I. Case Study: Optimisation of the plunger for a 32-cavity medical syringe
Project Background: The 32-cavity needle valve hot runner mould of a medical accessory factory was unable to meet the consistency requirements of medical-grade products due to a filling time lag of 0.3 seconds, a product weight CV value of 3.2%, and a yield rate of only 72%.
Optimisation Measures: The runner layout was redesigned to incorporate a completely symmetrical X-shaped runner. The inner wall of the runner was polished to a level below Ra0.8, and the flow resistance deviation was limited to 4%.
The gates of the eight furthest compartments were opened 0.15 seconds earlier to compensate for flow lag, as the needle valve timing control was adjusted.
The injection speed was set at 90mm/s in the main filling section and was subsequently reduced to 25mm/s at the end to ensure uniform sealing. A three-stage injection speed curve was implemented.
Implementation Results: The filling time lag was reduced to 0.08 seconds, the product weight CV value was kept at ≤1.1%, the mass production yield was increased to 98.5%, and the single-shift production capacity was increased by 25%.
II. Case Study: Optimisation of a 16-Cavity Automotive Waterproof Sealing Ring
Background of the Project: A car parts factory was experiencing uneven filling of a 16-cavity LSR (Liquid Silicone Resin) hot runner mould, which led to localised material shortages and excess in the sealing rings. The per capita efficiency was low, and the defect rate reached 8%.
Actions for Optimisation:
A cross-sectional area difference of ≤0.8% between gates was guarantyd by standardising the gate dimensions for all cavities. Symmetrical venting channels were implemented.
Each hot runner section was subjected to independent temperature control, ensuring that nozzle temperature deviations were maintained at a maximum of ±2℃.
The filling stage was conducted at a high pressure of 80-100 bar, which was subsequently reduced to 50-60 bar during the holding stage to prevent overpressure overflow.
Implementation Results: The defect rate was reduced to 2%, the single-shift production capacity was increased from 2000 pieces to 8000 pieces, per capita efficiency was tripled, and overall production costs were substantially reduced by 40%.
III. Case Study: Optimisation of a 64-Cavity Precision Electronic Connector
Project Background: The 64-cavity hot runner mould at a 3C electronics factory was unable to satisfy the automated assembly requirements due to uneven filling, which resulted in connector pin misalignment and a 12% assembly defect rate.
Optimisation Measures: The feed rate of each cavity was adjusted through local runner size compensation, and the runner system was rebalanced using Moldflow simulation.
In order to guarantee a curve overlap of ≥95%, an in-mold pressure sensor was installed in each cavity to monitor the pressure curve in real time.
Ensuring a cooling water temperature difference of ≤1℃ between cavities and entirely synchronised cooling speeds, parallel conformal cooling water channels were implemented.
Results of Implementation: The assembly defect rate was reduced to 1.5%, and stable, automated mass production was achieved, with product dimensional deviations maintained at 0.01mm.
