Meaning
Force measurement instruments convert mechanical deformation into electrical signals to monitor clamping forces or melt pressure during polymer processing. A strain gauge transducer is attached to the tie bars of an injection moulding machine or integrated into the mould plate to track the forces acting on the tool. This sensor uses a thin metallic foil pattern that changes resistance as it stretches or compresses under load.
Accurate force monitoring is essential to prevent mold damage from over clamping and to ensure that the clamp force is sufficient to resist the injection pressure.
Force Measurement
Electrical resistance changes in the foil pattern convert to a voltage signal by a Wheatstone bridge circuit. This signal is proportional to the applied mechanical stress, giving the controller a precise measure of the clamp or melt force. This measurement must be highly stable to resist the vibrations and temperature changes of the production floor.
Clamp Monitoring
Monitoring the stretch of the tie bars ensures that the clamping force is distributed evenly across the mould face. Uneven force distribution can lead to part flash on one side and venting issues on the other. Using these transducers allows set up technicians to adjust the tie bar nuts to balance the load and extend tool life.
Signal Calibration
Regular zeroing of the sensor is required to maintain accuracy over long production runs. This calibration compensates for the thermal expansion of the machine components as they heat up during operation.
