Injection molding is a process of injecting hot molten plastic into the cold mold and forming the part. It consists of a hopper that hold raw plastic and feeds barrel. Plastic is melted in barrel and injected into the mold cavity through a screw. The plastic rapidly cools and solidifies due to the lower temperature of the mold. The part is then ejected after opening the mold.
Flow of Plastic in mold
Hot plastic is a viscous fluid termed as ‘Melt’ and ease of flow of melt is measured by Melt Flow Index (MFI). The flow of plastic is demonstrated in an animation below. The melt is forced to flow inside the mold cavity under high pressure. Plastic at the center will flow faster than plastic near the wall because flow speed of the plastic gets reduced due to the friction with wall and due to solidification of plastic near the wall.