B. Braun builds a high-tech production line for infusion solutions with GÜNTHER hot-runner systems using innovative valve-gate technology

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1 B. Braun builds a high-tech production line for infusion solutions with GÜNTHER hot-runner systems using innovative valve-gate technology In its implementation of a challenging project, B. Braun relies on the innovative valve-gate technology from GÜNTHER Heisskanaltechnik GmbH. As one of the largest infusion solution manufacturers in Europe, B. Braun Melsungen AG has started up a new high-tech production plant for infusion solutions in Melsungen, Germany. Under the name of L.I.F.E. (Leading Infusion Factory Europe), Braun has planned three new production lines to produce and fill infusion solutions, and completed implementation of the plan by putting the third line into operation in April. The entire process runs online: from the manufacturing of bottles made of polyethylene through bottle filling and closing to automatic labelling, packaging and storage. A plastic cap is placed on the filled and closed bottle, which is then overmolded with PE in a subsequent injection moulding process. This creates a liquid-tight connection between the cap and the bottle. When overmolding the cap/bottle, very even filling of melt into the cavities is necessary. There is otherwise a risk of overloading of individual cavities, which would lead to the rejection of bottles that are already filled. In conjunction with filling the cavities evenly with low injection pressure, very stringent requirements are also set for the gate quality, and importance is attached to a high level of process reliability and short cycle times. To be able to meet these demanding requirements, B. Braun formed a team in which specialists from GÜNTHER Heisskanaltechnik GmbH, Frankenberg, Germany, and the injection molding machine maker Arburg in Lossburg, Germany, were represented. The outcome of this cooperation was an injection molding machine specially suited for the tool and an efficient hotrunner system. High optical requirements resulting from the use of a larger injection gate cross-section and the required reduction in cycle time make it necessary to use a hotrunner system with valve-gate technology. The hot-runner system has to be able to fill 24 cavities with 1g polyethylene (PE) each with a minimum drop of pressure. Each of the five special injection molding machines has, divided into two rows, four 6-cavity molds, each of which can be replaced separately. The division into four molds results from the requirement of being able to change any of the units as quickly as possible in the event of a fault. This application uses the 5NLT type nozzle screwed to the manifold. This 230 V valve-gate nozzle is excellently suited for confined installation spaces. The pluggable thermal and power connections of the nozzle allow replacements without having to completely dismantle the wiring. Ecoflac infusion solutions from the new high-tech production line for infusion solutions Each of these 6-cavity molds is equipped with a separately controlled needle actuation unit. The sliding cam actuation mechanism consisting of a lifting plate, specially coated guiding rail and a pneumatic drive cylinder ensures that the gates open and close precisely and evenly. Each drive cylinder can be removed without dismantling the mold. The positions of the needles can also be adjusted when still mounted. For any questions, please contact our Application Engineering department at +49 (0) or

2 Customer information B. Braun builds a high-tech production line for infusion solutions with GÜNTHER hot-runner systems using innovative valve-gate technology The melt is distributed through a main distribution similar to a stack mould, consisting of a manifold, a connection piece and heated transfer elements. These special transfer elements make it easy to replace the individual 6-cavity molds. GÜNTHER valve-gate echnology is distinguished by a long service life. Short cycle times and excellent gate quality without vestige can be achieved. Another advantage is that all parts subject to high wear can be eaesily replaced. Accordingly, problems such as nozzle clogging, poor part filling, gate stringing and inadequate gate quality can be avoided and shorter process times obtained. In comparsion to the plant previously used, it has been possible to reduce the cycle time and therefore also the process times by approx. 20%. Due to the many years of good experience that B. Braun has had with GÜNTHER Heisskanaltechnik and the convincing advantages of the valve-gate system supported by the good technical service, the molds for the L.I.F.E. project were fitted with GÜNTHER hotrunners. The L.I.F.E. project was implemented without delay. The project started in August 2002, and the first bottles were filled in February The requirements such as cycle time reduction, process reliability and the high quality of the injection gates have been constantly met since the commencement of the production. Dipl. Ing. Jörg Essinger Applications Engineering Manager Hot-runner Cavity Segment of the mold View within the mold For any questions, please contact our Application Engineering department at +49 (0) or Subject to technical changes 11/14

3 Customer Heißkanaldüsen information Typ SLT/-DLT B. Braun builds a high-tech production line for infusion solutions with GÜNTHER hot-runner systems using innovative valve-gate technology Conveying the containers through the testing machine and labeller to the packaging section. Sliding cam actuation mechanism ensures that the gates open and close with precise consistency. Sliding cam mechanism detail GÜNTHER 5NLT valve-gate nozzle For any questions, please contact our Application Engineering department at +49 (0) or

4 Customer information B. Braun builds a high-tech production line for infusion solutions with GÜNTHER hot-runner systems using innovative valve-gate technology For any questions, please contact our Application Engineering department at +49 (0) or Subject to technical changes 11/14

5 Smallest cavity pitches with the new micro flat nozzle type SFT/NFT Thermal separation from the mold is achieved by an air gap and by means of a special titanium ring in the contact area of the tip. The standard diameters of the material channel of these nozzles range from 2.8 mm to 6.0 mm, and they are available in the lengths L of 60 mm, 90 mm or 110 mm. It goes without saying that custom/made solutions to meet special application requirements are also possible. In this case, we recommend contacting our engineering department. The advantages of this line of nozzles are shown in the following example of an interesting application. A high number of cavities in a small space for micro articles made from technical thermoplastics is increasingly becoming one of the demands to be met today by modern injection molders. In order to enhance the economical efficiency in the production of such small articles, the trend today is going towards direct injection by means of a hot-runner, in order to cut down on high sprue masses in comparsion to the part weight and to reduce cycle times determined by the sprue. The task was to realize direct gating of a part made of PPS GF30 with a weight of 0.1 g. The part is a housig of an electronic component and must be molded onto a punch-out strip for further processing. The customer also wanted to have separate thermal control of each gate. Thus, due to the specified size of the injection molding machine and the required number of 64 cavities, the job of the hot-runner system was clearly defined. GÜNTHER hot-runner systems have always been especially well suited for these applications, on account of their excellent temperature control, outstanding thermal separation between the hot-runner system and the mold, as well as technical innovations. The introduction of the SFT/NFT nozzle series has resulted in an additional wide range of possible applications. On account of their slightly different design as compared to conventional hot-runner nozzles, cavity pitches from 7 mm can be realized for open hot-runner systems, and from 9 mm for hot-runner systems with valve-gate technology. The flat nozzles of the series SFT/NFT consist essentially of a metal tube with a tip, open passage or needle guide, a thermocouple and a nozzle body with integrated heating elements. The constant excellent temperature control of these nozzles with simultaneous high heating output in the area of the tip is achieved by the use of nickel-plated brass (CuZn) as basic material of the nozzle body and the two heating cartridges, which are operated via one control circuit. The processing of this glass-fiber filled high temperature plastic requires the use of a nozzle tip made of a special hard metal alloy to reduce tip wear and the use of a thermocouple suitable for high temperature applications. In addition, the high temperature application also requires full insulation with a material able to withstand manifold temperatures up to 600 C, minimizing the heat dissipation from the manifold. For any questions, please contact our Application Engineering department at +49 (0) or

6 Customer information Smallest cavity pitches with the new micro flat nozzle type SFT/NFT The given dimensions of the punch-out strip resulted in a grid dimension with a distance of 122 mm between double rows of nozzles and a nozzle pitch of 15 x 9.35 mm for the position of the gates. It was no problem to implement the required nozzle pitch of 9.35 mm. However, the distance of 15 mm between a pair of rows and the separate control of each gate necessitated developing a twin flat nozzle 3SFT60S. has resulted in a very small pressure difference whith no negative impact on the production process. This complete hot-runner system requires 66 control points, 64 for the individual cavities and 2 for the manifold. As a Hot Half, i.e. with the clamping plate, frame plate and cavity nesting plate, the system was completely wired, assembled and tested before delivery to the customer. This twin flat nozzle 3SFT60S consists of a nozzle body incorporating two material tubes with hard metal tips and two separately controlled heating elements. It was decided to do without full balancing because of the low part weight and the consequently increased dwell time of the material in the hot-runner system. Due to the low part weight and the minimal pitches, the calculation of the pressure drop in a partially balanced hot-runner system For any questions, please contact our Application Engineering department at +49 (0) or Subject to technical changes 11/14

7 Stable and material saving processing of flame retardant polyamides with GÜNTHER hot-runner technology As a world leading supplier, Moeller GmbH (Bonn) produces components and systems for automation, command and control devices. Diverse electrical and electronic components made of plastic are used in these systems. Fig. 1 Pushbuttons in command and control equipment (photo: Moeller GmbH) For a long time now Moeller has been using molds with hot-runners for sprueless production of these parts. The advantages of hot-runner technology over a conventional gating system include savings in material and a reduction in cycle time. When selecting a plastic for electronic components, it is often necessary to take account not only of the design requirements but also of statutory provisions and standards. In the electronics industry, for example, plastic components that are in direct contact with live parts must conform to the IEC Standard (International Electrotechnical Commission) etc. A further requirement is that the plastic must be capable of extinguishing itself after catching fire. Here, Standard 94 of the Underwriters Laboratories has established itself throughout the world as the authoritative standard for classifying flame retardance in plastics. The classification in standard 94 of UL depends on the rate of combustion, time needed for extinction, formation of drops and afterglow time. Depending on the component's function, the following criteria must be met: UL94 V2: Vertical test specimen; self-extinguishing up to 30s after withdrawal of the flame, drips of flaming particles allowed; afterglow max. 60s. UL94 V0: Vertical test specimen; self-extinguishing up to 10s after withdrawal of flame; no drips of flaming particles; afterglow max. 30s. A lot of devices from Moeller are also used in areas subject to the ATEX directives (ATEX = Atmospheres Explosibles = potentially explosive atmospheres). Here the requirements set for flammability have recently been tightened so that these components must now meet the requirements in combustibility class UL94-V0. On account of this more stringent requirement Moeller has had to replace the type of plastic it had previously used in a lot of components by an appropriate one classified in conformance with UL94-V0. Depending on the polymer, various flame protection systems are necessary to make a plastic flame-retardant. In the case of the PA66 used here, red phosphorus is used to give flame retardancy. The combustibility class is usually influenced by the quantity of the flame protection system used. Depending on the quantity, the red phosphorus used here reacts more or less strongly to temperature. Accordingly overheating during processing can cause thermal damage to the flame retardant. The gases arising as a result can form deposits on the mold and lead to corrosion. Occasionally the gases can even inflame. The PA66 with 25% glass fibers originally used by Moeller (combustibility class in conformance with UL94- V2) could be processed easily with the existing hotrunner system. However, after changing to a PA66-GF25 conforming to combustibility class UL-V0, serious problems arose when processing with this hot-runner system. In spite of the processing temperatures of C being appropriate for the material, extremely severe deposits appeared on the molds. The molds had to be cleaned every 30,000 to 35,000 shots. In addition to cleaning the mould deposits, the mold inserts had to be replaced after every 250,000 shots because of corrosion. The reason for this heavy formation of deposits and corrosion in the mold was the significantly excessive rise in temperature in the hot-runner nozzles in connection with the higher quantity of red phosphorus in the PA66. With a temperature of 290 C set at the control unit, temperatures of approx. 360 C were sometimes measured in the nozzles. This caused a reaction in the flame retardant. Moeller usually uses PA66 reinforced with 25% fiber glass with flame retardant for housing of electrical or electronic components. This type of material complies with UL94-V2 combustibility grading as well as other standards. For any questions, please contact our Application Engineering department at +49 (0) or

8 Customer information Stable and material saving processing of flame retardant polyamides with GÜNTHER hot-runner technology At that time GÜNTHER Heisskanaltechnik GmbH, specialized in the processing of demanding plastics, was given an order by Moeller to test an optimized hot-runner system, at first for a 2K component. For the trial Moeller selected the button insertion guide for holding a pushbutton (Fig. 2, 3) made of a flame-retardant PA66 (with 25% glass fibers) and a TPE. The hot-runner nozzle with a two-part shaft developed and patented by GÜNTHER Heisskanaltechnik GmbH (Fig. 4) has been selected. Fig. 2 Pushbutton insertion guide for a pushbutton, made of PA 66 Gf25 (Moeller) Fig. 3 Pushbutton (Moeller) The following criteria were set for selecting the hotrunner system: processability of a PA66 with glass fibers and flame retardant (red phosphorus / UL94-V0) consistent temperature profile over the whole length of the nozzle no massive temperature increase in the nozzle low level of shear stress on the melt in the hotrunner. Fig. 4 Nozzle with shaft (Photo: GÜNTHER Heisskanaltechnik GmbH) This hot-runner nozzle is setting standards in precision and economic efficiency. Various design features in the two-component shaft of the hot-runner nozzle ensure excellent insulation in the front area of the nozzle and keep heat losses between the hot-runner nozzle and the cavity extremely low. Due to this thermal insulation between the hot-runner nozzle and the mold there is no problem in processing engineering plastics and high temperature polymers. From the lowest shot weights, as of approx g up to shot weights of approx g, a wide range of applications in technical and precision injection molding are covered by the GÜNTHER hot-runner technology portfolio. For any questions, please contact our Application Engineering department at +49 (0) or Subject to technical changes 11/14

9 Stable and material saving processing of flame retardant polyamides with GÜNTHER hot-runner technology Material tube Heater Melt Air Gap solidified plastic Shaft made of titanium alloy Open nozzle tip Fig. 5 Detail Nozzle with shaft and open nozzle tip (DHT nozzle) The optimal thermal insulation minimizes the heat loss of the nozzle through heat conduction. This assures consistent temperature control in the nozzle and prevents an excessive rise in temperature at which the temperature measured in the nozzle is much higher than the target temperature. This prevents any possible damage of the plastic melt or additives (flame retardant) caused by an excessive rise in temperature. Fig. 6 Vertical construction of the hot-runner system for pushbutton insertion guide, Component 1 (PA66- GF25): 4-drop, 2x 5DHT50 nozzle on sub-runner The opening characteristics of the nozzle are critical for a reliable process. Tests have shown that both nozzles with an open nozzle tip give an even filling pattern at the same temperature. These filling patterns carried out to different filling degrees can be reproduced over a large number of cycles. Figures 6 and 7 show the result of the filling analysis at 25% and 50% filling. To keep the shear stress on the melt as low as possible, the nozzle was provided with an open nozzle tip (Fig. 5) instead of a torpedo tip. This allows an unobstructed melt flow through the nozzle and intermediate gating into the cavity. As the parts are filled through a sub-runner, the gate vestige at the injection point is of little importance. Compared to a nozzle with torpedo tip the residual sprue is slightly bigger. For any questions, please contact our Application Engineering department at +49 (0) or

10 Customer information Stable and material saving processing of flame retardant polyamides with GÜNTHER hot-runner technology Fig. 7 Filling pattern with 25 % mold filling Fig. 9 2K-mold for insertion guide (4-fold) 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 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 hotrunner system, more than 1.2 million shots have been possible without corrosive wear. 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) or Subject to technical changes 11/14

11 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 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. 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. For any questions, please contact our Application Engineering department at +49 (0) or

12 Customer information Preventing flow marks on injection molded parts Apart from flow marks being avoided, two further quality features of the manufacturing process have caught Mr. Puppe's eye: Virtually no warpage and no sink marks on the whole length of the light covering panels, this is really amazing. We would not have been able to get such a result with conventional nozzles. Last but not least, the design of the new nozzle enables particularly fast color changes. This is because the melt channel is designed to optimize flow so that the material comes to rest nowhere, which results in an optimal melting process. Werner Puppe technichal manager, at Werner Langer, a plastics processing, company from Meschede Without a nozzle type with a multi-purpose pluggable tip, we would have had to use a 2-drop manifold for this application, adds Puppe, this would have forced up the prices. The costs of a nozzle with a multi-purpose pluggable tip are only marginally higher than those of a conventional nozzle. Thus, better product characteristics are combined with decreased process costs. Molds on hand can be retooled The multi-purpose pluggable tip is intended primarily for parts that have to meet demanding requirements for optical clarity, such as, for example, applications involving polycarbonate or PMMA, or perhaps POM homopolymers. No applications using fiberglassreinforced plastics have been implemented so far. However, they are also possible if the tip is made of hard metal, says Ehlert. The customer of Werner Langer chose an opaque white shade for the light covering panels, which limited the selection of the material right from the start. A PMMAtype material, optimized for transparency and lack of streaks, is used for this application. Since the part is closed on the one side and open on the other, different flow paths in the mold are the result. To obtain a proper nozzle position, a mold flow analysis was carried out to come up with an off-center positioning of the nozzle. During the sampling inspection as well as when starting up the mold, there was not a single problem with the hot-runner nozzle, says Puppe. Plug&Play, this is how he describes the change-over to the new nozzle concept. The tool is installed in an Engel injection molding machine, type 1050/200, with a clamping force of 2,000 kn. A linear handling device takes the parts and puts them on a conveyor belt where they are manually packaged. Molds on hand can be retooled with the new kind of nozzle. In fact, the installation of a nozzle with a multi-purpose pluggable tip requires just a little modification of the mold contour. However, only very small modifications are necessary to replace a GÜNTHER hot-runner nozzle, says Ehlert. The light covering panels are manufactured on an Engel injection molding machine, type 1050/200, with a clamping force of 2,000 kn. Wide range of applications It is only natural that recently developed products, such as the multi-purpose pluggable tip, which are relatively new on the market do not immediately become widespread in applications. First of all, it is necessary to gain experience, and test the basic applications in longterm studies. For one and a half years now, the multipurpose pluggable tip has been included in the product range offered by GÜNTHER. The market entry phase is over, and Ehlert sees large areas of application, for instance, in the automotive industry, as well as for every application which requires optical parts. For Werner Langer, the testing phase is over for some time already, at least with regard to the light covering panels; the production is a complete success. Puppe is confident: When it comes to the production of optically demanding parts, we will continue using the nozzle with a multi-purpose pluggable tip. For any questions, please contact our Application Engineering department at +49 (0) or Subject to technical changes 11/14

13 Hot-runner technology for medical products: Precision millions of times Mini-Spike and Transofix, these are the names of two products manufactured by B.Brown, a healthcare company. These medical products are provided with protective caps which, manufactured with high precision, are required in millions of units every year. To guarantee a trouble-free production, the company trusts in systems supplied by GÜNTHER Heisskanaltechnik. The first product serves as a withdrawal and injection spike for multi-dose containers, the second one as a transfer device for sterile liquids, e.g. for drug admixture. In spite of the high number of pieces, precision has the highest priority when producing protective caps. The force fit of the protective caps must be manufactured in such a way that on the one hand the caps do not get lost during transportation of medical products, but on the other hand can nevertheless be easily withdrawn, says Stefan Moser, a project manager at B.Braun Melsungen AG. And this must also be possible when the user is wearing Latex gloves which can additionally be moistened with liquids like solvents. Until the conversion of production at the beginning of 2007, the company had manufactured protective caps using two conventionally designed multi-cavity molds with multi-tip nozzles. Picture: Stefan Moser, project manager (left), Benjamin Koch, responsible for machine optimization (middle), and Joachim Hammer (right), machine setter and quality controller at Braun Melsungen The conversion of production was triggered by the fact that, first, those molds with a low number of cavities could no longer provide the required production volume and, second, the Mini-Spike tool had reached its wear limit. The tandem technology seemed to be appropriate to solve the quantity problem. By this method two different parts can be separately and individually injection molded in an overlapping injection cycle on an injection molding machine using a tandem mold provided with two parting lines. The volumes and the quantity of pieces can be set individually for each parting line. The gating system of the tandem mold consists of an alternating slider with a bayonet socket, with one of the sides respectively locked and the other one unlocked for opening. The design of the system is simple, rugged and not susceptible to malfunctions, says Joachim Hammer, a machine setter and quality controller at the supplier from Melsungen. Picture: Parting line 1 of the tandem mold is intended for manufacturing the Mini-Spike protective cap, parting line 2 (pictured) for manufacturing the Transofix protective cap

14 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 in the tandem mold, we first focused on a drop 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: 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. 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 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, valvegate technology was also provided for the injection molding machine along with the needle valve in the sprue bar Subject to technical changes 11/14

15 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. Picture: Hot half with view on the multi-tip nozzles 26ZHT with four tips 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

16 Hot-runner systems for plastics filled with metal or ceramic powders The MIM (Metal Injection Molding) and CIM (Ceramic Injection Molding) technologies use injection molding process to produce metal and ceramic components which could not, or only with considerably more effort, be produced by machining. With these methods threedimensional components, e.g. for medical engineering products, can be molded in only one working step with no need of subsequent machining. Without well adapted hot-runners it is hardly possible to ensure manufacturing process reliability. Metal and ceramic powder filled plastics are used in many different fields. Examples of use of MIM are components for consumer products like ballpoint pens or for medical engineering products. Products manufactured by CIM are in demand where ceramics are required for insulation, often in conjunction with high temperatures. Sample applications can be found in the lighting industry. Both of the processes are relatively easy to use and make it possible to produce components without subsequent machining. Complex components can be manufactured this way. An application example for the MIM technology is an implantable infusion pump used in pain management for chronically ill patients. This device, installed in the abdominal wall, is applied for the measured dispensing of pain medication into the human body. The base plate was formerly manufactured by machining from a special, relatively expensive titanium alloy. This method was not only time-consuming but also expansive because of swarf. However, to realize the idea of manufacturing this component by MIM was not so easy at the beginning. Although it is normally quite easy to manufacture three-dimensional components by injection molding, the difficulty in this case was that the base plate had a large diameter and significant changes in wall thickness. This problem has been solved by injection molding the component with three parallel hot-runner nozzles. It has resulted in short flow paths and more even pressure distribution to yield a component which is manufactured in only one working step without the necessity of subsequent machining. Lower production costs are yet another compelling factor. With the MIM and CIM processes, a metal or ceramic powder is mixed with a binding agent, often polyethylene or polyoxymethylene, and a special wax, and then granulated. Picture: The titanium alloy base plate (below) of an implantable infusion pump was formerly manufactured by a complex machining process. Today the MIM technology allows for scrap-free manufacturing without subsequent machining. (Photo: TiJet) This mixture, called a "feedstock", can be processed by injection molding like any conventional plastic material. The plastic material is then removed from the molding, the so-called "green part", by heating. After debinding, this component has a porous structure because of the removal of the plastic material and is called the "brown part". By sintering of this brown part the metal and ceramic constituents are baked together to form a component with a homogeneous structure whose density and resistance does not differ from a conventionally manufactured steel or ceramic component. The advantages of e.g. a metal component, like high mechanical resistance and high conductivity, are combined with a relatively simple way of manufacturing

17 Customer information Hot-runner systems for plastics filled with metal or ceramic powders Basically, conventional injection molding machines can be used for CIM and MIM. But if a manufacturer wants to use these processes on long term, wear-resistant cylinders, screws and non-return valves should be used because these components are submitted to an increased abrasion due to metal and, even to a higher extent, ceramic powders. Discussions with feedstock manufacturers and plastic processors have shown that 80 to 90% of the parts produced by using MIM and CIM are manufactured by means of a cold runner with a sprue rod. A big fraction of the sprue rod can be recycled, nevertheless it would be very promising to avoid this production step by using hot-runner systems. A very homogeneous temperature control in the hotrunner is required, since the materials have a very small processing window. Variations of the temperature lead to a segregation of binder and powder which results in shrinkage differences and finally in the formation of cracks in the component during the sintering process. For these applications, GÜNTHER Heisskanaltechnik GmbH recommends using its hot-runner nozzles e.g. of the _HT type which are designed to meet higher requirements. The patented two-stage nozzle shaft guarantees an excellent isolation at the forward section of the shaft, providing for an extremely low heat loss between hotrunner nozzle and cavity, and for a very homogeneous heat distribution within the nozzle. Material tube (25 W/mK) Heater Air (0,04 W/mK) Gap solidified plastic (0,2...1,2 W/mK) Picture: The two-stage shaft of the SHT type nozzle and the frozen plastic material which forms a "cap" around the nozzle provide for optimized isolation towards the cavity and therefore produce a homogeneous temperature profile in the nozzle. Melt Shaft made of titanium alloy (7 W/mK) Open nozzle tip (100 W/mK) In addition, the frozen plastic material forms a "cap" around the nozzle, thus providing thermal separation between hot-runner nozzle and cavity. However, this feature produces quite the opposite effect for metal filled plastic materials because of the metal powder conductivity. In this case the mixture of plastic material and metal powder would draw the heat off the nozzle. That's why the supplier equip the nozzles used for MIM with special insulating caps made of a highly heat resistant plastics like polyetheretherketone (PEEK) or polyimide (PI) to provide thermal separation. A tubular titanium shaft located around the hot-runner nozzle additionally improves the insulating effect. This is a certain distinctive feature of the products supplied by Günther, since most of the hot-runner nozzles on the market have no two-stage shaft and achieve the sealing by direct metallic contact with the material tube in the mold insert. This leads to a very high heat loss which has to be compensated by a higher temperature in the hot-runner nozzle. This causes an excessive rise of the temperature as well as temperature variations, and therefore the materials cannot be processed in a reliable way. With the MIM technology, the parts are often molded by direct gating, and not via a sub-runner. Nevertheless, a relatively large gating point must be used in this case to obtain the necessary throughput and to transfer sufficient heat into the gate point. This is necessary because the metal-filled material transfers some of the heat into the cavity, and the melt freezes quickly due to the high filler content. However, with the CIM technology a sub-runner is often used. Here, too, a large gate point is of importance in order to cause as little as possible shear stress and to transfer the melt as quickly as possible into the cavity. With regard to wear resistance, hot-runners have to meet severe requirements, for both MIM and CIM. The products of Günther Heisskanaltechnik have nozzle tips made of hard alloy to provide reliable wear protection. For this reason high life times are possible with no need to change components of the nozzle Subject to technical changes 11 /14

18 Hot-runner systems for plastics filled with metal or ceramic powders A further quality increase can be achieved by hot-runner nozzles and manifolds which are heated by a fluid. It is well known that in particular for the processing of CIM feedstock a very homogeneous temperature control is necessary in order to avoid segregation and inhomogeneities of the melt. This may cause void formation in the component. Because of the inertia of the fluid, a nozzle heated by a fluid provides an even more constant temperature behavior than an electrically heated hot-runner nozzle. Dipl. Ing. Jörg Essinger Applications Engineering Manager Picture: Hot-runner nozzles which are heated by a fluid provide a far more homogeneous heating as electrical heaters, and maintain the temperature at a considerably more constant level

19 Hot-runner systems for high injection speeds When Speed Counts When delicate parts with thin walls and long flow parts are required, quick injections are essential for reliable production processes. Rapid injection processes are often indispensable for large-volume parts too however. An adapted hot-runner technology allows perfect processes and products here. Even in conventional injection moulding processes high injection speeds are often necessary but there are two variants that set particularly high standards: expansion injection moulding and physical foaming. In expansion injection moulding the melt is compressed in the screw antechamber or in the hot-runner and used as a pressure storage medium. As shown in the PVT diagram, the plastic melt can be compressed approximately 10 % at a pressure of about 2000 bar. This behaviour is used during expansion injection moulding. It is necessary for a reproducible process however that the pre-compressed melt volume be kept constant. For that purpose the screw must be held in an exact position after compression because it would otherwise be subjected to high pressure at the opening of the valve-gate nozzle and an excessive amount of melt would enter the mould. This pre-condition is satisfied by electromechanically driven injection moulding machines, permitting an optional axial positioning within the system's confines and the maintenance of this position even under high pressure. If a hot-runner system is used in expansion injection moulding, a pressure of up to 2500 bar is built up and maintained for a defined time. This ensures an even pressure in all cavities. The internal pressure that arises as a result of the foaming process acts on all points of the component, whereby to a certain degree it takes over the task of the holding pressure and in this way can balance out or at least reduce sink marks, shrinkage and warpage. For both processes the injection moulding machines must be adapted to the altered requirements. In expansion injection moulding an electric injection moulding machine is necessary for a precise dosage and injection. The MuCell process requires a special screw and special units in order to be able to inject the blowing agent in the super-critical state into the melt. Both processes with just a few exceptions can be conducted with all common polymers. LCP cannot be processed with the MuCell method but it is very suitable for expansion injection moulding. Valve-gate systems essential In both processes valve-gate hot-runner systems must be used in order to build up and maintain the required pressure in the hot-runner system. In expansion injection moulding the hot-runner system not only has to withstand very high levels of pressure, it must also be ensured that all needles in a multi-cavity mould open exactly and simultaneously. This even needle movement enables a lifting plate, which works in accordance with the principle of the sliding plate mechanism. Here the hydraulic piston's axial movement is guided through connecting links into the plate's lifting movement and accordingly causes the needles to move. For the successful use of expansion injection moulding, an absolutely even opening of the needles is essential. Once the needles open, the melt that is precompressed in the hot-runner can expand like an explosion and fill the cavities evenly, allowing very thin-walled components to be filled. In physical foaming, for example with the MuCell process, the system is fed a physical blowing agent, which first dissolved in the melt under pressure. On injection into the cavity, the pressure reduces, the blowing agent expands and the melt foams. Here too it is necessary to be able to inject the melt at high speeds into the cavity in order to be able to foam the part selectively in the cavity. A light-weight component with a closed outer skin and foamed core emerges. This process can produce foam structures with walls thinner than one millimetre. Fig. A slide lock, pneumatically or hydraulically actuated by means of an external cylinder, allows the simultaneous actuation of all needles

20 Customer information Hot-runner systems for high injection speeds In an X-Melt trial conducted in cooperation with the injection moulding machine manufacturer Engel, GÜNTHER Heisskanaltechnik GmbH in Frankenberg, subjected a two-cavity mould to a pressure of 2800 bar for half a second and checked the system for leaks. The injection trials were conducted with a test strip made of various materials with a wall thickness of 0.5 mm. The time for shooting the melt into the cavity varied from material to material and was 0.1 s for polystyrene, for example, and 0.04 s for LCP. The following are the results of the trial: the hot-runner system remained completely leak-tight at 2800 bar. No melt came out of the valve-gate nozzles. Both cavities were filled simultaneously. A very high level of reproducibility could be attained. An example of an application for expansion injection moulding is the friction disk. A hot-runner nozzle specially designed for LCP processing was selected. The nozzle's material tube diameter was made narrower to reduce the viscosity of the LCP as a result of the higher shear. Abb. 8-fold hot-runner system NV - friction disk of LCP Fig. For the expansion injection moulding of the friction disk an eightcavity hot-runner system with flat nozzles of the type 4NFT60LA is used. Friction disk Material Particle weight Wall thickness Gate diameter-ø 0.8 mm Hot-runner Pitch center LCP 0.02 g 0.15 mm 8-fold NV Hot-runner nozzle 4NFT60 LA 14 mm Fig. The LCP friction disk weihing 0.02 g can be produced with process reliability only with the expansion injection moulding method. (Photo: Schiebl) As trials have shown, reliable processes are possible only with expansion injection moulding. In this application a plastic part is injected onto a metal strip serving as a substrate. The disk is made of LCP, weighs 0.02 g and has a wall thickness of 0.15 mm. The challenge in this project was to inject the very small quantity of material with process reliability. As the weight of the shot is so low, only valve-gate systems can be used. Reduced weights and costs An important factor in physical foaming is that instead of expanding in the hot-runner, the melt does not expand until it is the cavity. For that reason the hot-runner nozzles must maintain the pressure in the system after the injection of the melt and the subsequent closing until the blowing agent stays dissolved in the melt. This could be confirmed in trials. An example of an application is a car door lock housing with a wall thickness of 1.1 mm made of POM, which is produced with MuCell technology. The customer's aims were to cut costs by using less material and to shorten cycle time and reduce warpage and sink marks. The gas in the melt lowered the melt viscosity, which allowed a quicker injection. The microcellular foam allowed homogeneous shrinkage behaviour, which made it possible to avoid sink marks in thicker walls. The hot-runner nozzle used was a type 8NLT80 nozzle from the supplier. The needles were actuated by hydraulically activated single needle valves. The customer's aims were to cut costs by using less material and to shorten cycle time and reduce warpage and sink marks. The gas in the melt lowered the melt viscosity, which allowed a quicker injection. The microcellular foam allowed homogeneous shrinkage behaviour, which made it possible to avoid sink marks in thicker walls. The hot-runner nozzle used was a type 8NLT80 nozzle from the supplier. The needles were actuated by hydraulically activated single needle valves Subject to technical changes 11/14

21 Hot-runner systems for high injection speeds In general it is important in all valve-gate systems that the needle be centred exactly when closing and that it dip into the injection gate without the sealing area of the needle coming into contact with the needle guide. This counteracts wear on the system. The needle guide in the GÜNTHER hot-runner technology systems is made of powder metallurgical steel, which has a very high degree of hardness and strength. If an individual component is worn, it can be replaced on its own. As the needle guide dips down as far as the edge of the product, only the guide has to be changed in the case of wear. It is not necessary to work on the mould insert. Fig. This car door lock housing made of POM is produced with MuCell technology (Photo: ITW) Door lock housing Method Material Particle weight Wall thickness Gate ediametr-ø Hot-runner Needle control Weight reduction Mucell-technology POM 49.0 g 1.1 mm 2.0 mm 8NLT80 Single valve (hydraulic) 10 % When physical foaming is used, the needles are moved by means of single needle valves depending on the number of the cavities. MuCell technology made it possible to reduce the weight of the door lock housing by 10%. Homogeneous temperature control is important The valve-gate hot-runner nozzle with shaft (N_T nozzle) from GÜNTHER Hot-Runner Technology is very suitable both for expansion injection moulding and also for physical foaming. The advantages of this nozzle are the exact temperature control. In particular in the case of technical polymers, which are semi-crystalline plastics with a narrow processing window, it is essential to have homogeneous temperature control over the entire length of the nozzle. For the purpose of attaining a homogeneous temperature profile, the nozzles have a two-part shaft for insulation and the front area is made of a titanium alloy. Fig. To produce the car door lock housing, a four-cavity hot-runner system is equipped with type 8NLT80 nozzles. Expansion injection moulding and physical foaming offer new prospects for plastic processing operations in terms of saving costs and optimising products and processes. Adapted hot-runner systems are indispensable however to process materials reliably. The GÜNTHER hot-runner technology range includes valve-gate systems specially designed for this area of applications and they have proved effective in practice many times. Dipl. Ing. Jörg Essinger Applications Engineering Manager

22 Vliesolen Bamboo fibre reinforced plastics The firm of PMG Geotex in Chemnitz compounds plastics with exotic filling materials. Instead of the usual glass fibres special, they use bamboo fibres to modify the properties of polypropylene or polyethylene, for example. Depending on their length, the bamboo fibres can be used in different areas. For example, longer fibres are mixed into screed or concrete to prevent cracks forming during drying. The shorter bamboo fibres are compounded into plastics as reinforcement or filling material.these fibres, which are chemically linked with the polymer, make the plastics much stronger than those that are not reinforced. In addition this filling material also has an impact on the price of the product. The properties of a PP modified with 30% bamboo fibres rank between unreinforced polypropylene and polypropylene that is reinforced with approx. 20% glass fibre. There is no problem in processing these plastics conventionally with cold runners. However, more and more interested parties ask about the possibility of processing this material with hot-runners too. The trials carried out by PMG and GÜNTHER Heisskanaltechnik GmbH together show that it is possible to process plastics filled with bamboo fibres with hot-runners also. Three plastics (PP, PE LD /PE-HD), each with 30% bamboo fibres, were available for the processing trial: - Vliesolen BF30, natural (PP-2/30-HM1) - Vliesolen BF30, black (LDPE-2/30-HS2) - Vliesolen BF30 (HDPE-1/30-HM1) These materials were tested in a test mould (2-cavity: 1-gr washer), which was equipped alternatively with - nozzles of tip (5SHT50S) or - valve-gate nozzles (5NHT50LA Small sprue gates are not suitable because the bamboo fibres are longer than glass fibres and there is a risk of the sprue gate getting clogged up with fibres. The hot-runner nozzles used in the test feature a two-part shaft in the front area of the nozzle. This structural feature provides excellent thermal isolation between the hotrunner nozzle and the mold. This thermal separation also has a positive effect on the temperature control inside the nozzle. The hot-runner nozzles are suitable for processing standard, engineering and high temperature plastics. When processing filled plastics, nozzle tips made of a hard metal alloy with good heat conductive properties provide very good wear protection. Material tube (25 W/mK) Heater Air (0,04 W/mK) Gap solidified plastic (0,2...1,2 W/mK) Fig. Standard hot-runner nozzle 5SHT50 with two-component shaft (patented). Nozzle with excellent insulation in the front shaft area. Picture: The two-stage shaft of the SHT type nozzle and the frozen plastic material which forms a "cap" around the nozzle provide for optimized isolation towards the cavity and therefore produce a homogeneous temperature profile in the nozzle. Valve-gate nozzles can be recommended to achieve flash-free gate quality of the part. These nozzles are characterized by a long lifetime and short cycle times in operation. Melt Shaft made of titanium alloy (7 W/mK) Open nozzle tip (100 W/mK) If the injection gate diameter is 1.6 mm (5SHT50) or 1.4 mm (5NHT50LA), the above types of materials can be processed without restriction

23 Customer information Vliesolen Bamboo fibre reinforced plastics Another advantage is that all the wear parts can be easily exchanged. This can avoid problems such as clogging of the nozzles, poor part filling, stringing and poor gate quality, and achieve shorter process times. By using a valve-gate nozzle, the cycle time can be reduced by up to 20 %, depending on the application. The thermal resistance of the bamboo fibre reinforced polymers is relatively high; after a simulated machine idle time of 10 minutes there is no problem in starting the aforesaid materials with the two hot-runner nozzles in the test again. It is not necessary to have any higher nozzle temperatures. The parts do not show any thermal degradation. To summarise, it can be said that we did not experience any problem when processing the three tested plastics with bamboo fibre reinforcement in the hot-runner system from GÜNTHER Heisskanaltechnik GmbH. This makes it possible to manufacture a product economically with a good price-performance ratio. Dipl. Ing. Jörg Essinger Applications Engineering Manager Fig. Sample parts, produced with a 5SHT50 nozzle Thanks to the optimised temperature control in the hotrunner nozzles the material could be processed at the temperatures recommended by the manufacturer. Depending on the base polymer and type of nozzle, the injection pressure fluctuated between 700 bar and 1100 bar. On the whole, the parts make a convincing impression. The sample parts produced with the nozzle with tip showed a good gate quality. It was possible to realise a maximum tear-off height of approx mm. As expected, valve-gate nozzles can achieve optimum gate qualities with these types of materials too. Fig. mop holder made of vliesolen Subject to technical changes 11/14

24 Nozzle design for injection moulding on tandem tools 50% of cycle time can be saved by switching from standard injection moulding production to tandem technology. A precondition here is the ideal adaptation of the melt flow path and the nozzles to suit the altered process. To produce glass-fibre reinforced polyamide covers, GÜNTHER Hot-Runner Engineering developed within a very short time a nozzle construction that offered the advantages of low costs, reliable heat management and easy installation. Objectives which even in normal economic circumstances would rank among the most important for a new process are of particular significance in times of crisis. These are to manufacture components in as short a time as possible and at costs as low as possible. The fact that tandem technology in injection moulding can reduce cycle time by up to 50% induced a major German manufacturer of motor tools to change over to this technology for the production of glass-fibre reinforced polyamide covers for work tools. Tandem technology makes use of the unproductive cooling time in injection moulding. Ideally this doubles the output from a standard machine. The process runs as follows: after closing the first parting level of the mould and injecting the melt, the second parting level opens during the cooling process, the parts fall out of the mould, the parting level closes and the melt is injected. While the components are cooling in the second level, work can be continued in the first level. The advantages for the process of this overlapping are shorter time requirements and lower costs. Fig. Mould with tandem technology: One challenge is the melt flow path from the first to the second parting level. Before the process changed over to this technology the assembly, which consisted of two differently-sized components, was produced on two injection moulding machines in two different moulds. In tandem technology the production of the assembly could be combined in one mould so that there was no longer any need for a second machine. Keeping mould costs low To implement the technology, the injection moulder got in touch with T/Mould GmbH & CO KG, Bad Salzuflen, the sole supplier of tandem technology, at the beginning of A major challenge presented by such a project is to keep tool costs as low as possible, explains Daniel Gersmann, who is the supplier's Project Consultant. In the current project the main challenges were the design of the nozzle and melt flow path. The tandem technology side of the project did not present any great problems because the component geometry is relatively simple. To find the best solution, injection moulders and suppliers of tandem technology drew on the know-how of Günther Heisskanaltechnik GmbH in Frankenberg (Eder). The hot-runner specialist developed a system for the application in which the functionality of the complete 2+2- cavity mould could be produced with two nozzles. The alternative to this would have been a more complex hotrunner system with main manifold and sub-runners for injection for both components. The simple layout reduced the costs of the nozzle construction by more than half compared to the redirection system. Combination of hot-runner and cold-runner technology Looking back, we actually built the system twice, remembers Carlo Rasi, sales representative for the Frankenberg hot-runner specialist. The first solution comprised a large hot-runner system with which the melt was conducted through main manifolds and sub-runners to the hot-runner nozzles; the transfer nozzle was constructed as a valve-gate nozzle. The original idea was that in addition to the nozzle in the first level, two nozzles with their heads lying against each other would be used in the second level. However, this solution not only required a larger mould but also a larger injection moulding machine and would accordingly have increased costs. Furthermore, continues Rasi such a solution would not have been ideal because of the heat loss

25 Customer information Nozzle design for injection moulding on tandem tools To avoid these disadvantages, the hot-runner specialist in consultation with the heater supplier developed a special solution for the second level in the form of a transfer nozzle, which on the outside is identical to the suppliers' SHT nozzles with two-part shaft. Here, the basic idea of two nozzles was maintained and optimised so that they could be produced in just one component. Based on T-Mould's experience and the injection trials conducted in the hot-runner specialist's own pilot plant experimental facility, it was possible to define the wall thickness of the plate in a way that would ensure that the process would function perfectly as of the first shot. The process with the aid of the plastic plate has al-ready been in use in practice for a long time but so far usually with polymers that have not been reinforced. In the current case a semi-crystalline, glass-fibre reinforced material is used, which makes greater demands on process reliability. Low losses during thermal conduction In a very short time GÜNTHER and the heating supplier were able to find a solution in terms of the best possible way to heat the transfer nozzle. A two-component shaft with titanium cap as well as nozzle heating adapted for this application make it possible to minimise the heat loss in the nozzle so that only very little is lost in the conduction of heat to the nozzle tip. The nozzle heating consists of only one component so that there are no significantly cold areas. A further challenge presented by this project was the short time available, remembers Rasi. The individual parts of the nozzle were developed, designed and specially produced within four weeks. There was no time for any extensive tests before the installation of the nozzle assembly. Nevertheless the design functioned from the beginning without any problems occurring at all, which of course is very unusual for a completely new development. From the first shot, the temperatures were a uniform 280 C in the material manufacturer's default window. The pressure curves did not show any irregularities and there were no problems starting up again after an interruption in production. At no time were there any signs of damage to the material. The production of the new tandem tool commenced in the autumn of 2008; since then production has been running perfectly with a 40% reduction in manufacturing costs. Fig. The special nozzle design in the second parting level cuts costs and reduces the construction size. In the new system an open passage was fitted on the cold-runner side for the first parting level. During the injection into the first level a plastic plate with a defined wall thickness is formed which allows injection through to the second level. Before that this plate provides a closure between the first and second parting levels. When injecting into the second level, the melt pressure and enthalpy of the melt are sufficient to inject the melt jet through the plate to the transfer nozzle. In the meanwhile GÜNTHER has implemented more projects with the new nozzle design, which is basically suitable for every family of mould if there is not too great a difference in injected weights in the first and the second levels Dipl.-Ing. Jörg Essinger Applications Engineering Manager Subject to technical changes 11/14

26 Precision and costs under control Weißer+Grießhaber relies on BlueFlow hot-runner engineering for micro parts Extremely thin-walled products with ultra-fine structures are a speciality of Weißer + Grießhaber. In a pilot application of the new BlueFlow hot-runner nozzles from Günther Heisskanaltechnik GmbH, the company has engineered a more cost-effective production of precision filters, a safety component for the automobile industry, with greater process stability. Already in the year 2009 the plastics processor Weißer + Grießhaber ( from Mönchweiler, a town in the Black Forest area, was awarded the innovation award for the promotion of innovative achievements in medium-sized industrial and skilled trade enterprises for its directly injected filter. For the first time, filter screen fabric and threading were produced in pure injection moulding in one shot for these precision components for the automobile industry. This replaced the previous procedure, in which an existing metal or plastic screen fabric was overmoulded to obtain a ready-to-install component. The impact on costs was significant, which, depending on the product, sank by around 60 to 80 per cent. In the meantime, a large number of variants are produced, in quantities ranging from several tens of thousands to double-digit millions, for other industries too. Such polyamide filters with weights of about 0.1 grammes are used for example in ABS and ESP systems to filter out even the finest particles from the brake fluid and accordingly ensure reliable functioning. Thread thicknesses of 0.10 to 0.15 millimetres and mesh apertures as tiny as 0.07 millimetres are scarcely visible to the naked eye. Burring must also be reduced accordingly to under 5 micrometres. Weißer+Grießhaber spent about five years developing the directly injected filters. This concerned mould making above all and the moulds are still being constantly improved. The hot-runner and control engineering as well as the adaptation of the process parameters have had a decisive influence on the qualitty and process stability. One of the decisions taken by Weißer +Grießhaber as part of the continuous further development was to use BlueFlow, the new heating technology developed and produced by Günther Hot- Runner Engineering, in their own manufacturing before the launch on the market and to evaluate the experience with it. The first obvious result of using the new nozzles, explained Siegfried Kaiser, Head of Sales and Project Management at Weißer+ Grießhaber, was the much lower temperature and pressure levels compared to the systems used before which had also ranked among the top technologies. The temperature window used during the process is much smaller; the average temperature sinks and becomes more stable. That not only reduces the strain on the mould; it sustainably saves energy and substantially reduces downtime. Another aspect, which is at least just as important, is that the higher temperatures and pressure levels before used to cause unacceptable material damage and consequently rejects. Further-more, not all cavities in the 8-cavity mould were filled and the reject rate reached double-digit percentage levels. These problems are now over: GÜNTHER's hot-runner fills all cavities and the reject rate is less than 1 per cent. There is also a great improvement in injection gate quality. Fig. A particularly efficient and easily regulated heating technology allows slim high-performance nozzles. Fig. A micro filter (outlet valve for an automotive application) made of non-reinforced PA66 from Bada, injected in one processing step; 0.1 grammes and 1,848 apertures measuring 0.07 x 0.07 mm. The maximum permissible burring is 4.5 µm

27 Customer information Precision and costs under control Another aspect has been observed in practice: thanks to the fast heating and stable temperatures in the nozzles - nozzle temperature and setpoints are now at the same level for all eight nozzles -, the mould can be started up without any problem. Restarting after a fault is also easy now too. This also contributes greatly to reducing costs during the process and it increases process reliability. Keyword: BlueFlow nozzle technology The core element in the new nozzles are the thick-film heating elements developed by Günther and a project partner. The dielectric layer and the heating conductor paths are applied to a stainless steel casing in screen printing under clean room conditions and burnt in afterwards. A covering layer insulates and protects the heating element from external influences. The most important advantage of the thick-film heater: the heating traces can be brought closer to the material, allowing a much more precise output distribution over the entire heating tube because the conductor paths can be varied in terms of width (and output) and positioning. This makes it easier than before to achieve a high concentration of power in the front nozzle area, for example. Stable process with lower downtimes and accordingly a higher output. Heat loss is reduced, not only by the smaller outer contours of the nozzles but also by the low heat conductivity of the two-part nozzle shaft (patent: DE issued on 4 May 1995) with ist combination of materials, steel in the back and a titanium alloy in the front. In addition, the new heating technology benefits from other features in the redesigned mould, such as the narrower diameter compared to that of conventional systems. This allows smaller nest spacing and accordingly smaller moulds or a greater number of cavities with the corresponding improved efficiency and yield. A precise calculation of the cost per piece is not available for this application yet. However, the pay-off became evident in less than half a year, said Siegfried Kaiser. The entire heating element, is only about 1.00 mm. Compared to conventional brass heating elements, the new thick- film heaters are therefore much finer and have a narrower diameter. Other outstanding features in the heating elements are the high dielectric strength and non-hygroscopy, which puts an end to the previously customary slow heating to 100 C and subsequent interruption in heating to drive water vapour out of the hot-runner systems. The bottom line The BlueFlow technology is fundamentally compatible with previous nozzle systems and retrofitting is possible. The slight increase in investment costs must be viewed against the direct savings and increased reliability in Weißer+Grießhaber applications: Less downtime due to the faster and problem-free start-up, even after faults. Energy consumption is reduced by about to 30 per cent because the temperature is lower. Significantly less rejects due to the improved temperature control in the nozzles, reduced process temperature and lower pressure levels. The lower pressure allows the use of a smaller injection moulding machine as an alternative, which further reduces costs. Fig. Precision times eight the newly-designed Günther hot-runner nozzles reduce process temperature and the required pressure, which is also gentle on the material Subject to technical changes 11/14