Laser welding apparatus and laser welding method

Abstract

According to one embodiment, a laser welding apparatus (20) comprises a laser medium (50), an excitation light source (51) and a control unit (24). The control unit (24) provides a drive power to the excitation light source (51) to inject excitation energy into the laser medium (50). Prior to welding a first weld to be welded, the control unit (24) supplies a preliminary excitation power (Pw2) to the excitation light source (51) for a preliminary supply time (T2) longer than a pulse width (T1) of the drive power (Pw1), wherein the preliminary excitation power (Pw2) is smaller than the drive power (Pw1) of the pulse. After the preliminary supply time (T2) has elapsed, and after an interval (T3) has elapsed, the drive power (Pw1) of the pulse is supplied to the excitation light source (51) to weld the first weld.

Description

Technical Field

[0001] This invention relates to a laser welding apparatus and a laser welding method for welding multiple welded parts of a workpiece. Background Technology

[0002] Laser welding is used in some cases to weld workpieces made of multiple small metal plates, such as suspensions for disk drives. Examples of laser welding are discussed in JP 2005-95934 A (Patent Document 1) and JP H08-293299 A (Patent Document 2).

[0003] A suspension for a disk drive includes a base plate, a load beam, and a flexure. The load beam is made of a thin stainless steel sheet. The flexure is positioned along the load beam. To secure the flexure to the load beam, spot welding using a laser beam (hereinafter referred to as laser welding) is employed. Alternatively, laser welding can be used to secure the load beam to the base plate.

[0004] To form multiple weld joints on a single workpiece, so-called high-speed pulse welding is used to reduce welding time. For example, in high-speed pulse welding, more than one hundred weld joints are welded per second. However, in high-speed pulse welding, the laser beam output on the first weld joint to be welded among multiple weld joints may be unstable. Therefore, high-speed pulse welding can sometimes introduce disadvantages depending on the weld quality.

[0005] To prevent welding errors on the first weld, a process known as laser beam pre-firing is sometimes performed. One example of pre-firing is directing the laser beam onto a location outside the workpiece just before welding the first weld. Another example of pre-firing involves directing the laser beam onto an unused portion of the workpiece, unrelated to the weld area.

[0006] For small workpieces such as disk drive suspensions, it may sometimes be impossible to leave enough space for pre-firing. Another problem is that if pre-firing is performed while the workpiece is moving toward the welding table, the laser beam cannot be focused to the intended position. Therefore, ideally, pre-firing should be performed when the workpiece stops during the welding phase. However, this incurs additional time before the first weld, which reduces productivity.

[0007] According to the present invention, a laser welding apparatus and a laser welding method are provided, which can avoid welding errors in the first welding part by eliminating the need for laser beam pre-firing when forming multiple welding parts on a single workpiece. Summary of the Invention

[0008] According to one embodiment, a laser welding apparatus is provided for sequentially welding multiple weld portions of a workpiece using a laser beam output in pulsed form. The welding apparatus includes a laser medium, an excitation source, and a control unit. The laser medium emits a laser beam for the weld portions while excitation energy is injected into it. The excitation source injects excitation energy into the laser medium and simultaneously provides it with driving power. The control unit provides the excitation source with pulsed driving power for the excitation energy.

[0009] Before welding the first weldment among multiple weldments, the control unit supplies a preliminary excitation power (referred to as preliminary excitation power) lower than the driving power to the excitation source for a preparatory supply time longer than the pulse width of the driving power. Therefore, energy less than the excitation energy (referred to as preliminary excitation power) is injected into the laser medium before welding the first weldment. Furthermore, the control unit allows for a predetermined interval that can be used before welding the first weldment after the preparatory supply time has elapsed.

[0010] According to the laser welding equipment of this embodiment, when forming multiple welded parts of a workpiece, it is not necessary to perform pre-irradiation of the laser beam to avoid welding errors in the first welded part.

[0011] The laser welding equipment according to the embodiments may include a scanning mechanism comprising an electrical scanner for scanning multiple weld areas. A pulsed laser beam emitted from a laser medium sequentially illuminates the multiple weld areas via the electrical scanner.

[0012] The laser welding equipment of this embodiment may further include a workpiece support and a moving mechanism, wherein multiple workpieces identical to the workpiece are placed on the workpiece support. The moving mechanism moves the workpieces placed on the workpiece support towards the welding table and stops the workpieces to be welded on the welding table. The control unit provides initial excitation power to the excitation light source as the workpieces to be welded move toward the welding table.

[0013] According to another embodiment, a laser welding method is provided, comprising supplying an initial excitation power, lower than the driving power and forming excitation energy, to an excitation source for an initial supply time longer than the driving power during which a first weld portion to be welded is to be supplied. Thus, energy less than the excitation energy is injected into the laser medium. A predetermined interval is allowed after the initial supply time before welding the first weld portion.

[0014] After this interval, driving power is supplied to the excitation source, thereby injecting excitation energy into the laser medium. The laser beam for the first weld is emitted from the laser medium using the excitation energy.

[0015] Other objects and advantages of the invention will be set forth in the following description, and some of these other objects and advantages will become apparent from this description and may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by the means and combinations particularly pointed out below. Attached Figure Description

[0016] The accompanying drawings, which are included in and form part of this specification, illustrate embodiments of the invention and, together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.

[0017] Figure 1 It is a plan view of a workpiece that includes multiple welded parts.

[0018] Figure 2 This is a schematic perspective view of a laser welding apparatus according to one embodiment.

[0019] Figure 3 It is partially shown Figure 2 The image shows a front view of the laser welding equipment.

[0020] Figure 4 This is a schematic top view of the laser oscillator of a laser welding device.

[0021] Figure 5 This is a time graph showing the relationship between the power of the excitation source supplied to the laser welding equipment and time.

[0022] Figure 6 This is a flowchart illustrating the first half of a laser welding method according to one embodiment.

[0023] Figure 7 This is a flowchart illustrating the latter half of the laser welding method of this embodiment.

[0024] Figure 8 This illustrates the relationship between the number of launches counted from the first launch and the energy values ​​in the first to fourth embodiments, wherein the initial excitation conditions in the first to fourth embodiments are different from each other.

[0025] Figure 9 This illustrates the relationship between the number of launches counted from the first launch and the energy values ​​in embodiments five through eight, wherein the number of launches per unit time differs from one another in embodiments five through eight. Detailed Implementation

[0026] Now refer to Figures 1 to 9 A laser welding apparatus and a laser welding method according to one embodiment are described.

[0027] Figure 1An example of a suspension for a disk drive is shown, comprising a workpiece 1 with multiple welded parts. Workpiece 1 includes a base plate 10 made of stainless steel, a first plate (load beam) 11, and a second plate (flexible member) 12.

[0028] Both the first plate 11 and the second plate 12 are made of flexible stainless steel. The first plate 11 and the second plate 12 are fixed together by a plurality of welded parts 13. The welded parts 13 are formed by laser welding equipment 20 by the laser welding method described below.

[0029] The first plate 11 is made of stainless steel and has a thickness of 200 μm or less. The thickness of the first plate 11 is greater than the thickness of the second plate 12. The second plate 12 is made of stainless steel and has a thickness of 100 μm or less. The thickness of the first plate 11 is, for example, 30 μm. The thickness of the second plate 12 is, for example, 18 μm. A wiring portion 15 is formed along one surface of the second plate 12. The wiring portion 15 includes an insulating layer made of an insulating resin such as polyimide and a conductor made of copper.

[0030] The second plate 12 is made of the same metal as the first plate 11 (e.g., austenitic stainless steel such as SUS304). The chemical composition of SUS304 is as follows: C 0.08 or less, Si 1.00 or less, Mn 2.00 or less, Ni 8.00-10.50, Cr 18.00-20.00, and the remainder is Fe.

[0031] Figure 2 The laser welding equipment 20 is schematically shown. The laser welding equipment 20 has the function of sequentially welding multiple weld parts 13 of the workpiece 1 using a laser beam emitted in pulse form. Figure 2 The laser welding equipment 20 shown includes a workpiece support 21, a moving mechanism 22, a laser irradiation device 23, and a control unit 24. The workpiece support 21 can support multiple workpieces 1. The moving mechanism 22 moves the workpiece support 21. The control unit 24 includes electrical configurations for controlling the moving mechanism 22 and the laser irradiation device 23, software for control, and a memory for storing control data.

[0032] like Figure 3 As shown, the first plate 11 and the second plate 12 of workpiece 1 are stacked along the thickness direction. In this state, workpiece 1 is fixed to workpiece support 21 by a retaining clamp. Workpiece support 21 has the function of holding workpiece 1 on a predetermined welding table 25. Welding table 25 is provided at a position corresponding to laser irradiation device 23. Workpiece support 21 is made of, for example, ceramic. When workpiece support 21 is made of ceramic, it is possible to prevent molten metal generated in welding section 13 from adhering to workpiece support 21.

[0033] like Figure 2As shown, multiple workpieces 1 are connected to each other at a predetermined distance P1 along the direction of movement of workpieces 1 (indicated by arrow M1) via frame member 1a. The moving mechanism 22 includes a guide member 26 and an actuator 27. The guide member 26 extends along the direction of movement of workpieces 1. The actuator 27 is, for example, a servo motor electrically controlled by control unit 24. The actuator 27 moves the workpiece support 21 along the direction of the guide member 26 via a force transmission mechanism such as a ball screw.

[0034] The moving mechanism 22 moves the workpiece 1, placed on the workpiece support 21, toward the welding table 25. The moving mechanism 22 moves along... Figure 2 The moving mechanism 22 moves the workpiece 1 intermittently at intervals P1 in the direction indicated by the middle arrow M1. The moving mechanism 22 can stop the workpiece 1 to be welded, which is placed on the workpiece support 21, at the welding table 25.

[0035] like Figure 2 As shown, the laser irradiation device 23 includes a laser head 31 with an electronic scanner 30. The electronic scanner 30 functions as a scanning mechanism for scanning the laser beam. When the workpiece 1 stops, the electronic scanner 30 moves the focal position of the laser beam emitted from the laser irradiation device 23 to the welding part 13 to be welded on the workpiece 1. Through the scanning operation of the electronic scanner 30, the focal position of the laser optical system of the laser irradiation device 23 can be moved at high speed toward the welding part 13.

[0036] Figure 3 This is a schematic diagram showing part of the workpiece 1 and the laser welding equipment 20. Figure 3 The laser irradiation apparatus 23 shown includes a laser oscillator 40 as the laser beam generation source and an optical lens system 41. The lens system 41 has the function of focusing the laser beam 42 output from the laser oscillator 40 and irradiating the laser beam onto the welding portion 13 of the workpiece 1 when the energy density is increased. The laser welding equipment 20 is, for example, a solid-state laser using a yttrium aluminum garnet (YAG) rod. Note that a gas laser such as a CO2 laser can be used, or a semiconductor laser or fiber laser can be used if desired.

[0037] Figure 4 A laser oscillator 40 is schematically shown. The laser oscillator 40 functions as an optical resonator and includes a laser medium 50, an excitation source 51, a high-reflectivity mirror 55, and a low-reflectivity mirror 56. The excitation source 51 injects excitation energy into the laser medium 50 according to the provided drive power. The high-reflectivity mirror 55 and the low-reflectivity mirror 56 are positioned opposite each other. The control unit 24 provides drive power to the excitation source 51 for injecting excitation energy.

[0038] When the power for oscillating the laser beam is supplied to the excitation source 51, the excitation energy 57 radiated by the excitation source 51 is injected into the laser medium 50. When the excitation energy 57 is injected into the laser medium 50, the light 60 emitted from the laser medium 50 is amplified by resonance between the high-reflectivity mirror 55 and the low-reflectivity mirror 56.

[0039] When the energy of the amplified light 60 exceeds the energy loss of the laser medium 50, laser oscillation occurs, and a laser beam 42 is emitted from the low-reflectivity mirror 56. The energy injected into the laser medium 50 can vary depending on the power supplied to the excitation source 51. The wavelength of the laser oscillator 40 is, for example, 1.06 μm.

[0040] Now refer to Figure 5 The timeline shown and Figure 6 and 7 The flowchart shown illustrates the laser welding method of this embodiment. In this specification, an irradiation of the laser beam used for welding may, in some cases, be referred to as a single emission.

[0041] exist Figure 6 In step ST1, the workpiece 1 to be welded is moved towards the welding table 25 by the moving mechanism 22, and the workpiece 1 stops at the welding table 25. Step ST2 is performed either while the workpiece 1 is moving in step ST1 or when the workpiece 1 stops at the welding table 25. In step ST2, energy for initial excitation is injected into the laser medium 50.

[0042] In step ST2, just before welding the first weld portion 13 to be welded, energy for preliminary excitation is injected. In this specification, the power that generates excitation energy in the laser medium 50 is referred to as the driving power Pw1 (e.g., ...). Figure 5 (As shown). The power less than the driving power Pw1 is called the initial excitation power Pw2. In step ST2, the initial excitation power Pw2 is supplied to the excitation source 51 within an initial supply time T2 that is longer than the pulse width T1 of the driving power Pw1. Through step ST2, energy less than the excitation energy (called the initial excitation energy) is injected into the laser medium 50.

[0043] Step ST2 can be performed simultaneously with the movement of workpiece 1 toward welding table 25 in step ST1. In this case, step ST2 provides preliminary excitation power Pw2 to excitation light source 51 while workpiece 1 moves toward welding table 25. Therefore, in step ST2, preliminary excitation power Pw2 is supplied to excitation light source 51 for a preliminary supply time T2, which is longer than the pulse width T1 before welding the first part to be welded.

[0044] exist Figure 6In step ST3 shown, the scanning operation of the electrical scanner 30 is controlled. Through the scanning operation, the laser beam emitted from the laser irradiation device 23 is focused towards the first (first emission) weld of the workpiece 1.

[0045] After the initial supply time T2 in step ST2, and just before welding the first weld joint, the control unit 24 allows a predetermined interval T3 to pass in step ST4. The interval T3 is the same as or longer than the pulse width T1 of the drive power Pw1. Furthermore, the interval T3 is shorter than the initial supply time T2 and shorter than the pulse interval T4 of the drive power Pw1. Step ST4 serves to allow the predetermined interval T3 to pass before welding the first weld joint.

[0046] After interval T3 has passed, Figure 7 In step ST5, a pulsed driving power Pw1 is supplied to the excitation source 51. Therefore, excitation energy is injected into the laser medium 50. Due to the excitation energy injected into the laser medium 50, a laser beam for the first welding section is emitted from the laser medium 50 in step ST6. Step ST5 provides the driving power Pw1 to the excitation source 51 while the workpiece 1 is stopped on the welding table 25.

[0047] In step ST7, it is determined whether the welding of all welded parts of a workpiece is completed. If the welding of all welded parts is not completed (No in step ST7), the process proceeds to step ST8 to prepare for the second and subsequent welded parts.

[0048] In step ST8, the scanning operation of the electrical scanner 30 is controlled to direct the laser beam output from the laser irradiation device 23 towards the second welding section and the subsequent welding section. Then, through steps ST5 and ST6, the second welding section and the subsequent welding section are formed.

[0049] In step ST7, if it is determined that all welded parts of a workpiece have been welded ("Yes" in step ST7), the process proceeds to step ST9. In step ST9, it is determined whether the welding of all workpieces has been completed.

[0050] If it is determined in step ST9 that welding of all workpieces has not been completed (No in step ST9), the process returns to... Figure 6 Step ST1. In step ST1, the next workpiece (the second or subsequent workpiece) is moved to welding station 25. Then, steps ST2 through ST9 are repeated to weld the second and subsequent workpieces. If the spacing between multiple workpieces is small, steps ST5 and ST6 can be repeated for the welded portion of the next workpiece without returning to step ST1.

[0051] In the above embodiment, a common driving power Pw1 is provided to the excitation light source 51 for each weld joint. However, one workpiece may differ from another, and the thickness and material of the weld joint may vary. In this case, the output (energy value) of the laser beam can be adjusted by changing the driving power Pw1 according to the thickness and material of the workpiece.

[0052] The inventors of this invention conducted experiments on four examples in which the initial excitation power Pw2 and the initial supply time T2 were varied. Figure 8 The relationship between the number of launches and the corresponding energy values ​​for each of these examples (examples one through four) is shown. Figure 8 In the diagram, the number "1" on the horizontal axis represents the first launch (first weld). In each example, the number of launches per second (number of welds) is 200, and the excitation energy (driving power) for each launch is 100 W.

[0053] Figure 8 The black circle in the diagram represents the first example, where the initial excitation power Pw2 is 30W and the initial supply time T2 is 10ms. In the first example, the energy value of the first emission is 0.0772 J. Here, no energy decrease was observed compared to the energy value of the second emission. Therefore, welding errors in the first weld are avoided. In the first example, when the initial excitation power Pw2 is applied, slight laser emission is observed, but the energy is insufficient to melt the workpiece.

[0054] Figure 8 The white circle in the image represents the second example, where the initial excitation power Pw2 is 25 W and the initial supply time T2 is 10 ms. In the second example, the energy value of the first emission is 0.0767 J. Here, no significant decrease in energy was observed compared to the energy values ​​of the second and subsequent emissions. Therefore, welding errors in the first weld are avoided. In the second example, no laser emission was observed when the initial excitation power Pw2 was applied.

[0055] Figure 8 The white triangle in the diagram represents the third example, where the initial excitation power Pw2 is 20W and the initial supply time T2 is 10ms. In this third example, the energy value of the first emission is 0.0758 J. Here, the energy decrease of the first emission is significant compared to the energy value of the second emission. Therefore, a welding error occurs in the first weld.

[0056] Figure 8The black square represents the fourth example, where the initial excitation power Pw2 is 30W and the initial supply time T2 is 5ms. In the fourth example, the energy value of the first emission is 0.07459 J. Here, the energy is significantly lower than that of the second emission, thus causing a welding error in the first weld.

[0057] The inventors of the present invention further conducted experiments on four examples in which the number of firings per unit time varied under different conditions when welding could be performed without applying initial excitation energy.

[0058] Figure 9 The relationship between the number of launches and the corresponding energy values ​​for each of these examples (examples 5 through 8) is shown. Figure 9 In the diagram, the number "1" on the horizontal axis indicates the first transmission (first weld). Note that "PPS" is an abbreviation for pulses per second, meaning the number of transmissions per second.

[0059] Figure 9 The black circle in the image represents the fifth example, where the pulse rate is 42 pulses per second. In this fifth example, the energy value of the first emission is 0.0600 J. Here, no energy reduction is observed compared to the energy value from the second emission. In such slow-pulse welding, the quality of the first weld is not a problem. However, the welding time for each workpiece is extended, leading to reduced production efficiency.

[0060] Figure 9 The white triangle in the diagram represents the sixth example, where the pulse rate is 100 pulses per second. The energy value of the first emission in the sixth example is 0.0599 J. Here, a decrease in energy is observed compared to the energy value from the second emission. Therefore, in the sixth example, there may be a problem with the quality of the first weld.

[0061] Figure 9 The white square in the image represents the seventh example, where the pulse rate is 200 pulses per second. In the seventh example, the energy value of the first emission is 0.0598 J, and a decrease in energy is observed compared to the energy value at the start of the second emission. Therefore, in the seventh example, there may be a problem with the quality of the first weld.

[0062] Figure 9 The white circle in the diagram represents the eighth example, where the pulse rate is 500 pulses per second. The energy value of the first emission in the eighth example is 0.0582 J. Here, the energy is significantly lower compared to the energy values ​​starting from the second emission. Therefore, in the eighth embodiment, the quality of the first weld is deteriorated.

[0063] As mentioned above, in high-speed pulse welding with 100 pulses per second or more, the reduced energy value of the first pulse is a problem. High-speed pulse welding has the advantage of high productivity because a large number of welds can be made in a relatively short time, but the quality of the first weld becomes an issue.

[0064] Based on the above results, the following specific measures were found to be effective in preventing welding errors in the first welding section without reducing the efficiency of laser welding: In high-speed pulse welding with 100 or more pulses per second, an initial excitation power of 25 W or more is supplied to the excitation source 51 during an initial supply time T2 of 10 ms or more.

[0065] In implementing this invention, various modifications can naturally be made to the specific configurations of the laser irradiation device, control unit, workpiece support unit, etc. This invention can also be applied to welding workpieces other than those used for disk drive suspensions.

[0066] Other advantages and modifications will readily occur to those skilled in the art. Therefore, the invention is not limited in its broader aspects to the specific details and representative embodiments shown and described herein. Thus, various modifications can be made without departing from the spirit or scope of the overall inventive concept as defined by the appended claims and their equivalents.

Claims

1. A laser welding apparatus (20) for sequentially welding multiple weld portions (13) of a workpiece (1) using a laser beam (42) output in pulse form, said apparatus comprising: A laser medium (50) emits a laser beam for the weld (13) and injects excitation energy into it; An excitation source (51) injects the excitation energy into the laser medium (50) and simultaneously provides it with driving power (Pw1). and A control unit (24) provides the excitation light source (51) with a pulsed driving power (Pw1) for the excitation energy. Its features are, Before welding the first weld portion (13) among the plurality of weld portions (13), the control unit (24) By supplying an initial excitation power (Pw2) of 25 W or higher to the excitation source (51) for an initial supply time (T2) that is 10 ms or longer than the pulse width (T1) of the driving power (Pw1), the initial excitation power (Pw2) is lower than the driving power (Pw1) and insufficient to melt the workpiece (1), or no laser beam emission is observed at the initial excitation power (Pw2), energy less than the excitation energy is injected into the laser medium (50), and After the initial supply time (T2), an interval (T3) is allowed before welding the first weld (13), the interval (T3) being greater than or equal to the pulse width of the drive power (Pw1), the interval (T3) being shorter than the initial supply time (T2) and without the initial excitation power (Pw2) being applied during the interval (T3).

2. The laser welding equipment according to claim 1, characterized in that, Also includes: A scanning mechanism includes an electric scanner (30) that scans the plurality of welded parts (13) and sequentially irradiates the plurality of welded parts (13) with a laser beam (42) in the form of a pulse emitted by the laser medium (50).

3. The laser welding equipment according to claim 2, characterized in that, Also includes: A workpiece support (21) on which multiple workpieces identical to workpiece (1) are placed; and A moving mechanism (22) moves the workpiece (1) placed on the workpiece support (21) toward the welding table (25) and stops the workpiece (1) to be welded at the welding table (25). in The control unit (24) provides the initial excitation power (Pw2) to the excitation light source (51) while the workpiece (1) to be welded moves toward the welding table (25).

4. A laser welding method for sequentially welding multiple weld parts (13) of a workpiece (1) using a pulsed laser beam (42), characterized in that, The method includes: Before welding the first welded part (13) among the plurality of welded parts (13), by supplying an initial excitation power (Pw2) of 25W or higher to the excitation light source (51) within an initial supply time (T2) longer than the pulse width (T1) of the driving power (Pw1), the initial excitation power (Pw2) is lower than the driving power (Pw1) and insufficient to melt the workpiece (1), or no laser beam emission is observed at the initial excitation power (Pw2), energy less than the excitation energy is injected into the laser medium (50); After the initial supply time (T2), an interval (T3) is allowed before welding the first weld (13), the interval (T3) being greater than or equal to the pulse width of the drive power (Pw1), the interval (T3) being shorter than the initial supply time (T2) and without the initial excitation power (Pw2) being applied during the interval (T3); After the interval (T3) has elapsed, the excitation energy is injected into the laser medium (50) by supplying the driving power (Pw1) to the excitation source (51); and The laser beam (42) for the first welding part (13) is emitted from the laser medium (50) by the excitation energy.

5. The laser welding method according to claim 4, characterized in that, Also includes: The same level of driving power (Pw1) is supplied to the excitation light source (51) for each of the plurality of welding parts (13), and the plurality of welding parts (13) are welded by high-speed pulse welding of more than 100 pulses per second.

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