Understanding Automatic Cap Nut Welder

Posted on May 10, 2021

Automatic Cap Nut Welder

The automatic cap nut welder is the automatic welder that is particularly designed to join the cap nuts and M-thread, T-thread bolt, and so on.

What Are Cap Nuts?

Cap nuts are the fastener that features a domed end on one side. When using the cap nut with a threaded fastener with an external thread pattern, the domed end can enclose the thread, in order to protect the thread itself or other items near the thread. The dome design of the cap nut offers a smooth, finished profile. 

Typically made from brass, steel, and stainless steel, the cap nuts are mostly utilized to enhance the safety for joints, covering the ends of bolt threads and other applications today, and many of them serve broad purposes. In general, cap nuts with taller contours can offer more ideal protection.

In the body of a modern vehicle, there are at least 300 welded or punched fasteners like cap nuts, various bolts, or studs. The fabrication process and methods, which join the fasteners to the car body or essential components like front/rear axles, seat belts, steering column, wires, are extremely vital to the performance and safety of the final models.


Introduction to Automatic Cap Nut Welder

The automatic cap nut welder is the automatic welder that is particularly designed to join the cap nuts and M-thread, T-thread bolt, and so on. Also known as electric resistance welders, the welding equipment basically utilizes high heat generated from resistance to current and the proper amount of force applied to the weld joint to weld the parts together. Some resistance welding methods that are widely used to join the cap nuts include spot welding and projection welding, and projection welding is the most common way for cap nut welding. 

When it comes to the basic structure of the automatic cap nut welder today, it consists of an automatic cap and nut loading system with vibrators, the rotary table with designed sets of molds as well as the unloading devices, which are mostly automated, either. The automatic cap nut welders, which are the projection welders, offer annular projection parts or 3 to 4 separate projection parts to meet the need when handling nuts and bolts. 

When comparing the projection welding process in automatic cap nut welders using separate projections and annular projections, the annular projection style is most advantageous with the plastic insert. With the arrangement, some sorts of cap nuts can obtain a watertight weld joint, and the process is also suitable for connection subjected to fatigue stress and heavier loads. Also, the annular projection parts of the automatic cap nut welder reduce the amount of the crack initiation area.

Different from spot welding machines, these projection welding machines have the component parts used to obtain discrete individual point contacts to focus the current to join the cap nuts or other kinds of fasteners. More details of the projection welding process for cap nuts will be discussed in the next section.

:: Read more: Automatic Cap Nut Welder: A Nut Welding Guide


Cap Nut Projection Welding Process

Also known as resistance fastener welding, the projection welding used in automatic cap nut welders is similar to general resistance welding. However, the generated heat is not concentrated by the copper electrodes to the workpieces in the projection welder. Instead, the special projections or the arrangement can achieve the process. 

In some spot welding machine types of automatic cap nut welders, the contacting area of the electrode cap tip defines the current flow. On the other hand, in common projection welding type automatic cap nut welders, the current is limited to the critically-machined projection or embossment. 

The projection welding cycle in an automatic cap nut welding machine for bolt or nut welding includes 3 stages. First, the projection parts get in contact with the mating sheet. Next, the electric current begins to heat up the projection until reaching the weld temperature. Subsequently, the electrode force leads to the projection collapse in a short time when the metal fabrication takes place.


What Is Required When Using Automatic Cap Nut Welders?

To complete the projection welding, both AC and DC power sources are acceptable for cap nut welding. When it comes to the weld current of projection welders, it is typically less than one required in a spot welding machine. However, the weld current must be sufficiently high to create fusion prior to the collapse of the projections.

During the cap nut welding process, a short weld time which is advantageous for high volume production needs a higher level of amperage. In this case, the user of the automatic cap nut welder should be aware of the welding parameters, in order to keep overheating or expulsion conditions. When the user intends to attach the fasteners to some high-strength steel parts, thicker sheet, or weld materials with lower heat conductivity, impulse welding operations will be a more ideal option to regulate the heating rate.

On the other hand, the electrode force of the automatic cap nut welder should be appropriate to fully flatten the projection parts reaching the weld temperature, fusing the cap nuts with the sheet metals. The excessive force will lead to the premature collapse of the projection parts, as a result, the poor weld will have imperfect fusion in the center area.


Benefits of Automatic Cap Nut Welder

The automatic cap nut welder provides numerous benefits, making it an invaluable investment for fastener welding in automobile, motorcycle, aerospace, and many more industries. The versatile automatic cap nut welder is suitable for welding various bolts, dome cap nuts, hex caps, lug nuts, and so on. Typically, the projection welder for cap nut welding can handle a nut size ranging from M4 to M20.

The high level of automation of automatic cap nut welders offers reliability and accuracy with the development of the automatic feeding system. The automated loading of the nuts, caps, or bolts ensures positional accuracy and tight tolerance during production, carrying the workpiece to the welding unit. The automatic welding and unloading process also helps increase productivity, which can be up to 40 pieces each minute.

Also, the projection welder needs less heat and forced to join the pieces, which allows it to have a longer life than general welding machines. 


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