Sometimes the line around the spool could melt together. This condition results from ultrasonic resonance of the line within the spool. It can happen with any type of line, but is more prevalent with round shaped line than with square or hexagonal line.
Line melting or line welding can be produced by sustained high speed trimming against a hard stationary surface (fences, curbing, walls, etc.) and/or wrapping the line on the bump spool in a rotationally twisted manner.
You can minimize line welding by:
1
Using a lower head speed when trimming against hard objects and varying the throttle speed.
2
Let the line hang free and rotate the spool around the line when loading the spool. Most people hold the spool stationary and wind the line around the spool. This technique tends to twist the line rotationally which causes the line to bind and fuse together due to the ultrasonic vibration.
Take out the melted line and replace it with a new line of the type recommended in your product's operator's manual.