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In this method , an FFF 3D printer prints a resin mold that functions as a structural unit in a multi-material structure and as a sacrificial plastic mold for the addition of the metal material .
 FFF 3D printer, resin, mold, as, structural unit, multi-material structure, as, sacrificial plastic mold, metal material
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:
 FFF 3D printer, resin, mold, as, structural unit, multi-material structure, as, sacrificial plastic mold, metal material