Case Study Achieving homogeneous temperature control beyond the nozzles
Möller-Flex is a specialist for flexible plastics and products made of several materials. As its hot runner system supplier, the injection moulding company has chosen Günther because the hot runner nozzles meet their requirements for a constant temperature in an outstanding manner.
Günther hot runner technology and Möller-Flex can rightly be described as long-term partners. The innovative hot runner technology supplier and the specialist for flexible moulded parts from Delbrück in Westphalia have been working together since 1997. “We have been working successfully with Günther for a long time, especially in the area of our PVC products,” explains Bernd Mollemeier, Head of Technical Development at Möller-Flex. “Günther hot runner systems meet our requirements for a constant temperature in an outstanding manner. Furthermore, the very good personal support is to be regarded as a big plus.”
An important expertise of Möller-Flex is the production of moulded parts from various soft plastics, thermoplastics, TPEs and elastomers. The development and production of products made of several materials, which are manufactured in small and large series by injection moulding, are a particular strength. Composite products are often – but not exclusively – made of soft and hard PVC. Möller-Flex is part of the traditional Möller Group from Bielefeld, a family business with almost 300 years of history.
As a specialist for flexible plastics, Möller-Flex often works for manufacturers of so-called “white goods”, meaning household appliances such as vacuum cleaners or washing machines, for which bellows of various sizes, seals, covers and housings are manufactured. Other important customer areas are automotive, medical technology and mechanical engineering. Möller-Flex supplies its products to customers all over the world, including as far as India and China.
One of the most successful products of the Westphalian injection moulding specialist is the protective caps for the brake booster in automobiles. About one-third of the entire global market demand of these boosters is manufactured in Delbrück. A protective cap consists of 14.7 cubic centimetres of PVC, which is processed at 160 to 210 degrees in direct gating. Möller-Flex uses an HCP8B H distributor with eight open hot runner nozzles of the type 6DHT50C-0.7 with a 6-mm melt channel diameter and a 50-mm nominal length. Günther hot runner nozzles are characterised by their two-part shaft, which is made of titanium alloy and tool steel. In conjunction with the integrated air gap in the hot runner nozzle, optimum thermal separation and excellent overall insulation in the front nozzle area of the temperature-controlled mould are achieved.
Thanks to heaters pressed into the manifold on both sides, a homogeneous temperature control beyond the nozzles is guaranteed. The power connections are protected by steel and ceramic sleeves. Using only one single open hot runner nozzle, an engine compartment seal for vacuum cleaners, also made of PVC, is injected with a shot volume of 30 cubic centimetres. The processing temperature for the Molerit H85 is between 160° and 190°, whereby Günther hot runner nozzles enable applications with a process temperature of up to 450°. A single open nozzle 6DET80 with a nominal length of 80 mm and straight passage is used here.
Consistent temperature is extremely important
“A constant temperature profile is particularly important for PVC products such as the protective cap or the engine compartment cover,” says André Mühlenweg, technical developer at Möller-Flex. “PVC products are quickly damaged when temperatures are too high. However, thanks to our Günther hot runner systems, there are no problems at all.” Möller-Flex also uses an open Günther hot runner to produce the 12-gram bellows for a household appliance, although a thermoplastic elastomer (TPE) is used for this product.
In operation, a balanced, straight manifold with two 5DHT50 nozzles (4.8 mm melt channel diameter, 50 mm nominal length and straight passage in the gate) and a nozzle spacing of 180 mm is used, which, like the H distributor used for the protective cap, is characterised by a homogeneous temperature control.
“By using Günther hot runner systems, we save on residual plastic casting and thus significantly reduce cycle times and scrap rates,” emphasises Bernd Mollemeier. “When the innovative Günther Blue-Flow systems are in use, energy savings of up to 60 percent are achieved compared to systems with conventional heating elements. Our co-operation with Günther has been worthwhile for years and we already have several further joint projects in planning.”