Multi-zone heater control

ERO Electronic has launched a new heater controller, specifically for use within multi-zone plastic injection mould-tool hot runner systems.

Italian-based temperature controls company ERO Electronic has launched a new heater controller, specifically for use within multi-zone plastic injection mould-tool hot runner systems. The specially developed hot runner controller, Model LFS-S03, offers a number of features, including accurate set-point temperature control, heater ‘soft start’ function, as well as in-built protection from over-temperature and thermocouple fault conditions.

When used in a multi-zone hot runner system, each LFS-SO3 controller provides convenient set-point adjustment. A communication link between of up to 256 linked individual controllers allows all set-points to be adjusted proportionally, so if specific zones are set to different temperatures, the delta values between controllers are maintained automatically.

ERO’s digital retransmission communication technique eliminates the need to trim and adjust master and slave set-point inputs and outputs, which is usually necessary with conventional analogue methods. Instead, the software allows easy connection between one master and up to 255 slave controllers.

Drift is virtually eliminated, significantly reducing the need for routine re-calibration and maintenance.

Individual LFS-SO3 controllers within a hot runner control system automatically recognise whether they are designated as master or slave devices during power-up. They configure themselves automatically, simplifying maintenance and reducing ‘back-up’ stock holding to a single instrument.

Another important feature of the controllers is their heater ‘Soft Start’ capability. This automatically limits heater surge power during start-up, reducing potential thermal stress on the elements and the moulding tool. This facility provides both time and temperature threshold-based output power limit protection.

Up to two user-defined set-points may be selected using the LFS-SO3 isolated logic input. This provides the additional benefit of allowing un-isolated (grounded) thermocouples to be used for temperature feedback purposes, reducing total system cost and improving control performance.

In addition, the system is able to detect poor thermocouple connections and breaks, thus identifying open-circuit thermocouple connections, a common fault on hot runner systems. When an open TC is detected, the system automatically sets the power output to a safe user-preset value, allowing production to continue until maintenance is possible.

Possibly the most potentially hazardous hot runner system fault, however, is a short circuit SSR (solid state relay). The LFS-SO3 continuously monitors control loop temperature to detect these fault conditions. When an SSR short circuit faults is detected, the system automatically shuts down the main power supply to all of the controllers, preventing over-temperature damage to both heaters and mould tool. Two over temperature alarms are available.

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