JP6837682B2 - Zero-cut processing method for high-hardness materials and manufacturing method for high-hardness material structures - Google Patents

Description

The present invention relates to a zero-cut processing method for a high-hardness material for processing a high-hardness material such as cemented carbide using a femtosecond laser, and a method for producing a high-hardness material structure made of the high-hardness material.

Conventionally, a method for processing a high-hardness material using a femtosecond laser has been proposed. For example, in Patent Document 1, the processed material is processed by irradiating the processed material with a femtosecond laser beam, and the pulse energy is set lower than that at the time of processing with respect to the processed surface formed by the processed material. It is described that the femtosecond laser beam is irradiated to remove the deposits formed on the machined surface by the femtosecond laser beam having a low pulse energy.

Japanese Unexamined Patent Publication No. 2008-119735

In the method described in Patent Document 1, it is possible to remove the deposits formed on the processed surface when the high hardness material is irradiated with the femtosecond laser beam and processed, but the femtosecond laser beam is used. It does not enable highly accurate machining of the machined surface formation itself.

An object of the present invention is to enable high-precision microfabrication of high-hardness materials such as cemented carbide using a femtosecond laser.

In the zero-cut processing method for a high-hardness material of the present invention, when the femtosecond laser light is focused by a lens and irradiated to the processed surface of the high-hardness material, the focal position of the femtosecond laser light is set to a position away from the processed surface. Moreover, the cutting process of setting the machined surface from the position where the machined surface cannot be machined to a position closer to the machined surface by a predetermined amount of cutting, and the focal position of the femtosecond laser beam are set. It is characterized by including a zero cut step of performing a zero cut without changing from the cut position.

According to the zero-cut processing method for a high-hardness material of the present invention, a predetermined depth of cut toward the processed surface from a position where the processed surface of the high-hardness material cannot be processed if the focal position of the femtosecond laser beam is further away. By setting the notch position as close as possible and performing the notch processing, and removing the uncut portion by performing zero cut without changing the focal position of the femtosecond laser beam from this notch position, the cut amount is highly accurate. The hardness material is removed.

In the method for manufacturing a high-hardness material structure of the present invention, when the femtosecond laser beam is focused by a lens and irradiated to the processed surface of the work piece, the focal position of the femtosecond laser beam is set to a position away from the processed surface. Moreover, the cutting process of setting the machined surface from the position where the machined surface cannot be machined to a position closer to the machined surface by a predetermined amount of cutting, and the focal position of the femtosecond laser beam are set. It is characterized by including a zero-cut step of performing a zero-cut without changing from the cut position.

According to the method for manufacturing a high-hardness material structure of the present invention, a predetermined depth of cut toward the processed surface from a position where the processed surface of the workpiece cannot be processed if the focal position of the femtosecond laser beam is further away. By setting the notch position as close as possible and performing the notch processing, and removing the uncut portion by performing zero cut without changing the focal position of the femtosecond laser beam from this notch position, the cut amount is covered with high accuracy. The work piece is removed.

Further, it is desirable that the magnification of the lens is 50 to 100 times. By using a high-magnification lens with a shallow depth of focus of 50 to 100 times, the energy density in the focal region can be increased and the number of zero cuts can be reduced.

It is also desirable to process under mist spray. As a result, it is possible to prevent the workpiece from melting and increase the processing speed.

Further, it is desirable that the frequency of the femtosecond laser is 0.5 kHz or more. As a result, the energy applied to the unit area per unit time can be increased, and the processing speed can be increased.

(1) According to the present invention, the focal position of the femtosecond laser beam is set to a cutting position that is closer to the processing surface by a predetermined depth from a position where the processing surface cannot be processed if the distance is further away. By processing and zero-cutting at this cutting position to remove uncut parts, the processed surface is removed with high accuracy by a predetermined cutting amount, and a three-dimensional microstructure of high hardness material including a free curved surface is manufactured. It becomes possible to do.

(2) When the magnification of the lens is 50 to 100 times, the energy density in the focal region is increased and the number of zero cuts can be reduced, so that the processing speed can be increased.

(3) By processing under mist spraying, it is possible to prevent the workpiece from melting and increase the processing speed.

(4) When the frequency of the femtosecond laser is 0.5 kHz or more, the energy applied to the unit area per unit time can be increased, and the processing speed can be increased.

It is a schematic block diagram of the processing apparatus used in the zero-cut processing method of a high hardness material in embodiment of this invention. It is a flow chart of the zero-cut processing method of a high hardness material in embodiment of this invention. It is a schematic diagram which shows the relationship between the defocus and the removal depth about the machined surface orthogonal to the optical axis of a laser beam. It is explanatory drawing which shows the pre-processing process. It is explanatory drawing which shows the molding process of a machined surface. It is a figure which shows the relationship between the defocus and the removal depth of FIG. It is explanatory drawing which shows the curved surface processing example. It is a figure which shows the defocus and the removal depth in the Z-axis direction measured with respect to cemented carbide. It is a figure which shows the number of zero cuts required for removing a cut-out, and the cumulative removal depth. It is a figure which shows the defocus and the removal depth in the Z-axis direction when the magnification of a lens is changed. It is a figure which shows the defocus and the removal depth in the Z-axis direction at the time of mist spraying. It is a figure which shows the defocus and the removal depth in the Z-axis direction when the repetition frequency is changed. It is a figure which shows the defocus and the removal depth in the Z-axis direction when the number of zero cuts is changed. It is a figure which shows the scanning locus of the laser calculated for making 9 convex dimples with a diameter of 0.2 mm with respect to cemented carbide. It is a micrograph showing the convex dimples of 9 diameters laser-machined on a cemented carbide having a Vickers hardness of 2600 Hv.

FIG. 1 is a schematic configuration diagram of a processing apparatus used in the zero-cut processing method for a high-hardness material according to the embodiment of the present invention, and FIG. 2 is a flow chart of a zero-cut processing method for a high-hardness material according to the embodiment of the present invention. is there.

As shown in FIG. 1, the processing apparatus used in the zero-cut processing method for a high-hardness material according to the embodiment of the present invention is a femtosecond laser beam having a pulse width of a femtosecond level (hereinafter, simply referred to as “laser light”). A femtosecond laser oscillator (hereinafter referred to as a "laser oscillator") 1 that outputs a femtosecond laser light (which may be referred to as a "laser oscillator") 1, a laser light transmitter 2 that transmits a femtosecond laser light output from the laser oscillator 1, and a laser light transmission. It has a mirror array 3 that collects laser light transmitted by the vessel 2 and irradiates the workpiece 4.

The laser light transmitter 2 includes a half mirror 20A, a mirror 20B, a mirror 20C, a lens 21, a hollow fiber 22, a vacuum chamber 23, a camera 24, and the like. The hollow fiber 22 is a hololive photonic crystal fiber. The hollow fiber 22 is housed in the vacuum chamber 23 and is evacuated from the exhaust port 23A, so that the transmission efficiency of the laser beam is increased to nearly 70%.

The laser light output from the laser oscillator 1 is reflected by the half mirror 20A, focused by the lens 21 at the center of the hollow fiber 22, and transmitted to the mirror array 3 through the hollow fiber 22. The camera 24 is for aligning the lens 21. The camera 24 includes a CMOS image sensor, and the transmitted light of the half mirror 20A is reflected by the mirrors 20B and 20C to enter the light.

The mirror array 3 includes a mirror 30A, a mirror 30B, a half mirror 30C, a half mirror 30D, a mirror 30E, a mirror 30F, a lens 31, a camera 32, and the like. The lens 31 is an objective lens having a magnification of 50 to 100 times. The camera 32 includes a CCD image sensor. The mirror array 3 is mounted on a column of a precision vertical machining center (not shown) and is mechanically scanned at the machining center using existing CAD / CAM.

The laser light transmitted through the hollow fiber 22 is reflected by the mirrors 30A and 30B and the half mirrors 30C and 30D, collected by the lens 31, and irradiated to the workpiece 4. Further, in the mirror array 3, in order to make the processed surface of the workpiece 4 observable, white light is transmitted through the half mirror 30C, reflected by the half mirror 30D, and condensed by the lens 31 to be condensed by the workpiece 4. The processed surface of the above is irradiated, and the reflected light is collected by the lens 31, passes through the half mirror 30D, is reflected by the mirrors 30E and 30F, and enters the camera 32.

The workpiece 4 processed by the zero-cut processing method for a high-hardness material according to the embodiment of the present invention is a high-hardness material such as a cemented carbide. Examples of the high-hardness material structure made of this high-hardness material include cemented carbide dies such as glass microlens array dies and small motor core punching dies, and cemented carbide dies having a diameter of 0.1 mm or less. Examples include micro end mills.

As shown in FIG. 2, the zero-cut processing method for a high-hardness material using the processing apparatus includes a pre-processing step (S101), a cutting step (S102), and a zero-cut step (S103).

<Pre-processing process (S101)>
First, a pre-processed surface having no uncut surface is formed on the processed surface of the workpiece 4. The molding method of the pre-processed surface does not matter. When the pre-processed surface is formed by using the laser beam, it is removed to a position deeper than the focal position of the laser beam. Therefore, it is necessary to set (defocus) the focal position of the laser beam to a position away from the processed surface of the workpiece 4 to perform laser processing. When the focal position of the laser beam is moved away from the processed surface of the workpiece 4, the position where the processed surface cannot be processed is referred to as the maximum defocus position (Df) max in the following description.

FIG. 3 is a schematic view showing the relationship between the defocus and the removal depth with respect to the machined surface orthogonal to the optical axis of the laser beam. As shown in FIG. 3, the focus is moved (defocused) by a distance Df in the positive direction (direction away from the processing surface) of the Z axis (optical axis) from the processing surface, that is, the laser beam is moved to a position Df away from the processing surface. After setting the focal position of and performing scanning line processing, zero cutting is performed to remove the uncut portion, and the removal depth in the Z-axis direction becomes Δz. Further, the sum of Df and Δz is (Df) max as shown in the following equation.
Df + Δz = (Df) max

FIG. 4 is an explanatory diagram showing a preprocessing process. As shown in FIG. 4, scanning line processing is performed on a wavy pre-processed surface with the focal position of the laser beam as the maximum defocus position (Df) max to form a flat flat surface. When the maximum height Rz> (Df) max of the pre-processed surface, the cutting step (S102) and the zero cutting step (S103) described later are repeated several times.

<Cut step (S102)>
The focal position of the laser beam is located away from the processed surface of the workpiece 4, and if it is further away, the processed surface cannot be processed, that is, from the maximum defocus position (Df) max toward the processed surface. The process is performed by setting the cutting position closer to the predetermined cutting amount Δz.

FIG. 5 is an explanatory view showing the molding process of the machined surface, and FIG. 6 is a view showing the relationship between the defocus and the removal depth in FIG. As shown in FIG. 5, when the focal position of the laser beam is set to a cutting position closer to the pre-processed surface A by the depth of cut Δz from the maximum defocus position (Df) max, and the laser light is scanned once. The machined surface B including the uncut portion (Δz−Δz ′) is produced.

<Zero cut process (S103)>
Next, when the zero cut for removing the uncut portion is performed without moving the focal position of the laser beam, that is, without changing from the cut position, the machined surface C from which the uncut portion is removed is created. If the uncut portion is completely removed, there is a gap of (Df) max between the focal position and the machined surface C.

That is, in the zero-cut processing method for a high-hardness material in the present embodiment, as shown in FIG. 3, the focal position of the laser beam is set from the maximum defocus position (Df) max to the depth of cut (If) z toward the processed surface. By setting the notch position as close as possible to the notch and removing the uncut part by performing zero cut without changing the focal position from this notch position, the high hardness material can be accurately obtained by the notch amount (If) z. It is removed.

Next, an example of processing a curved surface by the zero-cut processing method of a high-hardness material in the present embodiment will be described. FIG. 7 is an explanatory view showing an example of curved surface processing.

In curved surface machining, as shown in FIG. 7 (A), the focus of the laser beam is defocused upward by (Df) max with respect to the flat pre-machined surface, and as shown in FIG. 7 (B), the depth of cut Δz. The laser beam is scanned and processed once, and zero cut is performed without changing the cut position to remove the uncut portion. Subsequently, as shown in FIGS. (C), (D), and (E), until the sum of Δz reaches R, cutting is performed by the depth of cut Δz, and zero cutting is performed without changing the cutting position. A hemisphere (curved surface) can be machined by repeating the process of removing the uncut portion. As described above, in the zero-cut processing method in the present embodiment, it is possible to manufacture a three-dimensional microstructure including a free curved surface with respect to a high hardness material.

A machining test was performed using the machining apparatus in the above embodiment. The specifications of the laser oscillator 1 used are as follows: Center wavelength: 1028 ± 5 nm
Maximum average output: <4W (variable)
Maximum pulse energy: <65 μJ (variable)
Pulse repetition frequency: 100 kHz to 1 MHz (variable)
Use pulse picker: <100kHz
Pulse width: 290 fs to 10 ps (variable)

<1> Machining a region of □ 1 mm of cemented carbide FIG. 8 shows the defocus and the removal depth in the Z-axis direction measured for the cemented carbide. The magnification of the lens 31 was 20 times, the repetition frequency was 0.35 kHz, the pulse energy was 30 μJ, the pulse interval was 2 μm, and the feed rate was 25 mm / min. As shown in FIG. 8, under this condition, the cemented carbide was hardly scraped in each case where the defocus was changed.

<2> Machining a pocket of □ 1 mm for cemented carbide at the focal position Fig. 9 shows the number of zero cuts and the cumulative removal depth required to remove uncut parts under the same conditions as in <1> above. There is. As shown in FIG. 9, under the same conditions as in <1> above, the uncut portion was not removed unless the zero cut was performed 200 times or more.

<3> The magnification of the lens 31 is changed to process the □ 1 mm region of the cemented carbide. Fig. 10 shows the defocus and Z-axis direction removal when the magnification of the lens 31 is changed and the □ 1 mm region of the cemented carbide is processed. Shows the depth. The pulse interval is 2 μm, there is no zero cut, and other conditions are as shown in the figure. As shown in FIG. 10, when a 20x objective lens was used as the lens 31, only about 5 μm could be removed at the focal position, whereas when a 100x objective lens was used, about 65 μm could be removed. When processed at the focal position using a 50x objective lens, it could not be removed at all because the cemented carbide melted and the melt accumulated in the pocket.

<4> Mist spraying of tap water toward a spot FIG. 11 shows defocus and removal depth in the Z-axis direction when tap water is mist sprayed toward a laser beam irradiation spot. A 50x objective lens was used as the lens 31. By processing under mist spray, the molten cemented carbide can be blown off by the volume expansion and pressure when the mist evaporates. As a result, the removal depth increased. That is, by laser machining under mist spraying, it is possible to prevent the workpiece from melting and increase the machining speed. When the cemented carbide was submerged in water and laser machining was performed in water, the removal depth decreased in each case where the defocus was changed.

<5> Change the repetition frequency and process a region of □ 1 mm. Fig. 12 uses a 100x objective lens, fixes the feed rate at 10 mm / min and the lateral feed amount at 2 μm, and changes the repeat frequency to □ 1 mm. It shows the defocus and the removal depth in the Z-axis direction when the region is machined. If the feed rate is kept constant and the repetition frequency is increased, the pulse energy (the number of pulses that hit the unit length) applied to the unit area per unit time increases, so the removal depth is different in each case where the defocus is changed. Increased. That is, by setting the frequency of the femtosecond laser to 0.5 kHz or more, the energy applied to the unit area can be increased, and the processing speed can be increased. For example, in order to increase the feed rate to 100 mm / min, the frequency may be increased 10 times, and the processing speed can be dramatically improved simply by increasing the frequency of the femtosecond laser.

<6> The number of zero cuts is changed to 5 times and 10 times, and the area of □ 1 mm is processed. Fig. 13 uses a 100x objective lens, the repetition frequency is fixed at 8 kHz, and the number of zero cuts is 5 times. It shows the defocus and the removal depth in the Z-axis direction when the area of □ 1 mm is machined by changing it to 10 times. As shown in FIG. 13, when zero cut was performed 10 times in defocus, (Δz) max / (Df) max reached 100%. In other words, if the zero cut is performed 10 times without making a cut after processing with a cut and the uncut portion is removed, the cemented carbide will be removed by the amount of the cut in the Z-axis direction. means.

<7> Creating nine convex dimples with a diameter of 0.2 mm for cemented carbide FIG. 14 shows a laser scan calculated to create nine convex dimples with a diameter of 0.2 mm for cemented carbide. It shows the trajectory. FIG. 15 is a photomicrograph showing 9 convex dimples with a diameter laser-machined on a cemented carbide having a Vickers hardness of 2600 Hv. The magnification of the lens was 100 times, the repetition frequency was 80 kHz, the pulse energy was 30 μJ, the scanning speed was 100 mm / min, and the lateral feed amount was 1 μm. After processing by moving the scanning locus of the laser calculated using commercially available CAD / CAM in the Z-axis direction, it was repeated until the depth of cut in the Z-axis direction reached 100 μm. It was found that three-dimensional fine shapes including curved surfaces can be laser-machined.

The present invention is used for manufacturing cemented carbide dies such as glass microlens array dies and small motor core punching dies, and high hardness material structures such as cemented carbide micro end mills having a diameter of 0.1 mm or less. It is useful.

1 Laser oscillator 2 Laser optical transmitter 3 Mirror array 4 Work piece 20A Half mirror 20B, 20C Mirror 21 Lens 22 Hollow fiber 23 Vacuum chamber 23A Exhaust port 24 Camera 30A, 30B, 30E, 30F Mirror 30C, 30D Half mirror 31 Lens 32 camera

Claims (6)

When the femtosecond laser beam is focused by a lens and irradiated to the processed surface of a high-hardness material, the focal position of the femtosecond laser beam is set at a position away from the processed surface and further away from the processed surface. A cutting process in which the cutting process is performed by setting the cutting position closer to the processing surface by a predetermined cutting amount from the position where the processing cannot be performed.
A zero-cut process in which zero-cutting is performed without changing the focal position of the femtosecond laser beam from the cutting position.
Zero-cut processing method for high-hardness materials, including repeating two consecutive steps. When the femtosecond laser beam is focused by a lens and irradiated to the processed surface of the work piece, the focal position of the femtosecond laser beam is set at a position away from the processed surface and further away from the processed surface. A cutting process in which the cutting process is performed by setting the cutting position closer to the processing surface by a predetermined cutting amount from the position where the processing cannot be performed.
A zero-cut process in which zero-cutting is performed without changing the focal position of the femtosecond laser beam from the cutting position.
A method for producing a high-hardness material structure, which comprises repeating two consecutive steps of. When the femtosecond laser beam is focused by a lens and irradiated to the processed surface of the work piece, the focal position of the femtosecond laser beam is set at a position away from the processed surface and further away from the processed surface. A cutting process in which the cutting process is performed by setting the cutting position closer to the processing surface by a predetermined cutting amount from the position where the processing cannot be performed.
A zero-cut process in which zero-cutting is performed without changing the focal position of the femtosecond laser beam from the cutting position, and
Wherein prior to the cutting step, the manufacturing method of the previous processing step and the including high hardness material structures forming the front working surface there is no left over to process the surface of the workpiece. The method for producing a high-hardness material structure according to claim 2 or 3, wherein the lens has a magnification of 50 to 100 times. The method for producing a high-hardness material structure according to any one of claims 2 to 4, wherein the process is performed under mist spraying. The method for producing a high-hardness material structure according to any one of claims 2 to 5, wherein the frequency of the femtosecond laser beam is 0.5 kHz or more.