Analysis to prevent hesitation

Analysis Outline

Purpose and description

In producing injection-molded pieces with thin-walls, ensuring smooth and consistent resin flow through the thin-walls is a key to product quality. However, thin-walls inherently have high flow resistance. In addition, the temperature of melted resins cool more rapidly and thus the viscosity tends to increase in thin-walls. This may lead to molding defects called "short shots". Altering the gate location may be effective in preventing these defects. This section introduces a case study of analysis to improve flow at thin-walls using PlanetsX for optimization of the gate location. It shows how melt fronts and pressure distribution change by altering the gate location, and how this leads to improvement in resin flow.

What is a hesitation phenomenon?

Cause

Relatively high filling pressure is required to fill thin-walls. So the resin will flow away to other unfilled areas if there are areas where the resin can flow into with lower pressures, which in turn will result in flow hesitation at the thin section.

Features of hesitation analysis with PlanetsX

• Feature 1
  Analyze injection mold flow during the filling stage with the gate set at any desired location.
• Feature 2
  Visualize changes in resin flow patterns by altering the gate location.
• Feature 3
  Visualize flow patterns in terms of pressure, temperature and viscosity distributions to indicate guidelines for the product design.

Countermeasure

Locate the gate away from the hinge so that the resin flow reaches the hinge part after the inner pressure has become sufficiently high.

Associated Case Analysis

Melt front Resin flow in the mold

Evaluation of weld lines and air-traps