Hot runners | moulds and components
Produced in PET, these demanding precision parts can measure up to 100mm in length and feature an average wall thickness of 1mm. The HRSFlow Multitech division last year developed
a system involving the use of MTV39 nozzles and a custom valve guide to produce PET blood tubes (a 75mm long format with a weight of 3.6g and a 100mm long format with a weight of 4.9g). The 32-cavity hot half system produces the 75mm tube on a cycle time of 7.1 seconds without take-out plate. This high level of performance was achieved due to optimum integration of the mould and injection machine and resulted in part weight homogeneity of ±1.5%, optimal concentricity, low energy consumption, and high transparency.
Assessing the fl ow During the development of the tubes a number of interrupted (short) shot tests were carried out to assess fl ow distribution. The interrupted shot obtained by loading a half dose demonstrated that melt feeding was not angled – the so-called “fl ute tip” - but perpendicu- lar to the longitudinal axis of the part (Figure 2). This indicates very good hot runner geometry - the melt fl ow in the cavity is almost axisymmetric with respect to the longitudinal axis of the piece. The absence of any preferential fl ow ensures the fi lling phase is regular and, as a result, leads to good external and internal cylindrical surface concentricity in the moulded component (Figure 3) and a very high quality gate fi nish (Figure 4). The Multitech product line is designed for production
of low weight parts at high volumes, offering a mini- mum pitch of 22mm and suitability for up to 96 cavities. Aside from medical components, the systems are
suitable for production of caps and closures and cosmetic parts. Aside from its manifold components, HRSfl ow also
manufactures conformally cooled mould inserts using SLM technology, where they have proven to be both effective and durable. SLM inserts provide a lifespan equivalent to that of the mould itself and are designed to withstand the demands of high volume production applications. Mechanical properties of the fi nished inserts are almost identical to those for forged steel and they can be surface treated by nitriding, nickel plating and PVD.
www.hrsfl
ow.com
Top image
(fi gure 2): Short shot trials show a highly even
fl ow front. Good concentricity is achieved
(Figure 3 above
left) as is a high quality gate
(Figure 4 above right)
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