technology | Hot runners
The FLEXflow system from HRSflow is designed for weld line manage- ment. This example shows how a car dash- board, originally sequen- tially injection-moulded with six hot runner gates, was filled through only four gates (M3 to M6) using the technology. In the original set-up, the two flow fronts (one starting from M3-M6-M4 and the other one from M5) formed a weld line that was uncontrolled in terms of its shape and position (picture top right, yellow-dotted line). Using FLEXflow control of the valve pins, the weld line becomes straight by simply throttling valve gate pin M6 (picture bottom right) and its position can be moved.
parts with small shot weights in high cavity moulds. Target applications include the packaging and medical industries, where the technology is already successfully being used in moulds with up to 192 cavities. The balanced micro-manifolds feature four screwed-
in heat conductive tip inserts - each with a flow channel diameter of 3mm and a melt seal at the gate. According to Ewikon, a fully balanced flow channel layout is achieved by placing a main manifold on a second level. Four gates only require one heating circuit, which reduces control technology complexity and cabling. As a result, space is freed up in the manifold to integrate additional support sleeves or domes into the plate.
Right: Ewikon micro-mani- folds feature standardised electrical
cabling and an integrated
cooling supply
Compact solutions The company claims that micro-manifold technology mould designs are more compact than conventional multi-cavity mould layouts. In addition, tip inserts can be exchanged easily after removing the contour plate without the need to dismantle the manifold system. Ewikon offers complete hot halves with micro- manifold technology as 16, 32, 64, 96, 128 and 192-drop versions with standardised dimensions built up as clusters of four micro-manifolds. The micro- manifolds are produced in three versions with different lengths of electrical connection. All feature an integrated cooling supply. HRSflow, the hot runner division of INglass SpA, has developed its FLEXflow technol-
44 INJECTION WORLD | November/December 2016
ogy for injection moulding of complex, large parts in multiple-gated and multi-cavity applications. Particu- larly suitable for cascade moulding, FLEXflow is a servo-driven regulated valve gate system that the company says has demonstrated surface quality improvement in production of large-format visible parts, especially with respect to weld line management. It has also shown quality improvements in production of thin-wall transparent headlamp lenses. According to the company, FLEXflow allows precise, sequentially coordinated opening and closing of the valve gate pins with selectable profiles and velocities. This permits accurate control of the flow rate in each individual hot runner nozzle and, as a consequence, the flow front in the cavity as a whole. In weld line management, for example, throttling back specific valve gate pins makes it possible to control the shape and progress of the flow fronts in the cavity to modify the form and position of any resulting weld lines. By enabling a more gentle opening and shutting of the valves, the pressure loss that often occurs with conventional cascade injection moulding through the abrupt on/off switching of the hot runner nozzles is avoided, says the company. This also helps to prevent flow marks on the moulded part. The more even pressure
distribution on the part that can be achieved through optimised position and speed control of central and peripheral valve
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