JPH10323781A - Laser processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively use the amount of heat inside a work to prevent the spatters from being scattered and to accomplish a piercing in a short time by setting a laser output as a continuous output when a piercing starts, and changing it as a pulse output in the course of the piling procession. SOLUTION: The work W is placed under the laser processing head 1. When piercing starts, the laser processing head 1 is positioned at the piercing point by a command from a NC unit 15. A laser oscillation controller 19 controls an oscillation condition of the oscillation machine 3. First, piercing is to be started by the continuous output laser beam LB from the laser processing head 1. After it elapsed a given time, the oscillation condition of the laser oscillation machine 3 is switched to a pulse oscillation, and the pulse oscillation output to the laser processing head 1 is kept continued for a period until the pulse output laser accomplishes the piercing processing. Since the method does not require a complicated pulse frequency control unit, the control unit can be simplified.

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, and more particularly to a piercing method applied to processing of a relatively thick work.

[0002]

2. Description of the Related Art Conventionally, when a work is cut by a laser processing machine, a method of first performing piercing (preparing a prepared hole for starting cutting) on the work and starting cutting from this piercing position is generally adopted. I have.

The above piercing includes a case where a continuous output laser is used and a case where a pulse output laser is used. In piercing with a continuous output laser, the piercing time is short, but spatters (oxidation products of molten metal) are scattered and ridges are formed around the piercing holes. Often adhere to the condenser lens. In comparison with the pulse output laser, the spattering is less scattered, but the piercing time is longer than the piercing by the continuous output laser.

In the above-mentioned piercing, piercing of a thick plate requires more time, and several methods for shortening the piercing time have been proposed. For example, Japanese Unexamined Patent Publication No. Hei 3-118989 discloses that piercing is started at an output lower than the optimum laser output at the time of piercing, then the output is gradually increased to the optimum laser output, and the state is maintained until the piercing ends. A laser processing method for reducing spatter and shortening the piercing time is disclosed.

Japanese Patent Application Laid-Open No. 5-138382 discloses that the pulse frequency of a pulse output laser at the start of piercing is set to be low, and the frequency is gradually increased with the progress of piercing to complete the piercing. Discloses a piercing method for reducing spatter and shortening the piercing time.

[0006]

SUMMARY OF THE INVENTION The above-mentioned JP-A-3-118.
In the method of No. 989, piercing requires a long time in order to prevent molten metal from spouting during piercing. Further, in the method disclosed in Japanese Patent Laid-Open No. 5-138382, it is necessary to perform another output control in which the frequency of the pulse is gradually increased with the progress of the piercing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce the scattering of spatter during piercing without performing a separate pulse frequency control during piercing. An object of the present invention is to provide a laser processing method capable of high-speed piercing.

[0008]

According to a first aspect of the present invention, there is provided a laser processing method in which a laser output is set to a continuous output at the start of piercing, and the laser output is pulsed during piercing. The point is to change the output to piercing.

Therefore, at the start of piercing, melting is promoted by continuous output (CW), and the laser is switched to a pulse output laser while the generated heat remains in the work, so that the heat amount inside the work is effectively used. The piercing can be completed in a short time while preventing scattering of spatter.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a laser processing machine that performs the laser processing method of the present invention. The laser beam LB emitted from the laser oscillator 3 and guided through the bend mirror 5 is supplied to the work W
A condensing lens 7 for condensing light on the surface is provided. An assist gas supply port 11 is provided below the condenser lens 7 to be injected from the nozzle 9 being processed toward the work W. The assist gas supply port 11 controls the flow rate of the assist gas through the assist gas controller 13. The supplied assist gas is supplied.

The laser processing head 1 includes an NC device 15
Is moved and positioned in the X, Y and Z axis directions (vertical direction) by a positioning device (not shown) driven by a servo controller 17 controlled under the above control. Further, the laser oscillator 3 is also NC
Control is performed as follows through a laser oscillation controller 19 controlled under the control of the device 15.

For example, an SS material, a work W having a thickness of 12 mm
Work W to be pierced by laser processing head 1
When the piercing is started by positioning the laser processing head 1 at the piercing position according to a command from the NC device 15, the laser processing head 1 is lowered in the Z-axis direction (vertical direction), The gap G between the tip and the work W is kept at the set value.

Thereafter, the laser oscillation controller 19 controls the oscillation conditions of the laser oscillator 3 in response to a command from the NC device 15, and as shown in FIG. 2, first, a continuous output (CW) laser beam LB is produced by a laser processing head. 1 and piercing is started. When time t1 has elapsed with continuous output, the oscillation condition of the laser oscillator 3 is switched to pulse oscillation, and the pulse output laser is output to the laser processing head 1 for time t2 until the piercing ends. That is, at the start of piercing, melting is promoted by continuous output (CW), and while the generated heat remains in the work,
By switching to the pulse output laser, the amount of heat inside the work can be effectively used to prevent scattering of spatter, and at the same time, piercing can be completed in a short time.

FIG. 3 shows one output pattern 1 using the processing method shown in FIG. This output pattern 1 is a continuous output (C
W), processing is performed for t1 time, and thereafter, processing is performed for t2 time with a pulse output having a peak output of 3 kW (average output P2). As a result of performing a piercing processing test on the output pattern 1 under the following processing conditions, the piercing time was significantly reduced to 2.0 seconds to 2.5 seconds compared to the conventional method, and the scattering of spatter was reduced to a very small amount. I was able to hold down.

Piercing processing conditions for output pattern 1 "workpiece; plate thickness: 12 mm (SS material); laser output: continuous output: 3 kW (t1 time); pulse peak output: 3 kW
(Time t2), pulse frequency 140 Hz, pulse duty 25%, piercing time T = t1 + t2. Assist gas pressure: 0.1 kgf / cm ² (at continuous output), 0.3
5kgf / cm ² (with pulse output) "

FIG. 4 shows an output pattern 2 in which the pulse frequency and pulse duty of the pulse laser having a peak output of 3 kW in the output pattern 1 are stepwise (three steps in the embodiment of FIG. 4). Increase (frequency initial value 10 Hz, duty initial value 12%, frequency increment value 10
Hz, duty increment value 1%), and the average pulse output increases to P2, P3, P4. As a result of processing the same workpiece using the output pattern 2, it has been confirmed that the processing can be performed with the same piercing time as the output pattern 1 and with less scattering of spatter.

Note that the same effect can be obtained by continuously increasing the pulse frequency in the output pattern 2 instead of increasing the pulse frequency stepwise.

[0018]

According to the first aspect of the present invention, the laser output is set to a continuous output at the start of piercing, and the piercing is performed by changing the laser output to a pulse output during the progress of the piercing. At the start of piercing, melting is promoted by continuous output (CW), and while the generated heat remains in the work, switching to a pulse output laser is used to effectively utilize the heat inside the work to prevent spatter scattering. At the same time, piercing can be completed in a short time.

Therefore, damage to the nozzle and lens due to the scattering of high-temperature spatter is reduced, and productivity is improved by shortening the piercing time. Further, since a complicated pulse frequency control device is not required, there is an advantage that the control device is simple and the cost does not increase much.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laser processing machine that performs a laser processing method according to the present invention.

FIG. 2 is a conceptual diagram of a laser processing method according to the present invention.

FIG. 3 is an example of an output pattern using the laser processing method according to the present invention.

FIG. 4 is another output pattern example using the laser processing method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser processing head 3 Laser oscillator 5 Bend mirror 7 Condensing lens 9 Nozzle 11 Supply port 13 Assist gas controller 15 NC device 17 Servo controller 19 Laser oscillation controller LB Laser beam W Work

Claims (1)

[Claims] 1. A laser processing method comprising: setting a laser output to a continuous output at the start of piercing; and changing the laser output to a pulse output during the progress of piercing to perform piercing.