TECHNOLOGY | MOULDS
possible to control the process successfully with a simple pressure control,” he says. “But we can obtain parts with consistent properties, cycle after cycle, using viscosity control. This is new.” Viscosity is directly related to flow. Priamus obtains a value by having two pressure/temperature sensors at different positions along the flow channel. “We detect when the melt passes each sensor, and from this we can calculate the absolute viscosity in Pascal-seconds.”
Bader points out that developments in commu-
Above: The Foboha production cell drew the crowds at K 2019
of small two-component rollers that go onto the baskets in dishwashing machines. The system was designed to streamline labour-intensive material logistics, eliminate intermediate storage of the prefabricated individual parts, and reduce space requirements by up to 60%. One component of the roller is in polypropyl-
ene, the other in an acetal (POM). The components are removed by a six-axis robot, which snap-fits them together by removing one set of components from one of the cubes, pushing them onto the components still held in the other cube, and then removing the finished parts to a conveyor. The cell can produce around 65 million parts per year for Bosch company BSH Hausgeräte, Europe’s leading home appliance manufacturer, by German proces- sor Hermann Hauff.
Each cavity has one temperature sensor, so that the flow balance of melt in the mould can be precisely controlled. In all, there are 104 sensors in the mould. “The idea is not new but the way we implement it is,” says Bader. “We do two things. We balance the two cubes, which involves adjusting the hot runner tip temperatures to get an even flow, so every part is filled at exactly the same time. We also use the same pressure and temperature sensors to control the injection machine (in this case an Arburg) settings, cycle by cycle. We control injection speeds and holding pressure, in a closed loop, through an OPC-UA interface. If there is any fluctuation in the process, we compensate for it by changing the settings, in real time.” Bader says this level of control is proving especially important when processing bioplastics like PLA, whose processing characteristics vary more than those of traditional materials. “It is not
36 INJECTION WORLD | November/December 2019
nications are making it easier for different elements in the injection process, as represented by different member companies of the Barnes Group, to work together. “If we interface with the injection ma- chine, there is no standard. There is the OPC-UA protocol, but it is open. It is up to us what informa- tion we send and receive.” There is also a new Euromap standard, 82.2, published in draft form at the beginning of this year; the final version is scheduled for publication in the first half of 2020. Identical to OPC 40082.2 and created by a joint working group of the OPC Foundation and Euromap, it describes the interface between injection moulding machines and hot runner devices (HRD) for data exchange. Euromap says the target of the standard is to provide a standard interface for hot runner devices from different manufacturers to ensure compatibility. The following functionalities are covered: general information about the hot runner device; status information; process data. Gammaflux was demonstrating a new controller
that combines servo and temperature control, with visualisation on the same screen, for high precision electric-driven axes in the injection mould: not only valve pin actuation, but also sliders and turntables. This incorporates the Euromap interface.
Servo controls on the up Servo-driven valve gate hot runners featured on numerous stands at
K2019.HRSflow, for example, showed a servo-driven valve gate with 21 drops for a mould producing two large automotive parts for a bumper (for a Ford Torneo Custom) made by Magna in 14% talc-filled PP, with a wall thickness of around 3mm. One part weighed 3.2 kg, and the other 2.0 kg. HRSflow has been supplying hot runner systems with servo controls for around five years. In all, it has around 1,000 systems in the field. Robert Harvey, Sales Director for HRSflow products at Inglass USA, claims HRS is years ahead of the pack in the field of servo controlled hot runner systems. “We’ve had five years of development, five years in the field.” HRSflow also had a demonstration hot runner
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PHOTO: PETER MAPLESTON
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