JP4444189B2 - Laser processing equipment - Google Patents

Description

  The present invention relates to a laser processing apparatus capable of preventing damage to a protective member that protects the apparatus when a workpiece is pierced by a laser beam.

  In cutting a steel sheet with a laser beam, it is common to start a target cutting operation after performing a piercing operation. In general, the piercing operation is performed by irradiating a workpiece 3 such as a steel plate with a laser beam 2 from a cutting nozzle 1 and supplying an assist gas 4 coaxially with the laser beam 2 as shown in FIG. Overheating and melting are performed by removing molten metal 6 from the piercing hole 5 formed in the workpiece 3 by irradiation of the laser beam 2 by the kinetic energy of the assist gas 4, and the laser beam 2 penetrates the workpiece 3. Is done. The irradiation time of the laser beam in this piercing operation is controlled by a program registered in advance in the memory.

  Since the laser beam 2 that has passed through the workpiece 3 during the piercing operation and the cutting operation is irradiated as it is inside the processing apparatus, there is a risk of damage to the processing apparatus itself. In particular, in the piercing operation at the start of cutting, the laser beam 2 is continuously irradiated to the workpiece 3 and the processing apparatus at the same location, so that the processing apparatus is damaged by the laser beam 2 that has passed through the workpiece 3. The risk of doing is very high. For this reason, normally, a protective member capable of maintenance and replacement is provided inside the processing apparatus to protect the processing apparatus main body from the laser beam.

  In Patent Document 1, a workpiece is divided into a plurality of adjacent sections, and the material of the workpiece, the thickness of the workpiece, the surface state of the workpiece, the shape of the cutting beam, the cutting locus, By using the ambient temperature and the cooling condition of the workpiece to be processed, the temperature in each section is calculated every predetermined time, and the output value of the cutting beam is controlled based on the temperature of the section where the cutting point is located, It is described that the target value output value of an appropriate cutting beam that does not give excessive heat input to the workpiece is determined.

JP 05-309484 A

  Controls such as drive shaft operation, laser beam irradiation start, and irradiation stop in the laser processing apparatus may be performed automatically in accordance with a program stored in advance, or may be directly manually operated by a push button or the like of the control apparatus. In conventional laser processing device control, protection control by continuous irradiation of the laser beam was not performed, so the same location on the workpiece and laser processing device due to programming errors, control button operation errors, etc. That is, when the laser beam is continuously irradiated without changing the relative position between the laser beam and the workpiece, the laser beam that has passed through the workpiece continues to irradiate the protective member, Damage may be caused by heat input. When damage is caused, maintenance work such as replacement of the protective member and costs are required. In particular, in order to meet the demands for higher processing speeds and thicker workpieces, when a high laser beam output or a long-focus condenser lens is used, the frequency of damage to the protective member increases. Therefore, there is a problem that maintenance costs increase due to an increase in replacement frequency. Furthermore, if maintenance of the protective member is neglected, there is a problem that the laser beam passes from the damaged portion of the protective member and the processing apparatus main body is damaged.

  Patent Document 1 discloses a method for determining a target output value of a cutting beam that does not give excessive heat input to a workpiece on the basis of the temperature of a section where a cutting point is located during cutting work. However, there is no disclosure about measures against damage to the protective member during the piercing operation of continuously irradiating a laser beam at the same location.

  This invention is made in view of the above, Comprising: Obtaining the laser processing apparatus which can prevent the continuous irradiation of the laser beam until a protection member reaches damage, and can reduce the maintenance frequency of a protection member. Objective.

  In order to solve the above-described problems and achieve the object, the present invention includes a protective member below the workpiece, and continuously irradiates a laser on the same position of the workpiece before cutting. In a laser processing apparatus for forming a piercing hole, a time measuring unit for measuring a continuous irradiation time of the laser to the protective member when forming the piercing hole, and a laser output, a member to be processed and a protective member when forming the piercing hole The continuous irradiation time of the laser to the protective member until the temperature of the protective member reaches the melting point of the protective member based on the distance to the protective member, the heat capacity of the protective member and the laser beam absorption rate of the workpiece, and the time measuring unit Control means for controlling the laser output to stop before the measured continuous irradiation time reaches the determined continuous irradiation time.

  According to the present invention, since the laser irradiation is stopped before the temperature of the protective member reaches the melting point, continuous irradiation of the laser beam until the protective member reaches damage is prevented, and the maintenance frequency of the protective member is reduced. There is an effect that can be done.

  Embodiments of a laser processing apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of the entire laser processing apparatus including a control system, FIG. 2 is a perspective view showing a conceptual configuration around the protective member, and FIG. 3 is a cross section showing a conceptual configuration around the protective member. FIG.

  As shown in FIGS. 1 to 3, the laser processing apparatus 18 is configured to cut the workpiece 3 using the laser beam 2, and generates a beam for generating the laser beam 2. And a XY table 8 for moving the workpiece 3 relative to the laser beam 2. The XY table 8 is driven to move in the XY directions by an X-axis drive motor 9 and a Y-axis drive motor 10. The laser beam 2 emitted from the beam generator 7 is irradiated to the workpiece 3 through an optical system such as a mirror 22 and a processing lens 17.

  As shown in FIGS. 2 and 3, a main body casing 21 of the laser processing apparatus is provided on the XY table 8, and a protection member 19 is mounted on the upper side of the main body casing 21. The main body housing 21 also functions as a housing portion that houses a cut piece of the workpiece 3 and metal powder such as sputtering. The protection member 19 includes an inclined portion that is inclined with respect to the workpiece 3 placed on the work table 20, and the work table 20 is provided above the protection member 19. The protective member 19 prevents the laser beam 2 penetrating the workpiece 3 from being irradiated to the main body casing 21 disposed on the lower side of the workpiece 3 and further the XY table 8 to be damaged. It is mounted in order to make it fall, and is inclined in order to drop the cut pieces of the workpiece 3 and metal powder such as spatter.

  Moreover, the laser processing apparatus 18 has the numerical control program memory 11, the numerical control part 12, and the servo control part 13, as shown in FIG. In accordance with a command from the numerical control unit 12 based on a program stored in the numerical control program memory 11, control such as irradiation start and irradiation stop of the laser beam 2 in the beam generator 7 is executed.

  The servo control unit 13 drives and controls the X-axis drive motor 9 and the Y-axis drive motor 10 in accordance with a command from the numerical control unit 12 based on the program stored in the numerical control program memory 11, whereby the laser beam 2 is preliminarily generated. The XY table on which the workpiece 3 is placed is controlled to move in the XY directions so as to move along the set cutting trajectory on the workpiece. In this case, the workpiece side is moved, but the laser beam side may be controlled to move in the XY directions.

  The laser processing device 18 further includes a constant setting memory 14, a time measuring unit 16, and a continuous irradiation control unit 15, and an error in programming or a push button operation on the control device due to these configuration requirements. For example, when the laser beam 2 is continuously irradiated to the same part of the workpiece 3 and the processing apparatus during the piercing operation or the like, the time for which the laser beam 2 is continuously irradiated is monitored. The laser beam 2 is controlled to stop the output of the laser beam 2 before the portion irradiated with the laser beam 2 on the protective member 19 reaches the melting point temperature, and excessive heat input to the protective member 19 is prevented. To prevent damage.

  The basic concept of the main part of the present invention will be described below. In order to accurately calculate the temperature of the protection member 19 at the site irradiated with the laser beam 2, the amount of heat input from the laser beam 2 that has passed through the workpiece 3 and the irradiation of the laser beam 2 on the protection member 19 are calculated. It is necessary to obtain the heat conduction to the surroundings of the position, the heat radiation amount, and the like. However, when the laser beam 2 is continuously irradiated to the same portion of the protection member 19 as in the piercing operation, only the heat input to the protection member 19 is dominant with respect to the temperature change. Ignore heat conduction and heat dissipation around the irradiation position.

The amount of heat input Q from the laser beam 2 at the laser beam irradiation position of the protective member 19 is proportional to the output value W of the laser beam 2 and proportional to the continuous irradiation time S2 to the protective member 19. Since the laser irradiation to the protection member 19 is performed by the laser beam 2 penetrating the workpiece 3, the continuous irradiation time S to the workpiece 3 and the time required to penetrate the piercing hole of the workpiece 3 From S1, the continuous irradiation time S2 to the protection member 19 is S2 = S−S1. Since it is very difficult to detect that the piercing hole has penetrated the workpiece 3 by the piercing operation, the time S1 required to penetrate the piercing hole of the workpiece 3 depends on the material and thickness of the workpiece 3. Depending on the piercing conditions such as the output of the laser beam 2, the type of assist gas, the pressure of the assist gas, and the like, it is obtained by experiment and experience. The shortest time S1 (min) in the range is registered in the constant setting memory 14. That is, the longest continuous irradiation time S2 (max) to the protection member 19 is expressed by the following equation (1), and the heat input by S2 (max) may be monitored.
S2 (max) = S-S1 (min) (1)

  As shown in FIG. 4, the workpiece member 3 is irradiated with the laser beam 2 focused on a smaller spot on the machining lens 17 or the like, so that the laser beam 2 penetrating the workpiece 3 has a diameter thereof. Progress while expanding. In other words, the energy density of the laser beam 2 penetrating the workpiece 3 decreases in proportion to the distance traveled, and the energy density of the laser beam 2 on the protection member 19 is the focal point of the processing lens 17 and the like. It depends on the distance.

  As described above, the protective member 19 attached to the laser processing apparatus 18 may be disposed in an inclined state in order to prevent metal powder such as cut pieces of the member 3 to be processed and spatter from being deposited. Many. Moreover, since the protective member 19 is installed according to the structure of the laser processing apparatus, the arrangement height differs depending on the installation location. Therefore, the distance L between the workpiece 3 and the protection member 19 differs for each irradiation position (X, Y) of the laser beam 2, and the amount of heat input by the laser beam 2 to the protection member 19 is different from that of the workpiece 3. It is inversely proportional to the square of the distance L to the protection member 19.

That is, the amount of heat input Q to the protective member 19 at each XY coordinate position is defined as follows. K is a coefficient obtained by experiment, experience, and calculation, W is a laser output, S2 is a continuous irradiation time to the protective member 19, When L is the distance between the workpiece 3 and the protection member 19, it is obtained by the following equation (2).
Q (x, y) = K * W * S2 / L (x, y) ² (2)
Note that the subscript (x, y) indicates the XY coordinate position where the laser beam 2 is irradiated.

The temperature change ΔT (x, y) at the laser beam irradiation position (x, y) of the protection member 19 is proportional to the heat input Q (x, y), and is unambiguous from the material, plate thickness, and area of the protection member 19. And the coefficient Hs representing the absorption rate (easiness of absorption) of the laser beam 2 on the surface of the workpiece 3 determined by the material and surface roughness of the workpiece 3 and the following equation (3 ).
ΔT (x, y) = Q (x, y) / (Hc * Hs) (3)

The temperature T (x, y) at a certain time at the laser beam irradiation position (x, y) of the protection member 19 is obtained by adding a temperature change amount ΔT (x, y) to the temperature T1 (x, y) before the laser beam irradiation. Which is expressed by the following formula (4).
T (x, y) = T1 (x, y) + ΔT (x, y) (4)

However, the temperature T1 (x, y) before the irradiation with the laser beam 2 can be considered to be substantially equal to the atmospheric temperature, and is a very small value compared to the temperature change ΔT (x, y) in the irradiation with the laser beam 2. Because
T (x, y) = ΔT (x, y) (5)
And can be approximated.

Here, when the melting point of the protection member 19 is U, the continuous irradiation time of the laser to the protection member 19 until the temperature of the protection member 19 reaches the melting point of the protection member 19 from the above formulas (2) to (5). S2 (U) can be expressed as in the following formula (6).
S2 (U) = {U * Hc * Hs * L (x, y) ² } / (K * W) (6)

  Therefore, the continuous irradiation time S2 (max) to the protection member 19 is actually measured based on the previous equation (1), and the measured continuous irradiation time S2 (max) is obtained from the above equation (6). If the laser output is stopped before the measured continuous irradiation time S2 (U) reaches the continuous irradiation time S2 (U) as compared with the continuous irradiation time S2 (U) of the laser until the melting point is reached, Damage to the protective member 19 due to excessive heat input to the protective member 19 can be prevented in advance.

  The constant setting memory 14 is a protection that is uniquely determined from the piercing hole minimum penetration time S1 (min) of the workpiece 3, the coefficient K obtained by experiment, experience, and calculation, the material of the protection member 19, the plate thickness, and the area. The heat capacity Hc of the member 19, the laser beam absorptance Hs of the workpiece 3, the distance L (x, y) between the workpiece 3 and the protection member 19 at each piercing coordinate position (x, y), and the melting point of the protection member 19 U and the like are set and stored.

  The time measurement unit 16 receives from the numerical control unit 12 an irradiation start command of the laser beam 2 when the piercing hole is drilled. When the piercing hole is drilled, the time measuring unit 16 acquires the constant piercing hole minimum penetration time S1 (min) of the workpiece 3 stored in the constant setting memory 14 from the constant setting memory 14. When the irradiation start command of the laser beam 2 is input from the numerical control unit 12, the time measuring unit 16 measures the time until the piercing hole shortest penetration time S1 (min) elapses from this point in time, and the time measurement ends. The time at which the piercing hole has penetrated the workpiece 3 is set, and the time measurement of the continuous irradiation time t (= S2) to the protection member 19 is started from this time. The measurement time t is sequentially input to the continuous irradiation control unit 15.

  The continuous irradiation control unit 15 receives from the numerical control unit 12 a laser beam 2 irradiation start command, a laser output command value (or average output or measured value) W, and the current piercing coordinate position from the numerical control unit 12. (X, y) is input. When the irradiation start command for the laser beam 2 is input, the continuous irradiation control unit 15 receives the piercing hole shortest penetration time S1 (min), the coefficient K, the heat capacity Hc of the protective member 19, and the workpiece 3 from the constant setting memory 14. Laser beam absorptance Hs, distance L (x, y) between workpiece 3 and protection member 19 corresponding to the current piercing coordinate position (x, y) and melting point U of protection member 19 are obtained. Using the obtained value and the laser output W from the numerical control unit 12, the continuous irradiation time S2 (U) of the laser to the protective member 19 until the melting point of the protective member 19 is reached is derived according to the above equation (6). To do. Then, the continuous irradiation control unit 15 compares the derived continuous irradiation time S2 (U) with the measurement time t input from the time measurement unit 16, and based on the comparison result, the measurement time t is the continuous irradiation time S2. Before reaching (U), a laser beam stop command is output to the numerical controller 12. When the laser beam stop command is input from the continuous irradiation control unit 15, the numerical control unit 12 outputs the laser beam stop command to the beam generator 7 to stop the laser output.

  For example, there are the following two methods for generating a laser output stop command before the measurement time t reaches the continuous irradiation time S2 (U) corresponding to the melting point U. In the first method, a predetermined slight time is subtracted from the continuous irradiation time S2 (U) calculated based on the equation (6), and when the measurement time t reaches the subtraction result, the laser output is stopped at this time. Generate a command. In the second method, the continuous irradiation time S2 (U) ′ of the laser to the protective member 19 until the temperature reaches a predetermined temperature U ′ slightly lower than the melting point U of the protective member 19 is derived according to the above equation (6). When the measurement time t reaches the continuous irradiation time S2 (U) ′, a laser output stop command is generated at this time.

  By performing such control at each piercing coordinate position, it is possible to reliably prevent damage to the protective member 19 when the laser beam 2 is continuously applied to the same portion of the protective member 19 as in piercing work or the like. Can do.

  FIG. 5 shows an average of the laser beam 2 when a piercing operation is performed on a workpiece 3 made of a mild steel material having a plate thickness of 12 mm at a predetermined piercing coordinate position when a mild steel material having a plate pressure of 9 mm is used as the protective member 19. The relationship between the output W and the continuous irradiation time S2 (U) until the protection member 19 is damaged is shown. According to FIG. 5, for example, when the laser output is 2000 (W), the protective member 19 is damaged when the laser beam is continuously output for more than 30 seconds. Therefore, the laser beam 2 is irradiated before the continuous irradiation reaches 30 seconds. The output will be stopped.

  As described above, in the first embodiment, during the piercing operation in which the laser beam 2 is continuously applied to the workpiece 3 and the laser processing apparatus (protective member 19), the continuous irradiation time of the laser to the protective member is set. Since the laser output is stopped before the measurement time reaches the continuous laser irradiation time until the temperature of the protective member reaches the melting point U, an error in programming or a push button operation on the control device Even if such occurs, damage to the protective member 19 due to excessive heat input can be prevented, and the maintenance frequency of the protective member 19 can be reduced.

  For easier control, L (x, y) is fixed to the minimum value, and the protective member 19 that is closest to the workpiece 3, that is, the most easily damaged protective member 19 is damaged. The continuous irradiation time of the laser beam 2 may be applied to all coordinates. Moreover, you may make it apply this invention to the thing in which the protection member 19 is not inclined.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, damage to the workpiece 3 due to the laser beam 2 passing through the piercing hole is prevented, but at a position where the workpiece 3 is not placed due to a programming error or an erroneous operation. The protection member 19 is also expected to be damaged by the laser beam 2 irradiation.

  In this case, since the laser beam 2 reaches the protective member 19 as the irradiation of the laser beam 2 starts, the temperature change also becomes abrupt and the possibility of damage is high. Further, since the assist gas 4 is sprayed on the irradiation position, the reaction heat cannot be ignored. Further, when the high-pressure assist gas 4 is sprayed, the molten material is scattered to accelerate the damage.

  Therefore, in the second embodiment, the workpiece detector 30 for determining whether or not the workpiece 3 is present at the laser irradiation position during piercing is provided, and the workpiece detector 30 does not have the workpiece 3. Is determined, the continuous irradiation time S2 (U) until the protective member 19 is damaged is calculated from the equation (6) except for the laser beam absorption rate Hs of the workpiece 3 and the constant setting memory 14 is obtained. The shortest piercing penetration time (S1 (min)) set and stored in S1 is set to S1 (min) = 0, and the measurement of the continuous irradiation time t to the protection member 19 is executed. That is, in this case, when the irradiation start command of the laser beam 2 is input from the numerical control unit 12 to the time measuring unit 16, this time is set as the time when the piercing hole has penetrated the workpiece 3, and from this time the protective member The time counting operation of the continuous irradiation time t to 19 is started. Further, when calculating the continuous irradiation time S2 (U), the laser beam absorption rate Hs is divided, and the workpiece to be processed corresponding to the coefficient K, the heat capacity Hc of the protective member 19, and the current piercing coordinate position (x, y). 3 and the protective member 19 and the melting point U of the protective member 19 are used to calculate the continuous irradiation time S2 (U). Then, in the same manner as in the first embodiment, the laser output is stopped before the measurement time t reaches the continuous irradiation time S2 (U) until the protective member 19 is damaged.

  As shown in FIG. 6, in general, a laser processing apparatus is provided with a scanning sensor 30 such as a capacitive sensor in the processing head in order to detect a gap between the workpiece 3 and the cutting nozzle 1. The machining head is driven and controlled in the Z-axis direction by the Z-axis drive motor 31 according to a command from the servo control unit 13 based on the control of the numerical control unit 12, and in this configuration, the scanning sensor 30 serves as a workpiece detector. Can be adopted.

  As described above, according to the second embodiment, when the workpiece detector 30 is provided and the workpiece detector 30 determines that there is no workpiece 3, the laser beam absorptance of the workpiece 3 from the equation (6). Since the continuous irradiation time S2 (U) until the protective member 19 is damaged except for Hs is obtained, and the measurement operation of the continuous irradiation time t to the protective member 19 is performed immediately after the start of laser irradiation, the workpiece is processed. When the member 3 is not present, the laser output can be accurately stopped before the measurement time t reaches the continuous irradiation time S2 (U) until the protective member 19 is damaged. Further, it is possible to prevent the protection member 19 from being damaged due to excessive heat input.

  As described above, the laser processing apparatus according to the present invention is useful for the piercing work before the cutting work.

1 is an overall view showing a laser processing apparatus according to a first embodiment. It is a perspective view of the protection member peripheral part of a laser processing apparatus. It is a cross-sectional view of the periphery of the protective member of the laser processing apparatus. It is a figure which shows the laser beam irradiated to a to-be-processed member. It is a figure which shows the relationship between a laser beam output and continuous irradiation possible time. FIG. 6 is an overall view showing a laser processing apparatus according to a second embodiment. It is explanatory drawing of the piercing operation | work in a laser processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cutting nozzle 2 Laser beam 3 Work piece 4 Assist gas 5 Piercing hole 6 Molten metal 7 Beam generator 8 XY table 9 X-axis drive motor 10 Y-axis drive motor 11 Numerical control program memory 12 Numerical control part 13 Servo control part 14 Constant setting memory 15 Continuous irradiation control unit 16 Time measuring unit 17 Processing lens 18 Laser processing device 19 Protective member 20 Work table 21 Body housing 22 Mirror 30 Work detector (copying sensor)
31 Z-axis drive motor

Claims (3)

In a laser processing apparatus provided with a protective member below a workpiece, and piercing holes by continuously irradiating a laser at the same position of the workpiece before cutting,
During the piercing hole formation, a time measuring unit that measures the continuous irradiation time of the laser to the protective member,
Protection member until the temperature of the protection member reaches the melting point of the protection member based on the laser output, the distance between the workpiece and the protection member, the heat capacity of the protection member, and the laser beam absorptance of the workpiece when forming the piercing hole A control means for controlling the laser output to be stopped before the continuous irradiation time measured by the time measuring unit is reached before reaching the determined continuous irradiation time;
A laser processing apparatus comprising: The protective member is inclined with respect to the workpiece,
The laser processing apparatus according to claim 1, wherein the control unit obtains a distance between the workpiece and the protection member for each position where the piercing hole is formed. Further provided with a workpiece detection means for detecting the presence or absence of the workpiece,
When the workpiece member is not detected by the workpiece detection means, the control means has a temperature lower than the melting point of the protection member based on the laser output, the distance between the workpiece and the protection member, and the heat capacity of the protection member. 3. The laser processing apparatus according to claim 1, wherein a continuous irradiation time of the laser to the protective member until reaching the point is obtained.

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