpiece W, the range in which oxygen acts can be narrowed. It is suppressed that the range where the oxidation reaction occurs is suppressed, and self-burning generated due to excessive heat input is further suppressed by a synergistic effect with the position of the focal point 11 of the laser light 9 being lowered in the thickness direction of the workpiece W. can do.

Further, according to the laser processing apparatus 1, when the workpiece W is laser processed, the assist gas 37 is blown into the holes and grooves formed by the laser processing, so that the range in which oxygen acts can be narrowed. Further, it is possible to suppress the range in which the oxidation reaction occurs in the workpiece W from being widened, and to further suppress self-burning that occurs due to excessive heat input.

Further, according to the laser processing apparatus 1, the position of the focal point 11 of the laser light 9 is positioned between the center CL of the workpiece W and the lower surface WU of the workpiece W in the thickness direction of the workpiece W. The energy density on the upper surface (surface) is reduced, the oxidation action on the upper surface of the workpiece W is suppressed, and the occurrence of self-burning on the workpiece W is suppressed.

This will be described in more detail with reference to FIG. FIG. 4A shows a conventional mode, and FIG. 4B shows a mode in the laser processing apparatus 1.

In the embodiment shown in FIG. 4 (a), even if the small diameter nozzle 21 is used, the area where the assist gas 37 acts is widened because the distance between the workpiece W and the small diameter nozzle 21 is large, and the oxidation reaction occurs over a wide range. As a result, self-burning is likely to occur. On the other hand, in the mode shown in FIG. 4B, the small gas nozzle 21 is used and the distance between the workpiece W and the small nozzle 21 is reduced, so that the range in which the assist gas 37 acts is narrowed. The range in which the oxidation reaction acts is reduced, the expansion of the oxidation reaction is suppressed, and self-burning that occurs due to excessive heat input to the workpiece W can be prevented.

Here, the result of actually cutting the workpiece W is shown.

FIG. 7A shows a focal position (distance between the upper surface of the workpiece W and the focal point 11) and a focused diameter (workpiece) when a plate-shaped workpiece W (soft steel; SS400) having a thickness of 12 mm is cut. The diameter of the laser beam 9 on the upper surface of W) and whether or not processing is possible (O; acceptable, x; impossible) are shown. The focal position is “+” when moving upward from the upper surface of the workpiece W, and “−” when moving downward from the upper surface of the workpiece W.

When the focal position is -5 mm (when the focal position is located 5 mm below the upper surface of the workpiece W), the condensing diameter is 0.463 mm, and the processing status is impossible. It is.

When the focal position is −6 mm (when the focal position is located 6 mm below the top surface of the workpiece W having a thickness of 12 mm; the focal position is located at the center of the workpiece W in the thickness direction). )), The condensing diameter is 0.540 mm, and the processing situation is acceptable.

Similarly, when the position of the focal point 11 is −7 mm, −8 mm, −9 mm, −10 mm, and −11 mm, the condensed light diameters are 0.613 mm, 0.677 mm, 0.751 mm,. They are 817 mm and 0.916 mm, and the processing status is acceptable.

When the focal position is −12 mm (when the focal position is located at the lower surface WU of the workpiece W), the condensing diameter is 0.987 mm, and the processing situation is impossible.

FIG. 7B shows a state of the side surface (cut surface) 39 of the workpiece W when the processing is possible. In FIG. 7 (b), six photographs showing the side surface 39 of the workpiece W are shown, but in order from the top, the focal positions are cut at −6 mm, −7 mm, −8 mm, −9 mm, −10 mm, and −11 mm. The case where it processed is shown.

More specifically, when the position of the focal point 11 is in the vicinity of -6 mm or below, the converging diameter appropriate for cutting the workpiece W having a thickness of 12 mm is obtained. When the position of the focal point 11 is higher than −6 mm, the processing accuracy is deteriorated. When the position of the focal point 11 is in the vicinity of −12 mm, the processing accuracy of the cutting process deteriorates due to the decrease in energy density and the limit of the condensing diameter of the cutting, which is not practical.

FIG. 8 (a) shows a shape when cutting a plate-like workpiece W (soft steel; SS400) having a thickness of 12 mm, and shows a state in which the workpiece W is viewed from this thickness direction. In the cutting process shown in FIG. 8 (a), a right triangle product or semi-finished product is cut out from the workpiece W.

FIG. 8B shows a case where the workpiece W is cut in the mode shown in FIG. 8A in the defocus area (the state where the focal point 11 is positioned above the workpiece center of the workpiece W), and in-focus. A mode shown in FIG. 8A on the workpiece W in an area (a state in which the focal point 11 includes the center CL of the workpiece W and is located below the center CL of the workpiece W and above the lower surface WU of the workpiece W). The presence or absence of the occurrence of self-burning in the case where the cutting process is performed is shown.

As can be understood from FIG. 8B, when cutting is performed in the defocus area, self-burning has occurred in 10 semi-finished products or all products, but when cutting is performed in the in-focus area. No self-burning has occurred for 10 semi-finished products or all of the products.

The result of FIG. 8B will be further described using photographs. In FIG. 9A, ten products or semi-finished products are cut out from one workpiece W by cutting in the defocus area. Self-burning occurs in all 10 products or semi-finished products shown in FIG.

In FIG. 9 (a), a portion that looks like a bump is a portion where self-burning has occurred. FIG. 9B is an enlarged view of one of the 10 products or semi-finished products shown in FIG. 9A, and FIG. 9C shows the product shown in FIG. Shows burn-out in semi-finished products. In FIG. 9 (c), a part of the hypotenuse of the triangle is recessed in a concave shape, and this part is a part where self-burning occurs.

10A, 10 products or semi-finished products are cut out from one workpiece W by cutting in the in-focus area. Self-burning does not occur in all of the ten products or semi-finished products shown in FIG. FIG. 10B is an enlarged view of one of the ten products or semi-finished products shown in FIG.

Next, the relationship between the laser output of the laser processing head 3 at the time of cutting and the feed speed (the moving speed of the laser processing head 3 in the horizontal direction with respect to the workpiece W installed in the workpiece installation unit 5) will be shown. A region 45 in the quadrangle shown in FIG. 11 is an appropriate region when the workpiece W is cut.

Note that the workpiece W to be subjected to laser processing (piercing processing and cutting processing) is SS400 having a thickness of 12 mm, and the assist gas (O2) 37 is blown onto the workpiece W at 0.07 MPa during laser processing.

When the laser output is 4 KW, the maximum feed rate is 1700 mm / min, and the minimum feed rate is 1400 mm / min. When only the feed rate is changed (change adjustment) without changing the laser output, cutting is not sufficiently performed if the feed rate is too fast. In addition, if only the feed rate is changed (change adjustment) without changing the laser output, if the feed rate is too slow, over-combustion will occur and the machined surface will be rough, so the minimum feed rate will be the maximum feed rate. It becomes about 80%.

When the laser output is 2 KW, the maximum feed rate is about 850 mm / min, and the minimum feed rate is about 700 mm / min.

FIG. 12 shows that assist gas (O2) 37 is blown onto a workpiece W (SS400 with a thickness of 12 mm) at 0.07 MPa, the laser output is 4 kW, and the feed rate is 1400 mm / min (F1400) or 1700 mm / min (F1700). ) Shows the state of the processed surface when processed.

“Fp-6”, “Fp-7” and the like shown in FIG. 12 indicate the position of the focal point 11 when cutting the workpiece W, and “Fp-6” indicates the vertical direction (the thickness of the workpiece W). This indicates that the distance between the upper surface of the workpiece W and the focal point 11 is 6 mm. In the state shown in FIG. 12, good cutting is performed in all cases.

In addition, you may grasp | ascertain the invention which concerns on the said embodiment as invention of the method shown next.

That is, it is a laser processing method for cutting a plate-shaped workpiece W using the laser beam 9 having a wavelength of 1 μm, and the position of the focal point 11 of the laser beam 9 when cutting the workpiece W is determined. Locating between the center CL of the workpiece W in the thickness direction of the workpiece W and the end surface WU of the workpiece W on the rear side in the traveling direction of the laser beam 9 in the optical axis direction of the laser beam 9; It may be grasped as a laser processing method including cutting the workpiece W using the laser beam 9 having a focal point at the position 11.

In the laser processing method, the workpiece W is a thick plate and is made of iron, steel, an iron alloy, or a material that generates heat by an oxidation reaction, and the workpiece W is cut from the small diameter nozzle 21 containing oxygen. An assist gas 37 blown toward the workpiece W is used. In order to suppress the occurrence of self-burning in the workpiece W when cutting the workpiece W, the inner diameter of the small diameter nozzle 21 is 0. .6 mm or more and 15% or less of the thickness of the workpiece W.

Alternatively, in the laser processing method, the workpiece W is a thick plate and is made of iron, steel, an iron alloy, or a material that generates heat by an oxidation reaction, and the workpiece W is cut from the small diameter nozzle 21 containing oxygen. When using the assist gas 37 blown toward the workpiece W, when cutting the workpiece W, when cutting the workpiece W in order to suppress the occurrence of self-burning in the workpiece W In addition, the assist gas 37 is blown into the holes and grooves formed by the cutting process.

In the laser processing method, when the workpiece W is pierced using the laser beam 9 before cutting, the position of the focal point 11 of the laser beam 9 when piercing is performed is determined in the plate thickness direction of the workpiece W. Thus, between the center CL of the workpiece W and the end surface (upper surface) of the workpiece W in the optical axis direction of the laser beam 9 and in the forward direction of the laser beam 9, or in the optical axis direction of the laser beam 9 The end surface (upper surface) of the workpiece W on the front side in the traveling direction of the laser light 9 and the end surface (upper surface) of the workpiece W on the front side in the traveling direction of the laser light 9 and in front of the laser light 9 in the traveling direction ( It is located between the part slightly away from the upper surface).

Claims

A laser processing method for cutting a plate-shaped workpiece using a laser beam having a wavelength of 1 μm band,
The focal position of the laser beam when cutting the workpiece is the thickness direction of the workpiece, the center of the workpiece, the optical axis direction of the laser beam, and the rear side of the laser beam traveling direction. Between the end face of the workpiece in
Cutting the workpiece using the laser beam having a focal point at the focal position;
A laser processing method including:
The workpiece is a thick plate, made of iron, steel, an iron alloy, or a material that generates heat by an oxidation reaction,
The cutting process with the workpiece is performed using an assist gas sprayed from a small-diameter nozzle toward the workpiece, containing oxygen.
2. The laser processing method according to claim 1, wherein an inner diameter of the small diameter nozzle is 0.6 mm or more and 15% or less of a thickness of the workpiece.
The workpiece is a thick plate, made of iron, steel, an iron alloy, or a material that generates heat by an oxidation reaction,
The cutting process with the workpiece is performed using an assist gas sprayed from a small-diameter nozzle toward the workpiece, containing oxygen.
The laser processing method according to claim 1, wherein when the workpiece is cut, the assist gas is blown into a hole or groove formed by the cutting.
When piercing the workpiece before performing the cutting process,
The position of the focal point of the laser beam at the time of the piercing process is the workpiece thickness direction, the center of the workpiece, the optical axis direction of the laser beam, and the front side of the laser beam traveling direction. Or the end surface of the workpiece on the front side in the laser beam traveling direction and in the vicinity of the end surface of the workpiece on the front side in the laser beam traveling direction. The laser processing method according to any one of claims 1 to 3, wherein the laser processing method is positioned between a position slightly away from an end surface of the workpiece on a front side in a traveling direction of the laser beam.
A laser processing head that emits laser light having a wavelength of 1 μm band toward a plate-like workpiece and is capable of changing the focal position of the laser light;
A workpiece installation section where the workpiece is installed;
When cutting the workpiece installed in the workpiece installation unit, the position of the focal point of the laser beam emitted from the laser processing head in the plate thickness direction of the workpiece, and the center of the workpiece, A control unit that controls the laser processing head so as to be positioned between the laser beam optical axis direction and the end surface of the workpiece on the rear side in the laser beam traveling direction;
Including a laser processing apparatus.
When the workpiece is a thick plate and is made of iron, steel, an iron alloy, or a material that generates heat by an oxidation reaction,
The cutting process with the workpiece is configured to be performed using an assist gas sprayed from the small-diameter nozzle toward the workpiece, containing oxygen.
The laser processing apparatus according to claim 5, wherein an inner diameter of the small-diameter nozzle is 0.6 mm or more and a value of 15% or less of a thickness of the workpiece.
When the workpiece is a thick plate and is made of iron, steel, an iron alloy, or a material that generates heat by an oxidation reaction,
The cutting process with the workpiece is configured to be performed using an assist gas sprayed from the small-diameter nozzle toward the workpiece, containing oxygen.
The laser processing apparatus according to claim 5, wherein the assist gas is blown into a hole or a groove formed by the cutting process when the workpiece is cut.
When the piercing process is performed on the work before the cutting process, the control unit is configured such that the position of the focal point of the laser beam emitted from the laser processing head is the center of the work in the plate thickness direction of the work. And the workpiece in the optical axis direction of the laser beam and the end surface of the workpiece on the front side in the traveling direction of the laser beam, or in the optical axis direction of the laser beam and in the front side in the traveling direction of the laser beam. The laser is positioned between the end surface of the laser beam and a position that is near the end surface of the workpiece on the front side in the traveling direction of the laser beam and slightly separated from the end surface of the workpiece on the front side in the traveling direction of the laser beam. The laser processing apparatus according to any one of claims 5 to 7, which controls a processing head.