Swiveling Hot Runner Manifolds

At K 2013 in Hall 1, Booth A09, MHS-Mold Hotrunner Solutions has introduced Rheo-Pro^® Slide™ Manifolds, a revolutionary type of hot runner system with rotating melt transfer joints that allow linked manifolds to move freely in order to distribute plastic anywhere inside the injection mold, the company states. The new technology now makes it possible to create injection points, or gates, directly inside the slides of a mold. It also allows molders to create continuous melt transfer connections that maintain contact, and therefore flow, even when the mold plates separate.

The patent-pending hinge design allows its rotating joints to maintain a constant seal while linking together multiple hot runner manifolds to create an uninterrupted, continuous melt path that is able to bend and move inside the injection mold, the company reports. The technology enables the melt channel to deliver material to the cavity across moving mold elements such as slides and lifters. Slide mechanisms are the only way to demold complex parts with exterior undercut side features. For example, many injection molded parts have details for customized functionality or side ribbing for rigidity requirements. During demolding, these design details can create insurmountable obstacles to the mold designer. Rheo-Pro^® Slide™ Manifolds solve this problem by allowing entire sections of the mold to move, without interruption to the flow of material in the melt channel. This flexibility also makes the systems ideal for new part designs using stack molds, tandem molds, as well as rotary and cube molds.

The process can be compared to running your melt channels through a flexible hose, only pressure inside the melt channel of an injection mold typically reaches between 10,000 and 20,000 psi, or upward of 1400 bar. That’s roughly 600 times the pressure inside a car tire, or 1.3 times the pressure of the Mariana Trench, the deepest part of the ocean, which has a pressure of 1,086 bar (15,750 psi). This is the first and only technology that reportedly exists to keep liquid plastic flowing through flexible runners, let alone under such extreme processing conditions.

One of the oldest challenges in mold design has been to find an uninterrupted path for the melt to flow from the machine barrel to the nozzle, despite moving plates and other dynamic mold components. These systems offer the solution by creating continuous melt transfers that bridge gaps between opening and closing mold plates. Bolting together manifolds in a static arrangement in order to move plastic around the mold is nothing new. However, moving manifolds in a hot runner has never been done before. It opens up a world of possibilities for injection molders and mold designers.

In large thin wall parts, Rheo-Pro^® Slide™ Manifolds overcome the challenge of flow path versus wall thickness ratio. Using cascade fill, very long flow paths can be realized, even in parts with extremely thin walls and large surface areas. A cascading injection sequence using multiple drops across the part can keep the melt pressure as well as the clamp force within limits. Having nozzles directly inside the slides of the mold is required in order for large parts with outside features and long sidewalls to fill completely and eject.