Injection Molding worked example

Hopper Residence Time with drying hopper holding capacity of 130 kg: a worked example in injection molding

This scenario runs the hopper residence time calculation on the strong side: drying hopper holding capacity of 130 kg, with every other input held at its documented default. Use this to confirm that resin spends enough time at drying temperature before reaching the press throat. Insufficient residence time causes splay, bubbles, and reduced mechanical properties.

The inputs for this scenario

  • Drying hopper holding capacity: 130 kg (raised for this scenario; the documented default is 50)
  • Press resin consumption rate: 15 kg/hr (unchanged)

Working through the calculation

  • Applying the documented formula (Residence time = Hopper capacity / Press consumption rate) to the inputs above produces each figure below.
  • At this operating point the engine returns 8.67 hrs for ratio, the number this scenario is built around.
  • At this operating point the engine returns 8.67 value for raw ratio.
  • At this operating point the engine returns 1 x for conversion factor.
  • At this operating point the engine returns 15 value for denominator.

How this compares with the baseline

  • Against the tool's baseline example, where drying hopper holding capacity sits at 50 kg and the headline result is 3.33 hrs, this scenario comes in 160% above the baseline at 8.67 hrs.
  • Use it when qualifying a new resin, changing cycle time, or troubleshooting moisture defects like splay and brittleness. Treat this as a target state: the delta against the baseline quantifies what the improvement is worth before you commit to chasing it.

Results at a glance

  • Ratio: 8.67 hrs (headline result)
  • Raw ratio: 8.67 value
  • Conversion factor: 1 x
  • Denominator: 15 value

Run it with your numbers

  • Every input above is editable in the live Hopper Residence Time calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.