Heißkanaldüsen Typ SLT/-DLT Customer information

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iA Heißkanaldüsen Typ SLT/-DLT Fig. 7 Filling pattern with 25 % mold filling Fig. 8 Filling pattern with 50 % mold filling The good insulation of the 5DHT50 B nozzle used allows the material to be processed at a nozzle temperature of 265...270°C to significantly reduce the emission of gases from the flame retardant. The intervals for the necessary maintenance work have been extended from < 35,000 shots before to > 50,000 shots now. With the previous system the inserts were worn after approx. 250,000 shots due to corrosion but now with the GÜNTHER hot runner system, more than 1.2 million shots have been possible without corrosive wear. Customer information Stable and Material Saving Processing of Flame Retardant Polyamides with GÜNTHER Hot Runner Technology Fig. 9 2K-mold for insertion guide (4-fold) Although nozzles with open nozzle pieces are used, the plastic melt does not drool when the mold opens. One of the reasons for melt drooling is imprecise temperature control in the hot runner nozzle. Excessively high temperatures in the hot runner can cause the melt to expand and plastic can exude even when the mold opening times are very short. In practice this effect is due to a very narrow process window: There are often only approx. 5K between the freezing and the explosion-type opening of the nozzle and the associated drooling of the melt. The changeover has had another effect, too: Using this hot runner nozzle has prevented the formation of streaks around the injection point. In the meantime the process capability of the GÜNTHER hot runner systems has been proving its worth for more than a year. Meanwhile, Moeller has equipped two further molds for processing this PA type (PA66 25% GF; UL-V0) with GÜNTHER hot runner systems (5DHT50B nozzles). Here, too, this type of material can be processed without any problems. Dipl. Ing. Jörg Essinger Applications Engineering Manager For any questions, please contact our Application Engineering department at +49 (0) 6451 5008-31 or -63. The information is given in accordance with our present-day knowledge and is meant to provide technical background. . www.guenther-hotrunner.com 1.5. 10 Subject to technical changes 7/12
Customer information Preventing flow marks on injection molded parts The requirements set on molded parts in the visible area are high, a clean injection point is indispensable. This is of particular importance for components which are backlit, as it is the case with light covering panels. Flow marks caused by flow separation of the melt in the nozzle can lead to quality problems. To ensure process reliability, nozzles with multi-purpose pluggable tips are used by Werner Langer Metall- und Kunststoffverarbeitung, a metal and plastics processing company. A PMMA-type material, optimized for transparency and lack of streaks, is used for light covering panels (between the mold halves). Plastics processing company Werner Langer produces three different kinds of light covering panels for Simon & Schelle, a lighting manufacturer. The production started in early 2007. “Our customer's quality standards as well as the requirements on the light covering panels were clearly defined,” says Werner Puppe, technical manager at the plastics processing company from Meschede- Berge, “a clean injection point, no flow marks or weld lines, little warpage, absolutely no sink marks on the side flanges of the covering panels, and a high-quality surface finish. After all, the light covering panels shall be used as mirror lightings in the bathroom.” Use of conventional nozzles is problematic Standard nozzles with screwed-in tips, sufficient for most of the injection molding applications, could not be used for production of light covering panels because their use goes together with flow separation of the melt. This would have caused flow marks on the opaque covering panels which would be visible when backlit. In search of a solution, the company contacted hot runner supplier GÜNTHER Heisskanaltechnik. For any questions, please contact our Application Engineering department at +49 (0) 6451 5008-31 or -63. The information is given in accordance with our present-day knowledge and is meant to provide technical background. www.guenther-hotrunner.com 7/12 Subject to technical changes iA “Since we have been in contact with this supplier since 1988, and have always appreciated is good consulting services and technical support, we were looking for collaboration on this application as well. For this purpose, we made the 3D design data of the part available for the hot runner specialist. As a result, GÜNTHER came up with a proposal to use a nozzle type with a multi-purpose pluggable tip.” This relatively new type of the tip enables the melt to be mixed in such a way that there are no longer flow marks seen on the molded part. This is a unique selling point of the multi-purpose pluggable tip on the market. “The design of the nozzle tip yields a very low shear potential,” says Walter Ehlert, in charge of consulting and sales at the hot runner specialist. “Competitive products do feature some design principles which should result in flow marks being avoided; however, these techniques often increase the level of shear stress in the melt, which may lead to degradation of the plastics. This can often be seen in the form of streaks on molded parts.” This problem arises particularly in the case of light covering panels: The molded part is very long, so it must be filled quickly. The multi-purpose pluggable tip, designed with its maximum depth of clearance, produces minimal pressure drop together with a very low level of shear stress. The new multi-purpose pluggable tip, here in a nozzle of the SET60S type, enables the melt to be mixed in such a way that no flow marks appear on injection molded parts. 1.5. 11
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