MOULDS | HOT RUNNERS
Right: MHS has developed third genera- tion iVG hot runners with a pneumatic actuator inside the nozzle body that does not require cooling
Below: Black Box bolt-on valve gate actuators from MHS can run extremely hot (require no cooling) to deliver simpler, tougher, more reliable
performance
MHS has developed third generation iVG hot runners that feature a compact, pneumatic actuator inside the nozzle body without cooling, lubrication or seal rings, making them reliable and virtually maintenance free. “The product group has been in operation for over ten years and the gating technology has created new possibilities, from high cavitation to single-drop hot runner systems,” said Schmidt. “Internal valve gate hot runner nozzles are defined by their durable internal or integrated piston. Every feature of the actuator is located directly inside the nozzle body so that everything takes place on the nozzle side of the manifold in a single, compact unit. The valve pin mechanically opens and closes the gate at the nozzle tip with timing down to the millisec- ond and accuracy down to two microns. An all-metal pneumatic piston drives this process. The piston produces more force and powerful shut-off stroke than traditional pneumatic actuators that have O-ring seals or electric actuators. IVG hot runners are ideal for high temperature applica- tions, however, virtually all valve gate projects operating at any temperature can benefit from the reliability and user friendly design of an internal valve gate nozzle, although not including micro- moulding. “When it comes to maintenance, lubricating the piston is not necessary. There are no soft seals, only specially-treated metal seals that do not wear or break down, which reduces machine downtime for maintenance and repair. This also makes internal valve gate nozzles a good fit for cleanroom environments. Under normal operating conditions, the piston should remain untouched inside the nozzle body for the life of the mould. For any quick nozzle maintenance that may occur outside of the
piston, like replacing a nozzle heater or thermocou- ple, all components are fully accessible from the cavity side of the mould while the mould stays inside the machine. The nozzles are seated, so there are no components inside the manifold - a feature of some older actuators. This gives the mould designer the option of running air supply channels directly inside the hot runner manifold, which further simplifies design and assembly. “The use of internal valve gate nozzles elimi-
nates the need to incorporate cooling lines into the hot runner design or to incorporate an external actuator outside of the nozzle. This saves space and energy costs over the life of the mould. It reduces the added expense associated with the hardware and assembly of cooling lines made from copper, steel or flexible tubing. Additionally, coolant causes common maintenance issues that cooling-free internal valve gate nozzles avoid, like leaks and blockages due to human error, poor water quality and corrosion.
With everything packaged inside a self-con-
tained, compact unit, mould designers can create smaller moulds that cost less to produce and operate in smaller injection moulding machines. Designers can also place gates into tight spaces. “A common application for iVG nozzles, which
eliminate traditional rear-mounted or manifold-inte- grated actuators, are stack moulds with two parting lines where the nozzles are arranged back-to-back instead of in an offset configuration. This makes internal valve gate nozzles ideal for high-cavitation moulds or large cavities requiring side gates. IVG nozzles can also be used in single-nozzle systems that require only one gate, drop or point of injection. The design’s simplicity enables the nozzle to align perfectly with the machine barrel, instead of being offset to accommodate the external actuator mechanism of a traditional solution.” Ewikon has developed a slim side gating solution for syringe and pipette production. The HPS III-MHR111 nozzle is specifically designed for the efficient production of long tube shaped parts, such as syringes or pipettes in the medical industry.
54 INJECTION WORLD | November/December 2017
www.injectionworld.com
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