Structural Foam Injection (SFI) as a solution for Warpage Problems

WHAT is Warpage

Warpage in the HPI technology is when the intended shape of
the plastic part is distorted during the process.
Warpage can cause the part to fold, bend, twist or bow.

WHY does warpage occur in injection molded parts?

The two main reasons of warpage in the High Pressure Injection technology are :

Variation in internal stresses across the part.
Non-uniform wall thicknesses in the product leads to non-uniform part shrinkage.

HOW can SFI help overcome Warpage Problems?

Adding a blowing agent in the melted polymer is the key to success :

After injection, the blowing agent expands in the polymer and causes an overall equal pressure in the product, which results in low internal stresses.
Volumetric shrinkage is much less, which results in a freedom of different wall thicknesses within the product.