JPH0557469A - Laser beam processing - Google Patents

Abstract

PURPOSE:To form a hole of a large diameter necessary for shifting to cutting by sufficiently admitting an assist gas into the hole and stably and well executing piercing at the time of boring in the laser beam processing method of executing the cutting of a work by a laser beam. CONSTITUTION:The focus P of the laser beam L is first held parted at a prescribed distance from the surface of the work W at the time of executing the piercing and the work is irradiated in this sate with the laser beam L by the higher laser output and higher assist gases pressure than at the time of the boring, by which a shallow recess C having the large diameter is formed on the surface of the work W. The focus P of the laser beam L is then aligned near to the surface of the work W and the work is irradiated with the laser beam L by the laser output an assist gaseous pressure at the time of the boring, by which the hole H is formed continuously from the bottom of the recess C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method for cutting a work with a laser beam, and more particularly to a laser processing method applied to processing a relatively thick work.

[0002]

2. Description of the Related Art Generally, in this type of laser processing, as shown in FIG. 2, a laser beam L output from a laser oscillator 1 is guided by a mirror 2 or the like and is incident on a lens 4 of a processing head 3. The lens 4 collects the light at a focal point P outside the nozzle 5. Further, the assist gas is supplied from the assist gas supply device 6 to the processing head 3, and the assist gas is ejected from the nozzle 5 coaxially with the laser light L to process the work W.

The machining head 3 is controlled by a servo control circuit 7 along a machining path, for example, in three axes in X, Y and Z directions. At the same time, the distance from the tip of the nozzle 5 to the surface of the work W, that is, the gap amount is detected by the gap sensor 8 provided in the nozzle 5 or in the vicinity of the nozzle 5, and the gap controller 9 is made based on the detected data. The height of the nozzle 5 is controlled so that the gap amount during processing becomes a predetermined value.

On the other hand, in this type of laser processing, it is necessary to perform drilling, that is, piercing, at the starting point of cutting. When the laser output at the time of piercing is set to the same condition as that at the time of cutting, the laser output is too strong, so that the heat of the laser light L is accumulated inside the work W before the hole is formed, and molten metal is formed. Cheap. Then, this molten metal suddenly scatters at once and an explosion occurs,
As a result, the molten metal jumps up to the lens 4, which may damage the lens 4.

In order to prevent such a danger, in the conventional laser processing, the laser output value at the time of piercing is set to a value lower than the output value at the time of cutting processing. However, when piercing is performed at such a low laser output value that explosion does not occur, the laser output is too weak, resulting in poor piercing efficiency and a long piercing time, resulting in a problem of reduced machining efficiency. there were.

[0006] In particular, with respect to the work W having a large plate thickness, this problem becomes remarkable. Actually, when piercing a steel plate having a plate thickness of 12 mm by the conventional method, it takes a long time of 40 to 60 seconds until the end of piercing, and
The variation in the required time was also large.

For this reason, conventionally, the focus P of the laser light L is normally focused on the surface of the work W, and the piercing is performed in the state where the energy density of the laser light L is the highest.

[0008]

However, in the conventional processing method, the piercing time can be shortened, but the hole diameter formed is small because of the processing at the focal position.
In particular, for the work W having a large plate thickness, the diameter of this hole is as small as about 0.1 to 0.3 mm. And
If the hole diameter formed by piercing becomes smaller than the hole diameter required at the start of cutting, the assist gas does not flow into the piercing hole during cutting, so the oscillation condition and assist gas pressure are switched from piercing to cutting. At the same time, there is a possibility that assist gas may be blown up, causing molten metal to jump up as in the case of the explosion,
I couldn't move smoothly to cutting.

Further, as shown in FIG. 5, before the through holes are formed, the molten metal M generated during piercing is transferred to the work W.
Since the piercing hole adheres to the periphery of the piercing hole and rises, it is the same as the piercing hole becoming deeper by the height of the piercing hole, and the entrance of the piercing hole becomes narrower, so that the assist gas A into the hole becomes smaller. It was blocking the inflow. Therefore, the assist gas A is sufficiently filled in the piercing hole.
Since it was not supplied, heat was trapped inside and it was easy for an explosion to occur. Therefore, it becomes necessary to lower the laser output, and the diameter of the hole formed is further reduced.

The present invention has been made by paying attention to the problems existing in such a conventional technique, and the purpose thereof is to allow the assist gas to sufficiently flow into the holes at the time of drilling and to perform piercing. The present invention is to provide a laser processing method capable of stably performing satisfactorily and forming a hole having a large diameter necessary for shifting to cutting processing.

[0011]

In order to achieve the above object, according to the present invention, in a laser processing method for cutting a workpiece by laser light, when piercing is performed, the focus of the laser light is first focused. The laser beam is irradiated with a higher laser output and a higher assist gas pressure than when drilling with a predetermined distance from the surface of the workpiece to form a recess on the surface of the workpiece, and then the focus of the laser beam. The laser beam is irradiated with the laser output and the assist gas pressure at the time of drilling in the state of moving to near the surface of the work, and the hole is drilled from the bottom of the recess.

[0012]

[Operation] According to the laser processing method as described above, at the time of piercing, the laser beam is first moved with a relatively high laser output and a high assist gas pressure with the focus of the laser beam being separated from the surface of the work by a predetermined amount. Is performed to instantly form a large-diameter and shallow recess on the surface of the work. For this reason,
It is possible to prevent molten metal from adhering to the periphery of the recess on the surface of the work and causing swelling. Continuing,
The focus of the laser light is moved to the vicinity of the surface of the work, and the laser light is irradiated with the set laser output and assist gas pressure at the time of drilling, and the hole is continuously drilled from the bottom of the recess. At this time, the molten metal generated in the hole is guided to the recess together with the assist gas and widely blown outward.
Also, even if a slight amount of molten metal remains by the time the hole is made,
It can stay in a large-diameter recess, and it does not bulge on the surface of the work, stick to the periphery of the hole, and reduce or block the hole diameter. Therefore, the assist gas is guided to the recess in the hole and efficiently supplied. Therefore, the piercing can be stably and favorably performed, and the large-diameter hole required for shifting to the cutting process can be formed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a laser processing method embodying the present invention will be described in detail below with reference to FIGS.

Now, in the processing method of this embodiment,
When performing piercing on the work W, NC shown in FIG.
The processing head 3 is moved by the device 10 via the servo control circuit 7 in the Z-axis direction, that is, the optical axis direction, and the nozzle 5 is moved.
The amount of gap between the tip of the workpiece and the surface of the workpiece W is changed and controlled as shown in FIG. At the same time, the laser processing is performed while controlling the output value of the laser light L output from the laser oscillator 1 by the laser oscillation control circuit 11 shown in FIG.

That is, at the start of piercing, FIG.
As shown in FIG. 1, the gap amount G1 is set to be larger than the normal set value, and as shown in FIG. 1A, the focus P of the laser light L is set to be separated from the surface of the work W by a predetermined amount. Further, the output value of the laser light L and the pressure value of the assist gas A are set to values higher than the set values for drilling suitable for piercing. In this state, the surface of the work W has a predetermined time T
Irradiation with 1 laser beam L forms a shallow recess C having a large diameter.

When forming the recess C, the focus P of the laser light L is set above the surface of the work W by a predetermined amount, so that the laser light L is dispersed on the work W.
Even if the output value of the laser beam L is set to a high value, the molten metal does not adhere to the periphery of the recess C on the surface of the work W to cause swelling, and a large-diameter and shallow recess is formed. The location C can be stably formed.

Thereafter, as shown in FIG. 3, after a predetermined time T1 has elapsed from the start of the piercing, a recess C having a predetermined depth is formed on the surface of the work W, and then the gap amount G2 is set to the gap amount at the start of the piercing. Reduced from G1, Figure 1
As shown in (b), the focus P of the laser light L is set near the surface of the work W. In this state, the laser beam L is irradiated with the laser output and the assist gas pressure set so as not to cause the explosion on the surface of the work W, and the hole H is continuously formed from the bottom of the recess C.

Then, as shown in FIG. 3, the gap amount is gradually reduced from G2 to G3 during the predetermined time T2 from the start of forming the hole H to the end of forming the hole H, and the laser is formed in accordance with the formation of the hole H. The focus P of L is gradually driven into the work W.

At the time of forming the hole H, as shown in FIG. 4, the molten metal M generated in the hole H is guided to the recess C together with the assist gas A and widely blown to the outside of the hole H. Further, even if the molten metal M slightly remains before the hole H becomes clear, the molten metal M can stay in the large-diameter recess C, rise up on the surface of the work W, or around the hole H. It does not adhere to reduce the hole diameter or block it. Therefore, since the assist gas A is not blown up and the assist gas A is efficiently supplied into the hole H by being guided by the large-diameter recess C, the hole H can be formed stably and satisfactorily. , Large-diameter hole H required for shifting to cutting
Is formed. Incidentally, in the relatively thick work W having a plate thickness of 9 mm or more, the diameter of the hole H required at the start of cutting is 0.5 to 0.8 mm, but according to the processing method of this embodiment, the diameter is 0. A large hole diameter of 0.8 to 1.0 mm could be obtained. Therefore, when shifting from piercing to cutting, self-burning does not occur due to blow-up of the assist gas, the molten metal M does not jump up, and the transition can be performed smoothly.

The present invention is not limited to the above-described embodiment. For example, when forming the hole H after forming the recess C, the output value of the laser L and the pressure of the assist gas are set to the hole H. It is also possible to embody the invention by arbitrarily changing it, for example, by appropriately controlling the change in accordance with the formation of the above, without departing from the spirit of the present invention.

[0021]

As described above, according to the present invention, when piercing is started, a hole having a large diameter is first formed and then a hole is formed. Flow into. Therefore, since the assist gas is sufficiently fed into the hole, piercing can be performed stably and satisfactorily, and a large-diameter hole necessary for the transition to the cutting process can be formed, and the transition can be performed smoothly. It has an excellent effect that it can be performed. or,
When the recess is formed, the laser output value and the assist gas pressure value are set to values higher than those at the time of drilling, so that the recess can be formed very efficiently and instantaneously.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a laser processing method embodying the present invention in the order of steps.

FIG. 2 is a configuration diagram illustrating a control system of a laser processing apparatus in which the laser processing method is used.

FIG. 3 is a diagram showing a method of controlling a gap amount.

FIG. 4 is a schematic sectional view showing a flow of assist gas during piercing according to the present invention.

FIG. 5 is a schematic sectional view showing a flow of assist gas during piercing by a conventional method.

[Explanation of symbols]

L laser light, P focus, A assist gas, W work, C recess, H hole.

Claims (1)

[Claims] 1. In a laser processing method for cutting a work by laser light, when piercing is performed, first, a laser beam having a focal point separated from a surface of the work by a predetermined amount is higher than a laser beam when a hole is drilled. Laser light is irradiated with high output and high assist gas pressure to form a recess on the surface of the work, and then the laser output when drilling with the focus of the laser light moved near the surface of the work And a assist gas pressure to irradiate a laser beam to form a hole from the bottom of the recess.