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iv ) Constraints and limitations of current AM technologies , such as the critical angle of the overhanging structure and the difficulty in removing the supporting structure , should be involved in newly-developed topology optimization algorithms so that the designs could actually be fabricated by AM .
 manufacturing process: AM technologies; material: as; engineering feature: critical angle; concept or principle: overhanging structure; concept or principle: structure; material: be; engineering feature: topology optimization; concept or principle: algorithms; engineering feature: designs; material: be; manufacturing process: AM
Please list all entity words in the text that fit the category.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} 
Answer:
 manufacturing process: AM technologies; material: as; engineering feature: critical angle; concept or principle: overhanging structure; concept or principle: structure; material: be; engineering feature: topology optimization; concept or principle: algorithms; engineering feature: designs; material: be; manufacturing process: AM