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Support structures are required in powder bed fusion ( PBF ) additive manufacturing of metallic components with overhanging structures in order to reinforce and anchor the part , preventing warping during fabrication .
 engineering feature: Support structures; manufacturing process: powder bed fusion; manufacturing process: PBF; manufacturing process: additive manufacturing; material: metallic; machine or equipment: components; concept or principle: overhanging structures; concept or principle: warping; manufacturing process: fabrication
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: 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} 
 Entities: Support structures, powder bed fusion, PBF, additive manufacturing, metallic, components, overhanging structures, warping, fabrication 
Answer:
 engineering feature: Support structures; manufacturing process: powder bed fusion; manufacturing process: PBF; manufacturing process: additive manufacturing; material: metallic; machine or equipment: components; concept or principle: overhanging structures; concept or principle: warping; manufacturing process: fabrication