Comparison of Robotic Ultrasonic and Plasma Welding

FANUC R2000ib 125L R30ia Motoman MA1400 FANUC M710ic 50 Motoman HP6 NX100 FANUC Arcmate 120ic
Industrial robots are capable of automating a variety of welding processes. One of the better-known welding processes automated by robots is plasma welding. While advancements in robotic technology has led to the automation of more unconventional welding methods. One of those welding methods is ultrasonic welding. So how does the unconventional ultrasonic welding compare to the more traditional plasma welding? Below is a look at the similarities and differences between these two robotic welding applications.


Despite completely different methodologies there are some similarities between these two robotic welding applications. Both applications are quite versatile with the ability to be used with a variety of metals and metal thicknesses. Those with a high mix of workpieces can benefit from the plasma welding FANUC Arcmate 120ic or the ultrasonic welding Motoman HP20.

Another similarity between these welding methods is their speed. Both plasma welding robots and ultrasonic welding robots can complete welds at fast speeds helping to reduce cycle times. The high heat of plasma welding allows the ABB 2400 to complete welds with a single pass of the torch regardless of thickness. While ultrasonic welding robots can complete welds in under 500 milliseconds.

Both of these robotic welding applications also produce clean, high-quality welds. Ultrasonic welding robots produce clean, even, and smooth weld seams that do not require any additional finishing steps. Plasma welding robots are also known for their uniform welds. The highly concentrated heat affected zone produces clean welds without distorting the workpiece despite using incredibly hot plasma. Shielding gas also helps protect the weld pool from contaminants.


The main difference between these two robotic applications is their methodology. Ultrasonic welding robots are integrated with an ultrasonic head. The ultrasonic head is powered by electric voltage in order to generate ultrasonic vibrations. The vibrations produce heat that is able to fuse workpieces together. Plasma welding robots are integrated with a plasma torch. During welding an electric arc converts inert gas into plasma which is then used to melt workpieces and join them together.

Another difference between these two robotic welding applications is ultrasonic welding can be used on plastic workpieces while plasma welding is only for metal workpieces. This gives ultrasonic welding robots a slight edge over plasma welding robots in the versatility category. The ability to automate the welding of plastics has become particularly useful as manufacturers diversify their materials.

As mentioned earlier, both of these robotic welding methods are quite fast. However, with robotic ultrasonic welding no warmup time is required for tooling. In addition, no extra time is required for part cooling post weld. The elimination of both of these steps can further speed up cycle times for maximum productivity.

The last difference between these two types of welding automation is robotic plasma welding will require an electrode and shielding gas. Whereas robotic ultrasonic welding does not require additional equipment or consumables. The cost to maintain a robotic plasma welding system may be higher than an ultrasonic welding system. However, a robotic ultrasonic system may cost more upfront which could offset the difference in maintenance costs.

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