CANADA'S LEADING INFORMATION SOURCE FOR THE METALWORKING INDUSTRY

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CANADA'S LEADING INFORMATION SOURCE FOR THE METALWORKING INDUSTRY

CANADA'S LEADING INFORMATION SOURCE FOR THE METALWORKING INDUSTRY

How to Choose: Stud Welding or Spot Welding

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by Andy Gillings

Start by defining your priorities and application requirements

 

Stud welding and spot welding are commonly used welding methods to attach fasteners to metal. However, the two welding techniques achieve different results in terms of quality, durability and cost. To determine which process is optimal to your business, you should also consider which method best suits your priorities, requirements and application. 

Spot welding is a form of resistance welding that joins sheet metals and is commonly used in the manufacturing of electronics, batteries, metal furniture, vehicles and automotive parts. Stud welding fuses fasteners to metal surfaces by creating an electric arc between the parts. 

 

There are three main types of stud welding: 

1. Capacitor Discharge Stud Welding:
A high current pulse is released from capacitors with a pre-set voltage to generate an arc. The arc then melts metal’s surface and return pressure fuses the materials together. 

2. Drawn Arc Stud Welding: 
As the stud lifts to a pre-set height, a pilot arc is triggered by a pre-calculated current and weld time. The end of the stud and parent material melt, and once the stud returns to the molten pool onto the plate, a ceramic ferrule shapes and contains the molten metal.

3. Short Cycle Stud Welding:
Arc welding is used but applies shielding gas instead of ceramic ferrules to achieve the best results. This approach also uses capacitor discharge style studs. 

Type of material 
Low carbon steel is the most suitable material for spot welding because of its high resistance to electricity and lower thermal conductivity than the copper electrodes used to create the required electrical current. However, there is only a limited selection of base materials suited to this technique. 

Pure aluminum can qualify for spot welding but has a lower resistance to electricity and will require higher current levels. High carbon steels and aluminum alloys aren’t appropriate for this welding technique, as they form a brittle weld that is prone to cracking. 

Stud welding is suitable for a wide range of materials such as steel, aluminum, copper, and brass. However, the capacitor discharge process doesn’t suit curved or imperfect surfaces, but the short cycle and drawn arc stud welding methods are more tolerant of flawed materials. 

Speed
Stud welding doesn’t require access to both sides of the material, and the equipment is portable, making it easier to do the job efficiently. The drawn arc process is slightly lengthier as it involves ferrules to contain the molten metal pool between the stud and parent material, which adds more steps to complete each job. However, the short cycle method uses shielding gas instead, which achieves faster results. 

Spot welding is also a speedy procedure because it doesn’t require any fluxes or filler metal. One cycle of the weld time—simply applying the welding current to the metal sheet—is 1/50 of a second in a 50 Hz power system. 

Cost 
The efficiency of stud welding minimizes costs with fewer total hours spent completing the project. And the long-lasting results of stud welding also reduce the chance of unexpected maintenance and rework. 

The drawn arc method is the most expensive stud welding process because of the added steps involved, but it achieves stronger welds, making it a worthy candidate depending on the job specifications.  However, large production volumes are required for spot welding to be financially viable. 

Quality
Stud welding doesn’t impact the material’s surface appearance, as it’s conducted on one side of the parent material, making the finish practically invisible. It doesn’t leave marks on the reverse side of the material either. This technique doesn’t weaken materials or render them unsuitable for liquids by punching or deburring holes into them. Stud welding results tend to be incredibly durable and provide a weld that’s generally stronger than the original components on their own. 

When spot welding, the weld’s strength depends on the cleanliness, temperature and force of the metal and electrodes. However, this process has a tendency to warp materials. 

Spot welding is a popular choice for mass production of specific applications, but limited materials are suitable. In comparison, stud welding is extremely versatile. Both procedures offer speed, but stud welding can cut costs and ensure high quality results. SMT

Andy Gillings is the sales area manager at Taylor Studwelding Systems. Reach him at [email protected]

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