How can I reduce my spatter? (Part 2 of 2)
By Matt Brooks
January 14, 2008
Spatter that occurs in gas metal arc welding (henceforth GMAW) applications can cause a number of headaches that range from the inconvenience of sweeping up a dirty/dust covered work cell to a full surface grind and repair welding. In the most extreme situations, weld spatter can even cause harm to welders by burning through clothing and skin. In most situations, weld spatter can typically be reduced and save a fair amount of money and time by reducing the required repairs or clean up.
This article continues where part 1 of our discussion left off, with the discussion of some more of the simple techniques used to reduce spatter, helping you create a more ideal production environment.
This is part 2 of a 2 part series.
Technique #3 - Watch Your Torch Angle
Another factor that is often overlooked in welding spatter control is the angle and position of the welding torch. The torch angle controls the direction of forces involved in welding. Many welders prefer a push angle (where the wire is ahead of the torch) to create flatter and more aesthetically pleasing welds. However, a push angle drives the forces forward, forcing any droplets of spatter from the weld puddle and wire transfer forward. Changing to a straight angle or a pull (drag) angle forces these droplets back into the arc and weld pool.The result is that the spatter generated is roughly the same amount, but it is more contained and forced back into the weld puddle, hence less visible spatter is created.
Spatter occurrences also vary depending on the material being welded. In the case of aluminum, a push angle will allow the soot to blow away from the weld and created a cleaner welding surface similar to technique #2.
Another item to note is the ESO (electrical stick out, or tip to work distance). The ESO can affect the actual amperage and voltage through the amount of “air resistance”. This means that the longer the ESO is, the greater the electrical resistance created by the air, which then reduces the current and increases the voltage (referring to Ohm’s Law - V=IR if Resistance is increase either Voltage must increase or Current must decrease). The opposite is also true for a shorter ESO.
The result of large changes can cause an imbalance in the current to voltage relationship since most welding power supplies will maintain one of the parameters consistently. It is suggested that for each welding current a set ESO should be used, as recommended by the welding power supply manufacture. In order to help maintain this ratio, DAIHEN D-Series machines feature a constant penetration function, which senses changes in ESO and automatically compensates for it through changing one of the variables to maintain the balance between parameters.
Technique #4 - Check Your Welding Environment
(Including your ground cables, shielding gas pressure, atmospheric environment, and contact tip types!)
A simple way to help reduce spatter generation is to check the welding environment. This includes making sure the welding grounds are secure and on clean surfaces. A poor grounding connection can cause a lot variance in the welding parameters, including arc instability or poor arc generation. Grounding cables attached to unfinished surfaces such as painted or rusty welding tables can increase the resistance to the welding current and lead to poor welding conditions.
Another area to check is to make sure there is no wind or fans nearby that may disturb the shielding gas. This simply prevents atmospheric contamination of the weld pool. The gas pressure should be optimized, since too high or low of gas pressure can also cause contamination. A final environmental check is to make sure the contact tips being used are correctly. Too small of an inside diameter can cause wire drag; too large can cause arc wander or arc instability. Both of these effects can cause the welding variables to become erratic.
Technique #5 - Know Your Shielding Gas and Wire Types
The type of shielding gas and wire alloy can have a large effect on the amount of spatter generated in GMAW. In terms of shielding gas, increasing the amount of argon can help reduce the spatter generation by increasing the ease of spray transfer mode (as compared to levels of CO2). However, this can also lead to increased surface tension in the weld pool and prevent adequate wetting, resulting in poor penetration patterns or overlap.
Wire plays a small role in spatter generation in that it may contain deoxidizers, such as manganese and silicon, which help cleanse the weld pool by removing oxygen and other contaminations. Flux-cored wires are also known for their low spatter generation, however, they typically require post weld clean-up after each weld.
Technique #6 - Utilize Advanced Welding Technology
In recent years, DAIHEN has realized the problems that spatter can create and have developed more advanced technologies to compensate for these problems. Most of these technologies focus on reducing the arc welding forces and softening the welding arc (the drive that causes the splashing or explosions in the weld puddle are reduced and spatter generation is significantly lowered). This is accomplished through two major methods, both electronically and physically. The electronic method controls the welding parameters through the duration of the arc period and cuts down the parameters during sections where the forces are greatest and that cause spatter. The physical method involves controlling the wire feed, or in the case of robotic applications, manipulation of the robot’s arm. Here, the system creates a phycial pull on the wire during the periods that cause spatter, thereby reducing the arc forces.
Figure 3: CBT-Controlled Bridge Transfer, a new current control method for reducing spatter
