A new line of split-sheath cartridge heaters features a groove along the outside to accommodate a needle-type thermocouple that allows more accurate sensing and control for temperature-critical processing applications, such as molding heat-sensitive resins. The Watt-Flex split-sheath cartridge heaters from Dalton Electric (Ipswich, MA) feature a movable thermocouple that allows temperature measurement at any point along the heater sheath, as opposed to conventional heaters that are fixed and measure the temperature at either the middle or tip of the cartridge.
Dalton says its split-sheath construction allows each half of the heater to expand independently when energized for better metal-to-metal contact with the surrounding bore, which maximizes heat transfer even in oversized bores. The greater compaction of magnesium oxide around the coil provides superior heat conduction to the outer sheath, resulting in more responsive sheath temperatures, higher operating temperatures with cooler internal operation, and up to five times longer life. Because of their continuous-coil design, Dalton says Watt-Flex heaters have no cold spots between sections and produce a uniform temperature profile along the heater sheath. The company also notes that with no sections to burn out, the entire heater is either on or off, and the continuous coil also allows a hot-tip option. When the heater is de-energized, the split sheath contracts uniformly for easy removal, and Watt-Flex heaters are actually warranteed as removable from bores and sleeves....