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Why Should I Have Venting on My Mold?

Injection Molding


In injection molding process, the air trapped in the mold cavity needed to be discharged. If the air can’t be discharged completely, it will potentially cause incomplete filling or even burning on the molded part. This is the reason we need venting on the Injection Mold, and how to set the venting and how many venting directly bears on the part’s quality.


The number of vents and the location of vents needed to be considered at the mold design stage. Also, the size of vents depends on what material you will inject. Typically, the higher the viscosity of a material the lager the vents dimensions should be. Vents can be placed on anywhere along the parting line, generally, they will be set on the end of last filling areas, you can space it every 25mm theoretically, and the distance can be longer actually. Beside opening vents along the parting line, we can consider to opening vents on ejector through the clearance between pin and hole, also, we can have this way on the insert of Mold.


Inadequate venting may result in various molding defects such as:

Burnt spot

Weak and visible weld lines

Poor surface finish

Poor mechanical properties

Incomplete filling, especially in thin sections

Irregular dimensions

Local corrosion of the mold cavity surface


Are you looking for Injection Molding Company from China? TEAM Rapid offers customized injection molded part at low cost but high quality, contact our team at today and get a free quote now!

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