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Liquid silicone rubber (LSR) technology supplier Elmet has expanded on its SMARTshot E servomotor-driven cold runner system launched at Fakuma 2021 with the patent-pending SMARTshot I cold runner measurement and control concept. This system incorporates servo-actuated nozzle needles, which Elmet says make automatic startup possible, as well as family molds with variable-volume cavities, which won’t require additional sensor systems. In addition, Elmet says the SMARTshot I will enable cascaded injection processes with time-delayed opening and closing movements or injection processes with partially open needles for simultaneous cavity filling with different volumetric flow rates per nozzle.

Elmet says the new SMARTshot I LSR cold runner system can automatically balance fill, including into family molds. Source: Elmet

In tests with a 16-cavity mold, Elmet says the cold runner was fully, automatically balanced within 20 shots with molded parts exhibiting weight fluctuations of just 1.5%. In addition, process startup times were reduced by approximately 90% compared to manual adjustment by an operator.

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Based on SMARTshot E, the SMARTshot-I development concept applies additional rheology-based features to improve control of the injection process by using AI with self-learning functionality. Elmet says molders can set up or retrofit this upgrade on any existing SMARTshot E mold. In combination with compatible injection machines that have a suitable interface, it will then be available to any user.

The “I” technology is based on inline rheometry for continuously optimizing the process and determining the actual material viscosity and shear rate range. This technology correlates the volumetric flow rate of the press with the geometric constraints of the cold runner, and the force at the needle to identify and quantify batch-to-batch fluctuations, essentially converting the cold runner into a rheological measuring instrument.

In learning mode, the system automatically detects the volume of material required to fill a cavity, facilitating setup and optimization, especially with family molds with cavities of differing sizes. Elmet says the system is set up to support self-controlled injection molding machines if SMARTshot I control is integrated into a machine at a later date.

The system applies highly responsive, brushless 24-V, 50-W DC motor that generates minimal waste heat and can withstand three times the rated load for short periods. The motors are compact enough to enable narrow nest spacings from 44 mm. The effective stroke is 4 mm, and the system achieves an accuracy of 0.09° per revolution, reducing the error range to ± 0.05% or ± 0.002 mm. The servoelectric drive powers real-time control of needle position, including permanent position monitoring. The needle’s anti-twist feature enables the tips’ geometries to be contoured to the cavity, minimizing witness marks at the gate. Needle opening can be adjusted to an accuracy of 0.002 mm, with needle opening and closing times on the order of hundredths of a second.