Advanced Series hot runner - DME

Casting Resins &Mold DesignChemical ProductsHot Runner TerminologyInfoThis illustration is divided into two halves (valve side and non valve side) from typical DME hot runner systems. Theterminology associated with the various components are listed below.3241510148156791112131. Air gap2. Central heated adapter3. Locating ring4. Central adapter5. Dowel6. Center support pad7. Center dowel8. Manifold9. Nozzle10. Upper support pad11. Thermocouple12. Heater13. Gate seal14. Valve support pad15. Hydraulic/Pneumatic unitMold SteelDesigning a ‘rigid’ mold is a critical step in ensuring continuous problem free operation of the hot runner system. Themain factors involved in designing a rigid mold hot half are listed bellow.Manifold plate steel must be sufficiently hardto prevent excessive setting of the surfaces or hobbing by the hot runner components. For this reason, the minimumplate hardness must be at least 32HRC. DME strongly recommends that a prehardened steel from 35 to 40HRC (Suchas stainless steel AISI 420) be used. Failure to use a sufficiently hard steel, or the use of aluminum plates will lead tomaterial leakage and possible system component damage.Hot Runner system clearanceThe uniform “air gap” clearance around the hot runner system acts as an insulator to prevent excessive heat losswhich leads to system temperature imbalances. Too much clearance or open sides around the hot runner can provedetrimental to the successful operation of the system. Open sides will drain sufficient heat from the hot runner(chimney effect) that the system will contain severe temperature imbalance and possibly never reach the processingtemperature. Of equal importance is the fact that open sides dramatically weaken the mold. Exceeding therecommended clearance around hot runner has the same effect in reducing mold rigidity.22/12/2010www.dmeeu.com - 7