System and method for training welding technique by arc shape correction

Abstract

To solve problems of quality dispersion such as a welding defect, generation of the welding defect, and difficulty of control caused by torch operation training not based on a shape of an arc in arc welding.SOLUTION: To provide a system and a method for training welding technique by arc shape correction in which welding conditions are set so that an arc generated between the tip of a welding torch and a material to be welded during arc welding has a shape with the welding torch side as a vertex and the material to be welded side as a base, and a welder is notified within one second when the arc deviates from the set shape.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a welding training system and method that can produce high-quality welds by optimizing the shape of the arc during arc welding. [Background technology]

[0002] There are various methods for joining metal materials, such as metallurgical joining methods like welding, soldering, and brazing, as well as mechanical joining methods using bolts, but arc welding is widely used in manufacturing sites to join steel materials because it requires low capital investment, is highly efficient, and provides excellent strength. Furthermore, if the welding conditions are not correct, defects such as blowholes and poor penetration are likely to occur during welding, leading to the collapse of the structure, so it is important to perform welding that minimizes defects.

[0003] Currently, welding training is mostly done through on-the-job training, where experienced welders use their own experience to teach inexperienced welders, and companies with a shortage of welders are expending a great deal of effort on training. Also, although videos of welding work are available on the Internet, it is not possible to learn actual welding just by watching videos. Given this situation, several proposals have been made so far regarding training methods for welders.

[0004] JP 2020-98288 A, "Semi-automatic gas-shielded arc welding training system and method therefor" (Patent Document 1), proposes a training system and method to support efficient training to acquire proper torch operation for semi-automatic gas-shielded arc welding. The system uses an optical information detection device to read torch operation during semi-automatic gas-shielded arc welding work, and when the torch operation deviates from the appropriate range, notifies the welder in real time by vibration and prompts them to make corrections.

[0005] However, this method relied on the movement of the torch held by the welder, and welding was carried out without knowing whether the arc, which is the key, was being generated properly, resulting in inconsistency in the quality of the welds.

[0006] Japanese Patent Application Publication No. 2004-90041, "Manual Welding Support Device, Manual Welding Training Device, and Manual Welding Training Method" (Patent Document 2), proposes a training system that measures the arc length using a light meter or the like, and notifies the welder by voice or vibration that the arc length should be set to a preset standard length.

[0007] In this case, a reference length of the arc is required, but direct measurement is generally difficult, so torch height is used as an alternative, as described in

[37] and

[49] in Reference 2. Figure 4 shows the relationship between irradiance and torch height. For example, in case (a), the irradiance is 1 lux for every 1 mm of torch height change. The optimal height range is about 3 mm, which corresponds to 3 lux, but this level of irradiance change is within the empirical range of variation for arc light and cannot be controlled, so it cannot be used.

[0008] Unexamined Utility Model No. 58-71466 (Device for Determining Appropriate Arc Length of Arc Welder) (Patent Document 3) proposes using voltage to determine the arc length during welding.

[0009] However, although the structure of the device and the training method are described, there are no examples. Even if it were to be implemented, the inventors have experienced that the voltage during welding varies greatly, and the lack of examples makes it impossible to apply.

[0010] JP 2019-18240 (Welding control system, welding gloves, and welding training method) (Patent Document 4) proposes attaching acceleration sensors and angular acceleration sensors to welding gloves, and using a vibration device to inform the welder to optimize the heat input, welding speed, and welding angle based on the information.

[0011] However, this method also relies on the movement of the torch held by the welder, and it is unclear whether the arc is properly formed. Furthermore, while the contents of the training device are described in detail, there is no mention of the quality of the device, i.e., whether it reduces welding defects, except for a brief summary. Therefore, this invention cannot be used if the goal is to reduce welding defects.

[0012] Advances in technology have led to the proposal of many training systems using virtual reality (VR) in recent years. For example, Patent No. 7212822, "Welding Training System, Welding Training Method, and Program" (Patent Document 5), is available. However, VR is merely a simulation and is a desktop training method. Actual welding generates arc light, which is dazzling, hot, and produces spatter, making it both tedious and dangerous for humans. Since movements must be adjusted appropriately under these conditions, practicing with VR does not necessarily translate to actual welding. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Patent Publication No. 2020-98288 "Semi-automatic gas shielded arc welding training system and method" [Patent Document 2] JP 2004-90041 "Manual welding support device, manual welding training device and manual welding training method" [Patent Document 3] Published Utility Model No. 58-71466 "Device for determining the appropriate arc length of an arc welding machine" [Patent Document 4] Patent Publication No. 2019-18240 "Welding control system, welding gloves, and welding training method" [Patent Document 5] Patent No. 7212822 "Welding training system, welding training method, and program" Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention is a training system and method for welding that uses an actual arc to reduce defects during welding. It solves the problems that have been encountered in the past, such as variations in quality, the occurrence of welding defects, and difficulty in control, which are caused by torch operation training that is not based on the arc shape. [Means for solving the problem]

[0015] The inventors have conducted extensive research into the shape of the arc during arc welding and the occurrence of welding defects, and have discovered that in welds with few welding defects, the arc generated between the tip of the welding torch and the workpiece is often triangular, with the welding torch at the apex and the workpiece at the base, and that the angle between the workpiece and the arc is between 20 and 80°, preferably between 40 and 60°. In other words, maintaining constant the distance between the torch and the workpiece, the current, and other parameters to ensure the arc shape is as described above will enable good welding with few defects. Incidentally, when the workpiece has a groove and is tilted, the arc shape is the shape of the arc at its lowest point as seen from the side, that is, the angle between the workpiece and the arc when viewed from a 90° angle relative to the line connecting the electrode and the workpiece at the shortest distance.

[0016] The inventors have attempted to optimize welding current, voltage, amount of shielding gas, welding torch movement, and distance from the welding material using motion capture, but these ultimately constitute indirect control parameters for optimizing the arc shape. While the arc shape cannot be seen with the naked eye, it can be observed using a camera or other device through a filter, making it the most direct control parameter. However, because observing the arc shape has not been easy until now, training using indirect control parameters such as the above-mentioned conventional technology has been proposed. However, recent advances in camera and filter technology have made it possible to observe the arc by passing various filters through a camera. Therefore, the inventors devised a method using a high-speed camera to measure the angle between the workpiece and the arc under each condition in advance to determine the optimal range of conditions, and then providing feedback to the welder via a vibration device or other device when the condition deviates from that range. In this case, it is desirable for the angle between the workpiece and the arc to be between 20 and 80°, preferably between 40 and 60°.

[0017] Figure 1 shows the shape of the arc generated between the welding torch and the workpiece during semi-automatic welding and TIG welding.

[0018] Figure 2 shows the different arc shapes, where θ corresponds to the angle between the material to be welded and the arc, and the shape changes depending on the conditions.

[0019] Figure 3 shows the relationship between the angle between the workpiece and the arc (base angle) and the index used to score defects that occur when a welded test piece is bent. Defects were calculated based on the length and depth of cracks, blowholes, undercuts, and poor penetration, and points were deducted from a maximum score of 100. A zero-defect score was 100 points, while a crack length of 6.5 mm or longer, for example, was 0 points. The higher the score, the fewer defects there are and the better the welded material. Figure 3 indicates that an angle between the workpiece and the arc of 20 to 80° is rated as 50 points, and a value of 40 to 60° is rated as 100 points, indicating a welded material with fewer defects. Therefore, in the present invention, it is desirable for the angle between the workpiece and the arc to be between 20 and 80°, preferably between 40 and 60°. [Effects of the Invention]

[0020] By using this invention, defects in welding materials are reduced, welding quality is improved, and its variation is reduced. Furthermore, the training period for welding techniques is shortened, so the working hours of both the instructor and the student are reduced, and the problem of labor shortage is solved, so it is very valuable. [Brief explanation of the drawings]

[0021] [Figure 1] The diagrams show the arc shape between the welding torch and the workpiece during welding. (a) shows the shape of the arc between the welding torch and the workpiece during semi-automatic MAG welding, and (b) shows the shape of the arc between the welding torch and the workpiece during welding. [Figure 2] FIG. 10 is a diagram showing types of arc shapes. [Figure 3] FIG. 10 is a diagram showing the relationship between the angle (base angle) between the material to be welded and the arc and the number of welding bending test points. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be described in detail below. The welding technique training system using arc shape correction of the present invention is a training system in which an actual arc is generated to weld. This solves the problems that have been encountered in the past, such as quality variations and the occurrence of welding defects, and difficulty in control, which are caused by torch operation training that is not based on the arc shape.

[0023] Specifically, we provide a welding technique training system that sets welding conditions so that the arc generated between the tip of the welding torch and the workpiece during arc welding forms a triangle shape with the welding torch side at the apex and the workpiece side at the base, and notifies the welder within one second if the shape deviates from the set shape.In this case, the angle between the workpiece and the arc is set to 20 to 80 degrees, preferably 40 to 60 degrees.

[0024] The shape of the arc is affected by various factors, such as the current, voltage, type of shielding gas, gas pressure and flow rate, type and diameter of the welding rod or wire, the distance between the torch tip (or the tip of the welding wire in semi-automatic welding) and the material to be welded, as well as whether the torch is used forward or backward, posture, etc. Therefore, in this invention, rather than specifying and optimizing each of these conditions, we have attempted to optimize the shape of the generated arc.

[0025] The inventors have been investigating the effect of arc shape on welding defects. As a result, it was found that the arc shape is mountain-shaped, with the torch tip at the apex and the material to be welded at the base, as shown in Figures 1 and 2, and that the angle of the base is important. However, if the welding torch is moved away from the material to be welded and the arc is generated, the current value decreases, and the shape shown in Figure 2(C) may result.

[0026] In a bend test of a weld, which is commonly performed to evaluate weld defects, the effect of the angle of the base, or bottom angle, on the "weld bend test score," which is deducted according to the type, depth, and length of the defect, is shown in Figure 3. As mentioned above, the higher the score, the fewer defects there are and the better the weld material.

[0027] As shown in Figure 3, if the angle between the workpiece and the arc is between 20 and 80 degrees, the score is 50 points, and if it is between 40 and 60 degrees, the score is 100 points, resulting in a welded material with few defects. For this reason, in the present invention, it is desirable that the angle between the workpiece and the arc be between 20 and 80 degrees, preferably between 40 and 60 degrees. Within this range, there are few welding defects and little variation, making it easier to control.

[0028] The training procedure is as follows. First, the arc shape is observed with a high-speed camera and the base angle of the base is measured under each condition. The base angle is then compared for each distance between the torch tip and the workpiece to determine the distance corresponding to a set range of base angles, e.g., 40–60°. During training, the torch tip position is measured with a motion capture camera, and the distance to the workpiece is measured in real time during welding. If the distance deviates from a preset range, a signal is sent to a vibration device, which can alert the welder to an abnormality in near real time. A vibration device attached to the foot can be activated when the distance falls below a lower limit, and a vibrator attached to the arm can be activated when the distance exceeds an upper limit, making the welder intuitively aware of the abnormality. Notification methods include vibration, flashing light, and sound. The welder can then instantly adjust the distance between the torch and the workpiece to bring the arc shape within the appropriate range, thereby achieving the optimal arc shape and ensuring proper welding with fewer defects.

[0029] We mentioned that the quickest way to change the base angle during welding is to adjust the distance between the torch tip and the material to be welded, but instead of distance, you can also use the current value or gas pressure. Any factor that can be correlated with the arc base angle in advance and can be controlled to vary in real time during welding is fine. Furthermore, it would be even better if you could control the welding conditions while observing the arc shape in real time, rather than using a method that determines the correlation with the arc shape in advance.

[0030] When the base angle is below the lower limit, the distance between the torch and the material to be welded is too close, which makes it easier for too much current to flow and leads to defects such as undercuts.

[0031] When the base angle exceeds the upper limit, the arc shape becomes elongated and the current becomes small due to the distance between the torch and the material to be welded being too great, which results in less penetration and is more likely to cause defects such as poor penetration.

[0032] If the notification time is less than one second, the real-time nature of the notification will be poor and defects will occur in the welds made before the welder can make the corrections, so this number was set to notify as quickly as possible. This technology of providing feedback within one second is at a level where there are no particular problems in terms of communication speed. [Example]

[0033] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In semi-automatic MAG welding, 200 x 125 mm, 9 mm thick SS400 steel plates were butted together at a groove angle of 60°, a backing metal was attached, and a mixture of 80% Ar gas and 20% carbon dioxide was used as the shielding gas. The pressure was set to 0.3 MPa, the flow rate was set to 10 liters / min, and 1.2 mm diameter YGW12 welding wire was used. The welding was performed in a downward position. The welding machine current was set to 180 A, and three passes and three layers were performed. A high-speed camera was used to observe the arc shape under each condition in advance, measuring the angle (base angle) with the workpiece, and the distance between the torch and the workpiece was determined to be between 20 and 80 degrees. The training system measured the position of the torch tip using motion capture, and if the torch tip exceeded the lower limit of a predetermined optimum distance (±2 mm in both vertical and horizontal directions), it activated a vibrator attached to the left foot, and if it exceeded the upper limit, it activated a vibrator attached to the right arm to notify the abnormality. The notification time was generally around 0.1 seconds, but for experimental purposes, experiments were also conducted in which the time was intentionally delayed using a signal delay generator. The notification time was measured using a delay counter. The evaluation involved quantifying defects found in bending tests of welds according to their length and depth, and then subtracting points from a maximum score of 100. The bending tests were conducted in two ways: front bending, where the welded surface was bent with the convex part, and back bending, where the back surface was bent with the convex part. The higher the score, the fewer defects there were, and the better the welded material. Table 1 shows the experimental results.

[0034] (Table 1) JPEG2026021808000002.jpg69114

[0035] Inventions 1, 2, 3, 4, 5, and 6 all had arc base angles of 20 to 80°, and the time it took to notify the welder of an abnormality was within one second, so they received high scores in the welding bending test. Of these, Inventions 1, 2, and 3 were in the most preferable range of 40 to 60°, so they received a perfect score of 100 points for both front and back bending, and there was no variation in quality.

[0036] In Comparative Examples 1 and 3, the base angle was less than 20°, so undercuts occurred and the bending test scores were low.

[0037] In Comparative Examples 2 and 4, the base angle exceeded 80°, which resulted in poor penetration and low scores in the bending test.

[0038] Comparative Example 5 was under the same conditions as Invention 4, and the base angle of the arc was within the appropriate range, but as can be seen from Figure 3, it was in a region where some defects occurred, and therefore a correction of the operation was required. Invention 4 notified the welder of the abnormality within one second, allowing for the correction of the operation and earning a high score, but in Comparative Example 5, the time exceeded one second, which meant poor real-timeness and the welder was unable to correct his operation, resulting in many defects and a low score. [Industrial Applicability]

[0039] The use of this invention reduces defects in welding materials, improves welding quality, and reduces its variation. Furthermore, it shortens the training period for welding techniques, shortens the working hours of both the instructor and the student, and solves the labor shortage problem, so the potential for industrial application is very high. [Explanation of symbols]

[0040] 1. Nozzle at the tip of a semi-automatic welding torch 2 welding wire 3. Arc 4. Welding material 5 TIG welding torches 6 tungsten electrodes 7 Angle between the workpiece and the arc (base angle)

Claims

1. A welding technique training system comprising: an information processing unit that inputs the relationship between the angle between the arc generated between the workpiece and the welding torch tip during arc welding, with the arc having the welding torch side as the apex and the workpiece side as the base, that is, the base angle of the arc, and the distance between the workpiece and the torch tip, and further inputs the distance corresponding to the appropriate base angle; a judgment unit that judges when the distance during welding corresponding to the appropriate base angle falls outside the appropriate range; and a notification unit that notifies the welder of the deviation.

2. 2. The welding training system according to claim 1, wherein when the welding distance deviates from the appropriate distance, a signal is sent by a vibration device, and the time required to notify the welder is within one second.

3. 3. A welding technique training system according to claim 1, wherein the arc welding is semi-automatic welding.

4. A welding technique training method including a preparation step including a step of observing the shape of the arc during arc welding with a high-speed camera, a step of measuring the angle between the arc and the workpiece when the arc generated between the tip of the welding torch and the workpiece is shaped with the welding torch side as the apex and the workpiece side as the base, i.e., a step of measuring the base angle, and a step of determining the correlation between the distance between the torch tip and the workpiece and the base angle and grasping the appropriate distance corresponding to the appropriate base angle, and a training step including a step of measuring the distance between the tip of the torch and the workpiece when the distance deviates from the appropriate distance, sending a signal to a vibration device to notify the welder of the abnormality, and the notified welder correcting the distance to the appropriate distance.

5. 5. The welding technique training method according to claim 4, wherein the base angle is 20 to 80 degrees, preferably 40 to 60 degrees.

6. 6. The welding technique training method according to claim 4, wherein the time required for sending a signal to the vibration device when the appropriate distance is exceeded and for notifying the welder of the abnormality is within one second.

7. 7. A welding technique training method according to claim 4, 5 or 6, wherein a motion capture camera is used to measure the distance between the torch tip and the workpiece.

8. 8. A welding technique training method according to claim 4, 5, 6 or 7, wherein the arc welding is semi-automatic welding.

Images