JPH0364236B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a method of laser processing a workpiece using a laser beam, and more particularly to a method of forming a hole in a workpiece using a laser beam.

"Prior Art" Conventionally, forming holes in a workpiece using a carbon dioxide laser processing machine has been widely practiced. When forming a hole in a workpiece, the workpiece is usually placed on a processing table, and then a laser beam is irradiated onto the workpiece while jetting assist gas from a focus head to cut it. A through hole is formed by passing the laser beam from the front surface to the back surface of the workpiece inside the virtual circle.

Next, while maintaining the penetration state of the laser beam, the focus head and the workpiece are moved relative to each other to move the laser beam to a predetermined cutting start position on the virtual circle, and then continue to move the laser beam onto the virtual circle. , and the laser beam is continuously moved until it reaches the starting position again to form a hole in the workpiece.

``Problem to be solved by the invention'' However, for example, when forming a hole in a thick piece of wood using a laser beam, a small protrusion protruding toward the hole side is created at the cutting end position, which is the initial cutting start position. Some remained.

In other words, in general, when cutting a workpiece with a laser beam, the focal position of the condensing lens built into the focus head is made to almost coincide with the surface of the workpiece, and the energy density of the laser beam increases in that area. That's what I do. As a result, the laser beam spreads out from the front side of the workpiece, which is the focus position of the condensing lens, to the back side, so the cutting width on the back side of the workpiece is larger than the cutting width on the front side of the workpiece. . Therefore, the cut surface when forming the round hole becomes a conical surface that is widened at the bottom.

In this case, the small protrusion protruding toward the hole described above will not remain on the conical surface, but if the wood is a die board used for cutting out cardboard etc., and the hole is If the die board has a round hole for fitting a cylindrical cutting blade, the cylindrical cutting blade will fit into the round hole with a conical surface, making it easy for the cutting blade to wobble. , undesirable.

In order to cut the workpiece so that the inner peripheral surface of the round hole becomes as cylindrical as possible, the workpiece may be cut at a relatively high speed. In other words, even in this case, the laser beam spreads out from the front surface to the back surface of the workpiece, but the cut surface is greatly affected by the flow of the assist gas injected toward the cutting part, so the assist gas If the relative movement speed is set so that the laser beam is moved relative to the workpiece when it penetrates the back side of the workpiece with a cutting width similar to the cutting width on the front side, the laser beam can be moved relative to the workpiece. The inner peripheral surface can be made into a cylindrical surface as much as possible.

However, in this case, the cutting on the back side of the workpiece is delayed compared to the cutting on the front side, so the moment the cutting position on the front side returns to the starting position, the cutting position on the back side is just before the starting position. Become. The assist gas flows from the cutting end side to the cutting start side at the moment when the cutting on the back side continues to the original starting position, so that the assist gas pressure at the cutting ending position becomes insufficient and the fuel efficiency decreases. As a result, the cutting width at that portion on the back side becomes narrower, and the above-mentioned small protrusion is formed, and such a protrusion also causes the cutting blade to wobble.

The small convex part formed on the inner peripheral surface of the hole can be scraped off with a laser beam, but if only the convex part is scraped off, the convex part and the contiguous part A slight step is formed at the boundary with other parts, which is not desirable.

On the other hand, by making the laser beam go around the virtual circle of the hole twice, the convex part formed in the first round is
It is also possible to scrape it off at the turn. In this case, the inner circumferential surface of the hole can be formed smoothly, but since the laser beam follows the same trajectory, the hole can be formed smoothly in the same way as when the laser beam is moved at a relatively low speed. There is a drawback that the cut surface becomes a conical surface that is widened at the bottom.

"Means for Solving the Problems" In view of the above-mentioned circumstances, the present invention irradiates the cutting start position of the workpiece with a laser beam, causes the laser beam to penetrate from the front surface of the workpiece to the back surface, and
Forming a hole surrounded by the first imaginary circle in the workpiece by continuously moving the laser beam on the first imaginary circle until it returns to the starting position while maintaining the penetrating state of the laser beam; Continue using the above laser beam,
The hole is formed into a hole of a desired size by moving on a second virtual circle larger than the first virtual circle while cutting down the cutting surface of the hole from the starting position to the starting position again. This is what I did.

"Operation" According to the above configuration, small protrusions generated on the inner peripheral surface of the hole by cutting the workpiece at a relatively high speed can be removed by continuously scraping off the cut surface of the hole with a laser beam. Therefore, it can be removed at the same time, and since the laser beam is used to cut off the cut surface of the hole and form the hole to the desired size, the inner circumferential surface of the hole is smooth. At the same time, it is possible to make the inner circumferential surface of the hole a plane parallel to the optical axis of the laser beam as much as possible.

"Example" The present invention will be described below with reference to the illustrated example.
In FIG. 3, a carbon dioxide laser processing machine 1 having a conventionally well-known configuration includes a work table 3 on which a workpiece 2 is placed and movable in the X direction on a horizontal plane and in the Y direction perpendicular thereto. A focus head 4 is provided above the work table 3 and is movable up and down in the vertical Z direction.

The movement of the work table 3 in the X-Y direction and the movement of the focus head 4 in the Z direction are each controlled by a control device 5, and the workpiece 2 on the work table 3 is exposed to the laser beam L. As shown in FIG. 1, a circular hole 6 having a desired diameter is formed.

When forming the hole 6, first, the laser beam L is irradiated at a predetermined position inside the hole 6 to be formed to form a through hole 7, and then the laser beam L is irradiated onto the hole 6 to be formed. Once the cutter is moved to the predetermined cutting start position A, the cutter is moved from there one round in a circle with a diameter slightly smaller than that of the hole 6 until it reaches the start position A again, thereby forming a hole 8 with a small diameter.

At this time, by moving the laser beam L at a high speed relative to the workpiece 2, the laser beam L is originally moved to the focal position of a condensing lens (not shown), as shown in FIG. Despite expanding from near the surface to the back surface of the workpiece 2 (see imaginary line), the flow of the assist gas allows the inner circumferential surface of the hole 8 to be made into a cylindrical surface as much as possible.

However, on the other hand, as shown in FIG. The convex portion 9 will remain.

Next, once the hole 8 is formed by making the laser beam L go around once from the starting position A until it returns to the starting position A, continue from the starting position A in the opposite direction to that in which the hole 8 was formed, i.e. The laser beam L is moved counterclockwise in FIG. 1, and the cut surface of the hole 8 and the convex portion 9 are moved while cutting off the cut surface of the hole 8 and the convex portion 9 until it reaches the starting position A again. Shape into 6 pieces.

Therefore, the cutting start position A of the hole 8 and the cutting start position A of the hole 6 are the same position, and the hole 8 is the same as the cutting start position A of the hole 6.
It comes to be inscribed at the cutting start position A.

The inner peripheral surface of the hole 6 formed in this way is
The continuous movement of the laser beam L along the virtual circle of the hole 6 creates a smooth surface without the convex portion 9, and since the cut surface of the hole 8 is ground down, the virtual circle of the hole 6 is The inner circumferential surface can be formed into a cylindrical surface as much as possible without forming a conical surface unlike the case where the upper part is rotated twice.

Furthermore, the width W for scraping off the inner peripheral surface of the hole 8 needs to be large enough to prevent the inner peripheral surface of the hole 6 from becoming a conical surface, but if it is made so large that the inner peripheral surface of the hole 8 cannot be scraped off, When the cut surface continues again with the inner circumferential surface of the hole 8, the continuous portion will not continue smoothly, so it is necessary to set it within a range that will not cause such a problem. As an example, when the workpiece is a die board with a thickness of 18 mm, the suitable cutting width W is about 0.2 mm.

Note that FIG. 4 shows a second embodiment of the present invention, and in this second embodiment, the laser beam L
After moving clockwise to form the hole 8, the laser beam L is further moved in the same direction to form the hole 8.
The inner circumferential surface of the hole 6 is cut off, thereby cutting off the protrusion 9 and forming the hole 6.

This second embodiment also provides the same effects as the first embodiment.

"Effects of the Invention" As described above, according to the present invention, even if the workpiece is a thick wooden board, the workpiece is smooth from the inner circumferential surface and is as close to the optical axis of the laser beam as possible. This provides the advantage of being able to form holes with parallel planes.

[Brief explanation of drawings]

FIG. 1 is a plan view showing one embodiment of the present invention, and FIG.
3 is a perspective view showing a conventionally known carbon dioxide laser processing machine, and FIG. 4 is a plan view showing another embodiment of the present invention. 1... Carbon dioxide laser processing machine, 2... Workpiece, 6, 8... Hole, 9... Convex portion, A... Cutting start position, L... Laser beam, W... Cutting width.

Claims (1)

[Claims] 1. Irradiate the cutting start position of the workpiece with a laser beam to make the laser beam penetrate from the front side of the workpiece to the back side, maintain the penetrating state of the laser beam, and return the laser beam to the above-mentioned starting position. A hole surrounded by the first imaginary circle is formed in the workpiece by continuously moving on a first imaginary circle until the laser beam reaches the starting position again. A method for forming a hole using a laser beam, characterized in that the hole is formed into a hole of a desired size by moving on a second imaginary circle larger than the first imaginary circle while cutting off the cut surface.