Capacitor discharge spot welding machine

The utility model relates to a capacitor-discharge type spot welding machine, which mainly comprises a transformer, a bridge rectifier, a capacitor bank and the like. The transformer is a voltage regulating transformer with a voltage regulating range between 0V and 220V, the capacitor bank consists of a bank of parallel connected electrolytic capacitors identical in capacity, and a typical parameter of each capacitor is 160V, 2200uF. When the capacitor-discharge type spot welding machine is used, objects to be welded are connected to a positive binding post and a negative binding post of an output end of the spot welding machine through leads, and according to different conditions of the objects to be welded, the number of the capacitors serially connected into a circuit is controlled by capacitor buttons so that discharge energy is changed, and spot welding between the objects to be welded can be realized through charge-discharge of the capacitors. The capacitor-discharge type spot welding machine is simple in structure and capable of performing spot welding of metal materials quickly, conveniently and firmly.


What is a capacitor discharge spot welding machine?

Also known as capacitive discharge spot welder, CD welding machine, or stud welding machine, the capacitor discharge spot welder is the fastest resistance spot welder type,  which is primarily used to fuse multiple sheet metals together. Involving spot welding machines like capacitor discharge spot welding machine, there are a wide variety of resistance welding methods that require high heat from resistance to current and pressure to melt and join the metal parts, creating a strong connection.

When it comes to capacitors in capacitive discharge spot welders, the capacitor is used to deliver power to the part, which is charged with a great amount of energy. As a result, the energy is quickly released into the parts, even within milliseconds during the welding cycle in a capacitive discharge spot welder. Then the copper electrodes act on the contacting weld joint on the surfaces of the sheet metals, where the electrode force is also applied. A permanent, reliable weld connection is completed, the most ideal resistive metal for welding in a capacitive discharge spot welder is the low carbon steels. 


Principle of resistance spot welding process

A capacitor discharge spot welding machine is a sort of electric resistance spot welding machine (ERW). In the ERW process, two or more sheet metals or materials that come in other forms can be joined together without inserting any filler material. Resistance spot welding processes in a capacitive discharge welder generally utilize copper alloy electrodes to deliver the electric current to the “spot” on the material. As a result, the “spot” will be melted due to the high heat when the thermal energy is focused on a small point. The proper amount of force is also required to complete the high-quality weld under a regulated period of time.

Through the process of transmitting a sufficient amount and density of current to the weld joint and forcing the sheets together as the current is removed, the weld can be finished after the product solidifies and cools down. The power supply of the capacitor discharge spot welding machine, the weld current, and time are all vital to the weld quality, excessive energy and heat will create an unwanted hole on the sheets’ surfaces while less than enough heat will lead to a poor weld.

In a capacitor discharge spot welding machine, the welding process depends on the metal resistance to joining the materials. The welding machines have to overcome the “contact resistance” as well as the “bulk resistance” of the material during the operations. On the micro-scale, in the beginning, the metal bridges which are melted permit other bridges to get contact with others in order to complete the weld, and finally the contact resistance will be zero when all the bridges are connected together.


How does a capacitor discharge spot welding machine work?

The capacitor discharge process makes the spot welder an extremely efficient and reliable solution in the modern metalworking environment. The process of capacitor discharge spot welding is also named as contact capacitor discharge stud welding process. There are basically four stages in the capacitor discharge process in a capacitor discharge spot welding machine, including contacting, ignition, stud placement, and finally closing the gap to create the weld.

When welding a fastener like nuts or bolts to the sheet metals, the fastener is held by the stud gun that controls the workpiece to get contact with the sheets. As the capacitor discharge gun is triggered, the stud tip at the end will be ignited and melted. 

Due to the high weld temperature, the “spot” underneath the head will also melt. Then the capacitor discharge gun can force the stud into the molten material, enclosing the gap of the fastener and the sheet to form the connection. The capacitive discharge spot welding process utilizing stud gun is also widely known as the contact capacitive discharge stud welding process.


Features of capacitor discharge spot welder

Timing and logic control based on high-performance 8-bit CPU.

Adopt 12-bit high-speed A/D conversion and real-time sampling of capacitor voltage.

The counting function is complete, and it can count the number of dots and the number of production.

Imported special capacitors for rapid charging and discharging are adopted, and the capacitor has a long life and stable capacity. The impact on the grid is small and the power factor is high.

The peak welding current is high, the time is short, and the specification is hard.

It is especially suitable for the welding of plates, wires and wires of metals with good electrical and thermal conductivity, such as aluminum and copper, and the precision welding of dissimilar metals.

The advantages of capacitor discharge spot welding machine

Capacitive discharge spot welding solution provides a great many benefits, most notable of which is its ability to handle repeatable productions in large volume and is in fact one of the most cost-effective fine-spot resistance welding solutions on the market. Let’s take a look below for its other benefits in detail:

Short Welding Times

Since the capacitive discharge spot welding process utilizes stored energy instead of using direct demand on incoming power for the conventional processes, the weld times are generally shorter – typically in 10 milliseconds or less.

Small Heat-affected Zone

This type of welding technique ensures the HAZ (if any) is minimized and makes sure that any changes in the metallurgy of the workpiece remain as small as possible.

Welding Capacity

By welding capacity, we mean the range of metals that you can weld using capacitive discharge spot welding. As a matter of fact, its nature of quick energy release makes it ideal for welding highly conductive metals such as copper.

Concentrated Welds

The resulting short weld times as we described above ascertains that the energy needed to spot weld remains concentrated in the weld zone. Furthermore, because the energy delivered during the capacitive discharge spot welding process is concentrated for such a short time (even at high levels), the electrode is less prone to wear compared to conventional welding processes. In fact, it is said that the electrode can last four to ten times as long.

Power Saving

Since the high electrical energy required is not directly harnessed from the power distribution network but large capacitors, you typically don’t need to upgrade the power service to your building. The bank of capacitors will store energy and recharge between welds. 

Energy Utilization

This type of spot welding is capable of repeatable energy release not subjected to line voltage fluctuations. It is also capable of exceptionally fine energy adjustment.


Applications of capacitor discharge spot welding machine

Capacitor discharge spot welding machine, which uses the stud welding method to melt and fuse the sheet metal parts, is demanding weld equipment due to the versatility, reliability, and efficiency. Also, the simple setups and ideal portability offer the users a ready electricity supply anywhere they need to complete the welds. 

These capacitor discharge spot welding machines, which require lower heat production, can ensure a cleaner and more rapid welding process with exceptional precision. There are no backside burning or distortion issues that may occur with excessive heat or pressure during the spot welding process. 

Capacitor discharge spot welding machines provide welds with clean finishes, which is advantageous for some users who need the products to have cleaner appearances. On top of that, the connection between the metal parts features great strength although formed in a short cycle.

With these advantages including easy installation and setups, reliable and high-quality welds, and efficient production, the capacitor discharge spot welding machine is widely used in component productions of automotive, aerospace, metal furniture, medical equipment, electronics, and also in the construction and rail industry.

Hazards and Precautions

This may seem obsolete for some but we cannot stress enough how important it is to know what kind of safety risks a welder can pose and what precautionary measures you can take to protect yourself or others from potential hazards. Some of the most notable hazards in relation to the use of any welder include burns, electric shock, fumes and gases, and even fire explosions. Burns usually occur when the operator is not mindful of hot parts on the equipment when it's operating; shock accidents are usually related to the inappropriate placement of the power circuit; fire explosions are generally attributed to sparks flying off of the arc into other combustible equipment, fluids, etc.; and fumes and gases are often the results of inadequate ventilation in the work area.

Thankfully, here are a few things you can do keep these potential hazards to the minimum:

a.) Always put your safety glasses on when working with a welder of any kind. This includes your weld heads as well.

b.) Refrain from touching weld spots immediately after ther welds have been created as they will be very hot. Also, avoid making contact with any part of your equipment that is hot during the operation.

c.) Be sure to not pinch fingers in moving weld head parts or between weld electrodes.

d.) Keep your personal accessories to the minimum. This means removing watches, jewelry, or anything that is susceptible to sparks and electricity. All welds should be performed at low voltage to ensure the safety of the operators.


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