There may be one or more reasons for the formation of shrink marks, including the method of mold processing, part geometry, material selection, and mold design. The choice of geometry and material is usually determined by the raw material supplier and is not easily changed. However, there are many other factors related to mold design that may affect shrinkage on the part of the molding manufacturer. Cooling runner design, gate type, and gate size may produce multiple effects. 5-Axis precision CNC milling service is a difficult geometry.
For example, small gates, such as pipe gates, cool much faster than tapered gates. Premature cooling at the gate reduces the filling time in the cavity and increases the chance of shrinkage marks. For molding workers, adjusting the processing conditions is one way to solve the shrinkage problem. Fill pressure and time significantly affect shrinkage. After the part is filled, excess material continues to fill the cavity to compensate for shrinkage of the material. Too short a fill phase will result in increased shrinkage and eventually more or more shrinkage marks. This method itself may not reduce shrink marks to a satisfactory level, but the shaper can adjust the filling conditions to improve the shrink marks.