Meaning
Automated adjustment of process inputs based on the measured deviation from a setpoint allows for the correction of drift during continuous production. Systems utilizing closed loop compensation monitor variables such as injection pressure or melt temperature and adjust the machine settings for the next cycle. Such feedback loops prevent small fluctuations in the environment or the material from affecting the final product quality.
Accurate control of these variables is a standard feature on high precision electric injection moulding machines.
Dynamic Adjustment
Adjustment of the screw speed or the hold pressure happens instantly when the controller detects a change in the viscosity of the resin. In a production run using regrind material, closed loop compensation accounts for the slight differences in flow behavior compared to virgin resin. This keeps the shot weight consistent across thousands of cycles.
Viscosity Stabilization
Stabilization of the melt flow is necessary when the barrel temperature or the moisture content of the pellets varies. If the resin becomes more viscous, closed loop compensation increases the injection force to maintain the target fill time. This mechanism ensures that the mould is filled completely without causing flashes or short shots.
The system measures the work done during the injection phase and adjusts the electric power to match the required profile. This level of control is necessary for thin walled parts where the window for a successful shot is very narrow.
Yield Protection
Protection of the production yield is the primary economic benefit of this technology. By reducing the number of rejects, the system lowers the overall cost per part and minimizes material waste.
