Combining cavity sensors with hot runner valve gate control

Related Vendors

HASCO Hasenclever GmbH + Co KG

Ramada Acos

Synventive Molding Solutions GmbH

Providing valve pin movement repeatability. Electric, pneumatic and hydraulic valve-gated systems with closed-loop valve-pin position control not only facilitate complex valve pin movements, but these advanced systems also provide repeatability of the valve pin movement, which translates into increased repeatability of part filling and part consistency.

Combining the two technologies yields interesting possibilities

Although individual technological advances in cavity sensors and hot runner valve gate control have changed the way parts are moulded, combining the two technologies yields some interesting possibilities. As discussed earlier, in sequential moulding, slowing the initial opening speed of the valve pin offers cosmetic benefits. Using a cavity sensor to trigger the valve pin to open when the flow front reaches a specified position eliminates the need to adjust the sequence separately when pin speed changes are made. This reduces the time required to set up the process and creates a more robust process.

In addition to simply triggering the opening of the hot runner valve gates based on flow front position, more advanced valve gate control systems can initiate other events as well. For example, valve pins can be moved to intermediate stroke positions to increase or decrease flow from a specific gate when the melt flow front reaches various points throughout the fill.

Going a step further, cavity sensors combined with full pin control allow fully closed-loop pressure control. Instead of the pin making predetermined movements based on various triggers, the moulder can set a desired pressure curve for a sensor near the hot runner gate and have the hot runner valve pin automatically adjust to maintain that target pressure curve. This combination of technology effectively allows each hot runner nozzle to control an individual injection unit at each gate. Although cavity sensor and hot runner valve gate control technologies individually offer impressive advantages for moulding, even greater gains can be achieved by combining these two technologies. In addition, new applications for these smart tools are being developed that will allow stable processes to be created for even the most challenging applications.

This article first appeared in MoldMaking Technology, published by Gardner Business Media, Cincinnati, Ohio, US.

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