Controlled additive metering supports LSR injection moldings for healthcare applications

  • High-resolution flow meter as key element
  • System maintains metering accuracy, thereby saving costs
  • Material utilization of over 99%

Manufacturing products for health-care applications entails very stringent requirements on the acquisition and documentation of process data. While liquid silicone rubber (LSR) injection molding (LIM) is well established in this field, the metering of additives and colorants has in the past been a potential source of problems because sufficiently sensitive control and associated data acquisition capabilities have not been available as standard. With the market launch of a high-precision, automatically controlled multicomponent dosing system, the company Elmet now enables processors to overcome these obstacles whilst at the same time optimizing their efficiency in adding coloring pigments and additives.

High-resolution flow meter as key element

The key element of this system is a high-resolution flow meter. Integrated as a closed-loop control instrument into the colorant and additive feeding system, it determines the dispensed volume with a resolution of 640,000 increments per liter. On the basis of these precise measurements, the system accurately controls the supply of colorants and additives, in line with the setpoint defined on the touch display. At the same time, the corresponding values are made available for documentation.

LSR dosing systm

Combining a high-resolution flow meter with sensitive control and comprehensive documentation of additive and colorant metering, Elmet meets the stringent demands placed by the health-care industry on liquid silicone rubber injection molding (source: Elmet Oftering/Austria)

System maintains metering accuracy, thereby saving costs

Processors of colorless functional additives, including certain active ingredients, will in particular benefit from such precision-controlled metering. Optically imperceptible and hence, potentially undetected deviations from the setpoint, e.g. due to wear, clogging strainers or changing properties (viscosity) of the additive charge, may cause significant extra costs and, in the worst case, may even have an impact on the health of the end user. The Elmet system, based on exact volume measurement, ensures that the necessary metering accuracy is maintained throughout by continually readjusting the feed rate to the originally acquired and stored reference value. As long as this readjustment remains within a certain tolerance range, the operator is informed of this situation so that action can be taken in time. However, if tolerances are exceeded, the system will automatically discontinue the production process to prevent rejects before they occur, thereby saving costs.

Material utilization of over 99%

The new flow meter is part of Elmet’s feature-packed TOP 3000 S multicomponent dosing system for LSR injection molding applications, which features particularly rugged and energy-efficient pneumatic drives and supports the use of both 20-liter and 200-liter drums. The system maintains the mixing ratio of the LSR A and B components unchanged over the entire drum content, ensuring material utilization of over 99%. Its maximum discharge rate is 2.5 l/min, with a rate of colorant addition of up to 10%. The associated process data for each individual shot can be exported via an USB, LAN or WLAN interface.

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