Trimmer line breaks easily or melts

The main causes of trimmer line breaking easily or melting:

• Contact with hard surfaces: Hitting concrete, fences, trees, or rocks can snap the line.
• Line too long: Extending the line beyond the cutter blade increases stress and breakage. Always operate the trimmer using the debris shield.
• Incorrect line size: Using a line that's too thin or not recommended for the trimmer can cause it to wear quickly. Always use the trimmer line diameter recommended for that model. 
• Worn or damaged trimmer head: Rough edges or sharp spots in the head can cut or fray the line. Replace a worn or damaged head.
• High friction/overheating: Running the trimmer at high speed for extended periods can generate enough heat to soften or melt the line, especially inside the head. Run the trimmer at the lowest effective speed to reduce heat buildup inside the head. 
• Poor-quality or old line: Line that's brittle, dry, or exposed to sun/heat for too long can break more easily. Store trimmer line in a cool, dry place; for best performance, soak line in water overnight to restore flexibility.

CONFIDENTIAL: In the early production of the Speed Feed® 500, we received reports of the center spool and the top cover melting. Most cases this was caused by weed wrapping around the gearcase and trimmer head housing. With larger displacement trimmers they can overcome this weed wrap and will continue running, generating high heat which can cause the spool housing to melt. To reduce the chances of this failure, the material used in the production of the knob, cover and spool has changed. The knob changed from 15% glass filled nylon to 33% glass filled nylon and the spool changed from 15% glass filled nylon to 35% high heat glass filled nylon. 35% Glass Filled nylon has a higher melting point and is more durable in extreme cutting conditions. Melting point of this material is 600 degrees F. A replacement trimmer head can be offered as goodwill, Part #99944200950.