7167
There is a statistically significant difference in surface roughness values from specimens built with identical laser exposure parameters but located at different positions on the build platform .
 surface roughness, laser, exposure, build platform
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:
 surface roughness, laser, exposure, build platform