Laser welding condition determination method and laser welding device

A method for determining a laser welding condition of the present disclosure includes a first step, a second step, and a third step. In the first step, workpiece information indicating characteristics of a workpiece is input. In the second step, laser information indicating characteristics of laser light is input. In the third step, a first welding condition is calculated based on the workpiece information and the laser information, and then displayed. The first welding condition is any one of a recommended laser power of the laser light, a recommended welding speed, a recommended welding pattern, an estimated strength of a welded portion, and an estimated weld depth of the welded portion. Furthermore, the workpiece information includes a joint shape of the workpiece. Thus, an optimum weld condition can be set while considering a shape of a joint in welding.

This application is a U.S. national stage application of the PCT international application No. PCT/JP2014/005538.

TECHNICAL FIELD

The present disclosure relates to a laser welding condition determination method for determining a laser welding condition in response to a workpiece in laser welding for welding a workpiece by laser light, and to a laser welding device.

BACKGROUND ART

In conventional laser machining, an operator sets a welding condition with respect to a workpiece based on the operator's experience and intuition. Alternatively, the operator changes the welding condition repeatedly while verifying welding results, and finds a welding condition suitable for the workpiece.

Thus, PTL 1 has proposed an interactive NC (Numerical Control) device capable of setting a laser machining condition (laser power, oscillating frequency, duty, and the like) in response to a welding speed for material and a board thickness of a workpiece, in order to lead a machining condition without the need for experience of an operator or verification for each machining.

With reference toFIG. 6, conventional interactive NC device101is described. As shown inFIG. 6, interactive NC device101includes interactive unit102, arithmetic processing unit103, and storage unit104. Interactive unit102includes display section105, and interactive input section106. Interactive input section106includes laser machining condition display key107, ten-key108, cursor key109, and page key110. Storage unit104stores laser machining condition table111. Arithmetic processing unit103includes a NC program, and selects a laser machining condition based on a command speed input in interactive unit102and laser machining condition table111in storage unit104.

Next, a method for setting a laser machining condition by interactive NC device101is described.

Firstly, formation of laser machining condition table111is described. An operator operates laser machining condition display key107, ten-key108, cursor key109, and page key110of interactive input section106, so as to set material and a board thickness of a workpiece. Then, the operator sets a laser machining condition (laser output, frequency, duty, and gas pressure) in response to a machining speed. Thus, laser machining condition table111is formed and stored in storage unit104.

Next, execution of the NC program using laser machining condition table111is described. An operator sets material and a board thickness of a workpiece by interactive unit102. Thus, the NC program is executed. Subsequently, when the operator sets a command speed by interactive unit102, the NC program sets laser machining conditions (laser output, frequency, duty, and gas pressure) using the formed laser machining condition table111.

As mentioned above, once an operator sets laser machining conditions corresponding to material, board thickness, and machining speed of a workpiece, it is not necessary to set subsequent laser machining conditions, and it is possible to set optimum laser machining conditions.

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

However, conventional interactive NC device101aims to cut a workpiece, and laser machining conditions are set only based on material and a board thickness of the workpiece. On the other hand, since in welding, optimum laser machining conditions differ depending on the shape of a joint, appropriate welding conditions cannot be set based only on material and a board thickness of a workpiece as described in PTL 1.

A method for determining a laser welding condition and a laser welding device of the present disclosure have an object to easily obtain an optimum laser welding condition.

In order to achieve the above-mentioned object, the method for determining a laser welding condition of the present disclosure includes a first step, a second step, and a third step. In the first step, workpiece information indicating characteristics of a workpiece is input. In the second step, laser information indicating characteristics of laser light is input. In the third step, a first welding condition is calculated based on the workpiece information and the laser information, and then displayed. Furthermore, the first welding condition is any one of a recommended laser power of the laser light, a recommended welding speed, a recommended welding pattern, an estimated strength of a welded portion, and an estimated weld depth of the welded portion. Furthermore, the workpiece information includes a joint shape of the workpiece.

Furthermore, a laser welding device of the present disclosure includes a laser oscillator, a laser head, a robot, a controller, and a welding condition setting unit. The laser head emits laser light, output from the laser oscillator, to a workpiece. To the robot, the laser head is attached. The robot moves the laser head. The controller controls an operation of the robot, and has a welding condition calculation section. The welding condition setting unit is connected to the controller. The welding condition setting unit includes a workpiece information input section, a laser information input section, and a display section. The workpiece information input section is configured to receive an input of the workpiece information indicating the characteristics of the workpiece. The laser information input section is configured to receive an input of the laser information indicating the characteristics of the laser light. The display section displays a first welding condition calculated by the welding condition calculation section based on the workpiece information and the laser information. Furthermore, the first welding condition is any one of a recommended laser power of the laser light, a recommended welding speed, a recommended welding pattern, an estimated strength of a welded portion, and an estimated weld depth of the welded portion. Furthermore, the workpiece information includes a joint shape of the workpiece.

According to the method for determining a laser welding condition and the laser welding device of the present disclosure, also in welding, an optimum weld condition can be set while considering a shape of a joint of the workpiece.

DESCRIPTION OF EMBODIMENTS

First Exemplary Embodiment

This exemplary embodiment is described with reference toFIGS. 1 through 3D.FIG. 1shows a schematic configuration of a laser welding device.FIG. 2is a flowchart showing a procedure to determine laser welding conditions.FIGS. 3A through 3Dare views each showing an example of a joint shape of a workpiece.

As shown inFIG. 1, laser welding device1includes laser oscillator2, laser head3, robot4, controller5, and welding condition setting unit6. Laser oscillator2is coupled to laser head3via fiber7(optical fiber wire). Laser oscillator2oscillates laser, and outputs oscillated laser light to laser head3through fiber7. Laser head3emits laser light output by laser oscillator2to workpiece8. That is to say, laser light9is emitted from laser head3to workpiece8. Robot4has laser head3attached at a tip of robot4, and moves laser head3. Controller5is connected to robot4and controls an operation of robot4. Furthermore, controller5is connected to laser head3and controls laser head3. Controller5is also connected to laser oscillator2and controls laser oscillator2. Furthermore, controller5has welding condition calculation section10for calculating welding conditions. Welding condition setting unit6is connected to controller5, and bilaterally communicates with controller5. Welding condition setting unit6includes workpiece information input section11, laser information input section12, and display section13.

Next, a method for determining a laser welding condition by laser welding device1before execution of welding is described with reference toFIGS. 1 through 3D.

As shown in step1inFIG. 2, an operator inputs workpiece information indicating characteristics of workpiece8into workpiece information input section11of welding condition setting unit6(a first step). The workpiece information includes material, a board thickness, and a joint shape of a workpiece. Examples material of a workpiece include soft steel, stainless steel, aluminum, and the like. Furthermore, when two workpieces are welded to each other, material and a board thickness of each of the workpieces are input into workpiece information input section11. Furthermore, arrangement of workpieces, corresponding to the joint shape, is also input into workpiece information input section11.

Herein, joint shapes are described more specifically with reference toFIGS. 3A through 3D.FIG. 3Ashows a “lap joint” for welding a portion in which workpiece81and workpiece82are overlapped onto each other.FIG. 3Bshows a “lap fillet joint” for welding an end portion of workpiece84overlapped onto workpiece83.FIG. 3Cshows a “butt joint” for welding a portion in which workpiece85and workpiece86are adjacent to each other when workpiece85and workpiece86are arranged.FIG. 3Dshows a “T fillet joint” for welding a portion in which workpiece87and workpiece88are brought into contact with each other when workpiece88is disposed perpendicular to workpiece87.

The material and the board thickness of a workpiece include the arrangement of the workpiece in the joint shape. For example, inFIG. 3A, the joint shape is a “lap joint” and the workpiece information includes the “material” and the “board thickness” of workpiece81“located in the lower side,” and the “material” and the “board thickness” of workpiece82“located in the upper side.”

Next, as shown in step2inFIG. 2, an operator inputs laser information indicating characteristics of laser light9into laser information input section12of welding condition setting unit6(a second step). The laser information includes a spot diameter of laser light9at a focal position, length from laser head3to the focal position (or focal length of laser light9by lens inside laser head3), a length from laser head3to workpiece8, and the like.

The workpiece information input into workpiece information input section11and the laser information input into laser information input section12are transmitted to welding condition calculation section10of controller5.

Next, a recommended value, a recommended pattern, and an estimated value of the welding conditions are calculated by welding condition calculation section10based on the workpiece information and the laser information as shown in step3inFIG. 2, and then displayed on display section13of welding condition setting unit6as shown in step4inFIG. 2(step3and step4together are defined as a third step). The welding conditions displayed at this time are defined as a first welding condition and a second welding condition. Each of the first welding condition and the second welding condition may be only one welding condition or two or more welding conditions. Each of the first welding condition and the second welding condition is a part of a plurality of welding conditions. Both the first welding condition and the second welding condition may constitute all the welding conditions. Both the first welding condition and the second welding condition may be a part of a plurality of welding conditions. The “welding condition” including the first welding condition and the second welding condition is, for example, a welding speed, laser power, and a welding pattern. A strength of a welded portion, a weld (depth) of the welded portion, and the like, which are derived from the above-mentioned conditions, are also included in the “welding condition.” Then, the “welding condition” is a combination of an “item” and a “value (or a pattern)” related to welding.

Herein, differences of heat input depending on the four types of joint shapes shown inFIGS. 3A through 3Dare described. Appropriate heat input for welding is different depending on the joint shape of workpiece8. Assuming that workpieces81to88are made of the same material and have the same board thickness inFIGS. 3A through 3D.

In the “lap joint” shown inFIG. 3A, heat input to melt two workpieces, that is, workpiece81and workpiece82, is required. This is because a plane portion of workpiece81and a plane portion of workpiece82are welded to each other.

In the “lap fillet joint” shown inFIG. 3B, heat input to melt more than one and less than two workpieces is required. Since a welded portion of workpiece84is an end portion, heat input necessary for only workpiece84is less than heat input to melt one workpiece, and workpiece83is melted by the remaining heat. This is because a plane portion of workpiece83and an end portion of workpiece84are welded to each other. When heat input that is the same as in the “lap joint” inFIG. 3Ais carried out to the “lap fillet joint” inFIG. 3B, burn through of workpiece83occurs. Therefore, the heat input must be reduced in the “lap fillet joint” inFIG. 3Bas compared with the case of the “lap joint” inFIG. 3A.

In the “butt joint” inFIG. 3C, since workpiece85and workpiece86are abutted to each other (arranged), heat input is required to be heat input to melt one workpiece. This is because an end portion of workpiece85and an end portion of workpiece86are welded to each other. Consequently, the heat input is reduced in the “butt joint” inFIG. 3Cas compared with the case of the “lap fillet joint” inFIG. 3B.

The heat input of “T fillet joint” inFIG. 3Dis required to be equal to that of the “lap fillet joint” inFIG. 3B. This is because a plane portion of workpiece87and an end portion of workpiece88are welded to each other in the “T fillet joint” inFIG. 3D, and because the welding conditions are near the conditions for welding of the “lap fillet joint” inFIG. 3B. In this way, heat input by laser light9is required to be changed depending on the joint shape of workpiece8.

Furthermore, a welding pattern as an irradiation locus of laser light9is described. In the case of the “lap joint” shown inFIG. 3A, a target position of laser light9may be displaced by about several mm. Therefore, welding can be carried out in a straight line, circular, and C-type welding patterns. However, in cases where straight line welding is carried out by laser light9with respect to the “lap fillet joint” inFIG. 3B, the “butt joint” inFIG. 3C, and the “T fillet joint” inFIG. 3D, when a target position of laser light9is displaced by about several mm, both the workpieces cannot be melted. This is because it is necessary to weld an end portion of at least one workpiece. When the target position is displaced by about several mm in straight line welding, one workpiece is not melted, and burn-through or perforation occurs in the other workpiece. Furthermore, since a joined area between the workpieces is small in circular or C-shaped welding pattern, a strength may be insufficient. Accordingly, use of welding patterns such as weaving can melt both the workpieces continuously widely, and can complement the displacement of the target position. Thus, it is necessary to weld a workpiece in a welding pattern suitable for the joint shape.

Furthermore, time necessary for melting a workpiece is different depending on material or a board thickness of a workpiece. Difference in melting is caused by difference in a melting point or thermal conductivity by material of a workpiece, and difference in thermal diffusion by a board thickness or a joint shape of a workpiece. Therefore, it is necessary to determine an appropriate welding speed based on the material, the board thickness, and the joint shape of a workpiece.

Based on the above, laser welding device1in accordance with this exemplary embodiment has a function of determining an appropriate laser welding condition as mentioned below.

Welding condition calculation section10of controller5includes a arithmetic equation or a database, which associates the workpiece information including a joint shape and laser information with welding conditions. The welding conditions include a welding speed, laser power, and a welding pattern. A strength of a welded portion, a weld (depth) of the welded portion, and the like, which are derived from the above-mentioned conditions, are also included in the welding condition. That is to say, welding condition calculation section10has a arithmetic equation or a database, which associates the workpiece information and the laser information with a recommended welding speed, a recommended laser power, a recommended welding pattern, an estimated strength of the welded portion, an estimated weld (depth) of the welded portion, and the like.

Herein, a welding condition to be calculated by welding condition calculation section10may be added. For example, in a case where assist gas is fed to a welded portion, types of gases or feed amount of gas may be calculated by welding condition calculation section10. Furthermore, for example, in a case where filler wire is fed to a welded portion, a diameter or feeding speed of the filler wire may be calculated by welding condition calculation section10. As mentioned above, in step3inFIG. 2, welding condition calculation section10calculates the recommended value, the recommended pattern, or the estimated value of welding conditions.

Then, in step4inFIG. 2, the recommended value, the recommended pattern, or the estimated value of welding conditions calculated by welding condition calculation section10are displayed on display section13of welding condition setting unit6.

Herein, an example of the method for determining laser welding condition of this exemplary embodiment is described specifically.

Subsequently, in step2, the operator inputs “spot diameter: 0.6 mm,” and “length from the laser head to workpiece8: 300 mm” as the laser information into laser information input section12.

Thereafter, based on the calculated welding conditions, laser welding device1welds workpiece8.

Thus, even for an operator having little experience of laser welding, time or labor for obtaining a welding condition can be reduced. Furthermore, it is possible to reduce workpieces to be used only for obtaining welding conditions and then to be discarded.

Note here that in the laser welding device of this exemplary embodiment, welding condition calculation section10is provided inside controller5. However, welding condition calculation section10may be provided inside welding condition setting unit6. Furthermore, a configuration in which welding condition setting unit6and controller5may be unitarily formed may be employed. Furthermore, the welded portion may be further provided with an assist gas feeder for feeding assist gas, and the assist gas feeder may be controlled by controller5. Furthermore, the welded portion may be provided with a filler wire feeder for feeding a filler wire, and the filler wire feeder may be controlled by controller5.

Furthermore, the arithmetic equation or the database provided in welding condition calculation section10may be constructed based on, for example, values measured by experimental laser welding. Furthermore, the input of a board thickness of a workpiece into workpiece information input section11is carried out every 0.1 mm. The input of the material of a workpiece into workpiece information input section11includes soft steel, galvanization, a plating amount, Aluminum 5000, SUS 430, and the like.

Second Exemplary Embodiment

This exemplary embodiment is described with reference toFIGS. 4 and 5.FIG. 4shows a schematic configuration of a laser welding device.FIG. 5is a flowchart showing a procedure to determine laser welding conditions. In this exemplary embodiment, the same reference numerals are given to the same configurations as in the first exemplary embodiment, and description therefor is omitted. This exemplary embodiment is different from the first exemplary embodiment in that when welding condition calculation section10calculates a recommended value, a recommended pattern, an estimated value of welding conditions, displays them on display section13, and then further changes the welding conditions, welding condition calculation section10recalculates (updates) the recommended value, the recommended pattern, and the estimated value of the welding conditions, and displays them on display section13.

As shown inFIG. 4, laser welding device21of this exemplary embodiment further includes parameter change input section14in welding condition setting unit6in laser welding device1in the first exemplary embodiment. Furthermore, as shown inFIG. 5, a method for determining a laser welding condition of this exemplary embodiment further includes step5, step6, and step7after step4of the first exemplary embodiment.

Next, a method for determining a laser welding condition by laser welding device21before execution of welding is described with reference toFIGS. 4 and 5. Steps1to4inFIG. 5are the same as steps1to4inFIG. 2of the first exemplary embodiment.

As shown in step5inFIG. 5, an operator can change a welding condition displayed on display section13, that is, a recommended laser power, a recommended welding speed, a recommended welding pattern, an estimated strength of the welded portion, and an estimated weld depth of the welded portion. In other words, the operator changes the first welding condition to a third welding condition. In detail, the first welding condition and the third welding condition are the same as each other in items and different from each other in values (or patterns). In step5, in a case where the operator does not change the welding conditions, the display of step4is maintained.

In this exemplary embodiment, a case where an operator changes, for example, a welding speed and laser power is described. In step5, the operator operates parameter change input section14and changes a recommended welding speed and a recommended laser power (a fourth step). At this time, display section13displays the changed welding speed and changed laser power.

As shown in step6inFIG. 5, welding condition calculation section10recalculates not-changed welding conditions (a welding pattern, a strength of a welded portion, and a weld depth of the welded portion) from workpiece information, laser information, and changed welding conditions (a welding speed and laser power) based on a arithmetic equation or a database stored inside welding condition calculation section10. Subsequently, as shown in step7inFIG. 5, the changed welding conditions and the recalculated welding conditions are displayed on display section13of welding condition setting unit6(step6and step7together are referred to as a fifth step). In other words, the second welding condition is changed to a fourth welding condition and then displayed. In addition, the second welding condition and the fourth welding condition are the same as each other in items and different from each other in values (or patterns).

Note here that in step6, as to the welding condition in which recalculated results are the same as those calculated in step3, display of step4is maintained in step7.

Herein, an example of the method for determining a laser welding condition of this exemplary embodiment is shown specifically. Steps1to4are the same as specific examples of the first exemplary embodiment.

In step5, an operator changes the “recommended laser power: 2 kW” and “recommended welding speed: 2 m/min” which are displayed on display section13to the “recommended laser power: 4 kW” and the “recommended welding speed: 3 m/min.”

With this change, in step6, welding condition calculation section10calculates the “recommended welding pattern: weaving,” the “estimated strength: 4500 N,” and the “estimated weld (depth): 0.8 mm” Herein, the estimated strength and the estimated weld (depth) are changed, and the recommended welding pattern is not changed. Then, in step7, display section13displays the above-mentioned new welding conditions.

As mentioned above, according to this exemplary embodiment, also when an operator changes the welding conditions calculated by welding condition calculation section10, other welding conditions that have not changed can be recalculated and displayed. Furthermore, change of the welding condition may be repeated two or more times. That is to say, it is possible to repeat steps5to7.

Thus, an operator can further make a fine adjustment to the welding condition. Also in the fine adjustment, the same effect as in the first exemplary embodiment can be exhibited again. That is to say, other welding conditions are optimized in response to the fine adjustment by the operator.

Note here that the welding conditions changed by an operator is not necessarily limited to two, and one or three or more welding conditions may be changed. In once change and recalculation of the welding conditions (one cycle of steps5to7), change of all the welding conditions cannot be carried out. However, as a result of changing the welding condition and recalculation two or more times, all the welding conditions can be carried out.

INDUSTRIAL APPLICABILITY

A method for determining a laser welding condition and a laser welding device of the present disclosure can set an optimum welding condition considering a shape of a joint even in welding, and industrially applicable.