TECHNOLOGY | HOT RUNNERS
Right: Fork using bio-based polymers processed with hot runners from Mold-Masters
eliminating hang-up spots and other design requirements are critical elements that need to be considered.
When moulding with bio-based plastics, a wide precise control distribution and thickness of the core layer. This is what
allows the injection of a higher percentage of PCR content compared with competitive systems, it claims. Where Mold-Masters can inject up to 50% PCR core, it says many competing systems are limited to incorporating up to 35%, which could limit sustainability targets and can significantly affect implementation of return-on-investment. Uni- form control allows Mold-Masters to achieve more consistent and fuller core fill. Mold-Masters adds that its ‘fold-over’ capabili-
Right:
Mold-Masters has recently launched the new Fusion Series G3 hot runner system
ties are a technical advantage that enable the highest core percentage to be achieved and ensures uniform distribution and complete coverage of PCR resins, which prevents contact of PCR with the product. Another significant differ- ence is the ability to position the core where it is required. For example, on packaging applications customers may prefer to keep any PCR core away from the injection point to avoid moulded in stresses, which can cause brittleness and result in drop test failures. According to Mold-Masters, one of the major advantages of co-injection technology is that there is no penalty to cycle time and existing tooling can be re-used. A variety of materials can be combined although those with similar melt temperatures are ideal for compatibility. Many applications are those that utilise the same material, for example, 50% virgin HDPE with 50% PCR HDPE. However, thermally isolated manifolds also make it possible to combine two thermally different resins. Indicating its experience with bio-based
plastics, Mold-Masters says these materials can be challenging to process compared to the common resins they typically aim to replace, which can make producing good parts difficult and sometimes impossible. Some bio-based grades can be easier to process than others, but it is common for many to have narrow processing windows due to thermal or shear sensitivities. Hot runner design needs to be optimised for bio-resins. Taking into consideration flow pattern,
36 INJECTION WORLD | November/December 2022
range of visual defects can appear based on the processing characteristics of the material and the hot runner configuration used. These defects include jetting, streaking, splay, flow marks, knit lines, burn marks and stringing. Mold-Masters says that it has spent extensive time testing a wide selection of these materials in its R&D facility and through a partnership with the University of Massachusetts, USA. In addition, the company has worked with leading converters and brand owners to select resins and to define a priority test se- quence. This research allows evaluation and understanding of their unique properties and effective processing requirements. Mold-Masters has also recently launched the
new Fusion Series G3 hot runner system. Fusion systems are shipped completely pre-assembled, pre-wired, plumbed and tested for fast, one-step installation. The company says that the Fusion G3 system incorporates several major enhancements that help optimise mould design and simplify and speed up installation. These enhancements include reduced nozzle bore cut-outs, new nozzle heater sleeves (optional), more compact actuators (PN and HY), and system installation at room temperature. FG3 nozzle bore cut-outs have been significantly
IMAGE: MOLD-MASTERS
reduced to minimise cut-out requirements to save time and money. FG3 nozzles currently offer a shot range of 50g to more than 5,000g per nozzle. Fusion nozzles incorporate field replaceable heater bands and gate seals to ensure moulders have the ability to respond and fix issues quickly to minimise downtime. New heater sleeves protect the nozzle and wiring from damage during installation and do not impact cut-out dimensions. FusionG3 also has the advantage that it is engineered to be installed and uninstalled at room temperature. It can be pulled directly from the shipping box and placed into the mould. This helps to reduce installation time, eliminate extra equipment such as a temperature controller and improve safety conditions during installation, assembly and removal. Symfill Technology signifi- cantly minimises core shift to improve part quality (straight- ness) of cylindrical, centre injected components having an aggressive L/D ratio. It
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IMAGE: MOLD-MASTERS
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