Injection Mold Venting Methods And Types

The design of the exhaust groove is very important for small parts or precision parts because it can eliminate various defects of the product and reduce mold pollution in addition to avoiding product surface burns and insufficient injection volume.

There are two main functions of the exhaust groove: one is to remove the air in the mold cavity when the molten material is injected; the other is to remove various gases generated during the heating process of the material.

Generally, in addition to exhausting the mold cavity on the parting surface, the purpose of exhausting can also be achieved by setting an exhausting groove at the end of the material flow of the gating system and leaving a gap around the ejector rod, because exhausting If the depth, width, and position of the groove are not selected properly, the flash and burrs generated will affect the beauty and precision of the product. Therefore, the size of the above-mentioned gap is limited to prevent flashing around the ejector rod.

Design method:

For product molds with complex geometric shapes, it is best to determine the opening of the exhaust groove after several mold trials. The biggest disadvantage of the overall structural form in the mold structure design is poor exhaust.

For the integral cavity core, there are the following exhaust methods:

(1) Use the groove of the cavity or the installation part of the insert;

(2) Utilize side insert seams;

(3) Partially made into a spiral shape;

(4) Install the slotted slat core and open the process hole in the longitudinal position.

General Exhaust Type:

(1) exhaust groove exhaust

For molds for forming large and medium-sized plastic parts, the amount of gas to be removed is large, and exhaust grooves should usually be provided. The exhaust grooves are usually provided on the side of the die on the parting surface.

(2) Parting surface exhaust

For small molds, the parting surface gap can be used to vent, but the parting surface must be located at the end of the melt flow.

(3) Exhaust through gaps in mosaic inserts

For combined dies or cavities, the combined gaps can be used to vent.

(4) Push rod clearance exhaust

Use the gap between the push rod and the template or core to exhaust, or deliberately increase the gap between the push rod and the template.

(5) Exhaust of powdered unsintered gold nuggets

Powder unsintered alloy is a material sintered with spherical particle alloy, which has poor strength, but loose texture, which allows gas to pass through. Placing a piece of such an alloy at the part to be vented can meet the venting requirements, but the diameter of the vent hole at the bottom should not be too large to prevent it from being squeezed and deformed by the pressure of the cavity.

(6) exhaust well exhaust

On the outside of the junction of the plastic melts, a cavity is provided to allow gas to be discharged into it, and a good exhaust effect can also be obtained.

(7) Mandatory exhaust

Install an exhaust rod at the part where the gas is closed. This method has a good exhaust effect, but it will leave traces of the rod on the plastic part, so the exhaust rod should be installed in a hidden place on the plastic part.