𝐓𝐨𝐝𝐚𝐲'𝐬 𝐊𝐍𝐎𝐖𝐋𝐄𝐃𝐆𝐄 𝐒𝐡𝐚𝐫𝐞 : 𝐓𝐡𝐞 𝐩𝐚𝐫𝐭 𝐩𝐚𝐬𝐬𝐞𝐝 𝐢𝐧𝐬𝐩𝐞𝐜𝐭𝐢𝐨𝐧. 𝐓𝐡𝐞 𝐬𝐮𝐫𝐟𝐚𝐜𝐞 𝐥𝐨𝐨𝐤𝐞𝐝 𝐩𝐞𝐫𝐟𝐞𝐜𝐭.

𝐓𝐨𝐝𝐚𝐲'𝐬 𝐊𝐍𝐎𝐖𝐋𝐄𝐃𝐆𝐄 𝐒𝐡𝐚𝐫𝐞

𝐓𝐡𝐞 𝐩𝐚𝐫𝐭 𝐩𝐚𝐬𝐬𝐞𝐝 𝐢𝐧𝐬𝐩𝐞𝐜𝐭𝐢𝐨𝐧.

𝐓𝐡𝐞 𝐬𝐮𝐫𝐟𝐚𝐜𝐞 𝐥𝐨𝐨𝐤𝐞𝐝 𝐩𝐞𝐫𝐟𝐞𝐜𝐭.

No sink marks. No flash. No burn marks.

But under load, it failed.

When the part was cut open, a hidden hollow pocket was found inside the wall.


That is a Vacuum Void — one of the most dangerous injection molding defects because it is completely invisible from the outside.

Why it happens


Vacuum voids form when the core of a thick section continues to shrink during cooling, but there isn't enough pressure or material flow to compensate.


Common causes:

① Insufficient pack pressure

② Thick wall sections or bosses

③ Premature gate freeze

④ Low melt temperature


How to prevent it

✓ Increase pack pressure

✓ Extend pack time

✓ Reduce excessive wall thickness

✓ Optimize gate size

✓ Validate using Moldflow pack analysis


Unlike a sink mark, a vacuum void hides inside the part while the surface still looks good.

That's why a part can pass visual inspection and still fail in service.

Pack it correctly. Cool it uniformly. Leave no hollow spaces.


💬 Have you ever cut open a failed part and discovered a void inside a thick section? Share your experience below.


source : IMTechnologies


#InjectionMolding #WallThickness #PackPressure #VacuumVoids #PlasticDesign #DFM #AutomotiveEngineering #MoldflowAnalysis

#PlasticEngineering #QualityControl

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