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There are three welding processes that are mainly used in WAAM : Plasma Arc Welding ( PAW ) , Gas Tungsten Arc Welding ( GTAW or TIG ) and Gas Metal Arc Welding ( GMAW or MIG ) .
 welding, processes, WAAM, Plasma Arc Welding, PAW, Gas Tungsten Arc Welding, GTAW, TIG, Gas Metal Arc Welding, GMAW, MIG
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 welding, processes, WAAM, Plasma Arc Welding, PAW, Gas Tungsten Arc Welding, GTAW, TIG, Gas Metal Arc Welding, GMAW, MIG