I. Fundamental Optimisation of Runner Balance
To guarantee that the path length and cross-sectional dimensions from each cavity to the main runner are entirely consistent, and the melt flow resistance deviation is maintained within 5%, implement an H-type or X-type symmetrical hot runner layout..
PID intelligent temperature control is implemented in all hot runner zones, ensuring that the temperature control accuracy is maintained at ±0.5℃. This prevents the occurrence of uneven melt viscosity, which can result in inconsistent filling in multiple compartments, which is a consequence of temperature differences.
The timing of the opening and closing of each gate can be controlled by needle valve hot runners, which enables the gates of distant cavities to open in advance, compensating for flow latency and achieving synchronous filling of all cavities.
II. Centralised Management of Venting Systems and Gates
The gates of all cavities are designed to have identical dimensions, positions, depths, and widths, with a gate cross-sectional area difference of ≤1%. This guarantees that the instantaneous flow rate of melt entering the cavity is consistent.
To prevent confined air in individual cavities from obstructing melt flow, causing filling lag and product burning defects, ventilators are symmetrically installed in each cavity with a uniform venting depth and position.
III. Coordinated Optimisation of Injection Moulding Process Parameters
The raw material's molten state is guarantyd to be homogenous and stable due to the unified barrel temperature. In order to guarantee that each injection has a consistent viscosity and melt density, the plasticising stage employs a stable screw speed and moderate back pressure.
Throughout the injection procedure, multi-stage, layered injection speed control is implemented. Initially, a low-speed, stable melt delivery is implemented. In the middle stage, uniform, overall filling occurs. At the end, the injection speed is reduced to ensure unified sealing, which ensures that all cavities are filled synchronously before a unified transition to holding pressure.
Control of injection pressure through multiple stages. In order to prevent overfilling and flash, as well as to compensate for cooling shrinkage and stabilise product dimensional accuracy, the pressure is gradually reduced during the holding pressure stage, while high-pressure, rapid mould filling occurs during the filling stage.
IV. Optimisation of the Cooling System and Mould Temperature Balance
Control of the temperature of a parallel water circuit. A mould temperature controller guarantees synchronised cooling rates for all cavities by ensuring that the cooling water temperature difference between cavities is ≤0.5℃ and the cooling time deviation is ≤±0.3 seconds.
Preventing uneven mould temperatures and eliminating filling speed deviations caused by temperature differences, regular cleaning of water circuit scale ensures unobstructed heat dissipation.
V. Optimisation of Operational/Maintenance Assistance and Digitalisation
Collect pressure-time curves for each cavity in real time by installing pressure sensors at the gate of each cavity. The pressure peak difference during the loading stage should be ≤3%, and the curve overlap should be ≥95%.
Develop a plan for the prevention of mould growth. To prevent the degradation of filling consistency due to mould ageing, check the cavity wear and clean the hot runner nozzles of carbonised residue after every 5000 mould cycles.
This system optimisation solution is entirely compatible with your current precision hot runner multi-cavity mould injection moulding production line. It is capable of maintaining a stable mass production yield of over 98%, a product weight variation coefficient (CV) of ≤1.3%, and a multi-cavity filling time difference of within 0.1 seconds after implementation.
