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#070 Constituent factors of an Injection Molding Cycle

Category : Cost
February18, 2011

In general, the following are the constituent factors of an injection molding cycle.

1. Mold closing time

This is the time until the mold is closed. The times of opening and closing the mold vary depending on the speeds of the mold opening stroke and the mold closing stroke of the injection molding machine.
Since the mold has considerable mass, if the mold closing speed is made too fast recklessly, it is possible that the mold may break at the time of closing the mold due to the kinetic energy, and hence it is necessary to consider applying brakes.

2. Filling time

The filling time is the time taken until the molten plastic flowing in from the sprue completely fills the inside of the cavity.
The filling time is determined by the injection speed of the injection molding machine (actually, by the injection volume per unit time = injection rate (cm3/sec) which is determined by the movement speed of the injection screw or piston and the diameter of the injection cylinder).
In addition, this is also affected by the viscosity of the molten plastic.

3. Holding time (Packing time)

The holding time is the duration of time during which pressure is being applied after filling the inside of the cavity with molten plastic until the gate part solidifies.

4. Cooling time

The cooling time is the time duration after holding has been completed while the cooling takes place until the molded product, the sprue, and the runners solidify to some extent.
In general, the cooling time tends to be the longest time in a molding cycle.

5. Charging time

The charging time is the time required for measuring the amount of molten plastic for the next injection molding. In general, the charging is carried out simultaneously with the cooling and the charging time is shorter than the cooling time.

6. Mold opening time

This is the time duration until the mold is opened completely. The mold opening and closing times vary depending on the speeds of the mold opening stroke and the mold closing stroke of the injection molding machine.

7. Taking out time

This is the time taken for taking out the molded product from the cavity. This includes the ejection time and the time of operation of the take-out robot.

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