I. Baseline differences in heating time for hot runners with different numbers of cavities:
Single/2-cavity small hot runners: Total heating time ≤ 45 minutes, runner plate mass ≤ 10 kg, extremely low thermal inertia, fastest heating rate.
4-8-cavity medium hot runners: Total heating time ≤ 75 minutes, runner plate mass 10-30 kg, heating time more than 60% longer than small hot runners.
16-32-cavity large multi-cavity hot runners: Total heating time ≤ 120 minutes, runner plate mass 30-80 kg, heating time more than 2.5 times that of small hot runners.
64-cavity and above ultra-large multi-cavity hot runners: Total heating time ≤ 180 minutes, runner plate mass ≥ 80 kg, heating time more than 4 times that of small hot runners.
II. Core Reasons for Time Differences
Differences in Thermal Inertia: The more cavities, the larger the total mass of the flow channel plate, and the more heat needs to be absorbed, naturally slowing down the heating rate.
Differences in Temperature Uniformity Requirements: Multi-cavity hot runners have large flow channel plate dimensions. To avoid excessive internal and external temperature differences leading to thermal deformation, the heating rate must be reduced and the holding time extended, further lengthening the overall heating time.
Power Supply Limitations: Ultra-large multi-cavity hot runners have extremely high total heating power. Due to limitations in workshop power supply capacity, it is impossible for all heating zones to output full power simultaneously. Staggered heating is necessary, slowing down the overall progress.
III. Compressible Space for Time Differences
When processing thermally stable general-purpose materials such as PP/PE, the heating time for all cavities can be reduced by 20%~30% from the baseline value.
When processing easily degradable sensitive materials such as PVC/POM, the heating time for all cavities needs to be extended by 50% from the baseline value to avoid localized overheating that could cause material degradation.
In high humidity environments, the heating time for all cavities needs to be increased by an additional 10 to 30 minutes for dehumidification and heat preservation to avoid moisture residue causing problems in subsequent processes.
