JP2000079475A - Automatic welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic welding machine that gives no adverse effect to an electric circuit even if a welding head is attached onto an insulator. SOLUTION: A pulse motor driving circuit 2 in an NC device 1 gives a command pulse to a pulse motor 4 installed in a welding head 3, and drives the motor so that a welding torch comes to a welding torch position determined by the NC device 1. The housing of the pulse motor 4 is insulated from the ground while the entire electric circuit is grounded only on the side of the pulse motor driving circuit 2 of the NC device 1. Consequently, as in the case of the welding of a plastic lined steel pipe, no adverse effect is given to the electric circuit even if the housing of the pulse motor 4 is not grounded by attaching the welding head 3, through an insulator, to an object to be welded since the circuit is originally designed on the assumption that the housing is used without grounding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic welding machine, and more particularly to a welding machine for welding a circumferential seam portion of a pipe without a backing metal. An automatic welding machine of the type that controls the moving speed etc. and generates an arc between the welding wire protruding from the tip of the welding torch and the workpiece and melts the welding wire to weld the workpiece. It is.

[0002]

2. Description of the Related Art FIG. 2 shows an example of the construction of a welding machine for automatically welding a circumferential seam of a pipe. In FIG. 2, a personal computer 21 is a CAD for automatic welding.
This is for creating data, and the created data is recorded on the flexible disk 21a. The control device (NC device) 22 is for performing substantial control of the automatic welding (control of the power source and the position of the welding torch, etc.)
The CAD data is read from the flexible disk 21a. Then, the control device 22 sets actual welding conditions using the read data, and sets various welding parameters in accordance with the set conditions by using data recorded in advance in a logic table.

Further, the control device 22 converts the set welding parameters into an NC language used for actual welding control, and records the converted language as control data in an internal memory in the form of a control table. The power supply device 23 and the welding head 24 are driven and controlled using the control data recorded in the memory, and the arc scanning related correction is performed using the measured and analyzed values of the pulse voltage waveform and the pulse current waveform. ing. The main control items of the control device 22 are the welding voltage and current of the welding head 24, the weaving of the welding torch 27 mounted on the welding head 24 with respect to the pipe groove 30, the moving speed of the welding head 24, and the like. is there.

[0004] The welding head 24 is connected to a power supply device 23 by a power transmission cable 28, and is mounted on a guide rail 29 wound around the outer circumference of the pipe so as to be movable in the circumferential direction. On the welding head 24, a wire supply unit 26 for supplying a welding wire to a welding torch 27 is mounted.

FIG. 3 shows an electrical connection between the control device 22, the power supply device 23, the welding head 24, and the pipe 25. As can be seen from the figure, a pulse welding voltage is applied from the power supply device 23 between the wire 31 of the welding head 24 and the pipe 25 via the power transmission cable 28. Thereby, an arc is generated between the wire 31 and the surface of the pipe 25. The wire 31 is fed at a constant speed, melted by an arc to become a deposited metal, and solidifies in the pipe groove 30 to form a base material.

FIG. 4 shows a detailed view of the welding head 24.
The welding head 24 is located on the outer circumference of the pipe (indicated in hours and minutes).
Servo mechanisms are provided for the X-axis, the Y-axis of the weaving groove of the welding torch 27 in the width direction (pipe axis direction), the Z-axis in the welding height direction (pipe radial direction), and the welding torch pivot axis. The four axes are controlled by the control device 22. Weaving is two-dimensional weaving.
That is, the welding torch 27 is moved along the groove in the Y-axis direction and the Z-axis direction orthogonal to the welding progress direction (X-axis).

[0007]

In such an automatic welding machine, the welding head 24 is, as shown in FIG.
In order to determine the X-axis position, the Y-axis position, the Z-axis position, and the rotation axis position of the welding torch, each has a servomotor 33 and a pulse generator 34, and is built in the control device 22. Positioning is performed by the servo amplifier 32. The housings of the servo motors 33 are dropped to the ground potential through the guide rail 29 and a conductive material such as a steel pipe as a welded body. In these servo motors 33, all leakage currents generated during driving are not returned to the control device 22 side, and a part of them is discharged to the ground through this ground circuit.

[0008] However, some objects to be welded, such as plastic lining pipes, have their surfaces covered with an insulator. When the guide rail 29 is installed on such a workpiece and the welding head is attached, the servomotor 33 housing cannot be grounded because of the insulator on the surface of the workpiece. Therefore, all the leak current generated in the servo motor 33 flows to the servo amplifier 32 side, and this current may damage the servo amplifier 32.

The present invention has been made to solve such problems, and an object of the present invention is to provide an automatic welding machine which does not adversely affect an electric circuit even when a welding head is mounted on an insulator. And

[0010]

A first means for solving the above-mentioned problems is that the position and the moving speed of a welding torch are controlled by an NC device, and a welding wire projecting from a tip of the welding torch and a workpiece to be welded. An automatic welding machine for welding an object to be welded by generating an arc between them and melting a welding wire, wherein a welding head for driving a welding torch is attached to the object to perform welding. An automatic welding machine is characterized in that a drive motor for positioning a welding torch is of a type in which a housing thereof and an internal electric circuit are insulated.

The drive motor of the present invention has a housing insulated from an internal electric circuit, and is not designed so that leakage current of the internal circuit flows to the ground through the housing. Therefore, even when the welding head is attached to the workpiece via the insulator, no trouble occurs because the housing of the drive motor cannot be grounded.

A second means for solving the above-mentioned problem is the first means, wherein the drive motor is a pulse motor (claim 2). The pulse motor has an advantage that it is easy to completely insulate the external housing from the electric circuit and does not require a feedback system, so that a pulse generator or a tachometer is not required.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is an NC device (control device), 2 is a pulse motor drive circuit, 3 is a welding head, 4 is a pulse motor for determining a welding torch position. The pulse motor drive circuit 2 in the NC device 1 issues a command pulse to a pulse motor 4 provided in the welding head 3 so as to drive the welding torch at the welding torch position determined by the NC device. As can be seen from a comparison between FIG. 5 and FIG. 1, the housing of the pulse motor 4 is insulated from the ground, and the entire electric circuit is grounded only on the pulse motor drive circuit 2 side of the NC device 1. Therefore, even when the housing of the pulse motor 4 cannot be grounded by attaching the welding head 3 to the work to be welded via the insulator, as in the case of welding a plastic-lined steel pipe, the housing is originally unmounted. Since the circuit is designed on the assumption that it is used with the ground, there is no adverse effect on the electric circuit.

Further, in this embodiment, since a pulse motor is used as a drive motor for positioning the welding torch, a feedback device such as a pulse generator or a tacho generator is not required. The drive motor is not limited to a pulse motor, but may be a servo motor as long as the housing is insulated from an internal electric circuit.

[0015]

As described above, according to the first aspect of the present invention, the drive motor for positioning the welding torch is of a type in which the housing and the internal electric circuit are insulated. Since the welding head is used, even when the welding head is attached to the workpiece through an insulator,
No trouble occurs because the housing of the drive motor cannot be grounded.

According to the second aspect of the present invention, since the pulse motor is used as the drive motor, it is easy to completely insulate the external housing from the electric circuit.
No pulse generator or tacho generator is required.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a configuration of a welding machine that automatically welds a circumferential seam of a pipe.

FIG. 3 is a diagram showing an electrical connection relationship of each device constituting the automatic welding machine.

FIG. 4 is a view showing details of a welding head of the automatic welding machine.

FIG. 5 is a block diagram showing a control circuit of a welding head drive motor in a conventional automatic welding machine.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1: NC device (control device) 2: Pulse motor drive circuit 3: Welding head 4: Pulse motor

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichi Maeda 1225-47 Tenjinbayashi-cho, Hitachiota City, Ibaraki Pref.

Claims (2)

[Claims] 1. An NC device controls a position, a moving speed, and the like of a welding torch, and generates an arc between a welding wire projecting from a tip of the welding torch and a workpiece to melt the welding wire. In an automatic welding machine for welding a welded body, in which a welding head for driving a welding torch is attached to a workpiece to perform welding, a drive motor for positioning the welding torch has a casing and an internal portion. An automatic welding machine characterized in that the electric circuit is of an insulated type. 2. The automatic welding machine according to claim 1, wherein said drive motor is a pulse motor.