How to cause flow lines (flow marks) and water ripples on the surface of the product

- Jun 21, 2019-

Analysis of the cause: traces of the flow of the plastic melt, the striped wave pattern centered on the gate. Numerous fine lines appearing perpendicular to the surface, resulting in fingerprint-like ripples on the surface of the article.


Countermeasure: The flow mark is caused by the rapid cooling of the plastic melt that originally flows into the cavity, and the boundary between the plastic melt that flows into it. The cold material remaining in the front end of the nozzle of the injection molding machine directly enters the cavity, causing flow marks. When the temperature of the plastic melt is low, the viscosity increases and flow marks occur. When the mold temperature is low, a large amount of heat of the plastic melt is taken away, so that the temperature of the plastic melt is lowered, and the viscosity is increased to cause flow marks. The injection speed is too slow, the plastic melt temperature decreases during the filling process, and the viscosity increases to cause flow marks. During the filling process of the mold, the temperature of the plastic melt in the cavity drops, filling with a high viscosity state, and the plastic melt contacting the die face is pressed in a semi-cured state, and the surface has numerous fine lines flowing in a vertical direction, resulting in a similar surface of the product. Ripple of the fingerprint. When the temperature of the plastic melt drops again, the filling does not completely solidify, resulting in insufficient filling. Corrugations often occur near the edges of the product and at the end of the fill.


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