1) Gas removal through vents
For molds that shape large and medium-sized plastic parts, a large amount of gas needs to be removed. Vent holes are usually created on the parting surface, on the side of the female mold. The location of these vents should be at the end where the melt flows; the size of the vents should ensure that gas can be easily expelled without overflowing. The width of the vents is generally around 3–5 mm. The depth at the front end of the vent holes is less than 0.05 mm, and their length is usually 0.7–1.0 mm. For more details on the appropriate depth of vents, refer to the <Plastic Molding Technology Manual>.

2) Gas removal through parting surfaces
For smaller molds, gas can be removed using the gaps between parting surfaces, provided that these gaps are located at the end where the melt flows.

3) Gas removal through joints in assembled components
For composite female molds or cavities, gas can be removed through the joints where the components are joined together.

4) Gas removal through the gap between the push rod and the template or core
The gap between the push rod and the template or core can be used for gas removal; sometimes, the gap between the push rod and the template is intentionally increased for this purpose.

5) Gas removal using powder sintered metal blocks
Powder sintered metal is a material made by sintering spherical alloy particles. It has low strength but is porous, allowing gas to pass through it. A block of such metal can be placed in areas where gas needs to be removed; however, the diameter of its ventilation holes should not be too large, so as to prevent pressure from causing deformation in the cavity.

6) Gas removal via a vent hole
A hole is created outside the area where the plastic melt converges, allowing gas to flow into it, thereby achieving good gas removal effects.

7) Forced gas removal
In areas where gas is trapped, a vent rod is installed. This method provides effective gas removal, but it may leave marks on the plastic part. Therefore, the vent rod should be placed in a hidden location within the part.