Injection Molding
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Severe warpage deformation of PBT injection molded parts
Problem Phenomenon
PBT injection molded products show severe warpage after demolding, especially thin-walled large flat products.
Cause Analysis
PBT has a fast crystallization rate and high crystallinity (40-60%), the shrinkage rate differs greatly in different directions (0.8-1.5% in the flow direction, 1.2-2.0% in the perpendicular direction), and the cooling of each part is uneven.
Solution
Raise the mold temperature to 80-100°C to make crystallization uniform; design the product with uniform wall thickness; optimize the gate position to balance the flow; use glass fiber reinforcement to reduce anisotropic shrinkage when necessary.
Key Takeaway
PBT warpage is the result of anisotropic shrinkage caused by its high crystallinity, and needs to be addressed from mold temperature and glass fiber reinforcement.
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