Optimum Injection Speed
The optimum injection speed allows us to maintain minimum injection pressure under given conditions. Injection speed should vary with cavity thickness. Compared with the thick ones, the thin ones possess a smaller effective flow cross-section. As a result, we need to raise injection speed, improve overall deformation rate and increase frictional deforming force, so as to stabilize flow temperature and minimize injection pressure.
Injection speed also varies greatly with the heat capacity, thermal conductivity and viscosity of resin materials. For materials (PC, PMMA) whose viscosity changes dramatically with temperature, the U-curve is smaller. For materials (PP, ABS) without this feature, the U-curve is much larger. Therefore, some materials are sensitive to injection speed, while some others are not.