Plastics Extrusion - Pipe, Film & Profile worked example

Melt Residence Time at 17% residence allowance: a worked example

Push residence allowance up to 17% and the picture changes. This example computes every intermediate figure at that operating point. Use it when checking heat history risk, color changes, purging plans, or residence-sensitive resins.

The inputs for this scenario

  • Estimated melt hold-up: 120 lb (unchanged)
  • Extruder output rate: 240 lb / hr (unchanged)
  • Residence allowance: 17 % (raised for this scenario; the documented default is 15)

Working through the calculation

  • Applying the documented formula (Base time = estimated melt hold-up รท extruder output rate) to the inputs above produces each figure below.
  • At this operating point the engine returns 0.59 hr for estimated residence time, the number this scenario is built around.
  • At this operating point the engine returns 0.5 hr for base hold-up time.
  • At this operating point the engine returns 17 % for residence allowance applied.
  • At this operating point the engine returns 240 pieces / min for extruder output rate.

How this compares with the baseline

  • Against the tool's baseline example, where residence allowance sits at 15% and the headline result is 0.57 hr, this scenario comes in 1.74% above the baseline at 0.59 hr.
  • It computes base residence time as melt hold-up divided by output rate, then adds a residence allowance to reflect dead zones and non-uniform flow. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Estimated residence time: 0.59 hr (headline result)
  • Base hold-up time: 0.5 hr
  • Residence allowance applied: 17 %
  • Extruder output rate: 240 pieces / min

Run it with your numbers

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

Last reviewed 2026-05-12.