JP2012011409A - Cutting and drilling method of composite material member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam machining method capable of speed processing, and reducing a heat-affected width around a cutting part without using a special device.SOLUTION: In the cutting and drilling method of a composite material member 2, the width of an allowable heat-affected zone 7 is defined, and the working speed of a laser beam 3 and the output of the laser beam 3 are set based on a heat conduction equation using the specific heat and the density of composite material member 2 so that a temperature in a circumference 8 of the heat-affected zone becomes a prescribed value or lower when the laser beam 3 is irradiated.

Description

  The present invention relates to a method for cutting and drilling a composite material member.

For structural members such as aircraft wings, composite materials such as carbon fiber reinforced plastic (CFRP) are used. The cutting / drilling of the composite material is currently performed by an abrasive water jet (AWJ) or machining. However, in the above method, tool consumption during processing is severe and the cost of consumables becomes high. Therefore, a cutting method using a laser has been developed as a processing method in which tools and the like are not consumed during processing.
Patent Document 1 discloses a method of drilling a MCrAlX layer or a ceramic layer using a short pulse laser. Patent Document 2 discloses a method of freezing a material to be cut in advance and then cutting high-strength fibers using a laser. Patent Document 3 discloses a method of cutting or drilling a plastic member or FRP member by a combination of a CO ₂ laser and an excimer laser.

JP-T 2009-523616 (Claim 1, Summary) JP-A-6-158528 (Claim 1) Japanese Patent No. 283215 (Claim 1)

When a laser is used for cutting or drilling a composite material, the periphery of the cut portion is melted by heat at the time of laser cutting, which causes problems such as deterioration in processing accuracy and delamination of the composite material. For example, when composite material delamination occurs, an additional process such as removing the heat-affected zone is necessary to maintain the quality. Therefore, it is required to make the heat-affected zone as small as possible.
In recent years, non-heating processing using a short pulse laser (fs (femtosecond), ps (picosecond)) has been proposed as a processing method using a laser that does not affect the periphery of the cut portion. However, since the output of the short pulse laser is low, there is a problem that the processing time becomes long when processing a thick material. In Patent Document 1, only the surface is precisely processed with a short pulse laser to reduce the processing time, but the processing accuracy in the entire thickness is not considered. In Patent Document 2, the heat-affected zone is minimized by freezing the material to be cut, but a device such as a freezing chamber is required separately.

  The present invention has been made in view of such circumstances, and provides a laser processing method capable of high-speed processing and reducing the thermal influence width around a cutting portion without using a special device. With the goal.

  In order to solve the above problems, the present invention defines the width of the heat-affected zone to be allowed, and when the laser beam is irradiated, the temperature of the outer periphery of the heat-affected zone is not more than a predetermined value. Provided is a composite material member cutting / drilling method for setting the laser beam processing speed and the laser beam output based on a heat conduction equation using specific heat and density.

  According to the present invention, the amount of heat input to the composite material member by laser light irradiation can be controlled by setting the processing speed and output of the laser light based on the heat conduction equation. As a result, high-accuracy machining is possible with almost no thermal influence on the periphery of the machining portion. The processing speed and output of the laser light can be increased depending on the combination or can be increased.

  In one aspect of the present invention, a reference point is taught on the surface of the composite material member, and light refraction is performed so that an outer edge of the laser light is incident at a perpendicular or acute angle with respect to a tangent of the composite material surface including the reference point. It is preferable to irradiate a laser beam through a member.

  In a general laser beam irradiation apparatus, a laser beam is condensed by a collimation lens, and a target processing member is irradiated with the laser beam. However, the tip of the focused laser beam has a conical shape, and the processing surface is inclined. Therefore, it is necessary to finish the processing surface to be vertical. According to the above aspect, by controlling the incident angle of the outer edge of the focused laser beam, it is possible to perform processing without inclining, and thus it is possible to omit the finishing process.

  In one embodiment of the present invention, a processing point is measured by irradiating a processing point with another laser beam having a wavelength different from that of the laser beam, and the processing point distance is fed back to an apparatus that controls the operation of the head unit. It is preferable to operate the head unit so that the processing point distance is kept constant.

  In the laser beam irradiation apparatus, the processing speed can be maximized by making the processing point distance and the focal length equal. The “processing point distance” is a distance from the head portion (under the electron gun or the ceiling of the laser beam irradiation chamber) to the processing point of the composite material member. In the conventional method, the processing speed is determined so that the processing point distance is equal to the focal length. According to the above aspect, since the machining point distance is measured using a laser beam having a wavelength different from that of the laser beam for cutting / drilling, cutting is performed at a desired machining speed while ensuring an optimum machining point distance. -Drilling can be performed.

In one embodiment of the present invention, it is preferable to irradiate the laser beam and the another laser beam with an output timing shifted.
By doing so, interference between the laser beam for cutting and drilling and the laser beam for measuring the processing point distance can be avoided.

In one aspect of the present invention, the composite in which the heat-affected zone does not reach the final processing surface under the conditions of laser beam processing speed and laser beam output capable of cutting and drilling the composite material member by single irradiation. You may provide the process of rough-processing a material member.
When the processing area is large, the processing time can be shortened by roughing a portion that does not need to consider the thermal effect.

  According to the present invention, by setting the laser processing conditions in consideration of the thermal characteristics of the composite material member, even when laser light is used, the thermal effect is small and the composite material member can be processed at high speed. Can be cut and drilled.

It is an image figure of drilling by the cutting and drilling method according to the present embodiment. It is a schematic diagram when a composite material member is irradiated with laser light. It is a graph which shows an example of the relationship between the output of the laser beam derived | led-out from Formula (A), and a processing speed. It is a figure explaining the composite material member drilled by repeating irradiation several times. It is a figure explaining an example using a photorefractive member. It is a figure explaining an example using a photorefractive member. It is a figure explaining the measuring method of a process point distance. It is an image figure in the case of performing roughing. It is an image figure in the case of performing roughing.

Hereinafter, an embodiment of a method for cutting and drilling a composite material member according to the present invention will be described with reference to the drawings.
The composite material member processed in this embodiment includes a layer in which a plurality of composite materials such as prepregs are stacked. The composite material is made of a resin reinforced with fibers. As the fiber, glass fiber, carbon fiber, organic fiber, or the like can be used. As the resin, thermosetting resins such as epoxy resins and phenol resins, and thermoplastic resins such as polyamide and polystyrene can be used. The composite material member may be a member in which a layer made of a composite material is formed on a metal material such as titanium.

  In this embodiment, a laser is irradiated by a pulse oscillation method or a continuous oscillation method using a commercially available laser irradiation device such as a YAG laser or a fiber laser. FIG. 1 shows an image diagram of drilling by the cutting / drilling method according to the present embodiment. During the cutting / drilling process, the head unit 1 of the laser irradiation apparatus is fixed in the horizontal direction with respect to the surface of the composite material member 2 and moves only in the vertical direction (vertical direction). Scanning with the laser beam 3 is performed by scanning. When cutting and drilling, the reference point 4 is taught on the surface of the composite material member 2.

  In the composite material member cutting / drilling method according to the present embodiment, the allowable width of the heat-affected zone is defined, and when the laser beam is irradiated, the temperature at the outer periphery of the heat-affected zone becomes a predetermined value or less. The heat conduction equation is solved based on the specific heat and density of the material member, and the processing speed of the laser beam and the output of the laser beam are set.

FIG. 2 is a schematic diagram when the composite material member 2 is irradiated with the laser light 3. The thermal influence width 5 is expressed as a distance from the laser light irradiated surface 6 (processed surface). The heat-affected zone 7 is preferably as small as possible, and the upper limit thereof varies depending on the application of the composite material member 2, so that it is appropriately defined as a desired heat-affected width 5.
In this embodiment, assuming that the composite material member 2 is applied to the outer plate of an aircraft wing, the distance from the laser beam irradiated surface 6 (heat affected width 5) is 0 so that sufficient processing accuracy can be obtained. The area within 3 mm is defined as the heat affected zone 7.

The heat affected zone 7 is generated when the temperature of the composite material member 2 rises due to heat input from the laser light irradiated surface 6 when the composite material member 2 is irradiated with the laser light 3.
The predetermined value of the temperature at the outer periphery 8 of the heat affected zone is appropriately set according to the type of fiber or resin contained in the composite material member 2 or the composition ratio of the fiber and the resin.
For example, the predetermined value of the temperature in the heat affected zone 7 may be based on the deterioration temperature of the resin. For example, the epoxy resin used for the composite material member 2 deteriorates when it is reheated beyond the maximum use temperature (designated at 120 ° C. this time). The term “deterioration” as used herein means a state in which the resin has changed in quality and loses its performance after curing. The temperature at which the resin is deteriorated varies depending on the type of resin.
The lower the temperature rise of the heat affected zone 7, the more the deterioration of the resin contained in the composite material member 2 can be suppressed. In the present embodiment, the predetermined value of the temperature in the heat affected zone 7 is set to a condition where there is almost no heat input due to laser light irradiation, that is, 30 ° C. based on the vicinity of room temperature.

The thermal characteristics (specific heat, density, etc.) of the composite material member 2 depend on the composition of fibers and resin contained in the composite material member 2. Therefore, the heat conduction equation (A) is solved using the thermal characteristics of the composite material member 2 to be cut and drilled. The initial temperature is room temperature.
θ−θ ₀ = 1 / πe × Q / cρ × 1 / r ² (instantaneous heat source) (A)
θ = temperature of the object (° C)
θ ₀ = initial temperature of the object (° C.)
e = 2.71828
Q = heat input per unit length (cal / cm)
C = specific heat (cal / g ° C.)
ρ = density (g / cm ³ )
r = distance from weld (cm)

  Based on the result of the heat conduction equation (A), when laser light is irradiated, the heat input of the laser light at which the temperature at a position 0.3 mm away from the processing surface 6 is 30 ° C. or less is obtained, and then an actual processing experiment is performed. From the data, the minimum machining speed below the heat input is derived.

As a specific example, the processing speed of laser light and the output of laser light in the case of using a composite material member in which carbon fiber is impregnated with an epoxy resin will be described. The composition ratio (volume) of carbon fiber / resin was 50/50 in Example 1 and 65/35 in Example 2 (Example 2). The temperature at which the resin burns was about 400 ° C. as the thermal decomposition temperature of the epoxy resin.
FIG. 3 shows an example of the relationship between the laser beam output derived from the formula (A) and the processing speed. In the figure, the horizontal axis is the output, and the vertical axis is the machining speed. According to FIG. 3, if the laser beam processing speed and the laser beam output included in the region above the line of Example 1 and Example 2 are combined, the position is 0.3 mm away from the laser beam irradiated surface. The temperature can be set to 30 ° C. or lower. Since Example 2 has a higher carbon fiber content than Example 1, more energy is required to cut the composite material member.

When the composite material member 2 is cut and drilled with a combination of the laser beam processing speed and the laser beam output, the cutting depth by one laser beam irradiation is about several tens of μm. Therefore, with respect to the thick composite material member 2, as shown in FIG. 4, irradiation is repeatedly performed a plurality of times.
In the conventional method that does not consider the heat input by the laser beam 3, for example, cutting and drilling are performed by irradiating the laser beam once at a processing speed of 300 mm / min and an output of 1 kW. The distance was reached. According to this embodiment, since the processing speed can be increased, the total processing time can be set within a desired time even if irradiation is performed a plurality of times. Considering the processing time, the laser beam 3 may be irradiated with a combination of an output of 5 kW or more and a processing speed of 10 m / min or more.

In the present embodiment, as shown in FIG. 5, the light refracting member 10 is disposed either before or after the collimation lens 9, and the outer edge 11 of the laser light is placed on the surface of the composite material member 2 through the light refracting member 10. It is also possible to control so that θ is 90 ° or less with respect to the tangent line passing through the reference point 4 provided in In the case of drilling, the photorefractive member is preferably a photorefractive plate having a line-symmetric structure.
The outer edge 11 of the laser beam means an edge where the condensed laser beam 3 is in contact with the processing surface 6. When the surface of the composite material member 2 is a plane, a tangent line passing through the reference point 4 is included in the plane. By doing in this way, as shown in FIG. 6, it becomes possible to set it as the composite material member 20 which processed the process surface 5 perpendicularly | vertically.

In this embodiment, the machining point distance (work distance) may be measured and fed back to the device 13 that controls the operation of the head unit, and the head unit may be operated so that the machining point distance is kept constant. FIG. 7 illustrates a method for measuring the processing point distance.
The focal length Lf of the laser beam 3 depends on the lens built in the head unit 1 of the laser irradiation apparatus. The processing point distance Lw is measured using the processing point distance measuring laser beam 11 having a wavelength different from the wavelength of the laser beam 3 used for cutting and drilling. The head unit 1 moves up and down so that the processing point distance Lw and the focal length Lf are substantially equal.

The laser beam 3 for cutting / drilling and the laser beam 12 for measuring the processing point distance may be irradiated with the output timing shifted. Thereby, interference with each other can be prevented.
By doing as mentioned above, since an optimal work distance can always be secured, the machining speed can be kept high.

In this embodiment, when the range of the cutting / drilling processing by the laser irradiation apparatus is wide, a step of roughing a portion that may be affected by heat may be provided. FIG. 8 and FIG. 9 show image diagrams when roughing is performed. FIG. 2 shows a precision processing region 14 processed by the cutting / drilling method according to the present embodiment and a rough processing region 15 subjected to rough processing. FIG. 8 shows a case where drilling is performed, and FIG. 9 shows a case where cutting is performed.
The roughing is performed at the processing speed and output conditions (output level and processing speed of the conventional method) of the laser beam 16 that can cut and drill the composite material member by single irradiation. The portion that may be affected by heat means the composite material member 2 located at a position away from the final processing surface to such an extent that the heat-affected zone generated by rough processing does not reach the final processing surface. By doing so, it becomes easy to remove the cut | disconnected composite material member from a process part. Moreover, the cutting area in consideration of the thermal effect can be reduced, and the processing time can be shortened.

  In this embodiment, when the layer made of a composite material is formed on a different material such as a metal, a mechanism for detecting the metal material surface and reviewing the processing conditions may be provided. The metal material surface can be detected by the wavelength of the laser beam and the reflected light intensity.

DESCRIPTION OF SYMBOLS 1 Head part 2 Composite material member 3 Laser beam 4 Reference point 5 Thermal influence width 6 Laser beam irradiated surface (processed surface)
7 Heat-affected zone 8 Perimeter 9 of heat-affected zone 9 Collimation lens 10 Photorefractive member 11 Laser beam outer edge 12 Processing point distance measuring laser beam 13 Device 14 for controlling operation of head portion Precision machining area 15 Rough machining area 16 Rough machining Laser beam 20 for composite material processed vertically

Claims (5)

  Based on the heat conduction equation using the specific heat and density of the composite material member so that the temperature at the outer periphery of the heat-affected zone is equal to or less than a predetermined value when the width of the heat-affected zone is defined and laser light is irradiated. A composite material member cutting / drilling method for setting a processing speed of the laser light and an output of the laser light.   A reference point is taught on the surface of the composite material member, and laser light is transmitted through the photorefractive member so that the outer edge of the laser light is incident at a perpendicular or acute angle with respect to the tangent of the surface of the composite material member including the reference point. The method for cutting and drilling a composite material member according to claim 1 to be irradiated.   The processing point distance is measured by irradiating a processing point with another laser beam having a wavelength different from that of the laser beam, and the processing point distance is fed back to a device that controls the operation of the head unit. The method for cutting and drilling a composite material member according to claim 1, wherein the head portion is operated so as to be held constant.   The method of cutting and drilling a composite material member according to claim 3, wherein the laser beam and the other laser beam are irradiated at different output timings. Claims for rough machining the composite material member at a position where the heat affected zone does not reach the final processing surface under conditions of laser beam processing speed and laser beam output capable of cutting and drilling the composite material member by single irradiation. A method for cutting and drilling a composite material member according to any one of claims 1 to 4.

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