Injection Molding Terms

• Injection pressure: Also known as Fill pressure is the pressure required to fill the mold to a certain level usually 95% of part volume
• Pack Pressure: The pressure applied once the mold has been filled, this is required to to ensure that the plastic fills all the corners and crevices of The mold cavity
• Hold Pressure: The pressure that is applied during the cooling phase to ensure that the plastic remains in contact with the mold surface and to minimize shrinkage in the part
• Injection Speed: The rate at which the plastic is injected into the mold, affecting the filling process and the quality of the molded part
• Melting temperature: the temperature at which the resin is melted at. The melt temperature affects the viscosity of the plastic. The higher the melt temperature, the lower the viscosity and weight.
• Clamping force: the force apple to the machine to hold the molds together during injection and cooling process
• Cooling Time: The time it takes for plastic to cool enough to be removed from the mold
• Back Pressure: The resistance applied to the back of the screw during the injection process. Back pressure can improve the shrinkage of the product surface
• Cycle Time: The total time needed to complete the stages of the molding process

The unintended twisting and bending caused by uneven shrinkage during the cooling process. To prevent warping its important to guarantee that the parts

Visible, squiggly flow patterns on the parts surface that decreases the strength of the part. This occurs when the resin enters the mold and has enough time to begin setting before the cavity fills.The best way to reduce jetting is by reducing the injection pressure allowing for the gradual fill of the mold.

Dents, Craters, or depressions in thick sections of a part. Thicker sections take longer to cool. This is a sign that the plastic needs more time inside the mold to properly cool and cure

A line that forms when two flows of molten resin come together as theft moves through the mold geometry. Weld lines reduce the overall strength and durability of the part. Raising the temperature of the molten resin can help reduce weld lines from occurring.

The instances in which the resin does not entirely fill the mold cavity resulting in an incomplete and unusable part. This is caused by the restricted flow inside the mold which can be caused by insufficient injection pressure. The mold temperature is also another way to prevent short shots.

Off color lines, streaks and other patterns that appear on the surface of a part. These are caused by the shot of molten plastic moving at different speeds throughout the mold. This is caused by low injection speed and/or pressure being too low.