HASCO Universal Needle Valves Z107101/... and Z107105/... New Variants
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Conventional single-shot needle valve solutions that split the melt flow are commonly used for hot runner applications and impose a variety of restrictions on the user which frequently lead to problems in practical application. Choice of nozzle length and diameter are also limited, and it is not possible to directly transfer the results gained from single-cavity development moulds to their multi-cavity counterparts because the nozzle type varies, and the size of the conventional single shot needle valve systems results in a large overall installation height demanding larger mould configurations.
With its modified Universal needle valve unit, HASCO has created an amazingly simple solution to address these problems. The basic concept for the needle valve system is, as before, focused on a universal and modular design.
The needle drive unit is available in two standard sizes and can be combined with all HASCO Techni Shot and Valve Shot nozzles. This offers the user a very wide choice of nozzle type and size, optimising runner diameters and nozzle lengths of up to 300mm, as well as flexibility in the design of the needle guide and gating area. Perfect solutions can be realised for varying article weights and fillers for both packaging and medical applications.
The system is extremely compact and can simply be integrated into small moulds with reduced build height.
A major advantage of the drive unit is that it can be used either as a single nozzle centrally mounted in the middle of the mould - or as a drive unit mounted offset between the manifold and nozzle. This means that the optimisation obtained in pre-production and prototype moulds with a specific type of nozzle configuration can be transferred without risk into a multi-cavity production mould. It is even possible to carry over the hot runner components, reducing the cost of gaining vital development knowledge before committing to the production mould.
When the Z107105/... is positioned between the manifold and the nozzle head, the unit has the added advantage that axial thermal expansion of the manifold block has no influence whatsoever on the valve pin position, thus preventing any needle deflection. The optimum L/D ratio through the short needle length extends the service life of the needle and gate aperture.
Priority has also been given to flexibility when it comes to the choice of drive unit. The Z107101/... is activated pneumatically through special cylinders mounted outside the mould, whereby the needle position can be finely adjusted at the cylinder. The connecting rod is moved centrally through the unit in order to minimise wear and adjustment forces.
With the Z107105/.., the drive is activated via compact hydraulic cylinders, connected via a tie-bar through the unit.
The valve pin stroke can, depending on the drive solution, be varied in a range of 2 to 7mm. This means that the units can be geared to suit to the application and the respective nozzle type.
The position of the needle valve is accurately fixed with a device on the needle head that prevents twisting and allows cavity form contours to be included on the pin.
From a rheological point of view, the HASCO Universal needle valves Z107101/... and Z107105/... have a lot to offer. No splitting of the melt means weld lines are completely avoided, and with suitable design of the melt channels, pressure losses in the system are kept to a minimum. Improved guiding of the melt though soft channels without dead spots, significantly improving colour change behaviour and prevents material degradation. When designing the unit, particular importance was given to a homogeneous, symmetrical temperature profile. The Z107101/... and Z107105/... can also be used for glass fibre-reinforced plastics, which are particularly demanding from a processing point of view.
A particularly interesting field of application with the Z107105/... is in stack and tandem moulds. With the needle valve drive system positioned between the nozzle and manifold, back-to-back arrangements with individual needle drives are easily accommodated. The overall height of the centre of the stack (gate-to-gate distance) can be reduced to 250mm.
Priority has also been placed on ease of maintenance with the modified drive unit. The heating unit, temperature sensors and needle guide element are very simple to replace when necessary.
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