Heißkanaldüsen Typ SLT/-DLT Customer information

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1.5. 14 iA Heißkanaldüsen Typ SLT/-DLT Customer information Hot runner technology for medical products: Precision millions of times Implementation of tandem technology requires an injection molding machine with a relatively high installation height of the mold and adapted programming. B.Braun decided to use a machine of the type Engel 200/90 V Electric with an electrical injection unit. “The hot runner system is the highlight of the tandem mold,” emphasizes Stefan Moser. “This system does not only guarantee an equal filling of the cavities on both sides of the mold, but also a faultless gate point at the protective caps.” “Because of the high number of cavities 24+48 in the tandem mold, we first focused on a 24+48drop hot runner system with individually controlled open single nozzles,” says Walter Ehlert, responsible for consulting and sale at GÜNTHER Heisskanaltechnik. For about 20 years B.Brown has been trusting in components provided by the company from Frankenberg. Picture: Open multi-tip nozzle of the type 26ZHT – all in all 24 nozzles are installed in the two parting lines of the mold: 12 of them with two tips each on the Mini-Spike side, and 12 of them with four tips each on the Transofix side Picture: Mini-Spike, a withdrawal and injection spike for multi-dose containers (above) and Transofix, a transfer device (below), each of them with a protective cap (green color): Such a protective cap made of polyethylene (Lupolen 3020K) barely weights 0.5g “But it would have been too demanding and expensive to install such a system within the planned compact mold,” Walter Ehlert continues to explain. Since the hot runner with multi-tip nozzles did function well in the mold in stock, this technical alternative solution has finally come into view. Ehlert describes the advantages of multi-tip nozzles for tandem production in the following way: “These nozzles have a very small structural shape, therefore they allow very small patterns in the mold, keeping the controlling effort low.” However, the use of multi-tip nozzles is often a compromise because there is only one control zone for four gates. Therefore the user cannot control the details of the process so well as with single nozzles. However, with “simple” materials this feature can be compensated for without any problems. The concept of the hot runner system comprises twelve open multi-tip nozzles per parting line; the ones of the type 26ZHT18/2/67-S with two tips on the Mini-Spike side, and the others of the type 26ZHT18/4/67-S with four tips on the Transofix side. Valve gate technology was originally planned only for the sprue bar. However, since the mold was thought to work with a stiff sprue bar which moves away when the parting line 1 opens, valve gate technology was also provided for the injection molding machine along with the needle valve in the sprue bar. 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 Subject to technical changes 7/12
Heißkanaldüsen Customer information Typ SLT/-DLT Hot runner technology for medical products: Precision millions of times This has the advantage that the machine is able to continue conveying even with the sprue bar moving away to eject the parting line 1. “However, at the beginning of the series production it was problematic with this configuration to evacuate the pressure quickly enough from the hot runner system, remembers Moser. In principle, due to tandem technology, the material for each injection molded part has to be injected and conveyed, and finally the pressure has to be removed again from the system in half of the cycle time. With the protective caps, the material squeezed out of the system on the injection side, and the parts initially showed extreme stringing.” The problem was basically solved with the following measures: The machine valve gate nozzle was replaced by an open nozzle, the inner cross-section of the connecting nozzle was enlarged, and the machine program was optimized. Today, the cycle time of the single part has been reduced by 10%, with two parts being produced at the same time due to tandem technology with alternating injection and cooling. To sum it up, good filling performance for all cavities, no stringing, good tear-off behavior are the parameters for which the hot runner system supplied by the Frankenberg company is substantially responsible. The company was founded 25 years ago. Today it employs about 200 people, and operates together with its partners all over the world. 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 Picture: “Hot half” with view on the multi-tip nozzles 26ZHT with four tips 1.5. 15
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