Function of Major Parts
You will learn about the names and functions of major parts used for an ejection system.
A push back pin and a coil spring are used for regular molds, whereas a push back pin and a gas spring are sometimes used for large size molds.
This figure illustrates an example of a large mold.
Ejector Stopper (Stroke End Pin)
A block that stops an ejector plate from going forward [
stop pin]
A pin has the edge of which is undercut to pull a part in mold opening and remove a sprue from a sprue bush.
After mold opening, this pin will function as an ejector pin and ejects the sprue from a aprue bush. Also it releases gas contained in molten plastic.
| Ejector Plate |
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Also called a push plate. A plate that supports an edge of an ejector pin or a push back pin to eject a part from a mold.
It is ejected by an ejector device of a molding machine, and returned to the original position when the edge of a push back pin collides with a cavity plate during mold clamping.
A stopper installed to keep an ejector plate horizontal or prevent the ejector plate from retreating too far and damaging a core adaptor plate.
An ejector guide pin is also called a push plate guide pin and functions as a guide for sliding of an ejector plate.
Because an ejector guide bush slides, a hard material is used.
An ejector guide bush is also called a push plate guide bush. It is a cylindrical part used to determine the position by matching the ejector guide pin.
A shaft linked to the force (hydraulic or mechanical) of the molding machine in order to get the ejector plate to work.
A gas spring forcibly pushes back an ejector plate. The strength of the spring is adjusted by adjusting the filling pressure.
When using a gas spring, make sure to avoid high temperature (heat may expand gas, deteriorating the original functions of a gas spring).
Calculating Filling Pressure
To figure out filling pressure (P) from early load (Wo):
P = 100 * Wo /C (C: constant)
To figure out corresponding spring constant (K) from filling pressure (P) and gas spring constant (G):
K =G * P / 100
To figure out force by displacement (x) from the top D.C. of the piston rod (W):
W = P (Gx + C)
* See the catalog of each manufacturer for constant (C) and gas spring constant (G).
A gas spring holder is a block used to fix a gas spring to an ejector plate.
Counter bore process for a bolt installation hole, for it also functions as an push rod.
A gas spring forcibly pushes back an ejector plate. The strength of the spring is adjusted by adjusting the filling pressure.
When using a gas spring, make sure to avoid
