JPH11170077A - Method and device for cutting molded work piece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cut a molded work piece by laser machining at high speed and also to suppress or eliminate dross generation at the time of this laser cutting. SOLUTION: A cutting gas 27 is supplied to the converging side of a condensing lens 13 in a laser machining head 9, with a laser beam LB and the cutting gas 27 injected from an injection nozzle 23 installed at the lower end of the laser machining head 9. In this case, a command is given from the controller 21 to a machining head elevation device 19, moving the laser machining head 9 vertically so that the focus C of the laser beam LB is positioned higher than the cutting position A of the molded work piece (work W). The focus C and the cutting position A are set in the manner that they bring such a defocusing quantity i as the work W is cut with a cutting width K which is nearly one half of the plate thickness t of the work W. Particularly, a metal having a low melting point like a magnesium alloy is cut with the laser beam LB having a comparatively low power density, with the sticking of dross suppressed as much as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for cutting an accessory of a molded article, and more particularly to a thin burr generated on a cast molded article such as a die casting or an injection molding made of a metal having a low melting point such as a magnesium alloy. The present invention relates to a method and an apparatus for cutting a molded article accessory for cutting a molded article accessory such as a dross generated at the time of laser cutting or a molded article accessory of a part outside a product such as a hot water stopper.

[0002]

2. Description of the Related Art Conventionally, cast products such as die-casting and injection molding are accompanied by molded product accessories such as thin burrs and portions outside the product such as a stopper and a sprue.

When a molded product made of a metal having a low melting point, such as a magnesium alloy, is laser-cut, a molded product accessory such as dross is generated during the laser cutting.

Conventionally, in order to remove the above-mentioned thin burr, molded product accessories such as a stopper and a sprue, machining methods such as milling, milling, and punching with a press die have been used.

[0005] Alternatively, the removal of the above-mentioned molded article accessories such as thin burrs and dross is performed manually by a file, sander or the like.

[0006]

However, in the conventional method for cutting a molded article accessory, the former machining method has a problem that the processing speed is slow in, for example, milling or milling. Since punching with a press die cannot remove fine thin burrs,
As a result, since the final finishing is manually performed with a file or a sander, it takes a long time, which causes an increase in cost, and there has been a problem that the finish is not uniform.

Further, when the object to be cut is a magnesium alloy, there is a danger that fire will occur if metal powder generated by a file or a sander accumulates, and the work itself will be dangerous.

[0008] In addition, when a molded article accessory is cut and removed by laser processing using a cutting gas of nitrogen gas, the thermal conductivity of a material having a low melting point, such as a magnesium alloy, is determined by the characteristics of the material properties. Because of its high viscosity and high reflectivity, it has a problem that dross is likely to adhere during laser cutting, as in the case of aluminum alloys.

Incidentally, when a workpiece W such as a stainless steel is cut by a normal non-oxidation laser using a high-pressure nitrogen gas as a cutting gas, as shown in FIG. The distance between the workpiece W and the nozzle 103 at the lower end of the laser processing head 101 is suppressed to 0.5 mm or less, and the kinetic energy of the cutting gas (cutting impact pressure Pi) and the light are condensed by the condensing lens 105 at high density. The laser beam LB is evaporated and removed, and as a result, dross-free cutting is obtained. However, magnesium alloy tends to adhere dross as described above.

In addition, there is a problem in that the gate part and the stop part require a manual operation especially in the separation step due to the difference in level and thickness from the product side.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to cut an accessory of a molded article at high speed by laser processing and to suppress or eliminate the generation of dross during the laser cutting. Another object of the present invention is to provide a method and an apparatus for cutting a molded article accessory for easily removing the molded article accessory such as a thin burr.

[0012]

According to a first aspect of the present invention, there is provided a method of cutting a molded article accessory according to the first aspect of the present invention, comprising the steps of: A cutting gas is supplied to a condensing side of a converging lens, and the cutting method of a molded article accessory for performing laser cutting by jetting the laser beam and the cutting gas from an injection nozzle provided at a lower end of the laser processing head, The focal point of the laser beam is positioned above the cutting position of the molded article accessory, and the positional relationship between the focal point of the laser beam and the cutting position is reduced to approximately one half of the thickness of the molded article accessory. It is characterized in that laser cutting is performed by setting the amount of focus defocus for cutting the accessory of the molded article by the width.

Therefore, since the molded article accessory is laser-cut with a large focus defocus amount, a relatively low power density is obtained especially for a molded article accessory made of a metal having a low melting point such as a magnesium alloy. The cutting is performed by the laser beam, the flow of the cutting gas becomes smooth, and the adhesion of dross is suppressed as much as possible.

According to a second aspect of the present invention, there is provided a cutting method of a molded article accessory, wherein a cutting gas is supplied to a converging side of the converging lens in a laser processing head containing a converging lens for converging a laser beam. In the cutting method of a molded article accessory, in which the laser beam and the cutting gas are injected from an injection nozzle provided at a lower end of the laser processing head to perform laser cutting, the focus of the laser beam is set at a cutting position of the molded article accessory. Laser cutting is performed at the same time, and after this laser cutting, the focal point of the laser beam is positioned above the cutting position and secondary laser processing is performed to remove dross on the cut surface generated during the laser cutting. It is characterized by the following.

Therefore, when ordinary laser cutting is performed, dross is generated on the cut surface. The focal point of the laser beam is positioned above the cut position with respect to this cut surface, and a secondary low power density is obtained. Dross is automatically removed by laser processing again with the laser beam without damaging the first cut surface.

According to a third aspect of the present invention, there is provided a method for cutting a molded article accessory, the method comprising detecting the presence or absence of thin burrs on the molded article accessory with a sensor provided in an injection nozzle provided at a lower end of a processing head. When it is detected that there is a gas, the cutting gas is supplied into the processing head and the thin burr is cut by the pressure of the cutting gas injected from the injection nozzle. Is stopped, and the machining head is axially moved at a speed higher than the cutting speed.

Therefore, the thin burr of the molded article accessory is low in strength, so that it can be easily cut in a good finishing state by the pressure of the cutting gas injected from the injection nozzle, and when there is no thin burr, the cutting gas is injected. In addition, since the moving speed of the processing head is high, the cutting work of the molded article accessory is performed with high efficiency.

According to a fourth aspect of the present invention, there is provided a method for cutting a molded article accessory according to any one of the first to third aspects, wherein the molded article is made of a magnesium alloy. It is characterized by the following.

Therefore, since cutting is performed at a low power density, it is particularly suitable for cutting a molded article accessory of a magnesium alloy molded article having a low melting point.

According to a fifth aspect of the present invention, there is provided an apparatus for cutting a molded article accessory, which supplies a cutting gas to a light-collecting side of the light-collecting lens in a laser processing head containing a light-collecting lens for condensing a laser beam. In a cutting device for a molded article accessory that injects the laser beam and the cutting gas from an injection nozzle provided at a lower end of the laser processing head to perform laser cutting, a processing head elevating device that raises and lowers the laser processing head is provided. The positional relationship between the focal point of the laser beam and the cutting position of the molded article accessory is defined as a focus defocus amount for cutting the molded article accessory with a cutting width of approximately half the thickness of the molded article accessory. To this end, the processing head elevating device is provided with a control device for generating a lifting / lowering operation command of the laser processing head.

Therefore, the operation is the same as that of the first aspect, and the laser processing head is automatically moved up and down by the operation of the working head lifting / lowering device according to a command from the control device, and the molded article accessory increases the focus defocus amount. And laser cutting, especially for molded product accessories made of low melting point metal such as magnesium alloy, is cut with a laser beam of relatively low power density, the flow of cutting gas becomes smooth and dross Adhesion is minimized.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for cutting a molded article accessory and an apparatus therefor according to the present invention will be described below with reference to the drawings.

Referring to FIG. 4, for example, a laser beam machine LB (laser beam) according to the present embodiment
The laser beam LB oscillated by the laser oscillator 3 passes through an intensity adjusting device 5 and is reflected by a laser processing head 9 provided at the tip of a laser beam guide irradiation unit 7 at a reflecting mirror. The light is reflected in a vertical downward direction through the line 11. This laser beam LB is condensed by a focusing lens 13 provided inside the laser processing head 9. The laser beam LB is focused on the work W transferred and positioned by, for example, a numerically controlled work transfer positioning device 17 (work transfer device) with respect to the irradiation optical axis 15 of the focused laser beam LB. Then, laser processing such as cutting into a desired shape is performed.

Referring to FIG. 1 in more detail, the laser processing head 9 is vertically movable by a processing head elevating device 19 so that the position of the focal point of the condenser lens 13 can be adjusted up and down. . This processing head elevating device 19 is electrically connected to the control device 21.

An injection nozzle 23 is screwed to the front end of the condensing lens 13 of the laser processing head 9 on the condensing side. A cutting gas supply pipe 25 provided on a side wall of the laser processing head 9 is provided between the injection nozzle 23 and the condenser lens 13.
Is supplied to the workpiece W from the tip of the injection nozzle 23.

The cutting gas 27 is generated when the laser beam LB passes through the condenser lens 13.
Is used to prevent the temperature from rising, prevent contamination of the lens surface due to spatter from the workpiece W, and improve the processing efficiency.

Actually, at the time of laser processing, the operating conditions of the laser processing machine 1 are slightly different depending on the laser processing conditions such as the cutting speed of the work W, the nozzle gap, the cutting gas pressure, and the plate thickness of the work W. It is necessary to set the optimal operation condition for.

For example, the tip of the injection nozzle 23 and the work W
The nozzle gap j between the laser beam LB and the processing position of the work W needs to be finely adjusted.

The control device 21 has an input device 2 for inputting data on various laser processing conditions as described above.
9, a display device 31, a memory 33 for storing the input data, and a comparison judging device 35 for comparing and judging the input data based on the arithmetic expression in the memory 33.
Is provided.

Next, as the work W, as shown in FIG. 3, a cast product made of a magnesium alloy formed by die casting, injection molding or the like is used as an example. A method for cutting a molded article accessory of an article will be described.

Referring to FIG. 3, a cast product 37 made of a magnesium alloy includes a thin product burr 39 generated at the time of casting, and a molded product accessory N which is a part outside the product such as a pouring portion 41 and a gate portion 43. And a step E generally occurs between the product and each molded article accessory N.

As shown in FIG. 2, a laser is formed from the base of the step E having a slope of, for example, about 10 mm where the slope of the inclination angle α is formed to the pool (the gate 43 and the stopper 41). The case where cutting is performed will be described. In the comparison / determination device 35 of the control device 21, the positional relationship between the focal point C of the laser beam LB and the cutting position A of the molded product accessory N indicates the thickness of the molded product accessory N to be cut. almost one-half for t
Focus defocus amount i so that it is cut by the cutting width K of
Is set to the machining head elevating / lowering device 19, a laser machining head elevating operation command is issued.

More specifically, the focal defocus amount i is the distance from the focal point C of the laser beam LB to the upper surface of the work W, as shown in FIG. Since the optical F-number (= f / D) for the lens diameter D is set in advance, there is a proportional relationship between the focus defocus amount i and the value of the cutting width K. That is, the value of the cutting width K changes in direct proportion to the change of the focus defocus amount i.

In addition, the energy of the laser beam LB at the cutting position A of the work W is also equal to the focus defocus amount i.
Changes in direct proportion to the change in That is, when the focus defocus amount i increases, the cutting position A becomes the laser beam LB.
The laser beam LB having a lower power density, and the cutting impact pressure Pi becomes lower.

As described above, since the focal length f from the tip of the injection nozzle 23 to the focal point C of the laser beam LB is set to be constant, the laser machining head 9 is moved up and down so as to adjust the nozzle gap j. Accordingly, the magnitude of the focus defocus amount i can be appropriately adjusted, whereby the energy of the laser beam LB at the cutting position A is adjusted and set.

In the case of magnesium alloy, the melting point is 590 °
C, and the thermal conductivity is about 70% of that of aluminum (167 w / m ° C for Mg). Therefore, as described above, the cutting width K is approximately one half of the plate thickness t. By performing the laser cutting with the laser beam LB having a relatively low power density while increasing the focus defocus amount i so that the flow of the cutting gas 27 becomes smooth, the adhesion of dross is suppressed as much as possible. .

Incidentally, according to the basic experiment results, when the cutting gas 27 is a nitrogen gas which is a quasi-inert gas, the optical F number (= f / D) is 6.35 and the defocus ratio (= f / I) is 20 and the thickness t of the work W is 1 to
In the case of 2 mm, the cutting width K formed in the work W is almost half (= t / 2) of the plate thickness t, and despite the low cutting impact pressure Pi in the nozzle gap j of 10 mm or more, the dross is reduced. Products with few Further, since the laser beam LB has a low power density, thermal damage to the slope of the step E of the work W can be reduced.

Next, another cutting method of the molded article accessory N will be described with reference to FIG. 5 and FIG.
An example in which the hole 45 is laser cut on the upper surface of the work W having a letter shape will be described. The processing head elevating device 19 is the same as that of the above-described embodiment, and the control device 2
1 electrically.

Referring to FIG. 7, first, the laser beam L
The focus C of B is adjusted to the cutting position of the work W, and the normal laser cutting is performed to perform the hole processing as shown in FIG. At this time, dross is generated on the cut surface of the hole 45 to be machined (step S1).

The controller 21 determines whether or not the laser has been cut to the end point of the preset processing position (step S2). When the laser cutting is completed, the focal point C of the laser beam LB is raised above the cutting position. A command is issued to the processing head lifting / lowering device 19 to perform the secondary laser processing by positioning, and dross processing for removing dross generated during laser cutting processing is performed.

That is, the laser processing head 9 is automatically raised by the operation of the processing head lifting / lowering device 19 as shown in FIG. 6, and the focal point C of the laser beam LB is shifted with respect to the cut surface by the first laser cutting. Secondary laser processing is performed again with the low power density laser beam LB as described above, which is positioned above the cutting position A. The dross is automatically removed by the low power density laser beam LB without damaging the first cut surface (step S3).

The controller 21 determines whether or not the dross processing of the laser cut surface has been completed (step S).
4), when this dross processing is completed, laser cutting of the next part is performed (step S5).

Next, regarding another cutting method, a thin burr 39 generated at the end of the work W as shown in FIG.
An example in which (the molded article accessory N) is automatically cut by the cutting device 47 will be described.

Referring to FIGS. 8 and 9, a cutting device 47 for a molded article accessory according to the present embodiment can be moved and positioned in the X-axis direction by an NC device (not shown) and a driving means on a main body frame 49. An X-axis carriage 51 is provided.
The axis carriage 51 is provided with a Y-axis carriage 53 which can be moved and positioned by an NC device and a driving means in a Y-axis direction orthogonal to the X-axis direction.

A processing head 55 is provided below the Y-axis carriage 53, and the processing head 55 can be moved and positioned also in the Z-axis direction (vertical direction) orthogonal to the X and Y axes. . An injection nozzle 59 for injecting the cutting gas 57 is provided at the lower end of the processing head 55, and the injection nozzle 59 is provided with a sensor 61 for detecting the presence or absence of the thin burr 39 on the work W. The sensor 61, the X-axis carriage 51, the Y-axis carriage 53, and a drive device for moving and positioning in the Z-axis direction are electrically connected to a control device (not shown). This control device has the same mechanism as the control device 21 described above.

A processing table 63 is provided below the processing head 55 on the bed of the cutting device 47.

The control device uses the sensor 61 to control the thin burr 39
If it is detected that the cutting gas 57 is present, a command is issued by the detection signal of the sensor 61 so that the cutting gas 57 is injected from the injection nozzle 59. The thin burr 39 is cut by the jetting cutting gas 57.

When the sensor 61 detects that there is no thin burr 39, the injection of the cutting gas 57 from the injection nozzle 59 is stopped by the detection signal of the sensor 61, and at the same time, the processing head 55 is moved faster than the cutting speed. A command is issued to move the axis at the speed.

With the above configuration, referring to FIG.
First, the injection nozzle 59 of the processing head 55 is positioned at the processing point of the workpiece W (Step S1). Cutting gas 57
Is injected, and the cutting feed of the processing head 55 is caused by the operation of the X-axis carriage 51 and the Y-axis
(Step S2).

The thin burr 3 of the work W is detected by the sensor 61.
9 is detected (step S3), and when the presence of the thin burr 39 is detected by the sensor 61, the injection of the cutting gas 57 from the injection nozzle 59 is continued by the detection signal of the sensor 61. Since the thin burr 39 of the work W is low in strength, the cutting gas 5 injected from the injection nozzle 59
It is easily cut in a good finish by the pressure of 7 (step S4).

However, the absence of the thin burr 39 is detected by the sensor 6.
When it is detected by 1, the cutting gas 57 is not injected by the detection signal of the sensor 61 and the moving speed of the processing head 55 is increased, so that the work of cutting the workpiece W is performed with high efficiency (step S5).

The cutting device 47 having the above-described structure can cut the thin burrs 39 using an ordinary laser beam machine into which a so-called cutting gas 57 is injected. That is, as shown in FIG.
A cutting gas supply device (not shown) for supplying a cutting gas 57 to the condensing side of the condensing lens 13 in the laser processing head 9 is the same as the laser processing head 9 that houses a condenser lens for condensing light. Is provided. Thin burrs 3 can be formed only by injecting a cutting gas using such a normal laser processing machine.
9 can be performed efficiently and in a good finished state.

The present invention is not limited to the above-described embodiment, but can be embodied in other modes by making appropriate changes. In the example of the present embodiment, a general laser processing machine has been described as an example, but the laser processing head is a laser processing machine or another laser processing machine provided in a portal-shaped processing machine body, or another cutting apparatus. It does not matter.

[0054]

As will be understood from the embodiments of the present invention as described above, according to the first aspect of the present invention, since the molded article accessory is laser-cut by increasing the focus defocus amount, the magnesium alloy is preferably used. The molded article accessory made of a metal having a low melting point can be cut with a laser beam having a relatively low power density, the flow of the cutting gas becomes smooth, and the adhesion of dross can be suppressed as much as possible. In addition, there is no danger of ignition because no metal powder is generated when finishing with a file or sander.

According to the second aspect of the present invention, when ordinary laser cutting is performed, dross is generated on the cut surface. However, the focus of the laser beam is positioned above the cut position with respect to this cut surface. By re-lasing with the next lower power density laser beam, the dross can be automatically removed without damaging the first cut surface.

According to the third aspect of the present invention, since the thin burrs of the molded article accessory are low in strength, the thin burrs can be easily cut in a good finish state by the pressure of the cutting gas injected from the injection nozzle. Moreover, when there is no thin burr, the cutting gas is not jetted and the moving speed of the processing head is increased, so that the cutting operation of the molded article accessory can be performed with high efficiency.

According to the fourth aspect of the present invention, since cutting is performed at a low power density, it is particularly suitable for cutting a molded article accessory of a magnesium alloy molded article having a low melting point.

According to the fifth aspect of the present invention, the effect is the same as that of the first aspect, and the laser processing head is automatically moved up and down by the operation of the working head elevating device according to a command from the control device, and the focus defocus amount The laser cutting of the molded article accessory with a large size makes it possible to cut the molded article accessory made of a metal with a low melting point, such as a magnesium alloy, with a laser beam having a relatively low power density. And dross adhesion can be suppressed as much as possible.

[Brief description of the drawings]

FIG. 1, showing an embodiment of the present invention, is a cross-sectional view of a main part of a laser processing head for explaining a method of cutting a molded article accessory.

FIG. 2, showing an embodiment of the present invention, is a cross-sectional view of a main part showing a cutting state of a work.

FIG. 3 is a perspective view showing a shape of a workpiece cut in the embodiment of the present invention.

FIG. 4 relates to an example of the embodiment of the present invention and is an overall front view of a laser beam machine.

FIG. 5, showing an embodiment of the present invention, is an explanatory view of a method for cutting another molded article accessory.

FIG. 6, showing an embodiment of the present invention, is an explanatory view of a method for cutting another molded article accessory.

FIG. 7, showing an embodiment of the present invention, is a flowchart illustrating a method for cutting another molded article accessory.

FIG. 8 is an overall perspective view of a cutting device according to the embodiment of the present invention.

FIG. 9 is a cross-sectional view of a main part showing a state of a processing head and a work in FIG. 8;

FIG. 10 shows an embodiment of the present invention, and is a flowchart for explaining a method for cutting another molded article accessory.

FIG. 11 is an explanatory diagram showing a cutting state by conventional ordinary laser processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser processing machine 9 Laser processing head 13 Focusing lens 19 Processing head elevating device 21 Controller 23 Injection nozzle 27 Cutting gas 37 Cast molding 39 Thin burr N Molding accessories j Nozzle gap t Plate thickness K Cutting width i Focusing di Focus amount C Focus f Focal length F number (= f / D) D Condensing lens diameter Pi Cutting impact pressure

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI B23K 26/16 B23K 26/16

Claims (5)

[Claims] 1. A cutting gas is supplied to a condensing side of a converging lens in a laser processing head in which a converging lens for converging a laser beam is housed, and the cutting gas is supplied from an injection nozzle provided at a lower end of the laser processing head. A method for cutting a molded article accessory that performs laser cutting by injecting a laser beam and the cutting gas, wherein a focal point of the laser beam is positioned above a cutting position of the molded article accessory, and a focal point of the laser beam and the cutting position. Laser cutting by setting a positional relationship between the laser beam and the focus defocus amount to cut the molded article accessory with a cutting width of approximately one half of the thickness of the molded article accessory. How to cut molded article accessories. 2. A cutting gas is supplied to a converging side of the condenser lens in a laser processing head containing a condenser lens for condensing a laser beam, and the cutting gas is supplied from an injection nozzle provided at a lower end of the laser processing head. In the method of cutting a molded article accessory which performs laser cutting by injecting a laser beam and the cutting gas, a laser cutting process is performed by adjusting a focus of the laser beam to a cutting position of the molded article accessory, and after the laser cutting processing, the laser A cutting method of a molded article accessory, comprising: removing a dross of a cut surface generated at the time of the laser cutting by performing a secondary laser processing by positioning a focal point of the beam above the cutting position. 3. A sensor provided at an injection nozzle provided at a lower end of the processing head detects presence or absence of a thin burr of a molded article accessory, and cuts into the processing head when the presence of the thin burr is detected. The thin burr is cut by the pressure of the cutting gas injected from the injection nozzle by supplying gas, and when the thin burr is not present, the injection of the cutting gas from the injection nozzle is stopped and the processing head is moved at a speed higher than the cutting speed. A method for cutting a molded article accessory, characterized in that the article is moved axially. 4. The method for cutting a molded article accessory according to claim 1, wherein the molded article is made of a magnesium alloy. 5. A cutting gas is supplied to a converging side of the converging lens in a laser processing head containing a converging lens for converging a laser beam, and a cutting nozzle is provided at a lower end of the laser processing head. In a cutting device for a molded article accessory that performs laser cutting by injecting a laser beam and the cutting gas, a machining head elevating device that raises and lowers the laser processing head is provided, and a focal point of the laser beam and a cutting position of the molded article accessory are provided. A command for raising and lowering the laser processing head to the processing head elevating device so that the positional relationship is a focus defocus amount that cuts the molded article accessory with a cutting width of approximately one half of the thickness of the molded article accessory. A cutting device for an accessory of a molded article, characterized by comprising a control device for generating the same.