I. What is Warpage?
Warpage refers to the deviation of plastic parts from their original mold shape after molding. It commonly occurs in flat or thin-walled components and cannot be fully eliminated solely through parameter adjustments. A comprehensive review of mold design, material selection, and manufacturing processes is essential.
II. Key Factors Causing Warpage
1️⃣ Mold Structural Design
Gate Design: Single gates often cause uneven radial and circumferential shrinkage. Multi-point or film gates should be used to homogenize melt pressure and stress distribution.
Cooling System: Uneven cooling causes temperature-differential shrinkage, inducing warpage. Design multi-loop cooling channels close to the cavity and employ dual temperature controllers.
Ejection System: Balance the number and placement of ejector pins. Insufficient area or improper positioning causes demolding deformation; use pneumatic/hydraulic assist ejection when necessary.
2️⃣ Plasticizing and Filling Stage
Uneven plasticizing creates temperature gradients, inducing internal stresses;
High-speed, high-pressure filling promotes molecular orientation and frozen layers, building residual stresses that cause warpage;
Uneven cooling rates result in non-uniform shrinkage, leading to thermal stress deformation.
3️⃣ Demolding Stage
Uneven ejection force or rough movement can cause product distortion;
Internal stress release during demolding instantly converts into warpage deformation.
4️⃣ Shrinkage and Material Properties
Anisotropic shrinkage is the fundamental cause of warpage;
Crystalline plastics (e.g., PA, POM) carry higher warpage risk;
Differences in thermal expansion rates between metal inserts and plastic can also cause localized deformation or cracking.
III. Summary Recommendations
✅ Warpage must be controlled simultaneously through design and molding processes.
✅ Optimizing mold design, material selection, and process control is essential for enhancing stability and yield.
✅ Systematic pre-production analysis outperforms post-production fixes.