During the injection process of a plastic injection machine, the speed at which the melt enters the mold (injection speed) does indeed affect the integrity of the mold filling. If not properly controlled, it can lead to defects in the finished product, such as incomplete filling, incomplete structure, etc. The introduction is as follows:

1. Effects of too fast injection speed:
Causing burrs: High speed injection can cause a significant increase in pressure inside the mold cavity. If the mold is not tightly closed, the melt may be squeezed out from the parting surface or exhaust gap, forming burrs and damaging the integrity of the product edge.
Gas retention and formation of pores: During high-speed injection, the melt quickly occupies the mold cavity space, and air cannot be expelled in time, which may form "pores" or "burn marks", causing local incompleteness or structural thinning.
Stress concentration and warping deformation: After rapid filling of the mold, the melt is prone to internal stress when cooled, resulting in uneven shrinkage of the molded part and affecting the overall flatness and stability of the structure.
Uneven flow leads to the formation of weld lines: The flow path of the melt at high speeds may diverge in the mold cavity and then converge again. If the pressure is insufficient or the temperature is not well controlled, weld lines will form at the confluence, affecting the strength and appearance integrity.

2. The impact of slow injection speed:
Incomplete filling (short shot): If the speed is too slow, the melt will start to cool and solidify before reaching the end of the mold cavity, causing the plastic to be unable to fill the mold, resulting in short shot phenomenon and damaging the overall shape.
Severe cold joint marks: Slow injection causes the front end of the melt to be in contact with the mold for too long, resulting in rapid cooling and the formation of "cold joints" or "seams" at the forefront of plastic flow, which reduces structural strength.
Surface roughness of the product: Local incompleteness or formation of discontinuous flow trajectories can easily lead to ripples, holes, and roughness on the surface of the product, affecting the visual and structural integrity of the mold filling.

3. Unstable injection speed fluctuations:
Discontinuous filling process: If the injection speed fluctuates greatly during the process, it will cause uneven filling rhythm, resulting in local gaps or uneven flow areas, which will destroy the consistency of the molding inside the mold.
Irregular flow path of the melt: Changes in velocity may cause the melt to advance along different paths, and complex areas within the mold cavity are prone to insufficient filling or stress concentration.

4. Improper matching of mold design and speed:
Complex molds are sensitive to speed: Multi channel or thin-walled products are more sensitive to speed control, and improper injection speed settings can easily lead to incomplete filling of certain parts of the mold.
Poor exhaust design is more likely to cause problems: when the injection speed is too fast, if the mold has poor exhaust, the gas cannot be discharged in a timely manner, which affects the subsequent filling of the melt and leads to incomplete local structure.