Inside the Molding Machine

Clamping Unit:

That portion of an injection molding machine in which the mold is mounted, and which provides the motion and force to open and close the mold to hold the mold closed with force during the injection. The mold can be closed in a horizontal or vertical direction.

Moving Platen or Plate:

That member of the clamping unit is moved toward a stationary member. The moving section of the mold is bolted to this moving Platen. This member usually includes the ejector (Knockout) holes and mold mounting pattern of bolt holes or “T” slots.

Stationary Platen or Plate:

The fixed member of the clamping unit on which the stationary section of the mold is bolted. This member usually includes a mold mounting pattern of bolt holes or “T” slots, A standard pattern is recommended by the SPI (Injection Machinery Division Methods and Procedures, Sep 1958). In addition, the stationary platen usually includes provisions for locating the mold on the platen and aligning the sprue bushing of the mold with the nozzle of the injection unit.

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Tie Rods, Bars, or Beams:

Those members of the clamping force actuating the mechanism that serves as the tension members of the clamp when it is holding the mold closed. They also serve as a guide member for the movable platen.

Ejector (Knockout):

A provision in the clamping unit that actuates a mechanism within the mold to eject the molded part(s) from the mold. The injection actuating force may be applied hydraulically or pneumatically by a cylinder(s) attached to the moving platen, or mechanically by the opening stroke of the moving platen.

Fully Hydraulic Clamp:

A Clamping unit attached to a hydraulic cylinder that is directly connected to the moving platen. Direct fluid pressure is used to open and close the mold, and to provide the clamping force to hold the mold closed during the injection.

Toggle Clamp (Hydraulic Actuated, Mechanical Actuated):

A clamping unit which toggle mechanism directly connected to the moving platen. A hydraulic cylinder. or some mechanical force device is connected to the toggle system to exert the opening and closing force and hold the mold closed during the injection. The clamping force to hold the mold closed during injection is provided by the mechanical advantage of the toggle.

Slow Mold Breakaway:

A provision in the machine designed to provide a slow platen movement for an adjustable distance before the mold face comes in contact.

Clamp Close Slow Down:

A provision in the machine designed to slow down the moving platen for an adjustable distance before the mold faces come in contact.

Clamp Open Slow Down:

A provision in the machine designed to slow down the moving platen for an adjustable distance before it reaches its maximum open position. This sequence is often employed to reduce the effect of knockout impact when the mechanical knockout is used. It is sometimes referred to as the ejector or clamps open cushion.

Clamp Close Stroke Interruption:

A complete stop of the clamp closing stroke to allow an auxiliary operation(s) before completion of the closing stroke.

Clamp Open Stroke Interruption:

A complete stop of the clamp opening stroke to allow an auxiliary operation(s) before completion of the opening stroke.

Clamp Open Preposition

A provision in the machine circuit to allow the clamp to open fully and then close to a predetermined position. It is generally used to allow the ejector (knockout) mechanism to retract so that inserts can be placed in the mold.

Low-Pressure Mold Closing:

A provision in the machine to lower the clamp closing force during the clamp closing cycle. The lower clamp forces minimize the danger of mold damage caused by parts caught between the mold faces. Provisions are also provided for parting mold faces at a time interval in case of an obstruction.

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