Modification and Application of Spot Welding Machine and Seam Welder in Coiling Factory

Welders are the most critical equipment in the steel drum manufacturing industry. The quality of the welds is a direct proportion of the finished steel drums. At present, in order to improve the quality and efficiency of welds and improve the product qualification rate, we Focusing on the research and modification of the domestic seam welding machine control system, the KJF-160 seam welding machine control system has been successfully developed. The control system has the following features.

1. The whole machine adopts a modular structure;

2, using frequency conversion technology and three-phase different motor drive;

3, the use of air-cooled SCR silicon welding module, adjust the welding current;

4, the whole machine adopts PLC control;

5, the current regulation adopts digital given, high adjustment accuracy;

6, welding voltage, current, given value, motor speed digital display.

Second, seam welding principle

Seam welding is pressure resistance welding. Resistance welding, also known as contact welding, is the use of the resistance heat (Q=I2Rt) generated by the contact between the two weldments as the welding heat source, heating the welding locally to high temperature plasticity, and forming a firm joint under pressure. method.

Because the contact resistance between the weldments is limited, in order to allow the welding to reach a high temperature in a very short time (0.01 seconds - several seconds) to reduce the heat loss, so the use of high-power (tens of thousands - tens of thousands of volts) high-power power supply . Resistance welding has the advantages of high production efficiency, small welding distortion, good working conditions, no need to add filler metal, and easy automation. However, the equipment is more complex and consumes more power. It has certain restrictions on the thickness and cross-sectional shape of the weldment, and it is generally suitable for mass production in batches.

Resistance welding can be divided into three types according to different types of joints. Among them, spot welding and seam welding are most widely used in the barrel making industry.

(I) Spot welding

The two thin plate weldments are placed between the upper and lower cylindrical electrodes and pressed to heat them (Figure a). Because the electrode made of a copper alloy with good thermal conductivity is used, and the water in the middle is cooled, the heat generated by the contact resistance between the electrode and the weldment is quickly lost. The heat is mainly concentrated at the contact between the two weldments. The metal is partially melted to form a nugget, and then the power is turned off to maintain or increase the pressure of the electrode. The nugget metal cools and crystallizes under pressure, which forms a dense solder joint. Spot welding can be performed one by one at a single point, or at multiple points.

When there are multiple solder joints on the workpiece, there must be a certain distance between the solder joints and the solder joints. Because when welding the second solder joint, a part of the current passes through the soldered solder joint. This phenomenon is called the shunt phenomenon at the time of spot welding (Figure b). The shunt will reduce the welding current of the second spot welding and affect the welding quality. The shunting phenomenon is related to the material and thickness of the weldment. The thicker the weldment, the better the conductivity of the material, the more severe the shunting phenomenon. In order to reduce the shunt phenomenon, a certain distance must be separated between the two solder joints. See Table 1 for the minimum distance between solder joints.

Table 1: Minimum spacing between solder joints

Weldment thickness (mm) Dot pitch (mm) Structural steel heat-resistant steel aluminum alloy 0.5 10 8 15 1.0 12 10 15 1.5 14 12 20 2.0 16 14 25 3.0 20 18 20

The quality of spot welding is mainly related to welding current, energization time, electrode pressure and the surface of the weldment. If the welding current is too small, the power-on time is too short, the electrode pressure is insufficient, or the surface of the weldment is not clean, there is a possibility that the welding cannot be performed. On the contrary, the outer surface of the weldment will be indented, resulting in waste.

Spot welding is mainly used for welding all kinds of sheet metal stamping members. The thickness of the workpiece is generally 0.5-4mm. It is widely used in the departments of automobile, airplane, rolling stock, and agricultural machinery.

(b) seam welding

Seam welding is also called seam welding. The seam welding process is similar to spot welding except that the disc-shaped electrode (steel alloy roller) replaces the cylindrical electrode (Figure c). During welding, the roller electrode pressurizes and energizes the weldment, and the rotation of the roller electrode drives the weldment forward. As a result, a continuous weld consisting of a series of overlapping solder joints is formed on the weldment.

Seam welding, because of the overlapping of each welding point, so better sealing, it is mainly used for the manufacture of high sealing performance thin thickness of the following 3mm containers, such as tanks, tanks, chemical containers and silencers. As the solder joints overlap each other, the shunting phenomenon is serious. In order to save electric energy and keep the weldment and equipment cool for a long time, most of the welds use the method of blocking feed and intermittent power, see Figure c.

Third, the factors affecting the quality of the weld

Due to heat Q=VIt, Q=V2t/R is obtained according to Ohm's law I=V/R

From the Q=V2t/R formula, it can be seen that the heat Q is determined by the welding power source V, the contact resistance R, and the welding wheel speed v(t), and the stability of the welding seam quality can be stabilized by the stability of the three parameters.

1. Factors affecting welding voltage (V)

A, SCR adjustment given;

B. Fluctuations in grid voltage.

2. Factors that affect the contact resistance (R)

A, the size of the welder pressure;

B, the size of the edge.

3, the factors that affect the welding speed v (t)

A. The frequency converter regulates the given.

Fourth, the main technical parameters and indicators

1, output: 1 / (10-15) seconds

2, push the motor power: 1.1KW

3, air source pressure: 0.1-0.4MPa

4, power supply voltage: 380V

Fifth, the control system can make the equipment achieve the following effects in actual use:

1. The current is steady at work, sparks are small or there is no spark;

2, weld smooth hairless, low barrel rate;

3, welding current, welding voltage, welding heat energy and various parameters are displayed with digital meters, which enhances the visibility of welding parameters;

4, welding current and other parameters given by the digital instrument, high precision;

5. The drive of the welding wheel is driven by a frequency converter and a three-phase asynchronous motor, the speed is adjustable, and the wiring is simple;

6. The system has the function of automatic barrel retreat and automatic barrel turning, which greatly reduces the amount of manual labor.

Six, spot welder, seam welder mechanical part of the transformation

1. Replace the “Z” type clamp of the welding machine, replace the positioning clamp with 10mm when it is overlaid, and use a positioning clamp with a 4mm edge (see figure);

2. When the seam welding machine is working, the vat pushes the car before the transformation, and the roller is transferred after the transformation.

Seven, operating procedures

(a) boot

1, open the cooling water: to ensure that the system of various cooling water flow;

2, open the air source switch: to ensure that the air source is open, determine the electrode pressure with the regulating valve;

3, open the main power;

4, open the control cabinet power.

(B) the function of the panel

1. Ammeter: indicates the size of the welding current;

2. Voltmeter: indicates the welding voltage of the upper and lower welding wheels;

3, heat / current regulator: indicates the welding active power, may "â–³" and "?" given current (operation details see LU-906 specification);

4. Waveform integrity rate: indicates the thyristor phase shift electrical angle 0o-180o. Upper and lower limit alarm prompt shift;

5, power indicator: indicates whether the power is turned on;

6, for high-end: Tips to change the transformer stage to high-end (gear map see schedule);

7, downshift: prompt to change the transformer stage to low (gear map see the attached table);

8, control power switch: control power is turned on;

9, single turn: In the "adjust" state, the foot switch starts, the welding wheel rotation transformer and the upper head pressure cylinder does not work, this function is used to polish the welding wheel and adjust the motor;

10, single welding: In the "adjust" state, the foot switch starts. Welding transformer work, this function is used to adjust the no-load voltage (electrode) after shifting;

11, single pressure: In the "adjust" state, the foot switch starts. Only the cylinder on the head is working, then the pressure between the welding wheels can be adjusted;

12, manual / automatic: manual, automatic switching;

13. Work/Adjustment: Work Mode Switching:

(1) Work: Can be welded;

(2) Adjustment: There are three ways, single transfer, single weld, single pressurization;

14, current increase: no - no current increase; strong: 15S in the current increase of 10%; weak - 30S in the current increase of 10%.

15, foot switch: step on the foot board, start. Then stop and stop, the mushroom head switch only stops use;

(III) Working methods:

1, manual: hit the "manual" file, start with the foot switch.

Work order (figure omitted)

Then step on the foot switch and the welding stops.

2, automatic: hit the automatic file, foot switch start.

Work order (figure omitted)

The above sequence is continuously cycled through the PLC and the seam welding is automatically completed. In the working state, the foot switch can be used to stop.

(d) Adjustment

1. Current: given by LU-906 smart meter;

According to the different plates used for welding, and the quality of the welding, through the dial "â–³" and "?" Adjust;

2, pressure: gear point to "adjust", "single pressurization" start, adjust the air pressure range of 0.1-0.4MPa;

3. Speed: The welding wheel adopts three-phase motor AC frequency conversion control and the speed can be given by the inverter. Change the frequency by inverter "â–³" and "?" to adjust the speed (for details, refer to the inverter manual) range 0-50Hz;,.

(5) Common problems and solutions

1, fan, inverter loses power

(1) The welder stops working for more than 20 minutes, and is reset by the foot switch.

(2) Check whether the single frequency switch of the fan frequency converter trips;

(3) Check the circuit by professionals.

2. When the barrel is rolled, the front opening

Adjust the photoelectric switch to move in the direction of the barrel.

3, the front of the barrel is not welded

(1) Adjust the photoelectric switch to move in the opposite direction of the barrel;

(2) The front-end amount is too large, reminding spot welders to pay attention.

4, weld the barrel with trachoma

(1) The spot welding current is too large to adjust the spot welding current;

(2) Check if the wheel is clean and polished.

5, welding quality is not stable, the phenomenon of welding can not be replaced with welding wear

(1) Check whether the air pressure is appropriate and whether there is air leakage in the air path;

(2) Check whether the plate is smooth and the material is qualified. If the plate is a qualified product, small current and low speed welding can be used to improve the welding quality.

6, matters needing attention

(1) The surface of the selected plate should be smooth and free of rust;

(2) The plate material should be uniform without uneven thickness;

(3) The barrel body is 4-6mm wide, and the difference between the front and the back of the barrel is less than 0.5mm, and the diagonal error is small;

(4) The current should be controlled within 300A to ensure the normal operation of the transformer.

Figures:

1, transformer gear indication map (slightly)

2, seam welder electrical schematics four (slightly)

3, seam welder program map three (slightly)