Troubleshooting flow problems

 

Troubleshooting Melt flow problems

 

Flow problems manifest themselves in a variety of ways, including overpacking, insufficient packing, and visual defects.

Topics in this section

• Hesitation
  Hesitation, which occurs when the melt flow slows down or stops along a particular flow path, can lead to asymmetrical and unpredictable flow patterns.
• Volumetric shrinkage
  Volumetric shrinkage is the contraction of polymer due to the change in temperature from melt temperature to ambient temperature.
• Shear stress
  Shear stress is stress that is experienced by the melt as it flows through the mold. It occurs as a result of friction between layers of plastic flowing in the cavity.
• Overpacking
  Overpacking occurs when extra material is compressed in one flow path while other flow paths are still filling.
• Racetrack effect
  The racetrack effect occurs when flow races through thick sections of the cavity before the thin sections have filled.
• Unbalanced flow
  Unbalanced flow is plastic completely filling some flow paths in the mold before other flow paths have filled.
• Underflow
  Underflow is when a flow front reverses direction.