6425
Below the critical energy , a lack of fusion due to insufficient melt tracks and discontinuous beads was observed .
 fusion, melt, beads
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:
 fusion, melt, beads