JPS62161478A - Welding control method - Google Patents

Abstract

PURPOSE:To enable the automatic correction for the variation in welding current by keeping the variation in the control signal I by the input of the welding current corresponding to the variation in the control signal E by the input of the impressing voltage of a wire feeding motor in about a fixed quantity by a differential control signal. CONSTITUTION:The figure (d) shows the instantaneous value example of the differential control signal ID in case of the welding arc being changed in wavy shape and the height of a welding torch 2a varying. The figure (e) shows A.ID<-1> that the reference amplifying degrees A are divided by a signal ID and the figure (f) shows the relation of the peak holding value A. (ID<-1>) of A.ID<-1> of the figure (a) to the reference threshold value S for discriminating by comparing therewith. The figure (g) shows the discriminating result example [A.(ID<-1>)'-S] discriminated by performing the substraction of A.(ID<-1>)' by the figure (f) from the threshold value S by a substraction means 8B. And said discriminating result of the figure (g) becomes the value corresponding to the dissociation in the height of the torch 2 and the set reference value. The servo mechanism 8F in Z axial direction can therefore be driven by driving a servomotor 8E by passing it through a dead zone width operating means 8C and servo amplifier 8D.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a welding control method applied to an arc welding robot or an automatic arc welding device.

[Prior Art] FIG. 7 shows an example of the configuration of a conventional welding arc sensor discriminator. In FIG. 7, a DC voltage is applied from a welding power source 5 between the workpiece 1 (base metal) and the welding torch 2, and the welding wire 3 is held between rollers 4a and is driven by a wire feeding motor 4.

As shown in FIG. 7, the input signal related to the welding current
1, performs discrimination using a discrimination threshold value S, and outputs the results.

[Problem that the invention seeks to solve]

FIG. 8 shows the wire feeding motor applied voltage EM and wire feeding speed Wy1 when operated according to the functional configuration shown in FIG. 7.
An example of an electrical characteristic curve of a welding arc due to a change in wire protrusion length Ex is schematically shown.

As can be seen from Fig. 2, the welding arc, which was initially stable at the operating point Po (arc characteristics Ao N 1! flow Io), changes to the operating point P1 (arc characteristics A1, current It) on the same power source characteristics. If the voltage shifts from EMO to EM, the cause is (1+)
This is because the wire feeding speeds W and Q have changed to Wrl.

(2) This is due to the wire protrusion length changing from EXO to EXl.

There are two possibilities.

According to similar logic, there are two possible causes for the transition from operating point P to P2. However, for the arc sensor function, only the change in welding current due to the change in Ex described in item (2) above is an effective information source, and changes in welding current due to other causes are noise sources. This hindered the stability, accuracy, and operability of the system.

As can be seen from the explanation of FIG. 8, the only information necessary for the arc sensor is the change in the welding current I due to the change in the wire protrusion length Ex, and the information on the applied voltage Eu of the wire feed motor 4 (i.e., the wire feed speed). The change in welding current due to the change in Wr) is unnecessary and must be eliminated.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional art, and is capable of automatically correcting changes in welding current and ensuring excellent operability. The purpose of this invention is to provide a welding control method that can be easily installed.

[Means for solving problems]

The welding control method of the present invention sets a control signal I by inputting a welding current I and a control signal EM by inputting an applied voltage of 2M to the wire feeding motor, and changes the control signal 1 due to a change in the control signal E. A differential control signal ID having a substantially constant value is calculated by canceling the control signal EM, regardless of the value of the control signal E, and this differential control signal ID is used as a control signal source for the arc sensor. This is the next one.

[Effect]

This invention maintains the change in the control signal l caused by the change in the control signal EM at a substantially constant value using the differential control signal In, and based on this, the distance between the welded material and the welding torch, and the distance between the welded material and the contact tip in the welding torch. Set either distance or welding torch height □ Automatically follow the standard value.

〔Example〕

Embodiments of the welding control method of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the basic functional configuration of a welding control device applied to one embodiment, and FIG. 2 shows a specific example of the configuration of the differential control signal ID program circuit. .

In FIGS. 1 and 2, the same parts as in FIG. 7 will be described with the same reference numerals. First, FIG. 1 shows a MIG

FIG. 2 is a basic functional configuration diagram for calculating a differential control signal ID in the present invention for butt welding and fillet welding performed by C02 arc, inch shield arc, and submerged arc welding methods.

In FIG. 1, a welding voltage is applied between the workpiece 1 (base metal) and the welding wire 3 by a welding power source 5 to generate an arc between the workpiece 1 and the welding wire 3. I'm trying to do some welding.

The welding wire 3 is fed into the welding torch 2 by a loaf '4&, and the roller 4a is driven by the wire feed motor 4.

Further, 7 indicates the voltage EM applied to the wire feed motor, and 6 indicates the welding current (■). This welding current 6 and the wire feed motor applied voltage EM7 are the differential control signal ID calculation circuit 8.
I am trying to input it into . This differential control signal IO calculation circuit 8 outputs a differential control signal ID9.

Next, according to FIG. 2, the differential control signal 1. A specific example of the configuration of the arithmetic circuit will be explained. In this second factor, variable resistors VRJ and VR2 are connected between the input terminals tl and t2 and the common terminal 00M, respectively.

A welding current I6 is input to the input terminal t, and a wire feeding motor applied voltage EM7 is applied to the input terminal t2.

The movable terminal of the variable resistor VRI is the (a) of the operational amplifier OPI.
The ←) input terminal of the operational amplifier OPI is connected to the common terminal COM through the resistor R1t-, and the ←
) A resistor R3 is connected between the input terminal and the output terminal.

From the output terminal of the operational amplifier OPI, a control signal (IT pressure) caused by the welding current is applied to the (g) input terminal of the operational amplifier OP3 via a resistor R4. The input terminals of the operational amplifiers OP and 9 are connected to the common terminal COM K via a resistor R5.

On the other hand, the wire feeding motor applied voltage E and the input control signal (voltage) 5M are applied to the subtracter D from the movable terminal of the variable resistor VR2.

Further, a variable resistor VRJ is connected between the power supply VCC and the common terminal 00M, and a bias voltage E is generated at the movable terminal of the variable resistor VRJ.
A bias voltage Ea is applied to the subtracter DJ.

The subtracter DJ subtracts the bias voltage E3 from the control signal EM, and applies the subtraction result to the ←) input terminal of the operational amplifier OP2.

The ←) input terminal of the operational amplifier OP2 is connected to the common terminal COM via the resistor R2.

A feedback circuit K is connected between the H input terminal and the output terminal of the operational amplifier OP2. From the output terminal of the operational amplifier OP2, a control voltage ΔEMt'' is applied to the input terminal of the operational amplifier OP3 via a resistor R6.

This control voltage ΔEM is the control voltage calculated by K(EM-EB) (K is the amplification degree related to εM-EM, which is nonlinear)
shows.

There is a resistor R7 between the input terminal and output terminal of the operational amplifier OP3.
is connected. The output of this operational amplifier OP3 is passed through a Lono bus filter LPF to produce an output signal JD-1-i.
I am trying to output E.

Next, FIG. 3 shows a specific configuration example of a welding control device (arc sensor) for detecting a welding torch height deviation and automatically following the height setting value based on the differential control signal LD. Figure 3 (,) shows the configuration near the joint in butt joint # welding, Figure 3 (b) shows the configuration around the joint in corner joint welding, Figure 3 (el is the configuration of the welding control device, W
Fig. 3 (d) to Fig. 3 (g) are the control bag T in Fig. 3 (,).
Each of the control signals for the calculation process by itK is shown.

Next, the welding control method of the present invention will be explained. Fourth
The figure shows wire feed motor applied voltage 8M1 wire feed speed W
An example of a change in welding current (■) due to a change in is shown. This fourth
As can be seen from the figure, the wire feeding motor applied voltage EM
(i.e., the wire feed speed W, ) and the equitangent DC I are almost proportional to each other, and the part of the change in the welding current I that is due to the change in the pressure EM applied to the wire feed motor is , which can be calculated and determined from changes in the voltage EM applied to the wire feed motor.

FIG. 5 shows the detection principle of the differential control signal In (arc sensor control signal source) based on the specific configuration example shown in FIG.
Figure 6 shows the differential control signal ID using the operating principle shown in Figure 5.
The detection functions are shown respectively.

As can be seen from these figures, the differential control signal ID basically consists of a control signal chamber due to the welding current ■ input and a control signal E due to the wire feed motor applied voltage EM input, io=Ten. K (EM-El) where Em is a bias voltage and K is a quantity given by a coefficient (nonlinear), which is used as an input signal for welding control.

Next, the operation of the configuration example shown in FIG. 3 will be explained. Fig. 3(d) shows an example of the instantaneous value of the differential control signal ID when the welding arc changes in a wave-like manner and the height of the welding torch 2a fluctuates, and Fig. 3(,) shows the reference amplification degree A. is divided by the differential control signal ID in FIG. 3(d).
ID-1 is shown, and Fig. 3(f) shows A/l in Fig. 3(,).
Fig. 3(g) shows the relationship between the peak hold value A ・(Jo-')' of o-1 and the standard threshold value S for comparison discrimination of A, (lo-1)'. f) A.
Example of discrimination result [A・(
In-')'S) are shown respectively.

The discrimination result in FIG. 3(g) [A・(LD-')'-8
] is a value corresponding to the difference between the height of the welding torch 2 and the set reference value, so this is passed through the dead band width calculating means 8C and the servo amplifier 8D to the servo motor 8Ef! : By driving, the z-axis direction servo mechanism 8F is driven.

〔Effect of the invention〕

As described above, according to the welding control method of the present invention, a control signal based on the welding current input and a control signal based on the wire feed motor applied voltage input are set, and a change in the former control signal is caused by a change in the latter control signal. By canceling the difference with the latter control signal, we calculated a differential control signal with a nearly constant value, and used this to automatically follow the distance between the welding material and the welding torch in accordance with the set reference value. , automatic correction is made for changes in welding current, providing excellent operability.

Furthermore, it can be easily installed on existing arc welding robots or automatic arc welding equipment, and it is possible to improve these functions and reduce costs.

Furthermore, the main parts can be configured with simple analog circuits, making it possible to achieve low cost and automatic control of welding-related equipment.
This will provide an effective clue to realizing labor savings through robotization.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic functional configuration of a welding control device applied to an embodiment of the welding control method of the present invention, and FIG.
Welding diagram? 1TIJ Σ differential control signal ID in control device
Block diagram showing the specific configuration of the arithmetic circuit, FIG. 3(a)
3(b) shows the configuration near the joint in butt joint welding to which the welding control method of the present invention is applied, and FIG. 3(b) shows the configuration near the joint in corner joint welding to which the contact control method of the above is applied. Figure 3(c) is a block diagram showing the detailed configuration of the welding control device shown above, and Figures 3(d) to 3(g) are calculations by the welding control device shown in Figure 3(c), respectively. Fig. 4 is a diagram showing the welding current change due to changes in wire feed motor applied voltage and wire feed speed in the welding control method same as above, and Fig. 5 is a diagram showing the welding current change in the welding control method same as above. A diagram showing the control signal detection principle; FIG. 6 is a diagram showing the differential control signal function based on the operating principle of FIG. 5;
Fig. 7 is a diagram showing the configuration of a conventional arc sensor discriminator for melting and tanning, and Fig. 8 is a diagram showing the voltage applied to the wire feed motor, the wire feed speed, and the wire protrusion of the arc sensor discriminator for welding shown in Fig. 7. FIG. 3 is a schematic diagram of a magnetic characteristic curve of a welding arc with a change in length; DESCRIPTION OF SYMBOLS 1... Material to be welded, 2... Welding torch, 3... Welding wire, 4... Wire feeding motor, 4a... Roller, 5... Welding power source, 6... Welding current , 2... Wire feeding motor applied voltage, 8... Differential control signal calculation circuit, 9... Differential control signal ID output. Applicant Enoki Patent Attorney Takehiko Suzue Figure 7 Figure 8

Claims (1)

[Claims] A welding voltage is applied between the workpiece and the welding wire from a welding power source with DC constant voltage characteristics to generate an arc between the two, and a wire feeding motor that feeds the control signal A based on the welding current input and the welding wire. A control signal B is set based on the voltage applied to the wire feeding motor to be applied to the wire feed motor, and a change in the control signal A due to a change in the control signal B is offset by the control signal B to calculate a differential control signal C having a substantially constant value. This differential control signal C is input to the welding control means, and any one of the distance between the welding material and the welding torch, the distance between the welding material and the contact tip in the welding torch, and the welding torch height is set in accordance with the set reference value. A welding control method characterized by automatic tracking.