JPH02217168A - Automatic arc welding method using robot - Google Patents

Abstract

PURPOSE:To release welding in the exceedingly short time and to safely move a robot by moving the robot when a prescribed counted value is attained by impressing the high voltage in synchronization with a point of time when a welding current detection signal is turned off. CONSTITUTION:The robot is moved after a prescribed count is executed from the time when a coast of a wire is finished according to a welding finishing signal from the robot and a welding current is not made flow. As a result, the necessary voltage is impressed simultaneously with the finishing of the coast and the time when the robot can be moved is decided only by detecting the welding current without detecting separately the release of the presence or absence of welding. By this method, the sure welding release is carried out in the exceedingly short time and the robot is prevented from being moved in a welding state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic arc welding method using a consumable electrode using an arc welding robot.

[Conventional Usage Technology] In automatic arc welding methods using arc welding robots, welding of the welding wire at the end of welding is a major problem that hinders automation. It is necessary to detect welding at the end of welding, apply a large welding voltage, and automatically release the welding.

Conventionally, the following method has been used to detect welding at the end of welding and apply a large welding voltage.
In Publication No. 9-87983, a welding detection voltage is applied from the robot side in synchronization with a welding end command from the robot, a voltage drop due to welding is detected, and a core wire cutting tool is installed facing the welded part. It is issuing a command to activate. In addition, in JP-A-59-92172, after cutting off the welding current at the end of welding, a detection voltage is applied between the welding wire and the workpiece, and when current flows, it is determined that welding has occurred, and a large welding current of about the same magnitude is applied to the welding wire. I'm trying to apply voltage. Furthermore, in Japanese Patent Application Laid-Open No. 59-229288, the value of the armature current of a wire guide rotation motor due to bending of the wire guide for feeding the wire is detected, and the increase in the detected current is used to feed the wire. The system detects the condition and stops welding work when the wire buckles or the feed rate decreases.

In addition, in Japanese Patent Application Laid-Open No. 63-93476, the welding state is detected when the arc generation has stopped, even though the welding wire is being fed immediately after the start of welding and during welding, and there is inert gas, and the welding state is detected when the arc generation has stopped. If there is, a welding release current is supplied to release the welding. Further, when welding is completed, welding is similarly detected, and if welding is present, welding release current is supplied to release the welding.

[Problems to be Solved by the Invention] As described above, in the method of detecting welding and releasing the welding, it is necessary to provide a separate cutter device for operating the core wire cutting tool when welding is detected. , which detects the armature current of the wire feed motor, because the wire feed motor of a normal welding machine is equipped with a large reducer, changes in the armature current of the feed morph due to changes in the feed resistance are It is very difficult to detect changes in feed resistance that are small and change as the wire bends.

Furthermore, the method of detecting welding by applying a voltage between the welding wire and the work from a welding detection device at the end of welding and detecting the voltage or current has a problem in the timing at which the voltage is applied from the welding detection device.

In other words, even if the robot sends a welding end signal to the welding machine, the welding machine does not immediately end welding.
Welding voltage is applied for a few tenths of a second in order to burn off the loose part of the wire and adjust the shape of the tip of the wire. This time varies somewhat depending on the state at the end of welding, but during this time an arc is generated, the wire is ignited, and when the arc is cut off, a no-load voltage is applied between the wire and the workpiece.

In other words, if the voltage for detecting welding is applied while the welding voltage is applied at the time of application, the detected voltage,
The current is not stable depending on the conditions of the welding voltage and welding current, and reliable welding detection cannot be performed.

Furthermore, if a method is used in which the welding detection voltage is applied after the welding voltage has become unloaded, a wasted time of several tenths of a second will occur, as the welding voltage must be waited until the application of the welding voltage is finished.

In addition, applying a detection voltage after cutting off the welding current at the end of welding can reliably detect welding, but after confirming that the welding current has been cut off, applying a voltage for detecting welding is applied to detect welding. Based on the results, if it is welding, a high welding voltage must be applied. This increases the time it takes to detect welding and release welding, making it difficult for robots to weld in seconds. Not suitable for work.

The present invention has been made in view of the above problems, and
The purpose is to reliably release welding in as little time as possible and to move the robot safely.

[Means for Solving the Problem] In order to achieve this object, the present invention does not detect welding by applying a welding detection voltage between the welding wire and the workpiece in automatic arc welding using an arc welding robot. The first feature is that only the welding current flowing through the welding wire is detected at the end of welding.

This means that while the welding current is flowing, the arc state
Regardless of the welding state, the robot must not move, and in particular, it is not necessary to stop the robot only in the welding state. Therefore, welding state and welding No distinction is made between the detection states, so there is no need to consider the timing of welding detection, and there is no need for a device to apply a voltage for welding detection.

In addition, regardless of whether there is welding or not, the welding machine applies a high welding voltage in synchronization with the time when welding current stops flowing, and the robot counts the time when no current is flowing through the welding wire and continuously The second feature is that the robot is prevented from moving until a predetermined count value is obtained. Therefore, if welding of the wire occurs, the wire at the welded portion is blown away by a high voltage, and a welding current flows. The robot's counter is reset and starts counting again when the welding is released. Based on this count, the robot waits at that point without moving until the welding current stops flowing for a certain period of time, and moves to the next point after confirming that no current flows for a certain period of time and there is no risk of welding.

In this way, the present invention detects welding, instructs to apply a high voltage in response, and detects release of welding and lowers the voltage, allowing the exchange of signals between the robot and welding machine. There is no wasted time associated with communication.

Furthermore, since a high welding voltage is applied to the welding terminal after welding is completed to release the welding, and the robot synchronizes the counter with the welding current value, large welding such as the tip itself sticking to the workpiece does not occur. If the welding is not released even when a large voltage is applied, too much current may flow and the welding machine may malfunction due to overcurrent. In this case, the welding machine malfunctions and the welding current stops flowing, so welding starts and the robot moves without welding. Therefore, in the present invention, before the robot moves, it is checked whether the welding machine is normal or not. Is going. If the welding machine is not working properly, there is no point in continuing welding work, so the robot is stopped.

(Function) As described above, the present invention is configured such that the robot is moved after a certain count is performed from the time when the wire extension is finished and the welding current stops flowing due to the welding end signal from the robot. Therefore, by applying the necessary voltage at the same time as the welding ends, it is possible to determine when the robot can move only by detecting the welding current, without separately detecting the presence or absence of welding.

[Example 1] The present invention will be specifically explained based on a time chart shown in the drawings.

FIG. 1 shows a time chart when no welding occurs. When the welding execution command signal 1 from the robot is turned off, the wire feed motor stops feeding, and the welding voltage 2 is switched to a low voltage for burning out the wire and adjusting the shape of the wire tip. . Since the feed motor is stopped, the welding current flows until the welding current ignites and then stops. When the welding current stops, the welding current detection signal 3 changes from on to off. Welding current detection signal 3
When the welding voltage 2 is turned off, the welding voltage 2 is switched to a high voltage that can be removed even if welding occurs, and at the same time the robot starts counting 4.

If the welding current detection signal is off continuously for a certain period of time or more, it means that no welding has already occurred, so the robot is allowed to move, and at the same time the welding voltage 2 is set to no voltage.

Then, after confirming that the welding machine is normal, 0bot starts the next operation.

Next, FIG. 2 shows a chart when welding occurs.

When the welding execution command signal 1 from the robot is turned off, the wire feed motor stops feeding, and the welding voltage 2 is switched to a low voltage for burning out the wire and adjusting the shape of the wire tip. . Since the feed motor is stopped, the welding current flows until the welding current ignites and then stops. When the welding current stops, the welding current detection signal 3 changes from on to off. When the welding current detection signal 3 turns off, the welding voltage 2 switches to a high voltage that can be removed even if welding occurs, and at the same time the robot starts counting 4.
Start. If welding occurs during counting, it is instantly blown away by the high voltage and welding current flows. When the welding current flows, the welding current detection signal 3 changes from off to on, so the robot's count is cleared. When the welding is blown away by the high welding voltage 2 and the welding current stops again, the welding current detection signal 3 changes from on to off.

When welding current detection signal 3 turns off, the robot starts count 4. If the welding current detection signal is continuously off for a certain period of time or more, it is determined that there is no welding and the robot is brought into a movable state, and at the same time the welding voltage 2 is set to zero.

After confirming that the welding machine is normal, the robot starts the next operation.

(Effects of the Invention) As explained above, in the present invention, a welding current is detected, a high welding voltage is applied in synchronization with the time when the welding current detection signal is turned off, and the off time is counted. Since the robot is moved when the count reaches a certain value, there is no need to apply a welding detection voltage during the unstable period immediately after welding, and stable welding release can be performed. Since no signals are exchanged with the welding machine, there is no wasted time associated with the exchange.

As a result, when robot welding requires only a few tenths of a second, welding can be reliably released in as little time as possible, and the robot can be prevented from moving in a welded state, allowing robots to perform welding quickly and reliably. You can get effects such as:

[Brief explanation of the drawing]

FIG. 1 is a time chart in the case where no welding occurs in the present invention, and FIG. 2 is a time chart in the case where welding occurs. ■=Welding execution command signal from robot 2: Welding voltage 3: Welding current detection signal 4: Robot count

Claims (1)

[Claims] 1. In automatic arc welding using an arc welding robot and a consumable electrode, the welding current flowing through the welding wire at the end of welding is detected, and the welding current flowing through the welding wire is synchronized when the current stops flowing through the welding wire. Along with applying a large voltage from the welding machine, the robot counts the time during which no welding current flows, allowing the robot to move to the next point when no current flows continuously for a certain period of time. An automatic arc welding method using a robot characterized by: 2. The robot counts the time during which welding current does not flow, and at the same time checks whether the welding machine is experiencing an abnormality such as overcurrent, and if an abnormality occurs, it stops the movement of the robot. An automatic arc welding method using the robot according to claim 1.