JP6609392B2 - Laser cutting nozzle and laser cutting processing method - Google Patents

Description

  The present invention relates to a laser cutting nozzle and a laser cutting processing method.

  As a processing nozzle used for laser cutting processing, a double nozzle in which an inner nozzle and an outer nozzle are integrated is known, and an example is described in Patent Document 1.

In the processing nozzle described in Patent Document 1, the tip position of the inner nozzle is at a position where the tip position of the inner nozzle is pulled in more than the tip position of the outer nozzle.
Then, the laser light is emitted from the central hole at the tip of the inner nozzle to the outside of the nozzle through the tip assist gas outlet of the outer nozzle.
On the other hand, the assist gas merges the gas that has passed through the center hole of the inner nozzle and the gas that has passed through the bypass notch provided between the inner nozzle and the outer nozzle, and ejects the gas from the assist gas ejection hole to the outside of the nozzle. It is like that.

Japanese Patent No. 3749356

When the machining nozzle described in Patent Document 1 is used for cutting with a carbon dioxide laser using oxygen as an assist gas, it can cut well regardless of the plate thickness when cutting a mild steel plate.
On the other hand, it has been empirically understood that when this machining nozzle is used for cutting with a fiber laser that has been rapidly widespread in recent years, the amount of bevel tends to increase in a relatively thick workpiece of mild steel sheet.
Here, the bevel amount is an increment of the kerf width on the nozzle opposite side (back surface side of the workpiece) with respect to the kerf width on the nozzle side (work surface side) after cutting. That is, when the bevel amount increases, the inclination of the cut surface becomes larger with respect to the optical axis, and the cut width on the opposite side of the nozzle is widened.

A method for suppressing the increase in the bevel amount according to the plate thickness has not yet been established, and the present situation is that processing is performed while searching for the optimum condition setting.
For this reason, there has been a demand for a device that can stably and efficiently execute a good cutting process regardless of the thickness of the workpiece.

  Therefore, the problem to be solved by the present invention is to provide a laser cutting nozzle and a laser cutting processing method capable of stably and efficiently performing a good cutting process regardless of the thickness of the workpiece.

In order to solve the above problems, the present invention has the following configuration and procedure.
1) An inner nozzle that has a through hole on the axis and has a tubular shape with one end reduced in diameter, and has an incision extending in the axial direction on the outer peripheral surface on the other end;
An outer nozzle that fits to the outer peripheral surface of the inner nozzle and forms a ventilation path that includes the cut portion and communicates between both ends in the axial direction;
With
The laser cutting nozzle according to claim 1, wherein a minimum flow path cross-sectional area of the air passage matches an opening area of the cut portion on the end face on the other end side.
2) A laser cutting method for laser cutting a workpiece using the laser cutting nozzle described in 1),
As the laser cutting nozzle, the laser cutting nozzle corresponding to the thickness of the workpiece to be cut next is selected and used from a plurality of types of the laser cutting nozzles having different opening areas of the cut portion. This is a laser cutting method characterized by the above.
3) The opening area is made to correspond to the flow rate ratio of the outer flow to the inner flow when the assist gas is divided into the inner flow ejected from the through hole and the outer flow ejected from the vent passage, and Understand the flow rate ratio at which the bevel amount generated by laser cutting is below a predetermined value according to the thickness of the workpiece,
The laser cutting nozzle having the opening area corresponding to the flow rate ratio in which the bevel amount is equal to or less than a predetermined value in the thickness of the workpiece to be cut next is used as the laser cutting nozzle. ).

  According to the present invention, it is possible to obtain an effect that good cutting can be stably and efficiently performed regardless of the thickness of the workpiece of the mild steel plate.

FIG. 1 is a cross-sectional view for explaining a nozzle 51 that is an example of a laser cutting nozzle according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the inner nozzle 1 constituting the nozzle 51. FIG. 3 is a top view of the inner nozzle 1. FIG. 4 is a sectional view of the outer nozzle 11 constituting the nozzle 51. FIG. 5 is a cross-sectional view at the position S1-S1 in FIG. FIG. 6 is a cross-sectional view at the position S2-S2 in FIG. FIG. 7 is a cross-sectional view at the position S3-S3 in FIG. FIG. 8 is a cross-sectional view for explaining the state in which the nozzle 51 is attached to the housing 62 of the processing head 61 and the flow of the assist gas. FIG. 9 is a graph showing the relationship between the channel cross-sectional area Sa and the outer flow FL2. FIG. 10 is a graph showing the relationship between the plate thickness T and the flow rate ratio Q at which the bevel amount falls within the allowable range. FIG. 11 is a graph for explaining a first association between the plate thickness T and the flow rate ratio Q to be set. FIG. 12 is a table for explaining the correspondence among the plate thicknesses T11 to T15, the flow rate ratios Q11 to Q15, and the nozzles 511 to 515. FIG. 13 is a graph for explaining the second association between the plate thickness T and the flow rate ratio Q to be set. FIG. 14 is a table for explaining the correspondence among the plate thicknesses T21 to T25, the flow rate ratios Q21 to Q25, and the nozzles 521 and 522. FIGS. 15A and 15B are diagrams illustrating a modification of the base 1a of the nozzle 1. FIG. 15A is a diagram illustrating the base 1aA, and FIG. 15B is a diagram illustrating the base 1aB.

  The nozzle for laser cutting according to the embodiment of the present invention will be described with reference to the nozzle 51 of the example. The nozzle 51 is detachably attached to a processing head having a known structure in a fiber laser processing machine.

First, the configuration of the nozzle 51 will be described with reference to FIGS. In the following description, the vertical direction is defined in the direction of the arrow in FIG.
As shown in FIG. 1, the nozzle 51 is configured as a combination of an inner nozzle 1 and an outer nozzle 11. First, each will be described in detail.

(Inner nozzle 1: see FIGS. 1 to 3)
2 is a longitudinal sectional view of the inner nozzle, and FIG. 3 is a top view. FIG. 2 is a cross-sectional view at the SS position in FIG.

The inner nozzle 1 is formed in a tubular shape having an axis CL1 as a central axis.
The inner nozzle 1 is connected to a base portion 1a extending in the vertical direction with an outer diameter D1, an intermediate portion 1b having an outer diameter D2 smaller than the outer diameter D1 connected to the lower portion of the base portion 1a, and a lower portion of the intermediate portion 1b. And a reduced diameter portion 1c whose diameter is reduced at an inclination angle θa and whose tip becomes the outer diameter D3. The inclination angle θa is an inferior angle formed by the reduced diameter portion 1c and the axis CL1 in FIG.

The base portion 1a is formed with a plurality of D-cut portions 1a1 to 1a3 formed as cut portions at an angular pitch Pt1 in the circumferential direction. In this example, the angle pitch Pt1 is 120 °, and three D-cut portions 1a1 to 1a3 are formed.
The D cut portions 1a1 to 1a3 are parallel to the axis CL1 and extend in the vertical direction, and are formed as parallel planes having a distance L1 with respect to the axis CL1. Here, the maximum cutting amount of the D-cut portions 1a1 to 1a3 is defined as a distance L2.
That is, distance L2 = (outer diameter D1 / 2) −distance L1.

Three abutting portions 1a5 projecting downward in an arc shape are formed on the peripheral edge of the lower end of the base 1a where the D-cut portions 1a1 to 1a3 are not formed (illustrated by broken lines in FIG. 3).
In other words, based on the manufacturing process of the inner nozzle 1, the abutting portion 1a5 has a ring-shaped portion that protrudes downward before forming the D-cut portions 1a1 to 1a3 by forming the D-cut portions 1a1 to 1a3. Is removed and remains in an arc shape.

  The inner nozzle 1 has a through hole 2. The through hole 2 opens to the upper end surface 3 of the inner nozzle 1 and is connected to the inner reduced diameter portion 2a that is reduced in diameter toward the lower side and the lower portion of the inner reduced diameter portion 2a, and is output to the lower end surface 4 with the same inner diameter. 2b.

(Outer nozzle 11: See FIGS. 1 and 4)
The outer nozzle 11 is formed in a tubular shape having the axis CL11 as a central axis.
The outer nozzle 11 is connected to the lower surface side of the flange portion 11b, a base portion 11a having a male screw portion 11a1, a flange portion 11b having a contact surface 11b1 orthogonal to the axis CL11, and projecting radially outward. As it goes, it has a reduced diameter portion 11c that is reduced in diameter by a curved surface recessed toward the axis 11a side.

The outer nozzle 11 has a through hole 12 that connects the upper end surface 15 and the lower end surface 16.
The through hole 12 has an inner diameter D5 smaller than the inner diameter D4 by forming a base hole portion 12a extending in the vertical direction with an inner diameter D4 and an upper step portion 13 having an abutting surface 13a orthogonal to the axis CL11 at the lower end of the base hole portion 12a. An intermediate hole portion 12b extending downward and a lower step portion 14 having a stepped surface 14a orthogonal to the axis CL11 at the lower end of the intermediate hole portion 12b are formed, and the diameter is reduced toward the lower portion. And a reduced-diameter hole 12c that opens. The reduced diameter hole portion 12c is inclined at the same inclination angle θa as the reduced diameter portion 1c of the inner nozzle 1.

The diameter difference between the inner diameter D4 and the inner diameter D5 is, for example, 0.4 mm. Accordingly, the radial width of the abutting surface 13a is 0.2 mm.
On the other hand, the distance L2 (FIG. 3), which is the cutting amount of the D cut portions 1a1 to 1a3, is set to 0.6 mm.
The inner diameter D4 of the outer nozzle 11 is set to have an optimum press-fitting margin with respect to the outer diameter D1 of the base 1a of the inner nozzle 1.

In assembling the nozzle 51, the inner nozzle 1 and the outer nozzle 11 are integrated by strongly fitting the inner nozzle 1 from above to the through hole 12 of the outer nozzle 11.
Specifically, the base 1 a of the inner nozzle 1 is press-fitted into the base hole 12 a of the through hole 12 of the outer nozzle 11.

The position of the inner nozzle 1 in the axial direction with respect to the outer nozzle 11 is positioned by the abutting portion 1a5 of the inner nozzle 1 coming into contact with the abutting surface 13a of the outer nozzle 11.
In this positioned state, in the nozzle 51, the upper end surface 3 and the lower end surface 4 of the inner nozzle 1 and the upper end surface 15 and the lower end surface 16 of the outer nozzle 11 are substantially the same surface (same axial position). Yes.

As shown in FIG. 1, the nozzle 51 communicates between both end surfaces in the axial direction (vertical direction) between the inner nozzle 1 and the outer nozzle 11 independently of the through hole 2 of the inner nozzle 1. The air passage GR that enables distribution is provided.
Specifically, the air passage GR has approximately three portions from the upper side, that is, an upper air passage GRa, an intermediate air passage GRb, and a lower air passage GRc.

  These three parts will be described with reference to FIGS. 5 to 7 are cross-sectional views at positions S1-S1 to S3-S3 in FIG. 1, respectively. Here, FIG. 7 at the position S3-S3 is a cross-sectional view in a direction orthogonal to the inclined extending direction of the lower air passage GRc.

  First, as shown in FIG. 5, the upper air passage GRa is formed as a gap (halftone dot portion) extending vertically between the D cut portions 1 a 1 to 1 a 3 of the inner nozzle 1 and the base portion 11 a of the outer nozzle 11. In this example, the total of the cross-sectional areas of the three gaps (an arcuate cross-sectional area surrounded by the arc and the chord) is defined as a flow path cross-sectional area Sa.

As shown in FIG. 6, the intermediate air passage GRb is formed as one annular space by connecting three upper air passages GRa at the lower part.
Specifically, the intermediate air passage GRb is formed as a vertically extending gap (annular halftone dot portion) between the outer peripheral surface 1b1 of the intermediate portion 1b of the inner nozzle 1 and the inner peripheral surface 12b1 of the intermediate hole portion 12b of the outer nozzle 11. The The cross-sectional area of the annular gap is defined as a flow path cross-sectional area Sb.

  As shown in FIG. 7, the lower air passage GRc is a gap (annular) that expands and contracts in diameter between the outer peripheral surface 1 c 1 of the reduced diameter portion 1 c of the inner nozzle 1 and the inner peripheral surface 11 c 1 of the reduced diameter portion 11 c of the outer nozzle 11. Halftone dot portion). The lower air passage GRc is opened as an opening GRc1 surrounding the output hole 2b of the through hole 2 on the lower end surface of the nozzle 51. In this example, the opening GRc1 is annular, and the area of the opening GRc1 is defined as an opening area Sc.

In the nozzle 51, the flow passage cross-sectional area Sa of the upper air passage GRa is set to be smaller than the flow passage cross-sectional area Sb and the opening area Sc.
More specifically, the flow passage cross-sectional area Sa of the upper air passage GRa is equal to the opening area Sa1 in the inflow opening GRa1 (see FIG. 1) of the upper end surface 15 of the nozzle 51, and is larger than the upper air passage GRa in the air passage GR. It is set smaller than the cross-sectional area at any position below.

As a result, the flow passage cross-sectional area of the air passage GR becomes the narrowest minimum flow passage cross-sectional area Smin in the upper air passage GRa, and the flow rate when the gas flows through the air passage GR is regulated by the upper air passage GRa.
Therefore, when the nozzle 51 having a different cross-sectional area of the air passage GR is manufactured, the flow rate that can flow through the air passage GR can be determined by the difference in the opening area Sa1 of the inflow opening GRa1 when the nozzle 51 is viewed from above. is there.

FIG. 8 is a longitudinal sectional view showing an example of a state where the nozzle 51 described above is attached to the machining head 61. The nozzle 51 is detachably screwed to the tip of the housing 62 of the processing head 61. In a state where the nozzle 51 is screwed to the housing 62, the axis line CL1 coincides with the optical axis CL63 of the condenser lens 63.
Laser light LS supplied from a fiber laser oscillator (not shown) to the nozzle 51 is condensed by the condenser lens 63 and emitted downward through the through hole 2 of the nozzle 51.

The housing 62 is provided with a gas supply port 64, and assist gas (oxygen or the like) is supplied from the outside to the internal space Va of the housing 62 through the gas supply port 64.
The assist gas supplied to the internal space Va is divided into an inner flow FL1 and an outer flow FL2, and is ejected to the outside. That is, a part of the supplied assist gas is jetted downward as an inner flow FL1 through the output hole 2b of the through-hole 2, and the rest enters the upper ventilation path GRa as an outer flow FL2 from the inflow opening GRa1 and passes through the intermediate ventilation. The inner flow FL1 is independently jetted downward from the opening GRc1 of the lower ventilation path GRc through the path GRb so as to surround the ring.

  Here, the flow rates of the inner flow FL1 and the outer flow FL2 are Q1 (L / min) and Q2 (L / min), respectively. The pressures of the inner flow FL1 and the outer flow FL2 are branches from the common internal space Va shown in FIG. 8, and are equal.

The inventors paid attention to the flow rate ratio Q (= Q2 / Q1) between the outer flow FL2 and the inner flow FL1, and examined the relationship between the flow rate Q and the bevel amount by experiments.
Specifically, the shape of the through hole 2 of the nozzle 51 is assumed to have the same flow path cross-sectional area, and the flow path cross-sectional area Sa of the upper ventilation path GRa is changed, for example, by changing the distance L2 that is the cut amount. Different types of nozzles 51 having different flow ratios Q (= Q2 / Q1) between the outer flow FL2 and the inner flow FL1 were created.
Then, using the relationship between the flow path cross-sectional area Sa and the flow rate ratio Q and the respective nozzles, workpieces with different plate thicknesses of mild steel plates were cut, and the bevel amount of the obtained cut surfaces was examined. An SS400 plate was used as the mild steel plate.

As a result, first, as shown in FIG. 9, in the practical region where the channel cross-sectional area Sa of the upper air passage GRa is not extremely small, the channel cross-sectional area Sa and the flow rate Q2 of the outer flow FL2 are approximately positive. It was found that the correlation was linear.
Further, when the flow rate ratio Q at which the bevel amount is within an allowable range was extracted in the cutting of each workpiece having different plate thicknesses, the result shown in FIG. 10 was obtained. Here, the allowable range of the bevel amount is set to 0.15 mm or less.
FIG. 10 shows the relationship between the thickness T (horizontal axis) of the workpiece of the mild steel plate and the range of the flow rate ratio Q (vertical axis) in which the bevel amount of the cut surface is within the allowable range.
Hereinafter, the plate thickness of 12 mm will be described as a plate thickness T1, and the plate thickness of 25 mm will be described as a plate thickness T2. The plate thicknesses T1 to T2 are a general plate thickness range of mild steel plates used for fiber laser cutting.

The results shown in FIG. 10 will be specifically described.
The flow rate ratio lower limit characteristic Qa indicates the lower limit value of the flow rate ratio Q in which the bevel amount is within the allowable range from the plate thickness T1 to T2.
The flow rate ratio upper limit characteristic Qb indicates the upper limit value of the flow rate ratio Q in which the bevel amount is within the allowable range from the plate thickness T1 to T2.
The flow rate ratio central characteristic Qc indicates the median value of the flow ratio upper limit characteristic Qb and the flow ratio lower limit characteristic Qa from the plate thickness T1 to T2.
The plots corresponding to the plate thicknesses of 16 mm, 19 mm, and 22 mm are described as a part of a plurality of actual measurement data measured to obtain the characteristics shown in FIG.
Specific data for each plot is as follows.
Plate thickness 16 mm: Flow rate Q1 of inner flow FL1 = 19.6 (L / min)
Flow rate Q2 of outer flow FL2 = 20.0 (L / min)
Flow ratio Q = 1.02
Bevel amount: 0.07mm
Plate thickness 19 mm: Inner flow FL1 flow rate Q1 = 22.1 (L / min)
Flow rate Q2 of outer flow FL2 = 27.7 (L / min)
Flow ratio Q = 1.25
Bevel amount: 0.08mm
Plate thickness 22 mm: Flow rate Q1 of inner flow FL1 = 24.9 (L / min)
Flow rate Q2 of outer flow FL2 = 31.7 (L / min)
Flow ratio Q = 1.27
Bevel amount: 0.09mm
Here, the range between the flow ratio upper limit characteristic Qb and the flow ratio lower limit characteristic Qa at an arbitrary plate thickness Tk (T1 ≦ Tk ≦ T2) is defined as an appropriate flow ratio range ΔQk.

The following was found from the results shown in FIG.
In the range from the plate thickness T1 to the plate thickness T2, there is a range of flow rate ratio Q (appropriate flow rate range ΔQk) in which the bevel amount is within an allowable range by cutting using the nozzle 51.
The appropriate flow rate ratio range ΔQk is substantially constant in the range from the plate thickness T1 to the plate thickness T2.
The flow rate ratio central characteristic Qc tends to increase as the plate thickness T increases in the range of the plate thicknesses T1 to T2.
In other words, within the range of the plate thicknesses T1 to T2, the flow rate ratio Q is such that an appropriate bevel amount can be obtained by cutting a thin workpiece (for example, a thin plate thickness), and the other (thick plate thickness). It shows that an appropriate bevel amount is not always obtained when a workpiece having a plate thickness is cut. This can be said to support the tendency that the bevel amount increases and a preferable cut surface cannot be obtained when the plate thickness is large in the conventional fiber laser cutting using a double nozzle.

  Although not directly obtained from FIG. 10, as an incidental result, it was found that the flow rate ratio central characteristic Qc is the flow rate ratio at which the quality of the cut surface after processing is the most preferable in the appropriate flow rate range ΔQk.

From this result, it is preferable that the bevel amount is suppressed by performing the cutting process with the fiber laser of the workpiece, which is a mild steel plate, using the nozzle 51 having the flow rate ratio Q suitable for the plate thickness T of the workpiece to be processed. It has been found that a good cutting quality can be obtained.
Therefore, the cutting with a fiber laser using the nozzle 51 may be performed by the following method, for example, and will be described with reference to FIGS.

(S1) The flow rate ratio lower limit characteristic Qa and the flow rate upper limit characteristic Qb are obtained in advance by trial machining for each standard plate thickness determined by JIS or the like, and the appropriate flow rate ratio range ΔQk is grasped. Here, it is assumed that the flow ratio lower limit characteristic Qa and the flow ratio upper limit characteristic Qb are obtained as the characteristics shown in FIG.
(S2) The nozzles 511 to 515 having flow ratios in the appropriate flow ratio range ΔQk corresponding to the plate thicknesses T11 to T15 of the standard plate thickness of the workpiece are created.
Here, as shown in FIG. 12, the nozzles 511 to 515 are created to have flow rate ratios Q11 to Q15 that are flow rate center characteristics Qc corresponding to the plate thicknesses T11 to T15, respectively.
(S3) The nozzles 511 to 515 corresponding to the plate thicknesses T11 to T15 of the workpiece to be processed next are selectively mounted on the processing head 61 to perform the main processing. For example, when cutting a workpiece having a thickness T13, the nozzle 513 is selected and mounted, and the main machining is performed.

  In creating the nozzle 51, it is desirable to adopt the value of the flow ratio central characteristic Qc as the flow ratio Q set corresponding to the plate thickness T from the viewpoint of obtaining good cut surface quality. However, the value of the flow rate ratio Q to be adopted is not limited to this, and each plate thickness in the appropriate flow rate ratio area ARR (hatched area surrounded by points P1 to P4 in FIG. 11) obtained in the appropriate flow ratio range ΔQk. Any value corresponding to T may be used.

Therefore, instead of preparing different nozzles 51 for each plate thickness of the workpiece to be processed, adjacent plate thicknesses included in the appropriate flow rate ratio area ARR may be associated with the same nozzle 51 as much as possible.
This method will be described with reference to FIGS.

The flow ratio lower limit characteristic Qa and the flow ratio upper limit characteristic Qb in FIG. 13 are the same as those in FIG. 11 for the sake of convenience in the range of the plate thicknesses T21 to T25.
As shown in FIGS. 13 and 14, for the plate thicknesses T21 to T23, the flow rate ratio Q21 included in the proper flow rate ratio region ARR is set for all of them. And the nozzle 521 used as the flow rate ratio Q21 is created, and it matches with plate | board thickness like FIG.

  On the other hand, for the plate thicknesses T24 and T25, the flow rate ratio Q21 deviates from the appropriate flow rate ratio region ARR. Therefore, a flow rate ratio Q22 different from the flow rate ratio Q21 within the appropriate flow rate ratio region ARR is set for both the plate thicknesses T24 and T25, and a nozzle 522 having the flow rate ratio Q22 is created and associated with the plate thickness.

  According to this method, it is not always necessary to create a nozzle for each plate thickness having a different flow rate ratio central characteristic Qc. Therefore, the cost can be reduced from the viewpoint of manufacturing and nozzle management, the nozzle replacement time can be shortened, and the decrease in production efficiency can be suppressed.

The nozzles having different flow rate ratios Q, for example, the nozzles 511 to 515 shown in FIG. 12, have an axial positioning structure of the inner nozzle 1 with respect to the outer nozzle 11 as follows.
That is, the radial width of the abutting portion 1a5 of the outer nozzle 11 against which the abutting portion 1a5 of the inner nozzle 1 is abutted is set sufficiently small with respect to the maximum cutting distance L2 of the D cut portions 1a1 to 1a3, and the abutting portion 1a5 is The minimum aperture is not set.

As described above, the portion of the ventilation path GR that has the minimum restriction, that is, the minimum channel cross-sectional area Smin is set to the upper ventilation path GRa.
The difference in the flow rate ratio Q is reflected as the difference in the opening area Sa1 between the upper end surface 3 and the upper end surface 15. That is, the nozzles 511 to 515 can be distinguished on the appearance.
Thereby, the possibility that the nozzles 511 to 515 are erroneously attached to the casing 62 of the machining head 61 is reduced, and the optimum cutting process according to the plate thickness T of the workpiece can be more reliably performed.

As described above, the nozzle 51 has the lower end surface 4 of the inner nozzle 1 and the lower end surface 16 of the outer nozzle 11 at substantially the same height position (axial position).
As a result, the inner flow FL1 and the outer flow FL2 are not mixed and ejected, but are jetted onto the work as independent air streams.
Therefore, the flow rate ratio Q directly affects the cutting mode, and is effective as a parameter for controlling the bevel amount.
Of course, even if the lower end surface 4 of the inner nozzle 1 and the lower end surface 16 of the outer nozzle 11 are different in height and have a step, if the inner flow FL1 and the outer flow FL2 are jetted to the workpiece as independent airflows, The flow rate ratio Q is effective as a parameter for controlling the bevel amount. Further, even if the level difference in the height direction of the lower end surfaces 4 and 16 (the difference in position in the height direction) increases and the degree of independence of the inner flow FL1 and the outer flow FL2 decreases, a certain degree of independence is ensured. If so, it goes without saying that the bevel amount control effect of the flow rate ratio Q is exhibited even if the degree is small.

As described above, the reason why the increase in the bevel amount can be suppressed by increasing the flow rate ratio Q in a relatively large plate thickness region is assumed as follows.
In other words, increasing the flow rate ratio Q means increasing the flow rate ratio of the outer flow FL2 ejected as an inclined annular flow that converges on the axis CL1 with respect to the inner flow FL1, and at the lower part of the workpiece (opposite the nozzle). This is probably because the expansion of the flux of the assist gas as a whole is suppressed and an excessive supply of oxygen can be avoided.

  The embodiment of the present invention is not limited to the above-described configuration and procedure, and may be modified as long as it does not depart from the gist of the present invention.

Although the base portion 1a of the inner nozzle 1 has been described as having three D-cut portions 1a1 to 1a3 as cut portions that form the upper air passage GRa, the number N of cut portions is not limited to three.
For example, as shown in FIG. 15A, the base 1a may be a base 1aA having four D-cut portions 1aA1 to 1aA4 as cut portions. Moreover, the cross-sectional shape may not be a D-cut mode. For example, as shown in FIG. 15B, the base 1a may be a base 1aB having grooves 1aB1 to 1aB4 as cut portions extending in the vertical direction, for example, in a rectangular cross section.
15A and 15B, halftone dots are added to portions corresponding to the air passage GRa formed by the cut portions.

The difference in the flow rate ratio Q between the plurality of nozzles shown in FIGS. 12 and 14 may be made to correspond to the number N of cut portions that form the upper air passage GRa.
Nozzles with different flow rate ratios Q can be sorted by the number of notches, not the difference in opening area Sa1, in other words, by the number N of inflow openings GRa1, so that the separation work can be performed with high efficiency and with a small number of discrimination errors. Yes.

In the case of creating nozzles with different flow rate ratios Q, the example in which the inner diameter dimension of the through hole 2 of the inner nozzle 1 is made common has been described, but the inner diameter dimension of the through hole 2 may be varied.
When the inner diameter dimensions of the through holes 2 are different, the difference in the opening area Sa1 of the upper air passage GRa does not directly correspond to the difference in the flow rate ratio Q. Therefore, the number N of notches and the flow rate ratio Q are made to correspond. It is desirable.

  The example in which the flow ratio lower limit characteristic Qa and the flow ratio upper limit characteristic Qb are determined based on the criterion that the bevel amount is equal to or less than the predetermined value has been described. However, not only the bevel amount but also the entire quality of the cut surface including the bevel amount is determined by the flow rate. It depends on the ratio Q. Therefore, the flow ratio lower limit characteristic Qa and the flow ratio upper limit characteristic Qb may be determined based on items other than the bevel amount, for example, the size of the surface roughness or the amount of deposits. Of course, you may determine by the quality of the total quality of a cut surface.

The flow passage cross-sectional area of the air passage GR may be the minimum flow passage cross-sectional area Smin, which is the opening area Sc at the opening GRc1 of the lower air passage GRc. In this case, the flow rate when the gas flows through the ventilation path GR is regulated by the opening GRc1.
In other words, the opening area Sc of the opening GRc1 in the lower air passage GRc is set to be smaller than the flow passage cross-sectional area Sa of the upper air passage GRa and smaller than the flow passage cross-sectional area Sb of the intermediate air passage GRb. .
In this case, when the nozzle 51 having a different minimum channel cross-sectional area Smin is manufactured, the amount of flow that can flow through the ventilation path GR can be determined by the difference in the opening area Sc of the opening GRc1 when the nozzle 51 is viewed from below. Become.

1 Inner nozzle 1a, 1aA, 1aB Base 1a1 to 1a3, 1aA1 to 1aA4 D cut part (cut part)
1aBa to 1aB4 Groove portion (cut portion), 1a5 abutting portion 1b intermediate portion, 1b1 outer peripheral surface, 1c reduced diameter portion, 1c1 outer peripheral surface 2 through hole, 2a inner reduced diameter portion, 2b output hole 3 upper end surface 4 lower end surface 11 outer nozzle 11a base part, 11a1 male thread part, 11b flange part 11b1 contact surface, 11c reduced diameter part, 11c1 inner peripheral surface 12 through hole 12a base hole part, 12b intermediate hole part, 12b1 inner peripheral surface 12c reduced diameter hole part 13 upper stage part, 13a Abutting surface 14 Lower step portion, 14a Stepped surface 15 Upper end surface 16 Lower end surface 51, 511 to 515, 521, 522 Nozzle 61 Processing head 62 Housing 63 Condensing lens 64 Gas supply port ARR Appropriate flow ratio area
CL1, CL11 axis, CL63 Optical axis D1, D2, D3 Outer diameter, D4, D5 Inner diameter FL1 Inner flow, FL2 Outer flow GR ventilation path GRa Upper ventilation path, GRa1 inflow opening, GRb Intermediate ventilation path GRc Lower ventilation path, GRc1 Aperture LS Laser light, L1, L2 Distance N (number of notches) Pt1 Angular pitch P1-P4 Points Q, Q11-Q15, Q21, Q22 Flow ratio Qa Flow ratio lower limit characteristics, Qb Flow ratio upper limit characteristics, Qc Flow ratio Central characteristics Q1, Q2 Flow rate Sa, Sb Channel cross-sectional area Sa1 Open area, Sc Open area, Smin Minimum channel cross-sectional areas T1-T2, T11-T15, T21-T25 Plate thickness Va Internal space θa Inclination angle ΔQk Proper flow rate ratio range

Claims (3)

An inner nozzle having a through-hole on the axis and having a reduced diameter at one end, and an incision extending in the axial direction on the outer peripheral surface of the other end;
An outer nozzle that fits to the outer peripheral surface of the inner nozzle and forms a ventilation path that includes the cut portion and communicates between both ends in the axial direction;
With
The laser cutting nozzle according to claim 1, wherein a minimum flow path cross-sectional area of the air passage matches an opening area of the cut portion in the end face on the other end side. A laser cutting method for laser cutting a workpiece using the laser cutting nozzle according to claim 1,
As the laser cutting nozzle, the laser cutting nozzle corresponding to the thickness of the workpiece to be cut next is selected and used from a plurality of types of the laser cutting nozzles having different opening areas of the cut portion. A laser cutting method characterized by the above. The opening area is made to correspond to the flow rate ratio of the outer flow to the inner flow when the assist gas is divided into the inner flow that ejects the assist gas from the through-hole and the outer flow that ejects from the ventilation path. Understand the flow rate ratio at which the bevel amount generated by laser cutting is below a predetermined value according to the thickness,
The laser cutting nozzle having the opening area corresponding to the flow rate ratio in which the bevel amount is equal to or less than a predetermined value in the thickness of the workpiece to be cut next is used as the laser cutting nozzle. Item 3. The laser cutting method according to Item 2.

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