Expandable Cartridge Heaters

At any given temperature the maximum watt-density that can be applied to a conventional cartridge heater depends on the clearance between the cartridge and the insertion hole of a die or a mold. The larger the clearance the less efficient is the heat transfer from the cartridge to its surrounding. Excessive clearances might cause premature failures Expandable cartridge heaters are made for insertion holes that through wear has become oversized or intentionally are made larger than acceptable tolerances to facilitate the removal of failed cartridges.

Expandable cartridge heaters have two legs that are joined together at the tip. The two legs are made from single tubular heater that has a semicircular cross-section. When Expandable heaters energize, the two semicircular legs expand with respect each other and press against the insertion hole wall.

1 - Energized Standard Cartridge Heaters
2 - Unenergized Expandable Cartridge Heaters
3 - Energized Expandable Cartridge Heaters