由於每種產品使用的材料不同, defects occasionally occur in the IMD injection molding process. For instance, rigid plastic products often exhibit ripple marks. 所以, what causes these ripple marks, and how can they be effectively resolved?
Causes of Ripple Marks in Injection Molding
In rigid plastics like PS, dense ripple patterns often form near the gate, centered around it—this phenomenon is known as ripple marks. The primary cause is the high viscosity of the melt, which leads to sluggish flow during mold filling. When the leading edge of the melt contacts the cavity surface, it cools and contracts quickly, while the following melt expands and continues forward. This alternating effect results in the formation of ripple marks on the surface.
Solutions for Eliminating Ripple Marks in Injection Molding
- Increase Barrel and Nozzle Temperatures: Raise mold temperatures simultaneously to reduce melt viscosity.
- Increase Injection Pressure and Speed: Enhance pressure and speed to ensure the melt fills the mold cavity quickly.
- Optimize Runner and Gate Dimensions: Design runners and gates appropriately to prevent excessive flow resistance.
- Ensure Proper Mold Ventilation: Set sufficiently large cold wells to improve ventilation.
- Avoid Overly Thin Product Design: Design the product with adequate thickness to prevent ripple marks due to thinness.
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