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Wire and arc additive manufacturing ( WAAM ) is an additive manufacturing ( AM ) technology that uses wire-form materials and arc discharges as the energy source .
 Wire and arc additive manufacturing, WAAM, additive manufacturing, AM, technology, materials, arc, as, source
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:
 Wire and arc additive manufacturing, WAAM, additive manufacturing, AM, technology, materials, arc, as, source