JPS6272485A - Consumable electrode type arc welding machine - Google Patents

Abstract

PURPOSE:To delay the timing to translate to the main welding speed from the wire slowdown speed at the touch starting time and to reduce the generation of spatters by combining the discrimination of the touch start and the wire feeding speed control. CONSTITUTION:In case of a touch start, arc is generated with a short circuit current being passed simultaneously with a welding output control element 4 being driven. The arc voltage is therefore generated without any no load voltage being caused between output terminals 6. This state is detected by a no load voltage detecting circuit 10 to discriminate from the ordinary start. And when the signal of the touch start is inputted into a timer circuit 11 by the no load voltage detecting circuit 10, the timer circuit outputs the signal which changes to the main welding feeding speed from the slowdown speed after the preset time counting.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a consumable electrode type arc welding machine that performs arc welding by automatically feeding a wire, which is a consumable electrode.

Conventional technology Conventionally, in consumable electrode type arc welding machines such as CO2/M 80 welding machines, when welding starts, shielding gas starts flowing at the same time as the start switch input signal, and the arc The welding output control element is driven after the atmosphere shield guaranteed time. At the same time, the wire begins to be fed toward the welding base material. At this time, the wire is fed at a slowdown speed that is slower than the main welding feeding speed during steady welding. Eventually, the tip of the wire short-circuits to the welding base metal, a short-circuit current flows, and the energy causes the tip of the wire to melt and generate an arc between it and the base metal.

At this time, a welding current detection circuit built into the welding power source detects the short circuit current and outputs a welding current detection signal. After receiving the welding current detection signal, the wire is switched from the slowdown speed to the main welding feed speed during a period of 5 mS after receiving the welding current detection signal.

In the above sequence, arc generation can be performed very smoothly for a so-called normal start in which welding begins with the wire tip separated from the welding base metal.

Problems to be Solved by the Invention However, in robot welding, which has become rapidly popular in recent years, the welding torch is twisted or bent significantly from the end of welding to the start of the next welding, so the tip of the welding torch is The length of wire protrusion from
This is often a so-called touch start.

In such a case, if the conventional welding start method 7 is used, a large amount of spatter will be generated when the arc is generated, and this will adhere to the welding base, the shielding gas nozzle, etc., and will significantly deteriorate the welding quality.

Means for Solving the Problems In order to solve the above problems, the present invention provides a current detection circuit for detecting a welding start current, a no-load voltage detection circuit for detecting a no-load voltage, and a current detection circuit for detecting a no-load voltage. a timer circuit that counts time using the detection signal as a starting point and switches the time count setting value based on the output signal of the no-load voltage detection circuit; and a feeder that controls the speed of the wire feed motor in response to the output signal of the timer circuit. It is equipped with a speed control circuit,
When welding is started when no-load voltage is generated, the timing of switching from the wire feed slowdown speed to the main welding feed speed is delayed compared to when no-load voltage is generated.

Operation As described above, the present invention solves the conventional problems by combining touch start discrimination and wire feed speed control.

Among these, touch start determination is performed by the following actions. That is, in a normal start, the wire tip is away from the welding base material when the start switch for starting welding is turned on, and the wire tip is not in contact with the welding base material even immediately after the welding output control element is driven. Therefore, a no-load voltage appears across the output terminals.

Then, the wire is fed toward the welding base material at a slow-down speed, and only when the wire tip comes into contact with the welding base material, welding current flows and an arc is generated.

On the other hand, in the case of touch start, welding is started with the wire tip in contact with the welding base material, so welding current flows at the same time as the welding output control element is driven. Therefore, no no-load voltage appears between the output terminals.

In this manner, it is possible to distinguish between a touch start and a normal start depending on whether a no-load voltage appears between the output terminals.

Note that in a consumable electrode type arc welding machine, the no-load voltage is usually set to about twice the maximum arc voltage, and it is easy to distinguish between the two.

In the present invention, by delaying the timing of switching from the slowdown speed to the main welding feed speed during a touch start, the amount of wire fed can be reduced compared to a normal start.

This timing is determined mainly by the internal diameter of the passage in the welding torch, the length of the passage, and other specifications of the welding torch, and can be adjusted by the time count setting value of the timer circuit.

In this way, even during touch start, the amount of wire fed can be kept to a minimum, reducing the amount of spatter generated.
can be significantly reduced.

Embodiments Hereinafter, embodiments according to the present invention will be explained based on the attached FIGS. 1 and 2. FIG. 1 shows the configuration of this embodiment,
Figure 2 schematically shows a time chart of the output signals and voltages of each part in Figure 1, where a is a touch start;
b is for a normal start.

In the case of a normal start, when the start switch is pressed, a shield gas actuation circuit (not shown) is activated, and then the welding output control element 4 is driven by the output control circuit 8. Note that at startup, in order to make startup smooth, it is customary to output a larger output than during steady arcing.

At this time, since the wire tip is not in contact with the welding base material 14, a no-load voltage appears at the output terminal.

At the same time as the welding output control element 4 is driven, the wire 13 is fed toward the welding base material 14 by the wire feeding motor 15, but in order to start smoothly, the welding feeding speed is lower than the actual welding feeding speed during steady arc. The feeding speed control circuit 1e also controls the feeding speed to a low slowdown speed.

Therefore, after a certain period of time, the wire tip becomes the weld base material 1.
4, a short-circuit current flows, and the energy melts the wire, turning it into an arc. At this time, the output terminal voltage changes from a no-load voltage to a normal arc voltage waveform.

During this time, a no-load voltage appears at the output terminal 6, and the no-load voltage detection circuit 10 detects that no-load voltage is applied, and normal start wire feeding speed control is performed. That is, the current detection circuit 9 detects that the current has shifted to an arc, and the timer circuit 11 starts the feeding speed control after counting the time of 0 to 5 mS, which is preset in the timer circuit 11 for a normal start, using the detection point as a starting point. A signal is sent to the circuit 16 to switch from the smee-down speed to the main welding feed speed. In this way, the wire feed motor 15 changes from the slowdown speed to the main welding feed speed within 0 to 5 mS after current detection.On the other hand, in the case of touch start, the welding output control element 4 is driven. At the same time, a short circuit current flows and an arc occurs. Therefore, an arc voltage is generated between the output terminals 6 without a no-load voltage appearing.

This state is detected by the no-load voltage detection circuit 10 and is distinguished from the normal start. When a touch start signal is input to the timer circuit 11 by the no-load voltage detection circuit 1o, the timer circuit 11 causes the feed speed control circuit 16 to slow down the speed after counting a preset time for touch start. Outputs a signal to switch from to the regular welding feed speed. The time count setting value at this touch start is determined by the specifications of the welding torch, but in the case of the commonly used 37ff)-chi, it is 1 o to 60 m.
5, and 4QmS was set in this example.

As another example, only the time count setting value for touch start is set in the timer circuit, and in the case of a normal start, the current is not passed through the timer circuit 11, and the main welding is started from the slowdown speed immediately after the current is detected. It has been confirmed that a configuration including a switch circuit that switches depending on the output state of the no-load voltage detection circuit 1o to shift to the feeding speed has the same effect as the above embodiment. The time count setting value of the timer circuit 11 in this case is the same as in the previous embodiment.

Effects of the Invention As described above, according to the present invention, the amount of spatter generated during arc startup is reduced by delaying the timing of transition to the regular welding feed speed in the case of touch start and adjusting the amount of wire feeding at arc startup. can be significantly reduced.

In this case, it is particularly effective for automatic welding such as robots, which have a very high probability of touch start, and can greatly contribute to improving welding quality and reducing the number of maintenance steps for shielding gas nozzles, etc.

FIG. 1 is a block diagram of a consumable electrode type arc welding machine showing one embodiment of the present invention, and FIGS. 2a and 2b are signal waveform diagrams of various parts in FIG. 1.

9... Current detection circuit, 1Q... No-load voltage detection circuit, 11... Timer circuit, 13.
... wire, 14 ... welding base material, 16.
...Wire feeding motor, 16...Feeding speed control circuit.

Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
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Claims (1)

[Claims] a current detection circuit that detects a welding start current; a no-load voltage detection circuit that detects a no-load voltage; and a current detection circuit that performs time counting using the current detection signal of the current detection circuit as a starting point and based on the output signal of the no-load voltage detection circuit. It is equipped with a timer circuit that switches the time count setting value, and a feed speed control circuit that receives the output signal of the timer circuit and controls the speed of the wire feed motor. , a consumable electrode type arc welding machine characterized in that the timing of switching from the wire feed slowdown speed to the main welding feed speed is delayed from when no-load voltage is generated.