Hot runner technology

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Hot run­ner tech­nol­o­gy is the gener­ic term for the man­u­fac­ture and ap­pli­ca­tion of hot run­ner sys­tems which are used as func­tion­al com­po­nents of form­ing tools for the ma­chine pro­duc­tion of mold­ed parts made of met­als or en­gi­neer­ing plastics.

In the in­jec­tion mold­ing of ther­mo­plas­tics, hot run­ner tech­nol­o­gy or the hot run­ner sys­tems in the sprue sys­tem of the molds are of de­ci­sive im­por­tance. The most im­por­tant func­tion of hot run­ner tech­nol­o­gy is the pre­cise and re­li­able tem­per­a­ture con­trol of the plas­tic melt flow­ing in­to the mold. When a hot run­ner sys­tem is used, the sprue sys­tem is ther­mal­ly sep­a­rat­ed from the mold en­vi­ron­ment and is tem­pered sep­a­rate­ly to en­sure the flowa­bil­i­ty of the melt. The plas­tic can­not so­lid­i­fy and no sprue forms on the mold­ed part. Hot run­ner sys­tems al­so al­low longer flow paths to be re­al­ized, as they pre­vent both pres­sure loss­es in the gat­ing sys­tem and vis­cos­i­ty in­creas­es in the cool­ing melt. Mod­ern hot run­ner sys­tems can be con­trolled very pre­cise­ly. Func­tion­al com­po­nents of hot run­ner sys­tems for heat sup­ply are, for ex­am­ple, car­tridge heaters, coil heaters or flex­i­ble tubu­lar heaters. How­ev­er, pre­cise mon­i­tor­ing of the tem­per­a­ture in the hot run­ner is al­so cru­cial to en­sure a smooth process. Dif­fer­ent tree shapes of ther­mo­cou­ples are used for this pur­pose. Specif­i­cal­ly, min­er­al in­su­lat­ed ther­mo­cou­ples with di­am­e­ters of Ø 1.0 mm and Ø 1.5 mm or ther­mo­cou­ples with a flange mount­ing (al­so called type 68) are of­ten used here.

Structure of a hot runner system

A hot run­ner con­sists of the hot run­ner man­i­fold bar and the hot run­ner noz­zles. The liq­uid melt comes from the plas­ti­ciz­ing unit and flows through the man­i­fold bar to the noz­zles. The noz­zles are the last heat­ed zone be­fore the liq­uid plas­tic en­ters the in­jec­tion mold for cooling.

Cascade injection molding

Cas­cade in­jec­tion mold­ing is pos­si­ble with hot run­ner tech­nol­o­gy, which en­ables the pro­duc­tion of large com­po­nents. Due to the nu­mer­ous noz­zles in the hot run­ner, mul­ti­ple gates can be used to fill the mold­ed part.

Who builds hot runner systems?

Hot run­ner sys­tems are a sep­a­rate man­u­fac­tur­ing di­vi­sion. They are usu­al­ly not man­u­fac­tured by the mold and die shop but are pur­chased as a pur­chased part for the mold. Nu­mer­ous com­pa­nies have de­vel­oped in the in­dus­try whose sales mod­el is based sole­ly on the man­u­fac­ture of hot run­ner systems. 

What is a mold?

A form­ing tool is a com­plex, two-part con­struc­tion, made of steel, alu­minum or cast iron, de­pend­ing on the ap­pli­ca­tion, and of­ten con­tain­ing com­plex tem­per­a­ture con­trol sys­tems and hot run­ner systems.

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