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MIG Welding vs Ultrasonic Welding

There is no shortage of welding applications that can be automated by industrial robots. MIG welding is one of the oldest and most common processes for robotic welding. As manufacturers have moved towards more fully automated factories and more diverse materials, they are automating welding processes that fall outside traditional methods. Ultrasonic welding is one of those and has seen rapid growth in robotics over the past decade. So how does the unconventional ultrasonic method compare to the traditional MIG method?

MIG Welding

MIG (metal inert gas) falls under the arc welding category and is one of the most popular applications for arc welding robots. The MIG welding process uses a filler wire in the form of a consumable electrode. This filler wire is fed between two metal workpieces as an electric arc creates the heat needed to melt the filler wire. The melting of the filler wire fuses workpieces together, avoiding having to completely melt the metal workpieces. Most arc welding robots are capable of automating MIG applications. Yaskawa Motoman is known for their arc welding robots which include Motoman MA3100 and VA1400. While the FANUC Arcmate 100ic is ideal for MIG welding.

Ultrasonic Welding

Ultrasonic welding, sometimes shortened to sonic welding, involves using ultrasonic vibrations to join workpieces together. Robots are integrated with an ultrasonic head, also called an ultrasonic actuator, for the end-effector. During welding electrical voltage is used to generate ultrasonic vibrations. These ultrasonic vibrations produce heat that melts and joins workpieces together. Six-axis robots are recommended for automating ultrasonic welding, for example the ABB 4600-20.

Key Differences

There are many key differences between these two robotic welding methods. The first is the types of materials they can weld. Both can obviously weld metals; however, ultrasonic welding robots can also weld plastics. The ability to weld plastic workpieces is one of the reasons for the growth of ultrasonic welding robots. MIG welding robots can only weld metals, mainly thick metals with very high melting points such as steel.

Another key difference is MIG welding requires a consumable electrode while ultrasonic welding does not. This means the costs of maintaining a robotic ultrasonic welding system may be less than a robotic MIG system. With a robotic MIG application consumable costs will be higher since the electrode will need to be replaced.

Weld quality is another area where both of these robotic welding methods differ. Both produce strong welds; however, the finish of the weld varies. The use of a filler wire in robotic MIG welding can produce spatter. After the FANUC Arcmate 120ic is finished a MIG process, additional steps will likely be needed to remove the spatter and clean up the workpiece which adds to cycle times. Ultrasonic welding robots produce precise and clean welds. Weld seams are smooth and do not require additional finishing steps.

Lastly, ultrasonic welding does not require time for tooling warmup or part cooling post weld while MIG welding does. Robotic ultrasonic welding decreases cycle times by avoiding idle times before and after welding.

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