The Lab · Rheology

Pressure Drop

Short-shoot to the end of each section of the flow path and record peak pressure. The tool shows what each section costs you, and whether filling the part leaves anything for pack.

Cumulative pressure by section
Material
Melt °C
Mold °C
NOZZLE (psi)SPRUE (psi)RUNNER (psi)GATE (psi)PART (psi)
Machine max (psi)
Intensification ratio

Enter the cumulative pressure to fill through at least two sections.

  • Each reading is the peak pressure to fill through that section, not the loss across it.
  • Start with an air shot for the nozzle, then short shots stopping at each section in turn.
  • Run every shot at the injection velocity the viscosity curve fixed.
  • Add the machine maximum to see how much headroom is left for pack.
Predicted · not measuredPressure drop from a flow model

Model one simple channel — a round runner, or a slit such as a gate land or a strip of wall — and compare the predicted drop with the section you measured. Isothermal and steady: no frozen skin (which raises the real drop in a thin channel) and no shear heating (which lowers it). A cross-check on the measurement, not a substitute for it.

Your viscosity coefficients

Stays in this tab: not in the share link, not in saved studies, never sent to us. The Lab ships no default coefficients — fitted cards are licensed data we cannot redistribute — and a press study cannot fit them either: it never measures the true shear rate.

Channel

Enter all seven coefficients — missing n, τ*, D1, D2, D3, A1, Ã2.

How to run this study

Find out where injection pressure is consumed along the flow path, so you know which section to change and whether the part leaves any pressure for pack. A section taking a disproportionate share is the one worth opening up.

Procedure

  1. 01Set injection velocity to the optimal value from the viscosity-curve study and leave it there for every reading — pressure drop is velocity-dependent.
  2. 02Disable pack/hold. Record peak injection pressure on an air shot: that is the nozzle figure.
  3. 03Fit the mold and short-shoot to the end of the sprue. Record peak pressure.
  4. 04Short-shoot to the end of the runner, then to the gate, then to a just-full part, recording peak pressure each time.
  5. 05Enter the five cumulative readings in flow order — the tool derives each section’s share.
  6. 06If your readings are hydraulic rather than plastic, enter the machine’s intensification ratio so the numbers convert.