Process safety and energy efficiency are hot topics in hot runner technology. Precision parts and parts with special surface quality for example are particularly demanding. Modular, low-maintenance systems are required for productive, multi-cavity tools.
The requirements of our customers are similar across all industries," says Dr Stefan Eimeke, director of development at Ewikon Heißkanalsysteme in Frankenberg, Germany: "Faster and more cost-effective production with higher quality and precision." Compact and maintenance-friendly multi-cavity hot runner systems are highly sought after in order to achieve high productivity at the smallest possible injection moulding machine sizes.
Expert register two trends in this respect: Firstly, a great demand for mult-tip nozzle concepts, in particular with nozzles for lateral connection. These allow very compact system layouts that are also easy to maintain. And secondly, an increasing share of valve gate application, regardless of the processed materials and the system’s multi-cavity-properties.
This was mainly due to the increase in process reliability, of course combined with the perfect cut quality this technology provides. Furthermore, modern technologies like electric valve gate technology with stepper motor drives allow users to actively impact processes, for example by traveling to several needle positions during one cycle, or through quick fine adjustment of parameters during production.
Reduced cycle times, elimination of additional energy consumers
Regarding energy efficiency, Eimeke observes, "that a hot runner system is inherently more energy efficient when compared to conventional runner systems (cold runner), where material must be both heated up and then cooled down again." In hot runner systems, once the melting has been heated up, its temperature must only be maintained. Benefits in terms of energy efficiency also come from reduced cycle times and the elimination of additional energy consumers like sprue mills: "When upgrading an 8x-cold runner system to a hot runner system, you can for example achieve energy savings of 30 to 45% through the corresponding reduction of cycle times."
The total energy consumption and thus the efficiency of a hot runner system is largely dependent on the losses occurring during the process. Heat conduction losses at direct contact points between hot runner components and tools are particularly relevant in this respect, As they are responsible for almost 90% of the energy loss of a hot runner system. In order to improve energy efficiency, "one must start here", says Eimeke.
In the processing of thermally sensitive plastics it is of key importance to keep shear at a minimum, to avoid long dwell times in the hot runner system, and at the same time to eliminate dead spaces in the system. For clean room applications, valve gate solutions have proved ideal because unlike with pneumatic or hydraulic actuators, there is no particle emission with this system.
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