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Additively manufactured parts made with polymer extrusion techniques can be 50–75 % weaker in the z-direction ( across layers ) than in the x- and y-directions .
 Additively manufactured, polymer extrusion, be, z-direction
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:
 Additively manufactured, polymer extrusion, be, z-direction