An Introduction to Capacitive Discharge Spot Welder

Posted on May 2, 2021

The capacitor discharge spot welder is the fastest resistance spot welder type,  which is primarily used to fuse multiple sheet metals together. 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.

What Is a Capacitive Discharge Spot Welder?

Also known as capacitor 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 capacitive discharge spot welders, 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 capacitive discharge spot welder 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 capacitive discharge spot welder, 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 capacitive discharge spot welder, 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. 

:: Read more: An Overview of Capacitive Discharge Spot Welder


How Does a Capacitive Discharge Spot Welder 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 capacitive discharge spot welder, 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. 


Applications and Advantages of Capacitive Discharge Spot Welder

Capacitive discharge spot welder, 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 capacitive discharge spot welders, 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. 

Capacitive discharge spot welders 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 capacitive discharge spot welder is widely used in component productions of automotive, aerospace, metal furniture, medical equipment, electronics, and also in the construction and rail industry.


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