moulds and components | Hot runners
A fully-optimised hot runner will improve part quality, reduce energy consumption and reduce start-up scrap, explains HRSfl ow Multitech operations manager Massimo Rossi
Optimised design improves productivity
Main image: Optimised manifold fl ow dynamics helped maintain high levels of concentricity in this 32-cavity medical blood tube moulding project
Figure 1: Simulation tools allow
aspects such as thermal characteristics to be modelled
Optimisation of all aspects of the moulding process is critical to meet today’s high technical standards and economic requirements. Energy consumption is fast becoming one of the most important considerations for processors. Machinery and equipment makers are working hard to integrate energy saving features into their product offerings but it is important not to overlook the mould and the hot runner system, the latter in particular can be a signifi cant consumer of power, especially in a multi-cavity installations. Successful development of a hot runner system will include detailed analysis of the mouldings to be produced, using appropriate software simulation tools to model the thermal, fl uid dynamic and structural behaviour characteristics (Figure 1). System homogeneity should also be assessed at this
early stage, including full estimations of energy consumption per cycle and checks for pressure drop
and required weight balancing of shots. A good hot runner system designer will take great
care to minimise transfer of energy from the hot half of the tool into the moulding system, which is a key consideration in reducing energy consumption. However, energy loss is not the only factor to consider in development of the hot runner. Thermal regulation of the injection gate area is also an important aspect of the hot runner design as it can help speed up restarts (reducing production scrap), improve the quality of the gate, and can allow cycle times to be reduced by up to 25% in some cases. HRS Multitech designs use conformal cooling
technology. Manufactured using selective laser sintering (SLM) techniques, this allows cooling conduits to be placed very close to the gate and this, combined with good system design and optimisation, can allow very fast restarts. This is demonstrated in a recent Multitech system developed for a 72 cavity single-face mould for production of a fl at cap, which is able to begin production within 15 minutes with no need to increase the hot runner temperature.
Medical developments An area where a great deal of attention is paid to energy saving is medical diagnostics and disposables. It is also a sector where in-depth experience and high techno- logical performance are of paramount importance, and these aspects are especially critical when developing hot runner systems for blood tube applications.
44 INJECTION WORLD | April 2013
www.injectionworld.com
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