Meaning
Active heating of the injection mould cavity before polymer injection followed by rapid cooling during the solidifying phase defines an advanced thermal control technique. This process, commonly called variothermal injection molding, utilizes steam, pressurized hot water, or induction heating to maintain a high mold temperature while the cavity is being filled. High temperature prevents the polymer melt from freezing prematurely as it enters the mold.
Once filling is complete, the cooling system quickly lowers the mold temperature to solidify the part, making this technique ideal for reducing cosmetic defects like weld lines and sink marks.
Melt Flow
High mold temperatures during the filling stage significantly reduce the viscosity of the flowing polymer. Under these conditions, variothermal injection molding allows the resin to flow into thin sections and intricate features without high injection pressure. This flow improvement is particularly useful when processing high-viscosity resins or thin-walled consumer electronics housings.
Surface Quality
Weld lines occur when two flow fronts meet, often creating a visible line and a weak point in the part. By preventing the polymer from cooling too quickly, variothermal injection molding ensures that the flow fronts merge at a temperature high enough to allow molecular diffusion across the boundary. This molecular blending eliminates the visible weld line and maximizes the mechanical strength of the joint.
Cycle Optimization
Cycle time is a primary driver of production economics in high-volume manufacturing. While the heating phase adds seconds to the cycle, variothermal injection molding compensates by reducing cooling time through optimized high-efficiency cooling lines. This balance minimizes the cycle time penalty while delivering parts that are free of internal stresses and cosmetic defects.
