Spot Welding Machine

November 14, 2017 Facebook Twitter LinkedIn Google+ Uncategorized

Spot welding machine uses double-sided double-point over-current welding principle, the work of two electrodes pressurized workpiece so that two layers of metal in the two electrodes under the pressure to form a certain contact resistance, and welding current from one electrode through the other electrode When the two contact resistance point instantaneous thermal welding, and the welding current instantaneous flow from the other electrode along the two electrodes to form a loop, does not hurt the internal structure of the workpiece being welded.

Welding machine uses the positive and negative poles in the moment of short circuit generated by the high temperature arc welding electrodes to be welded and welded materials to achieve the purpose of their combination, in order to ensure nugget size and solder strength, welding time and welding current in Within a certain range can complement each other.

In order to obtain a certain degree of strength of the solder joints, you can use high current and short time (strong conditions, also known as hard norms), can also use small current and long time (weak conditions, also known as soft specifications).

Table of content

1. Basic introduction

2. working principle

3. Mechanical use

4. Use safety

5. Installation and maintenance

6. Troubleshooting

7. advantages and disadvantages

8. Steel spot welding machine

9. Spot welding safety rules

10.Other references

11.List of Spot Welding Machine manufacturers

1. Basic introduction

Spot welding in accordance with the use of points, a universal (general-purpose), special-purpose; according to the number of welding points at the same time points, there are single-point, double-point, multi-point; Bilateral; in accordance with the transmission mechanism of the pressure mechanism points, a pedal, the motor – cam, pneumatic, hydraulic, complex (gas hydraulic type); in accordance with the characteristics of the operation, there is non-automation, automation; The method of installation points, there are fixed, mobile or portable (hanging); according to the welding electrode (usually the upper electrode) of the moving direction points, a vertical stroke (electrode for linear motion), arc travel; Divided according to the way of electrical energy supply, there are frequency welding machine (using 50 Hz AC power supply), pulse welding machine (DC pulse welding machine, energy storage welding machine, etc.), frequency welding machine (such as low frequency welding machine).

When the workpiece and the electrode is fixed, the resistance of the workpiece depends on its resistivity. Therefore, the resistivity is an important property of the material to be welded. High resistivity metal poor conductivity (such as stainless steel) Low resistivity of the metal conductivity good (Such as aluminum). Therefore, the spot welding stainless steel easy to produce heat and heat difficult, spot welding aluminum alloy heat difficult and heat dissipation. Spot welding, the former available smaller current (thousands of amps), which must use a very large current Million amperes). Resistivity depends not only on the type of metal, but also the heat treatment of metal, processing methods and temperature.

In order to ensure nugget size and solder joint strength, welding time and welding current can complement each other within a certain range. In order to obtain a certain degree of strength of the solder joints, you can use high current and short time (strong conditions, also known as hard norms), can also use small current and long time (weak conditions, also known as soft specifications). The choice of hard or soft specifications, depending on the performance of the metal, the thickness and the power of the welder used. For different performance and thickness of the metal current and time required, there is an upper and lower limits, when used as the standard.

Electrode pressure on the total resistance R between the two electrodes have a significant impact, with the electrode pressure increases, R significantly reduced, while the welding current increase is not large, can not affect the reduction of R due to reduced heat production . Therefore, the total solder joint strength decreases with increasing welding pressure. The solution is to increase the welding pressure, while increasing the welding current.


Spot welding machine can be divided into general purpose (general, special type) spot welding machine;

According to the number of welding points at the same time is divided into: a single-point, double-point, multi-point;

Divided by the conductive mode: unilateral, bilateral;

According to the pressure transmission mechanism is divided into: pedal, motor – cam, pneumatic, hydraulic, composite (gas hydraulic type);

According to the characteristics of the operation is divided into: non-automated, automated;

According to the installation method is divided into: fixed, mobile or portable (hanging) spot welding;

According to the moving electrode of the welding machine (usually the upper electrode), the moving direction is divided into: vertical stroke (electrode for linear motion) and arc stroke.

2. working principle

Spot welding machine uses double-sided double-point over-current welding principle, the work of two electrodes pressurized workpiece so that two layers of metal in the two electrodes under the pressure to form a certain contact resistance, and welding current from one electrode through the other electrode When the two contact resistance point instantaneous thermal welding, and the welding current instantaneous flow from the other electrode along the two electrodes to form a loop, does not hurt the internal structure of the workpiece being welded.

Spot welding process for the opening of cooling water; the weldment surface clean, accurate assembly, into the upper and lower electrodes, between the pressure, to make good contact; energized so that the contact surface of the two workpiece heating, partial melting, the formation of Nugget; to maintain pressure after power off, nugget cooling and solidification under pressure to form a solder joint; remove the pressure, remove the workpiece. Welding current, electrode pressure, power time and the electrode surface dimensions and other spot welding process parameters have a significant impact on the quality of welding.

Spot welding using positive and negative poles in the moment of short circuit generated by the high temperature arc to melt the welding electrodes and welding materials to achieve their purpose. The structure of the welding machine is very simple, to put it in vain is a high-power transformers, 220V AC into low voltage, high current power supply can be DC can also be AC. Welding transformers have their own characteristics, that is, with a sharp drop in voltage characteristics.

After the electrode ignition voltage drop, welding machine voltage regulation, in addition to a 220/380 voltage conversion, the secondary coil also tap change the voltage, but also with the iron core to adjust the adjustable iron core. Welder is generally a high-power transformers, the use of the principle of inductance made. Inductance in the turn-on and turn-off will produce tremendous voltage changes, the use of positive and negative poles in the moment of short circuit caused by high-voltage arc to melt the solder on the welding rod. To achieve the purpose of combining them.

Spot welding is the weldment assembly joint, and pressed between the two electrodes, the use of resistance hot-melt parent metal, the formation of solder joint resistance welding method. Spot welding and more for the connection sheet, such as aircraft skin, aero-engine fire pipe, car cab shell. Spot welding welding transformer is spot welding appliances, its secondary only loop. The upper and lower electrodes and the electrode arm are used both for conducting the welding current and for transmitting the power. Cooling water through the transformer, electrodes and other parts, so as not to heat welding, the cooling water should be passed, and then turn on the power switch. Electrode quality directly affects the welding process, welding quality and productivity. Electrode materials commonly used copper, cadmium bronze, chrome bronze and other made; a variety of electrode shapes, mainly determined by the shape of the weldment. Install the electrode, pay attention to the upper and lower electrode surface to maintain parallel; electrode plane to keep clean, often emery cloth or file trim.

Welding cycle Welding and welding convex welding cycle consists of four basic stages (spot welding process):

(1) Pre-pressure stage – electrode down to the current phase, ensure that the electrode pressure on the workpiece, so that there is appropriate pressure between the workpiece.

(2) welding time – Welding current through the workpiece, heat to form a nugget.

(3) Maintain the time – cut off the welding current, electrode pressure continued to nugget solidified to a sufficient strength.

(4) Quiescent Time – The electrode starts to lift until the electrode begins to descend again, starting the next welding cycle. In order to improve the performance of welded joints, it is sometimes necessary to add one or more of the following to the basic cycle:

(1) increase the pre-pressure to eliminate the gap between the thick parts, so close fit.

(2) Preheat pulse to improve the plasticity of the metal, the workpiece easy to fit closely to prevent splashing; Projection welding so that the number of bumps in the welding before welding and flat uniform contact, in order to ensure that the point of heating the same.

3. Mechanical use

Spot welding machine use method:

1, Welding should first adjust the position of the electrode rod, the electrode just pressed to the weldment, the electrode arm to maintain parallel to each other.

2, the choice of current regulation switch series can be selected according to weldment thickness and material. After the power indicator light should be bright, the electrode pressure can be adjusted spring pressure nut to change its degree of compression obtained.

3, after completing the above adjustment, you can turn on the cooling water before switching on the power to prepare for welding. Welding procedure: The weldment is placed between the two electrodes, depressing the foot pedal and bringing the upper electrode into contact with the weldment and pressurizing the power contact switch while continuing to depress the foot pedal, so that the transformer begins working secondary The circuit is energized to heat the weldment. When welding after a certain time to release the pedal when the electrode rises, by the spring tension first cut off the power and then restitution, single-point welding process is over.

4, weldment preparation and assembly: Before welding steel weldment to be cleaned of all dirt, oil, scale and rust, the hot-rolled steel, the best welding the first pickling, sandblasting or grinding wheel to remove the oxide skin. Uncleaned welds allow spot welding, but severely reduce the life of the electrode, while reducing the spot welding production efficiency and quality. For low-carbon steel with a thin coating can be directly welded.

In addition, the user can refer to the following process data:

1, the welding time: In the welding of low carbon steel, the welder can use the strong standard welding (instantaneous power) or weak standard welding (long time power). In mass production should be used to standardize the welding method, which can improve production efficiency, reduce power consumption and reduce the deformation of the workpiece.

2, welding current: welding current depends on the size of the weldment, thickness and contact surface conditions. Usually the higher metal conductivity, the greater the electrode pressure, the welding time should be shorter. The current density required at this time also increases.

3, the electrode pressure: the electrode pressure on the weldment is designed to reduce the contact resistance at the solder joints, and to ensure the pressure required to form the solder joints.

4, the shape and size of the electrode: Electrode made of chrome zirconium copper. The diameter of the electrode contact surface is approximately:

δ ≤ 1.5mm, the electrode contact surface diameter, 2δ +3 (mm)
δ ≥ 2mm, the electrode contact surface diameter, 1.5δ +5 (mm)
δ-the thickness of two thinner weldment (mm)

The diameter of the electrode should not be too small, so as not to cause excessive heat and rapid wear.

5, the layout of the solder joints:

The smaller the distance between the solder joints, the current diversion increases, and the pressure at the spot welds is reduced, thereby weakening the strength of the solder joints.

4. Use safety

1) The use of the scene, should be equipped with rain, moisture, sun-proof hangar, and should be equipped with the corresponding fire equipment.

2) Within 10m of the welding site, no flammable or explosive materials such as oil, wood, oxygen bottles and acetylene generators shall be piled up.

3) welding operations and personnel must wear labor protection equipment as required. And must take to prevent electric shock, altitude crashes, gas poisoning and other accidents fire safety measures.

4) secondary tap joint copper should be pressed, the terminal should be washer. Before closing, the wiring nuts, bolts and other components should be inspected in detail and checked for completeness without loosening or damage. Posts are protective cover.

5) Before use, should check and confirm the primary and secondary wiring is correct, the input voltage meets the welding machine nameplate requirements, know the type and scope of welding current welding spot. Do not touch the live part of the primary circuit after turning on the power. First, the secondary wiring must be equipped with protective cover.

6) When moving the welding machine, the power should be cut off, and the welding machine should not be moved by dragging the cable. When a sudden power outage in the welding, should immediately cut off the power.

7) When welding non-ferrous metals such as copper, aluminum, zinc, tin, lead, etc., it must be done in well-ventilated place. Welding personnel should wear gas mask or respirator filter.

8) Multi-welding machine centralized use, should be tapped in the three-phase power network, the three-phase load balancing. Multiple welder grounding device, should be cited by the ground lead, not in series.

9) It is forbidden to carry out welding on pressure pipes in operation, containers with inflammable and explosive materials and force components.

10) When welding the preheating element, a baffle shall be provided to separate the radiant heat emitted by the preheating welding element.

5. Installation and maintenance

Welder must be properly grounded before use to protect personal safety. Welder before use 500V megger test Welder high voltage side and the insulation resistance between the cabinet not less than 2.5 megohms can be energized. Maintenance must first cut off the power before unpacking inspection. Welding machine water through the first welding, water is strictly prohibited work. Cooling water should be guaranteed at 0.15 – 0.2MPa inlet water supply 5–30 ℃ industrial water. After the winter welding work is completed, apply compressed air to purge the water in the pipeline so as not to freeze the pipe.

Welder lead should not be too thin too long, the voltage drop during welding should not exceed 5% of the initial voltage, the initial voltage can not deviate from ± 10% of the power supply voltage. Welder operation should wear gloves, aprons and protective glasses, so as to avoid flying Mars burns. Sliding parts should be kept well lubricated, should be cleared of metal splash after use. The new welder 24 hours after the screws should be fastened once the parts, with particular attention to the connection between the copper soft joint and the electrode must be fastened, after use should always remove the oxidation between the electrode rod and the electrode arm Things to ensure good contact. When the welding machine is used, if it is found that the AC contactor does not pull, it indicates that the grid voltage is too low, and the user should solve the power supply problem first and then use the power supply normally. It should be noted that the newly purchased welding machine within half a month if the quality of the main parts, you can replace the welding machine or replace the main parts. Welder host part of the year warranty, provide long-term maintenance services. Under normal circumstances the user notified the factory, according to the distance within three to seven days of service in place. The welding machine damage caused by the user is not covered under the warranty. Vulnerable parts, consumables are not covered under warranty.

Since the contact area of ​​the electrode determines the current density, the resistivity and thermal conductivity of the electrode material are related to the generation and dissipation of heat, so the shape and material of the electrode have a significant effect on the formation of nuggets. As the electrode tip deformation and wear, contact area increases, the solder joint strength will be reduced. Oxide, dirt, oil and other impurities on the workpiece surface increase the contact resistance. Too thick oxide layer can even make the current can not pass. Local conduction, due to the current density is too large, it will have a splash and burn the surface. The existence of the oxide layer will also affect the unevenness of the heating of each weld, causing fluctuations in weld quality. Therefore, thoroughly cleaning the workpiece surface is necessary to ensure access to quality joints.

6. Troubleshooting

1, tread pedal welder does not work, the power light does not shine:
a. Check the power supply voltage is normal; check the control system is normal.
b. Check the foot switch contacts, AC contactor contacts, splitter switch contact is good or burned.

2, the power indicator light, the workpiece is not pressed welded:
a. Check the pedal stroke is in place, the foot switch is in good contact.
b. Check if the pressure rod spring screw is properly adjusted.

3, there should be no splash when welding:
a. Check if the tip is seriously oxidized.
b. Check if the welding workpiece is seriously corroded and badly contacted.
c. Check the adjustment switch is too high gear.
d. Check the electrode pressure is too small, the welding process is correct.

4, severe solder joint indentation and extrusion:
a. Check if the current is excessive.
b. Check the welding workpiece is uneven.
c. Check the electrode pressure is too large, the tip shape, section is appropriate.

5, insufficient welding workpiece strength:
a. Check the electrode pressure is too small, check the pole is tightened.
b. Check the welding energy is too small, the welding workpiece is serious corrosion, poor contact with the solder joints.
c. Check if there is excessive oxide between electrode tip and electrode rod, electrode rod and electrode arm.
d. Check whether the cross section of the tip increases due to wear and tear resulting in reduced welding energy.
e. Check electrode and copper soft joint and the joint surface is seriously oxidized.

6, AC contactor noise when welding abnormalities:
a. Check whether the line voltage of the AC contactor is lower than the self-releasing voltage of 300 V during welding.
b. Check the power lead is too thin, causing the line pressure drop too much.
c. Check the network voltage is too low, can not work properly.
d. Check the main transformer for short circuit, resulting in too much current.

7, welding machine overheating phenomenon:
a. Check the insulation resistance between the electrode seat and the body is not good, resulting in a partial short circuit.
b. Check the inlet pressure, water flow, water temperature is appropriate, check the water system for dirt clogging, resulting in poor cooling so that the electrode arm, electrode rod, tip overheating.
c. Check the copper soft joint and the electrode arm, the electrode rod and the tip contact surface oxidation is serious, resulting in increased contact resistance heat serious.
d. Check whether the tip cross-section increase due to excessive wear and tear, so that the welding machine overheating and fever.
e. Check the welding thickness, the load sustained rate is excessive, so that the welding machine overheating and fever

7. advantages and disadvantages

Resistance welding has the following advantages:

1, the formation of nuggets, plastic ring has always been surrounded by melting metal and air isolation, metallurgical process is simple.

2, heating time is short, heat concentration, so the heat affected zone is small, deformation and stress are small, usually without having to arrange after welding correction and heat treatment processes.

3, do not need electrodes, welding wire and other filler metal, and oxygen, acetylene, argon and other welding materials, welding low cost.

4, simple operation, easy to mechanization and automation, improved working conditions.

5, high productivity, and no noise and harmful gases, in high volume production, and other manufacturing processes can be compiled into the assembly line, but the flash butt welding sparks, need to be isolated.

Resistance welding has the following disadvantages:

1, The lack of reliable non-destructive testing methods, welding quality can only rely on the destructive testing of process samples and weldments to check, and rely on a variety of monitoring techniques to ensure.

2, point, seam welding lap joints not only increase the weight of the components, and because of the formation of the angle between the two plates around the nugget, resulting in joint tensile strength and fatigue strength are low.

3, equipment power, mechanization, high degree of automation, so that equipment costs increase. Maintenance is more difficult, and commonly used high-power single-phase AC welder is not conducive to the normal operation of the grid, the need for separate distribution.

The main method of resistance welding a little welding, seam welding, convex welding, butt welding four.

8. Steel spot welding machine

Reinforced spot welding machine is used to spot welding steel mesh or reinforced skeleton of the special equipment to replace artificial steel wire banding, which not only saves metal materials, but also improve work efficiency.

Type of spot welder

1, spot welder classification Many types of spot welder, according to the type of power can be divided into power frequency, capacitor storage, secondary rectification, DC shock wave four; according to the electrode type can be divided into single head, double head, three The first three; according to the structure can be divided into fixed, hanging, portable three; press the pressure transmission can be divided into lever, pneumatic and hydraulic three. There are some variants of products such as steel mesh forming machine, CNC program control spot welder.

2, the type of spot welding spot welding machine model or JB1475-81 provisions of the preparation method, type codenamed DN, the main parameters of the code to nominal capacity, steel welding commonly used wieDN series of short arm fixed and DN3 series of long arm Fixed and DN7 series of multi-point welding machine.

Structure and working principle of spot welding machine

1, structure of the spot welding machine mainly by spot welding transformers, electrode arm, lever system, grading switch and cooling system and other components.

2, the working principle of spot welding, the surface smooth straight stack superposition together on the two electrodes, depressing the pedal, so that the intersection of the two steel contact close, while the circuit breaker is also in contact, connected The power supply makes the steel junction produce a large amount of resistance heat in a short time, the steel is heated to the melting point and melted quickly. Release the pedal, the circuit breaker cut off the current with the lever down, the role of the pressure, the molten steel junction cooling condensation into a welding point.

9. Spot welding safety rules

1)Before work, should be cleaned up, the next two electrodes oil. After power, the body shell should be no leakage.

2) Before starting, switch on the control line and switch on the welding current to turn on the small switch. Adjust the number of poles and connect the water source and gas source. Finally, turn on the power supply.

3) Welder power, should check the electrical equipment, operating agencies, cooling systems, gas system and the body shell leakage phenomenon. Electrode contacts should be kept bright and clean. When there is leakage, it should be replaced immediately.

4) Work, gas, water cooling system should be smooth. The gas should be kept dry. Drainage temperature shall not exceed 40 ℃, the displacement can be adjusted according to the temperature.

5) Do not increase the ignition circuit in the fuse. Do not close the ignition circuit of the control box when the load is too small to cause the arc in the ignition tube to fail.

6) When the control box is disabled for a long time, it should be energized and heated for 30 minutes every month. Replace the thyristor should be preheated 30min. The normal working time of the control box should not be less than 5min.

7) Welding operations and personnel must wear protective clothing as required. And must take to prevent electric shock, altitude crashes, gas poisoning and fire accidents and other safety measures.

8) The welding machine used on site should be equipped with rainproof, moistureproof and sunshade hangar, and should be equipped with the corresponding fire equipment.

9) High-altitude welding or cutting, must fasten seat belts, welding around and below should take fire prevention measures, and should be supervised.

10) When removing welding slag, wear safety goggles and avoid splashing spatter on the head.

11) Rain is not allowed in open air welding. When working in wet areas, the operator should stand in place with insulation and wear insulated footwear.

10.Other references

Welding Machine
Stamping Machine
Mould Design
Injection Moulding Machine
CNC Engraver
Gantry Milling Machine
Milling Cutter
CNC Turning Machine
Universal Milling Machine
Horizontal Milling Machine
Vertical Milling Machine
Tapping Machine
Water Jet Cutting Machine
Plasma Cutting Machine
EDM – Electrical Discharge Machining
ERP – Enterprise Resource Planning
CAM – Computer Aided Manufacturing
CAD(Computer Aided Design)
cnc router

11.List of Spot Welding Machine manufacturers