Transient Interfacial Macro Gap Prediction in Variotherm Injection Tooling
Coupled thermo-viscoelastic modeling of PVT shrink and tool expansion predicts variotherm macro gap formation and prevents optical distortion.
Variotherm Injection Molding
Meaning
Advanced thermal control techniques in injection molding dynamically heat and cool the cavity surface during each molding cycle. Implementing variotherm injection molding involves heating the mold to a temperature above the polymer glass transition point before injection, then rapidly cooling it for solidification. This method eliminates surface defects and reduces molded-in stress.
Dynamic Heating
Raising the cavity surface temperature prevents the molten polymer from freezing prematurely as it enters the mold. Through variotherm injection molding, high-temperature steam or pressurized water runs through specialized cooling lines just before the melt is injected. This dynamic heating ensures that the polymer replicates the finest surface details of the cavity.
Surface Finish
Eliminating weld lines and sink marks is the primary benefit of this molding technique. Because the melt does not freeze immediately upon contact with the tool, the polymer chains flow together more easily at weld lines. This results in a high-gloss finish without the need for secondary painting operations.
Process Efficiency
Dynamic thermal cycling requires robust energy management to balance the rapid heating and cooling phases. Molders use specialized temperature control units that switch between hot and cold water sources within seconds. Although the equipment cost is higher than standard cooling systems, the reduction in part reject rates compensates for the investment.
Proper insulation of the tool is necessary to prevent heat loss to the mold plates during the heating phase.