KR20030041125A - Bellows welding using pulse moderation Nd-YAG laser with the peak energy - Google Patents

Abstract

PURPOSE: An apparatus for welding bellows to which chilling for diaphragm fabricated of a circular coating treated steel product is coupled using pulse modulation Nd-YAG laser is provided. CONSTITUTION: The bellows diaphragm coupled bellows welding apparatus using pulse modulation Nd-YAG laser with stable output comprises a power supply part(2) of pulse modulation Nd-YAG laser(1) comprising switching mode power supply and high speed switching means; a pulse modulation laser for generating laser beam having peak energy by receiving pulse signals based on electrical signals supplied from the power supply part; a laser beam focusing lens for transmitting laser beam generated from the pulse modulation laser using the optical fiber; an optical fiber(6) for transmitting the laser beam focused by the laser beam focusing lens to a welding object(9); a laser welding head(4) to which a focusing lens is attached so that the focusing lens focuses the laser beam transmitted through the optical fiber onto a welding portion to increase energy density; a stage for varying x axis, y axis and z axis to position the laser welding head perpendicularly to the welding object or at a desired angle; a lighting means(11) attached to both side of the stage to illuminate the welding portion; a tracking part for enabling the welding portion to be welded by moving the laser welding head in realtime with the laser welding head(4) being interlockingly connected to displacement of the welding portion, thereby finding out the welding portion accurately; a rotation part of bellows and bellows diaphragm interlockingly connected to the tracking part to fix bellows and circular bellows diaphragm and induce constant rotation thereof; and an argon or inert gas supply means for preventing oxidation and performing clean welding.

Description

Bellows welding using pulse moderation Nd-YAG laser with the peak energy}

The present invention relates to an apparatus for welding a bellows in which a chilling for diaphragm made of a circular steel coated with a pulse is modulated using a Nd-YAG laser. The pulse modulated Nd-YAG laser used in the present invention, unlike conventional CO2 laser, CW Nd-YAG laser, general gas vapor laser and laser diode, uses an electrical pulse signal to implement a pulse modulated Nd-YAG laser. The input power supply is completely different from that used in the general laser, and the energy density per pulse can be led to a stable output, and the pulse energy used for welding is modulated by modulating the size, shape and frequency of the pulse as needed. Can change.

Until now, TIG welding, a common CW CO2 laser, a CW Nd-YAG laser, and a laser diode have been used to weld a thin metal plate such as a bellows. In the case of TIG welding, the energy focusing rate is lower than that of laser welding, so the input of heat input energy is impossible, and precise welding is impossible. Therefore, high quality welding cannot be expected in CW laser. It is difficult to expect high quality welding.

In more detail, the related art related to the bellows welding is U.S. Patent No. 5,478,983, U.S. Patent No. 5,410,123, and Korean Laid-Open Patent Publication No. 2001-0045143, all of which are manufactured using a general laser beam. The bellows welding apparatus which performs rose welding is described. That is, all of these inventions do not consider the heat input energy and the deformation of the thin metal plate that can be changed depending on the heat input energy, which are necessary to be considered in welding thin metal plates such as bellows. Accordingly, even in the welding, there is a problem in that a precise and good welding cannot be achieved because it does not include a description of precisely welding while tracking in real time based on an image signal.

The present invention recognizes the problems of the conventional bellows welding as described above, and performs the outer diameter welding of the bellows combined with the diamond ring chilling made of a circular steel coated with a pulse modulated Nd-YAG laser. In this case, the bellows welding made of thin metal plate is suitable to increase the speed of the peak pulse energy, which is important, and to supply the low-energy energy to the welded portion to minimize the deformation of the welded portion to minimize the deformation of the welded portion. To achieve welding.

That is, the present invention recognizes the problems of the TIG welding and the bellows welding using a laser in general, and by using a pulse modulation YAG laser, the peak value at the beginning of the pulse input to the laser is appropriately increased to the welding portion of the thin metal plate. The purpose is to achieve high quality bellows welding without deformation of welding area by increasing initial energy collection speed and reducing heat input energy of welding area.

Another feature of the present invention is to coat the bellows diaphragm and the bellows with a matt black coating for the round steel diaphragm to reduce the reflection of light generated by the illumination device to obtain a good image signal from the CCD camera and to obtain a good image signal. It moves along the welding part in real time based on the video signal, thereby preventing the malfunction of the laser head and enabling a fine bellows welding.

1 is a schematic diagram of a bellows welding device using a pulse modulated Nd-YAG laser with peak energy.

Fig. 2: Pulse signal shape input to the flash lamp of a pulse modulated Nd-YAG laser with peak energy.

Figure 3: Laser light absorbance when metal surface temperature rises.

Figure 4: Input parameters appearing on the monitor during bellows welding.

Fig. 5: Fixation of the bellows and round bellows diaphragm.

One; Pulse modulated Nd-YAG laser, 2; A laser power supply, 3; Laser chiller, 4; Laser welding head, 5; X-Y table (with AC servomotor), 6; Optical fiber for laser transmission, 7; Microprocessor, 8; A monitor, 9; Welding object, 10; A rotating body (motor), 11; Luminaire, 12; Camera 13; Inert gas input unit 14; Welding condition input, 15; Seam tracker

①; Shaft, ②; Stopper, ③; Stopper, ④; Collar, ⑤; Sleeve, ⑥; Bellows

The present invention is the outer diameter of the bellows is combined with a chilling (chilling, chilling, see Fig. 5) for the diaphragm made of a circular steel (SUS-based spring) coated with a matte coating using a pulse modulated Nd-YAG laser It relates to a device for welding. Nd-YAG used for laser generation in this device is an abbreviation of Neodymium-yttrium allumium garnnet, Nd is the doping material, and YAG is the host. In manufacturing the glass rod, Nd is composed of about 1% of the host by weight specific gravity. Nd-YAG rods are 6-10 mm in radius and 10 mm long, similar to glass rods. Place one or two lamps in the middle of an elliptical cavity with one or two foci and the Nd-YAG rods side by side or in the middle of one or two lamps. At this time, each position of the lamp and the Nd-YAG rod uses a common focus to effectively transmit the light generated from the lamp to the Nd-YAG rod to maximize its efficiency. When the lamp is powered, the light from the lamp is effectively delivered to the Nd-YAG rod to excite Nd ions to induce the generation of the laser beam. At this time, the light generated by the lamp generates various wavelengths, but Nd-YAG absorbs the light generated by the lamp and emits light with a constant wavelength of 1.06 um when the Nd element excited by the light emitted from the lamp falls to the ground state. do. The energy value of the laser beam generated at this time is closely related to the electrical signal supplied to the flash lamp.

In order to obtain the pulse output Nd-YAG laser, the bellows welding laser output desired by the user, the pulse signal supplied to the flash lamp should be made into a signal having the same or similar shape as the output of the desired energy. In order to obtain a laser output suitable for bellows welding, a thin metal plate such as a bellows can be fabricated by using a pulsed signal from a commercial three-phase 220V power supply and a high speed switching transistor (IGBT). A pulse signal (see Fig. 2) having an appropriate peak is initially produced which can be elaborately welded without large deformation due to heat input, and is supplied to the lamp. Control of the output, frequency and pulse width of the pulses is possible by opening the gate (turning the transistors on and off) at desired time intervals using IGBTs from the electrical energy obtained from the switched-mode power supply, which is then microcomputerized to the transistors. This is done by controlling the width of the pulse signal supplied to turn on / off (IGBT), and the maximum pulse modulation frequency can be modulated up to 300Hz according to the welding speed and the desired output energy.

The waveform of the pulse signal to be supplied to the pulse modulated Nd-YAG laser in order to achieve a fine and good welding of a thin metal plate such as a bellows is shown in FIG. 2. As the peak of the part is appropriately high, instantaneous input of low input energy is injected and the energy of the back part of the pulse is lowered to prevent continuous heat input at the welded part, thus preventing deformation of the thin metal plate, thereby achieving high-quality bellows welding. In the form of an optimal pulse signal. In other words, since the bellows material is a thin metal plate, if a lot of energy is continuously added, it is difficult to perform high-quality and precise welding due to thermal deformation of the metal material. A moderately high pulse peak output is required to raise the metal surface temperature before conduction. The pulse signal used in the present invention increases the laser light absorption coefficient by supplying an appropriately high energy to the pulse modulated Nd-YAG laser at the beginning, and thus it is possible to obtain a high quality and precise welding with low heat input energy.

In this regard, in FIG. 3, when looking at the change in absorption coefficient according to the temperature change of the metal, in general, the laser light absorption is not very high in the metal at room temperature. have.

The laser beam generated by the pulse-modulated Nd-YAG laser is transmitted through the optical fiber, and the laser beam is focused using an optical focusing lens and sent to the inside of the optical fiber having a diameter of 400 μm before being transmitted to the final target welding object. In this case, the optical fiber used was made of a material having low loss at the wavelength of the pulse modulated Nd-YAG laser (FQSI type, diameter 400㎛, length 10m).

The laser beam transmitted through the optical fiber is an optical unit for focusing the laser beam, a charge coupled device (CCD) camera, and an illumination unit for illuminating the welding region to obtain a good image signal to enable precise and good bellows laser welding. Construct a laser welding head.

The optical unit for focusing the laser beam transmitted through the optical fiber to a size suitable for the bellows welding using a mirror or a light focusing lens for focusing the light used to change the direction of the beam transmitted through the optical fiber It focuses the beam in the desired direction and delivers high-density energy to the welded area.The CCD camera is attached near the laser welding head to observe the welded area and receives the image signal from the welded area by the CCD sensor and displays it on the monitor. The purpose of the present invention is to more clearly observe an image signal of a welding part of a welding object on a monitor. The bellows welding device receives the welding object indicated by the illumination of the lighting unit from the CCD camera and follows the connection portion of the bellows diaphragm and the bellows on the X-axis in real time based on the image signal (image) displayed on the monitor. The servomotor is variable and precisely welded. The XY table controller employed in the present invention is driven by two AC servomotors and is capable of precisely moving up to 5/10000 mm, and moves in real time along the weld shown on the monitor in connection with a monitor that receives and displays the image signal. Thereby acting as a sophisticated welder.

The rotating object of the welding object which rotates at a constant speed by fixing the bellows diaphragm and the bellows to the jig (see Fig. 5) can be rotated in the reverse direction or the forward direction as necessary. The welding conditions can be input through a monitor in relation to the operation of the rotating body of the welded object and are shown in FIG. 4. The maximum speed among the variables input on the monitor shown in FIG. 4 is the speed at which the rotating body rotates in rpm. The initial velocity is expressed in pps as the number of pulses the laser emits per second, which is also related to the output of the welding laser. Acceleration time is the time required to reach the maximum speed from the standstill state, and deceleration time represents the time required to reach the stop state from the maximum speed.

In order to achieve better laser welding, the parameters that can be input on the monitor are the welding speed of the welding target, the number of pulses per second (laser output), acceleration time, deceleration time, and image signal to be welded. At the time of automatically tracking along the welded area, it is set to the accuracy of tracking and so on, and by controlling these variables well, fine bellows welding can be achieved. That is, while tracking while welding in real time by using the image signal of the welding part input to the monitor by CCD camera, it is used for tracking and rotating body which fixes and rotates the bellows and bellows diaphragm by one microprocessor. In conjunction with the AC servomotor that moves the XY drive shaft (laser head support) to be integrated with each other to enable optimal bellows welding.

In relation to the bellows welding, the inert gas injecting unit is a device which continuously blows inert gas into the welding portion during the welding period in order to prevent oxidation of the welding portion and to prevent impurities from being introduced in order to achieve better welding. .

The bellows diaphragm chilling used in connection with the present invention uses a steel wire (material; SUS) coated with a matte black, and the reason for the coating is to prevent the reflection of light emitted from the lights installed on both sides of the laser head. It is to induce more precise tracking by obtaining more accurate video signal.

Fig. 5 shows a shaft, a stopper, a rib, and the like which secures the bellows diaphragm and the chilling for the diaphragm.

(Example)

In one embodiment in connection with the present invention, a pulse modulated Nd-YAG laser power supply circuit has a switching mode power supply and a high-speed numerical position means, and has a peak signal at the beginning of a pulse supplied to a flash lamp as shown in FIG. Is supplied as the input signal of the flash lamp of the pulse-modulated Nd-YAG laser suitable for bellows welding, which is a thin metal material. In order to prevent oxidation and to enable high-quality welding by injecting into the welding part during the bellows welding, an inert gas is supplied, and a cooling device to cool the heat generated in the process of converting the light of the flash lamp into the laser beam. Start up.

Based on the principle of Figs. 2 and 3, the peak value at the beginning of the pulse is appropriately high to instantaneously inject less heat input energy, and at the same time lower the energy at the back of the pulse, so that the metal material at the welding part is continuously heated. It provides the pulse modulated Nd-YAG laser with the optimal electrical pulse signal to prevent deformation and to achieve good bellows welding. In other words, since the bellows material is a thin metal plate, if a lot of energy is continuously added, heat input energy increases and it is difficult to perform high-quality, precise welding. A moderately high peak output is required to raise the temperature before it can. The pulse modulated Nd-YAG laser, which supplies a moderately high energy to the beginning of the signal used in the present invention, instantly increases the laser light absorption coefficient and enables fine bellows welding of good quality with low heat input energy.

That is, the pulse modulated Nd-YAG laser used in the present invention can achieve high quality and precise bellows diaphragm and bellows welding by minimizing the deformation of the weld due to low heat input energy and continuous heat input by using the peak pulse. have.

In addition, the tracking means is attached to the laser-modulated Nd-YAG laser and the laser head to transmit the video signal of the welding site to the monitor through the camera and to follow the welding site based on the transmitted video signal to enable welding And the rotational speed of the welding target, the number of pulses per second (laser output) generating the laser beam, the acceleration time and the deceleration time of the servo motor are linked to the microprocessor.

Looking at the specific operation steps of the laser bellows welding,

First, the laser welding system is largely divided into a pulse-modulated Nd-YAG laser main body and a processing system. The processing system fixes a rotating body on which a welding object is fixed, a welding head composed of an optical fiber and an optical part, and XY tables It consists of a trekking unit with an AC servo motor attached to it.

The bellows laser welding system configured as described above is controlled by a computer program in conjunction with the pulse width and the pulse size of the rotating object of the welding object, the AC servo motor driving the X-Y axis, and the pulse modulated Nd-YAG laser. Looking specifically at the bellows welding controlled by a computer program step by step (see Fig. 4),

end. Power is supplied to the pulse modulated Nd-YAG laser, the rotor of the welding object, and the AC servo motor driving the X-Y axis, lighting device, monitor and cooling device.

I. When the power is supplied, the video signal of the welding part on the monitor is displayed through the CCD camera, and the movement to the desired position is performed by clicking through the mouse.

All. After moving to the desired position, set the number and spacing to be welded by entering the number and spacing in the machining settings, and click the machining button to automatically weld.

la. More specifically, the setting menu may include a moving setting, an origin search, a laser setting, a center display setting, an aspect ratio setting, and a machining setting.

If the movement setting is selected, the speed and position of the rotating shaft and the welding head feed shaft can be set. For horizontal position movement, input the value of the distance to move and press the move button to move to the fixed position. Rotation direction can be selected by moving the rotating body in the desired direction by selecting 'positive' and 'inverse'.

If you press the 'Speed' button, the speed can be set and the initial speed is displayed in pps (pulse per second), which is 1/10 of the maximum speed. The maximum speed is the maximum speed during movement, expressed in rpm and is valid only for the axis of rotation. Acceleration time is the time it takes to reach the maximum speed from the stop state, and deceleration time is the time it takes to reach the stop state from the maximum speed. In order to achieve good welding in the laser deceleration time and the acceleration time, it is preferable to set the welding so as to overlap about 10 degrees.

The auto-follow feature adjusts the speed and ratio. The fine adjustment speed determines the moving speed in the horizontal direction when welding, and it is generally desirable to set a small value at a high speed and a large value at a slow speed.

hemp. Origin search is a function to find a preset origin of the horizontal axis.

bar. In the laser setup, the laser output, frequency, intensity and processing time can be set. The high set sets the laser maximum power, and the rouset sets the laser minimum power. Depending on the laser intensity, the ratio of the highset and the lowset occupies varies. That is, the higher the laser intensity, the longer the highset, and the lower the intensity, the longer the lowset. The machining time is automatically set by modifying the rotational speed of position movement.

bar. The center mark setting can confirm the laser machining position.

four. The aspect ratio setting is to set the ratio between the visible distance and the actual distance on the screen.

Ah. In the machining menu, when the machining button is pressed, the welding process is performed under the welding conditions already set in the menu while moving from side to side along the welding line at the number and interval set in the machining setting.

character. Machining settings can set the number of machinings and the processing interval for continuous machining. Enter the number of cutting and processing interval, move to the first position and press the 'machining' button to perform the machining. Press 'Start' and 'Standby' buttons to move to the given position. If you increase the processing angle, it rotates a little more and the first part and the end part overlap (a little more rotation) and process.

The effect expected by the present invention recognizes the problems of the TIG welding and the bellows welding using a general laser, and gives a peak at the beginning of the pulse using a pulse modulated YAG laser to increase the initial energy concentration of the pulse and At the same time, the heat input energy of the welded part is reduced, thereby achieving a good bellows welding without deformation of the welded part.

Another effect of the present invention is to perform a welding of the bellows diaphragm and the bellows, and to coat the bellows diaphragm of the round steel with a matte black to reduce the light generated by the lighting device, thereby providing a better image signal from the CCD camera. It has the effect of enabling precise welding by tracking the welded area in real time from a good video signal.

Claims (5)

In the bellows outer diameter welding device combined with a die-filled chilling ring made of circular steel using a pulse modulated Nd-YAG laser with peak energy, A power supply unit of a pulse modulated Nd-YAG laser having a switching mode power supply and a high-speed leveling means for generating pulses of a desired shape with a stable output of the pulse modulated Nd-YAG laser; A pulse modulated laser for generating a laser beam having peak energy by receiving a pulse signal having a peak value optimal for welding a thin metal plate based on an electrical signal stably supplied from the power supply unit; A focusing lens for focusing a laser beam for transmitting a laser beam generated by the pulse modulated laser generating the peak pulse energy to an optical fiber; An optical fiber for transmitting the laser beam focused by the laser beam focusing lens to a welding target; A laser head for welding with a focusing lens for focusing a laser beam transmitted through the optical fiber on a welding part to increase energy density; A stage capable of varying the x-axis, y-axis and z-axis for positioning the welding laser head to which the laser beam focusing lens is attached at a direction perpendicular to the welding object or at a desired angle; Illuminating means attached to both sides of the stage to which the laser head is attached to illuminate the welded portion to be easily observed by a CCD camera; The welding area illuminated by the lighting means is inputted to the monitor through a CCD camera and displayed on the basis of the input image signal, and moves the welding laser head in real time in accordance with the displacement of the welding area to accurately find and weld the welding area. With a trekking unit to enable The rotating portion of the bellows and bellows diaphragm excellent by fixing the bellows and the circular bellows diaphragm in conjunction with the trekking part and inducing a constant rotation; Bellows diamond using a pulse modulated Nd-YAG laser with stable output, characterized in that the argon or inert gas supply means is provided to prevent oxidation and achieve clean welding when the bellows and bellows diaphragm are welded. Bellows welding device with combined ram. The method of claim 1, The bellows diaphragm chilling is coated on a black steel wire with a matte finish to reduce reflection by illumination to obtain a more accurate video signal and to accurately track the welded area based on the video signal. Bellows welding device combined with bellows diaphragm using pulse modulated Nd-YAG laser with stable output. The method of claim 1, The bellows diaphragm chilling is a bellows welding device incorporating a bellows diaphragm using a pulse modulated Nd-YAG laser having a stable output, characterized in that the steel wire is made of SUS circular steel. The method of claim 1, The electrical signal supplied to the flash lamp is a pulse modulated Nd having a stable output, characterized in that the peak energy is given at the beginning of each pulse signal to increase the energy density and input to the flash lamp to increase the initial energy of the laser beam. -Bellows welding device combined with bellows diaphragm using YAG laser. The method of claim 1, The pulse modulated laser is a bellows welding device incorporating a bellows diaphragm using a pulse modulated Nd-YAG laser having a stable output, characterized by modulating the number of pulses per second and the width of the pulse. .