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The distortions are caused by thermal expansion and shrinkage of the part during repeated melting and cooling processes , which is particularly an issue for large thin walled structures .
 concept or principle: thermal expansion; concept or principle: shrinkage; manufacturing process: melting; manufacturing process: cooling; concept or principle: thin walled structures
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:
 concept or principle: thermal expansion; concept or principle: shrinkage; manufacturing process: melting; manufacturing process: cooling; concept or principle: thin walled structures