Energy Saving in multi-cavity molds


Constant research into thermoplastic materials with increasing performance, due to technical and economic requirements, is leading to an ongoing evolution in molding. This phase involves the process stage, the machine, and the mold, where research into '"energy saving" results in being a highly detailed area, especially concerning the hot runner.

The excellent thermal stability, thanks to reduced thermal dissipation between system and hot half, combined with optimal canalization definition, make the HRS Multitech hot runners the ideal solution for many applications, including medical and technical applications, caps and closures, houseware and the cosmetic industry.

Another key aspect is the attention paid to the mold cooling optimization.For this important aspect, HRS Multitech uses "conformal cooling" - meaning inserts with conformal cooling channels strongly shaped to the molding surface and close to the gate, made by SLM - Selective Laser Melting technology.

A good example of an industry where a great deal of attention is paid to energy saving, is the medical sector. These aspects are required especially when considering hot runner systems for blood tube applications. The development of such a kind of application requires detailed knowledge of mold-hot runner assembly, in order to obtain a product that falls within the restrictive tolerances required by the customer. The application is critical since the material used is PET, with tube thickness averaging 1mm and the length 100 mm. The combination of these three factors involves the use of a system with very advanced performance. The use of the concepts described above has allowed to process the material inside the molding window recommended by the resin producer and to reduce the initial cycle time by 25%.

Specifically, the Multitech division of HRSFlow has recently developed a system that involves the use of MTV39 and of a special valve guide for the production of a PET tube (the 75mm-long version with a weight of 3.6g and the 100mm-long version with a weight of 4.9g). The hot half system's 32 cavities produce the 75mm format at a cycle time of 7.1s.
The required result meets all the needs and demands of the customer: part weight homogeneity (+ / -1.5%), optimal concentricity, low energy consumption and perfect transparency (Fig.1).

A test to evaluate flow distribution has been carried out to support the technical solutions chosen. The interrupted shot obtained by loading a half dose demonstrated that the melt feeding was not angled with the so-called "flute tip" but perpendicular to the longitudinal axis of the piece (Fig.2).The absence of preferential flows ensures the regularity of the filling phase and this leads to good concentricity between the external and internal cylindrical surfaces.