How Injection Speed Affects Product Surface Quality
Injection speed directly determines the melt filling rate; speeds that are either too high or too low can lead to various surface defects. Servo-driven injection molding machines allow for precise, multi-stage speed adjustment, ensuring consistent surface quality.
If the injection speed is too low, the melt flows sluggishly and cools rapidly, making the part prone to weld lines, flow marks, and matte or whitish patches; thin-walled parts may suffer from short shots or dull, incomplete surfaces. For materials with poor flowability, slow filling can cause visible "water ripple" patterns and poor visual consistency.
Conversely, if the speed is too high, the melt impacts the mold cavity at high velocity, easily causing gas marks, burn marks, and jetting marks. High-pressure impact can also lead to flash and surface scratches on precision parts. Furthermore, high-speed shearing can cause material degradation, resulting in yellowing and noticeable color discrepancies.
Servo-driven models support multi-stage injection profiles-such as low-speed buffering at the gate, uniform filling in the middle stage, and deceleration with pressure stabilization at the end. This ensures smooth melt flow and efficient air evacuation from the mold, effectively eliminating defects like flow marks, gas marks, and burns. The resulting parts feature a glossy, uniform surface, significantly improving the yield rate for visual quality.
