Molds & Tooling
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Warpage of glass fiber reinforced PP
Fenómeno do problema
GF-PP flat plates and bracket-type products warp along a fixed direction; adjusting the cooling time has little effect, and the repeatability is very strong.
Análise das causas
Glass fibers orient along the flow direction with the melt, making the shrinkage rate in the flow direction much smaller than in the perpendicular direction, forming anisotropic shrinkage; the gate position and number determine the fiber orientation pattern, so the warpage direction is stable and it is difficult to cure by adjusting cooling unevenness.
Solução
①Adjust the gate position/number to change the material flow and fiber orientation direction; ②use Moldflow etc. to perform fiber orientation and warpage analysis to predict deformation; ③balance holding pressure and cooling to reduce additional stress; ④switch to mineral/glass fiber hybrid filling or a low-warpage grade when necessary; ⑤design the structure symmetrically and avoid large flat surfaces.
Conclusão principal
The orientation-type warpage of GF-PP is a 'gate-determined material problem'; the main attack direction is gate design and orientation analysis, not cooling; treating warpage as a problem solvable by temperature adjustment often leads to the trap of repeated mold trials.
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