When considering the quality of your CD welds, what makes a good weld vs a bad weld?
Capacitive Discharge Stud Welding is a simple process. The most crucial part of the stud welding process is creating a secure bond between the fastener and the parent metal. There are many factors that contribute to weld quality and we’re going to explain how to interpret the signs of a good and bad CD weld.
Why Weld Quality is Important?
Firstly, it can be the difference between a structurally sound product and a product at risk of major failure. Operators must therefore understand the factors that cause a poor weld and how to avoid them.
Understanding the Factors of the Weld Gun
Heat and Electrical Current
Heat is produced by an electrical current when welding with a capacitive discharge stud welder. In CD welders, current, amperage, and heat are directly proportional: the more current you supply to the weld gun, the more amperage–and therefore the more heat–will be applied to the weld site.
Spring Pressure and Timing
The proper timing of the fastener’s plunge into the molten parent metal is of extreme importance as well. The major factor that affects the timing of the fastener’s application to the weld site is the amount of pressure applied by the weld gun’s spring.
Capacitive discharge weld guns utilize springs to force the fastener into the molten metal–higher spring pressure produces a quick plunge, whereas low spring pressure produces a slower plunge.
Both the amount of electrical current supplied to the weld gun and the pressure of the gun’s spring are often entirely adjustable. To best determine how much current and pressure is desirable for any weld, the operator must consider the parent metal’s material and thickness, as well as the material of the fastener itself.
Common Welding Errors
Cold Welds
“Cold welds” are welding errors most often caused by too little volts/heat or too little time during the weld cycle (or both!). Additionally, errors involving the tip of the fastener–such as insufficient pressure against the parent metal–can create cold welds. This weld is characterized by its lack of marking around the weld site and/or the appearance of the fastener being slightly raised above the parent metal.
Hot Welds
“Hot welds” in contrast, create an obvious “splash” effect around the stud. This “splash” is molten base metal that has been forced away from the fastener. Unlike a cold weld, hot welds are caused by too much time and/or too strong of an electrical current. This causes the tip of the fastener and the base metal to melt too quickly. The molten metal is then forced away from the center of the weld, where the strong bond between the metals will take place.
Other Welding Errors
Although cold and hot welds are the most common type of capacitive discharge welding error, there are other manifestations of a poor weld that can occur. For instance, if there is insufficient pressure on the weld or an incomplete connection, the weld site can crack. Additionally, a combination of too much pressure and too low of a current can create indentation at the weld site, which is a clear sign that the weld will not hold. This reinforces the need to have both the correct amounts of current and spring pressure. They are integral to weld quality.
Good Welds
A good, solid CD weld will have consistent welding around the entirety of the fastener. The perfect combination of sufficient pressure and electrical current creates a good weld that is stronger than the fastener itself. In other words, when a weld is poor, mechanical failure will occur in the weld. However, when a weld is good, the parent metal will break under stress before the weld does.
The Importance of Accessories
Besides proper use of the stud gun itself, the use (and lack of use) of accessories is the greatest factor affecting stud weld quality. Accessories such as collets and chucks hold the fastener correctly in place within the stud gun. Which helps eliminate some of the factors that cause both cold and hot welds.
More Information About CD Stud Welding
Be sure to check out our video on a Good vs Bad CD Welds. We also have a video that gives you 5 Tips for Aluminum CD Stud Welding to ensure the best quality welds with Aluminum studs.
As always, if you still have questions, call us at 800-252-1919 or email us at info@studweldprod.com. Our team members are always ready to help!
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