MOULDS | HOT RUNNERS
which the conical contact surface allows better thermal control of the needle temperature, while the precisely aligned cylindrical needle closure assumes the task of sealing. With a conventional conical configuration, when the valve closes there is always the formation of a plastic layer at the gating point. When the mould opens, this layer is torn off the part, which could lead to flash forma- tion. In order to get good detachment, fine adjustment of the process conditions is often required. Through the elimination of the layer due to cylindrical needle closure, the HPgate reduces the time required to optimise the process param- eters. Good moulding quality is attained much faster - equivalent to enlarging the process window. Further improvements in gate quality can be achieved by combining HPgate with FLEXflow technology, says HRSflow, where the needle position can be precisely controlled, reducing the influence of the process conditions. HRSflow has also developed space-saving nozzles and insulating pressure blocks for en- hanced application convenience in hot runner injection moulding. The company says the full compact nozzles house all the heating elements of the previous standard Pa type (screwed-in nozzles for shot weights up to 200g) in a space-saving design with a nozzle seat diameter of only 28mm along the entire length, instead of 33mm with the conventional design. The needle tip and end ring of the new screw-in nozzles are unchanged. With internal diameters of 6, 8 and 10mm and nozzle lengths from 75-450mm, they can be provided with one or two heating zones. They are also available in Classic Line and Fail Safe versions, the latter with two heating devices and two thermocouples. The nozzles are also suitable for reverse gating of mouldings and for all gating configurations (torpedo, free flow and valve gating). Their maxi- mum working pressure is 1,800 bar. Typical applications include small, complex-shaped parts,
Above: The main characteristic of the new HPgate concept from HRSflow (right) is the introduction of a hard metal insert screwed into the mould, in which a conical-cylindrical gate is machined. If it becomes worn, optimal closure can be restored without any of the usual cost-intensive work on the mould
such as loudspeaker grilles for vehicle interiors. The company adds that high clamp plate
Above: New full compact nozzles from HRSflow have a nozzle seat diameter of 28mm over their entire length, which is 5mm less than the equivalent standard nozzle
58 INJECTION WORLD | November/December 2017
stiffness under load and an optimum temperature profile in the hot runner system play a key role for the quality of a moulding. If this profile is not uniform, it can result in unbalanced spreading of the flow front, warpage and surface marks. HRSflow has developed new pressure blocks to meet these requirements to ensure an optimal moulding process. Produced from two special materials with low thermal conductivity, they act in two ways. Positioned on both sides of the hot runner, they firstly increase the stiffness of the platen so that the latter becomes less deformed under load. This results in mouldings of constant thickness within the narrowest of tolerances and without any flash formation. Secondly, they prevent heat transfer between this and the platen, which makes the temperature distribution in the hot runner far more uniform. The pressure blocks can be arranged in any desired position between the hot runner system and the mould (but not above the heating unit) without influencing the temperature profile. They are available with or without an adjusting plate and with thicknesses of 20mm (240°C maximum runner temperature, 50°C maximum mould temperature) or 30mm (300°C/100°C). Thermoplay has introduced a new version of the 3-zone temperature controller TH-M6, which is compact and low-cost. The company says that it is ideal for hot runner moulding applications with one and two points or single-nozzle injection systems and has the same characteristics as the 6 and 12 zone models. A graphic display of 240×64 pixels allows simultaneous visualisation of all information relevant
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