By fully automizing the production of a connector plug for an automotive seat adjustment motor the Italian mould making and injection moulding specialist O.C.S.A. in Creazzo (VI) has considerably increased the productivity compared to standard production methods. The plastic-metal composite component is insert moulded and consists of reinforced PA 6.6 and a copper alloy. The close cooperation with EWIKON starting at the early stage of the project allowed the process-reliable integration of a full hotrunner system for side gating. This significantly contributed to the raise of productivity.
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The part: connector plug with two metal contacts embedded in a housing made from PA 6.6 with 30% glass fibre reinforcement. The part is gated from the side. |
Considering the customer's very high annual requirement O.C.S.A. decided to set up a manufacturing cell with an ambitious maximum production capacity of 7,500,000 parts per year where all production steps are fully automated. This includes feeding, cutting and bending the metal contacts as well as overmoulding them with the plastic component and a 100% control of the finished parts. The aim was to gain maximum productivity and at the same time to keep the sizes of machine and mould at a minimum to allow the most space saving integration of the manufacturing cell and all required handling systems on the production space available. The injection mould with full hotrunner system works in the centre of the production line on a compact Engel insert 45 injection moulding machine with vertical clamping unit.
The part consists of two metal contacts with different shapes which are made from a tin-coated copper alloy. They are embedded in a plastic housing by overmoulding them with PA 6.6 reinforced with 30 % glass fibre. According to the strict quality standards in the automotive industry the customer demanded an absolutely precise positioning of the metal contacts in the connector plug as well as a high dimensional stability of the plastic housing. The part weight is 3.5 g. Because of its geometry the part can only be gated from the side. ”Up to now comparable parts have often been produced in low cavity moulds by using coldrunners“, explains Marco Milan, owner of O.C.S.A., ”so we decided to go for a solution which would help us to gain significant advantages in productivity and efficiency compared to potential competitors. Thus, right from the project start our key requirement was to integrate a full hotrunner side gating solution into the production process. Considering the expected large output as well as the fact that the material cannot be recycled we had to avoid any kind of sprue to save material costs. Furthermore, the removal of sprues would have required additional peripheral equipment and a more complicated process control.“
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Hotrunner system with 6 HPS III-MH200 nozzles arranged in a row with flush mounted flattened nozzle bodies (top) and view onto the hot half mounted on the machine (bottom). The easy accessibility of the nozzles for maintenance work is clearly visible. For replacement or cleaning of the heat conductive tip inserts only the end cover flange of the nozzle has to be deinstalled. |
A compact 12-drop mould with a size of 396 mm x 296 mm with the parts arranged in two rows proved to be the ideal configuration for the machine size used. EWIKON as a specialist for side gating was first choice for supplying the matching hotrunner solution. Six radial HPS III-MH nozzles with a length of 60 mm are arranged in a row with flush mounted nozzle bodies which have been additionally flattened so that a distance of 45 mm between the cavities could be achieved. The distance between the two cavity rows is 50 mm. Each nozzle features two oppositely arranged wear-resistant heat conductive tip inserts. The melt bearing pressure tubes of the nozzles are directly heated by coil heaters. This enables a very stable heating with minimized loss resulting in an even temperature profile along the whole length of the nozzle. The fully balanced manifold system is equipped with streamlined direction elements for smooth melt flow. ”No other hotrunner supplier except EWIKON was able to offer a solution which allows us to realize the cavity layout we requested and at the same time is suitable for processing the demanding reinforced resin“, says Marco Milan. ”We were especially impressed by the way EWIKON approached this challenging application with a realistic evaluation of the potentials but also limits of their technology. Beside that there was a very close cooperation from the early stages of the project on and EWIKON provided excellent support with moldflow analyses and material tests on short term.” As a result of these tests EWIKON decided to use MH200 nozzles which are designed for larger shot weights. This nozzle type features an even higher thermal performance and stability and furthermore has enlarged flow channel diameters. Thus, the shear rate in the system can be kept small which reduces the wear caused by the reinforced resin. Nevertheless, of course wear is omnipresent during operation and requires the periodic replacement of components. Here the very maintenancefriendly design of the EWIKON system proves to be a big advantage. The tip inserts which are mainly subject to wear can be cleaned or replaced from the parting line with only minimum downtime and without the need to dismantle the mould.
Both versions of the metal contact are delivered pre-cut on rolls. In the manufacturing cell they are fed into two processing stations which are arranged in parallel. Each processing station has a handling system placed at the end. The contacts are die-cutted, bent into shape, then picked up by the synchronously working handling systems and placed into collector stations. Six of these are arranged on a rotating plate. When filled up each collector station contains 6 pairs of contacts – the complete filling for one cavity row in the mould. It is picked up by the placement handling for the mould, checked for complete filling by an optical sensor and transferred into the injection moulding section. Here in order to achieve the best possible cycle time O.C.S.A. works with two identical mould halves which contain the ejector system and are fixed on a rotating plate. The first mould half turns into moulding position, the mould closes and the contacts are overmoulded with plastic. At the same time the second mould half is positioned in the removal and loading position. First, the removal handling takes out the finished parts from both cavity rows at once, supported by the ejector mechanism. It places the parts in the control section where they undergo an 100% optical checking procedure and are then collected in containers. Directly after the removal handling has picked up the parts from the mould the placement handling begins to load the cavities again in two working steps by inserting one row of contacts at a time.
Even though O.C.S.A. decided not to build a test mould the production cell went into production on schedule. Only minimum fine adjustments were required. The result is a perfect interaction of injection moulding technology, mechanical forming and handling robotics. With a cycle time of 24 s for the overmoulding process and synchronized peripheral equipment the required production figures can be easily realized. At the same time the direct gating with hotrunner allows a significant saving of material. The trouble-free operation of the production cell gives an impressive example for the processreliable integration of precision injection moulds with modern hotrunner technology into complex fully automated applications even when demanding resins are processed.
