Considered the fourth phase of the Injection Molding Process, Ejection is the process of removing the solidified part from the mold.

Common ejection methods include:  Ejector Pins, Ejector Sleeves,  Ejector Blades and Stripper Plate.

    Ejector Pins and Blades  and to a lesser extent the Stripper Plate and Ejector Sleeves, all leave a  "witness mark" on the finished part.  Furthermore, the ejector pin and blade will either 1)  leave an impression or 2) a protrusion, where the pin or blade is located on the part.

    Locating ejectors is important.  Balanced pressure on the part by all ejectors is important.  Accurate location of ejectors on part walls, ribs, and bosses is highly desirable.  Part appearance and function must be taken into consideration when designing the ejection system. Stripper Plate ejection is highly preferred due to the even pressure and minimal witness marks on the part.

    The number and size of ejectors (area thereof)  used  is dependant on the size and shape of the part. One major consideration for proper design is ensure that the sizes selected  will work, error on too much ejection (larger Diameter pins) than on too little area.  Ejector pins may require methods to eliminate rotation, if,  the pin end at the part is cut other than parallel to the head of the pin.

Draw Polishing is recommended for thin walls, ribs, or minimal draft areas. 

    Ejector Pins are frequently used to help eject the runner system from the mold.  If a Sub-Gate is used in the mold, an Ejector Pin is used near the beginning of the drop of the gate to help break the part from the runner/sub-gate.

    Accelerated ejector systems are sometimes needed to eject the part from a tall core.  An Early Return of the ejector sub-assembly may be required when some slides are used in the mold.

It is also possible to "Tip" a part to get the part to fall from the mold in a certain direction.

Guided Ejection                 Design Examples             Accelerated Ejection