Multi-nozzle applicators

Most applicators apply a single bead of adhesive but, where parallel beads are required, multi-nozzle applicators can be used to advantage however, care must be taken to ensure that the flow out of each nozzle is as required. 

One advantage over conventional systems is the minimized control complexity for multi-cavity applications. Only one control point per manifold is needed. These systems are suitable for processing polyolefin, styrene, and acetal. Applications for other plastics may also be possible after consultation with the manufacturer. Basically, shot weights are possible from 0.05 to 2 g per nozzle tip. The product made from polyacetal, which is shown in Figure 2.61,hasaproductweightofonly0.1 gand is produced in a four-cavity mold on a mini-injection molding machine babyplast . 

The drawback to a spring-powered drive is indirect control. The gate is opened under pressnre from the melt, which causes an explosive mould filling, and is then closed as a result of a fall in the melt pressure in the channel. If the fall in pressure in the manifold charmels in a multi-cavity mould is not uniform, there may not be simultaneous gate closure. Spring-driven nozzles are rarely used, but their low price makes them an interesting alternative for simpler technical applications. 

One disadvantage of this type of heating is the thick, rigid leads (16-25 mm cross-section), requiring extra space in the mould for their location (they make it difficult to place cavities next to one another). Nozzles heated by a 24 V current with a maximum power of 25 A have been developed for applications with a small nozzle pitch or in large multi-cavity moulds, and this has enabled the lead cross-section to be reduced to 4 mm. ... 

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