JP3110504B2 - Laser processing method - Google Patents

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 of 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 and is incident on a lens 4 of a processing head 3. This lens 4 causes the tip of the nozzle 5
Light is collected at the end focal point P. Also, the processing head 3
An assist gas is supplied from an assist gas supply device 6 connected to an assist gas source (not shown) , and the assist gas is ejected from the nozzle 5 concentrically with the laser beam L to process the workpiece W.

The machining head 3 is controlled by a servo control circuit 7 along a machining path, for example, in three directions, X, Y, and Z. 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 nozzle 5 or the gap sensor 8 provided in the vicinity of the nozzle 5, and based on the detected data, the gap controller 9 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 this 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 generated. easy to. Then, the molten metal suddenly scatters at once, causing an explosion. As a result, there is a danger that the molten metal jumps up to the lens 4 and damages the lens 4.

In order to prevent such a danger, in conventional laser processing, the laser output value during piercing is set to a value lower than the output value during cutting. However, in this way, when performing a piercing in a lower laser output value of a degree that does not cause an explosion, because the laser output is too weak, it takes a long pin ashing time, there is a problem that reducing the processing efficiency.

[0006] In particular, for a work W having a large plate thickness, this problem remarkably appears. Actually, when a steel plate having a thickness of 12 mm was pierced by a conventional method, it took a long time of 40 to 60 seconds to complete the piercing, and
The required time varied widely.

[0007]

[0008]

As described above, in the conventional processing method, the piercing time is long, and since the hole is formed at the focal point, the diameter of the formed hole is small. Become smaller.
In particular, for a work W having a large plate thickness, the diameter of the hole is as small as about 0.1 to 0.3 mm. And
If the hole diameter formed by piercing is 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 conditions and assist gas pressure are switched from piercing to cutting. At the same time, the assist gas may be blown up, and the molten metal jumps up as in the case of the explosion,
It was not possible to smoothly shift to cutting.

Further, as shown in FIG. 5, before the through hole is formed, the molten metal M generated at the time of piercing
Since the piercing hole adheres to the periphery of the piercing hole on the surface of the piercing hole and swells, the piercing hole becomes as deep as the swelling, and the entrance of the piercing hole becomes narrower. Was blocking the inflow. Therefore, there is sufficient assist gas A in the piercing hole.
Is not supplied, the heat is stored inside the work W, and an explosion is likely to occur. For this reason, lower the laser output
Therefore, it is necessary to perform piercing , so that the diameter of the hole formed becomes smaller.

The present invention has been made in view of the problems existing in such prior art, and an object of the present invention is to allow an assist gas to sufficiently flow into a hole at the time of drilling, and to perform piercing. It is an object of the present invention to provide a laser processing method capable of stably and satisfactorily performing the laser beam cutting and forming a large-diameter hole required for shifting to cutting.

[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, a laser beam is focused at a predetermined distance from the surface of the workpiece. Setting when drilling in the state
A first step of forming a recess in the surface of the work with a laser output higher than the value and an assist gas pressure, and then a laser lower than the first step with the focal point moved a predetermined amount in a direction to enter the inside of the work. The piercing is performed from the second step of piercing with the output and the assist gas pressure.

[0012]

According to the above-mentioned laser processing method, at the time of piercing, first, in a first step , a relatively high laser output and a high assist gas are applied in a state where a laser beam is focused at a predetermined distance from the surface of a work. Irradiation of laser light is performed with pressure to instantaneously form a large-diameter and shallow recess on the surface of the work. For this reason, it is possible to prevent the molten metal from adhering around the recess on the surface of the work and causing a bulge. Subsequently, as a second step, the focal point of the laser beam was moved by a predetermined amount in a direction to enter the inside of the work .
In this state, laser light irradiation is performed with a laser output and an assist gas pressure lower than those in the first step, and drilling is performed continuously 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 is widely blown outward. Also, even if a small amount of molten metal remains by the time the hole is made clear, it can remain in the large-diameter recess, swell on the surface of the work, or adhere around the hole to reduce the hole diameter. There is no obstruction. Therefore, the assist gas is guided into the recess in the hole and supplied efficiently. Therefore, piercing can be performed stably and favorably, and a large-diameter hole necessary for shifting to cutting can be formed.

[0013]

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

Now, in the working method of this embodiment,
When performing piercing on the work W, the 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, in the optical axis direction.
Is controlled from large to small as shown in FIG. At the same time, laser processing is performed while the output value of the laser light L output from the laser oscillator 1 is controlled by the laser oscillation control circuit 11 shown in FIG.

[0015] That is, when Piasshi <br/> ing the start of the first step, relatively gap amount as shown in FIG. 3
The large values G1, as shown in FIG. 1 (a), the focal point P of laser light L is set away a predetermined amount upward than the surface of the workpiece W. Further, the output value of the laser beam L and the pressure value of the assist gas A are set to values higher than a set value at the time of drilling as a second step described later . In this state, the surface of the work W is irradiated with the T1 laser light L for a predetermined time to form a large-diameter and shallow recess C.

When the concave portion C is formed, the focal point P of the laser light L is set above the surface of the work W by a predetermined distance, so that the laser light L is dispersed on the work W,
Even if the output value of the laser light L is set to a high value, the molten metal does not adhere around the concave portion C on the surface of the work W and no swelling occurs. Place C can be formed stably.

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 second step should be started.
And the gap amount at the start of piercing G1
It is reduced to a smaller value G2 than, the focal point P of the record laser light L
Is set near the surface of the workpiece W. Then, a predetermined time T
The gap amount is changed from G2 to G3 until 2 elapses.
The laser light L is irradiated with the laser output and the assist gas pressure set lower than the first step so as not to cause an explosion on the surface of the work W while gradually decreasing the surface of the work W. To form

As shown in FIG . 1B, when the gap amount is G
With the gradual decrease from 2 to G3, the formation of the hole H progresses.
And rows, gradually enters a focal point P of the laser beam L to the interior of the workpiece W accordingly.

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 is widely blown out of the hole H. Further, even if the molten metal M remains slightly before the hole H becomes clear, the molten metal M can remain in the large-diameter concave portion C, and swell on the surface of the work W, or around the hole H. It does not adhere and narrow or close the hole diameter. Therefore, the assist gas A is efficiently supplied into the hole H by being guided into the large-diameter recess C without blowing up the assist gas A, so that the hole H can be formed stably and favorably. , Large-diameter hole H required for transition to cutting
Is formed. Incidentally, in the case of a 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 working method of this embodiment, the diameter is 0 mm. A large hole diameter of 0.8 to 1.0 mm could be obtained. Therefore, at the time of transition from piercing to cutting, self-burning does not occur due to blow-up of the assist gas, and 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 the hole H is formed after the formation of the recess C, the output value of the laser beam L and the pressure of the assist gas are reduced. equal to appropriately configure the varying puff so that in accordance with the formation of H, without departing from the scope of the present invention, it is also possible to embody changed arbitrarily.

[0021]

According to the present invention, as described above, at the start of piercing, a hole having a large diameter is first formed and then drilling is performed. Therefore, at the time of drilling, assist gas is guided into the recess and smoothly enters the hole. Flow into Therefore, since the assist gas is sufficiently fed into the hole, piercing can be performed stably and favorably, and a large-diameter hole necessary for shifting to cutting can be formed, and the shift can be smoothly performed. The effect is excellent. or,
By setting the laser output value and the assist gas pressure value at the time of forming a recess to values higher than those at the time of drilling, the recess can be formed very efficiently and instantaneously.

[Brief description of the 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 using the laser processing method.

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

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

FIG. 5 is a schematic sectional view showing a flow of an assist gas at the time of piercing according to a conventional method.

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-150789 (JP, A) JP-A-57-181786 (JP, A) JP-A-54-11593 (JP, A) JP-A-60-1985 240393 (JP, A) Jiko 3-27752 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 26/00

Claims (1)

(57) [Claims] 1. A laser processing method for cutting a workpiece by using a laser beam, wherein a focus of the laser beam is set at a predetermined distance from a surface of the workpiece, and a setting value at the time of drilling is set.
A first step of forming a recess in the surface of the work with a high laser output and an assist gas pressure, and then moving the focus to a predetermined amount in a direction to enter the inside of the work.
Piercing is performed from a second step of piercing with a laser output lower than the step and an assist gas pressure.