Installation and maintenance of spot welding machines

Spot welding machines must be properly grounded before use to ensure personal safety. Before using the spot welding machine, a 500V megohmmeter should be used to test the insulation resistance between the high voltage side of the welding machine and the casing, which should not be less than 2.5 megohms before power can be applied. Cut off the power supply before opening the box for inspection during maintenance. The welding machine should be filled with water before welding, and it is strictly prohibited to work without water. The cooling water should ensure the supply of industrial water at 5-30 ℃ under the inlet pressure of 0.15-0.2MPa. After the winter spot welding machine is completed, compressed air should be used to blow off the water in the pipeline to prevent freezing and cracking of the water pipe.
Spot welding machine leads should not be too thin or too long. The voltage drop during welding should not exceed 5% of the initial voltage, and the initial voltage should not deviate from the power supply voltage by ± 10%. When operating a welding machine, gloves, aprons, and protective goggles should be worn to prevent sparks from flying out and causing burns. The sliding part should be well lubricated, and metal splashes should be removed after use. After 24 hours of use, the screws of each component of the new welding machine should be tightened once, especially paying attention to the connection screws between the copper flexible joint and the electrode. After use, the oxide between the electrode rod and the electrode arm should be regularly removed to ensure good contact.
If the AC contactor is found to be improperly engaged during the use of the spot welding machine, it indicates that the grid voltage is too low. The user should first solve the power supply problem, and only use it after the power supply is normal. It should be pointed out that if there are quality issues with the main components of the newly purchased welding machine within half a month, a new welding machine or the main components can be replaced. The main body of the welding machine is partially covered by a one-year warranty, and long-term maintenance services are provided. In general, after notifying the manufacturer, the service will be provided within three to seven days based on the distance traveled. Welding machine damage caused by user reasons is not covered by the warranty. Vulnerable and consumable parts are not covered by the warranty.
Due to the fact that the contact area of the electrode determines the current density, and the electrical resistivity and thermal conductivity of the electrode material are related to the generation and dissipation of heat, the shape and material of the electrode have a significant impact on the formation of the melt nucleus. As the electrode tip deforms and wears, the contact area increases, and the strength of the solder joint will decrease. The oxide, dirt, oil, and other impurities on the surface of the workpiece increase the contact resistance. An excessively thick oxide layer can even prevent current from passing through. Local conduction, due to excessive current density, can cause splashing and surface burning. The presence of oxide layers can also affect the uneven heating of various solder joints, causing fluctuations in welding quality. Therefore, thoroughly cleaning the surface of the workpiece is a necessary condition to ensure the acquisition of high-quality joints.

Troubleshooting
1. The spot welding machine does not work when stepping on the foot pedal, and the power indicator light does not light up:
a. Check if the power supply voltage is normal; Check if the control system is functioning properly.
b. Check if the foot switch contacts, AC contactor contacts, and tap shifter switches are in good contact or burned out.
2. The power indicator light is on, and the workpiece is tightly pressed and not welded:
a. Check if the foot pedal travel is in place and if the foot switch is in good contact.
b. Check if the pressure bar spring screws are properly adjusted.
3. Unexpectedly splashing during welding:
a. Check if the electrode head is severely oxidized.
b. Check if the welded workpiece is severely corroded and has poor contact.
c. Check if the adjustment switch is set too high.
d. Check if the electrode pressure is too low and if the welding procedure is correct.
4. Severe indentation and extrusion of solder joints:
a. Check if the current is too high.
b. Check for unevenness in the welded workpiece.
c. Check if the electrode pressure is too high, and if the shape and cross-section of the electrode head are appropriate.
5. Insufficient strength of welded workpiece:
a. Check if the electrode pressure is too low and if the electrode rod is securely fastened.
b. Check if the welding energy is too low and if the welded workpiece is severely corroded, resulting in poor contact of the welding points.
c. Check for excessive oxidation between the electrode head and electrode rod, as well as between the electrode rod and electrode arm.
d. Check if the cross-section of the electrode head has increased due to wear, resulting in a decrease in welding energy.
e. Check if the electrode and copper soft joint and bonding surface are severely oxidized.
6. Abnormal sound from AC contactor during welding:
a. Check if the incoming voltage of the AC contactor is 300 volts lower than its own release voltage during welding.
b. Check if the power lead is too thin or too long, causing a significant voltage drop in the circuit.
c. Check if the network voltage is too low to function properly.
d. Check if there is a short circuit in the main transformer, causing excessive current.
7. Welding machine overheats:
a. Check if the insulation resistance between the electrode holder and the body is poor, causing a local short circuit.
b. Check if the inlet pressure, water flow rate, and water supply temperature are appropriate, and check if the water system is blocked by dirt, which may cause overheating of the electrode arm, electrode rod, and electrode head due to poor cooling.
c. Check if the copper flexible joint, electrode arm, electrode rod, and electrode head contact surface are severely oxidized, causing an increase in contact resistance and severe heating.
d. Check if the cross-section of the electrode head has increased too much due to wear, causing the welding machine to overload and heat up.
e. Check if the welding thickness and load duration exceed the standard, causing the welding machine to overload and generate heat [1]
Advantages and disadvantages

Resistance welding has the following advantages:
1. When the molten core is formed, it is always surrounded by a plastic ring, isolating the molten metal from the air, and the metallurgical process is simple.
2. Due to short heating time and concentrated heat, the heat affected zone is small, and the deformation and stress are also small. Usually, there is no need to arrange correction and heat treatment procedures after welding.
3. No need for filler metals such as welding rods and wires, as well as welding materials such as oxygen, acetylene, and argon, resulting in low welding costs.
4. Easy to operate, easy to achieve mechanization and automation, improving working conditions.
5. High productivity, no noise or harmful gases. In mass production, it can be assembled together with other manufacturing processes on the assembly line. However, flash welding requires isolation due to spark splashing.
Resistance welding has the following drawbacks:
1. Lack of reliable non-destructive testing methods, welding quality can only be inspected through destructive testing of process specimens and welded components, as well as various monitoring technologies to ensure.
2. The lap joint of point and seam welding not only increases the weight of the component, but also results in lower tensile and fatigue strength of the joint due to the formation of an angle around the fusion nucleus between the two plates.
3. The high power, mechanization, and automation of the equipment increase the cost of the equipment. Maintenance is difficult, and the commonly used high-power single-phase AC welding machine is not conducive to the normal operation of the power grid, requiring separate power distribution.
The main resistance welding methods include spot welding, seam welding, projection welding, and butt welding.