Injection Molding
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PA66 high melt viscosity and insufficient injection pressure
Problem Phenomenon
Filling still difficult at full pressure, thin-walled parts short shot.
Cause Analysis
PA66 melt viscosity is sensitive to shear rate, viscosity is higher at low speed; equipment injection pressure upper limit insufficient; high viscosity is a material characteristic; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based solely on experience.
Solution
①Increase injection speed to utilize shear thinning; ②appropriately raise melt temperature to improve melt fluidity and plasticizing quality; ③appropriately enlarge the gate to reduce shear rate and pressure loss; ④calculate equipment pressure margin; ⑤select high-flow grades when necessary to reduce filling difficulty.
Key Takeaway
PA66 'use shear thinning characteristics to help filling': increasing speed is smarter than hard-pulling pressure; high-viscosity nylon should make good use of its rheological characteristics, and equipment pressure margin must also be sufficient.
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