Flow Path Calculator
Calculate the maximum flow path length of the polymer in the mold and the flow path to wall thickness ratio (L/T). The calculator estimates the number of gates and fill time — key parameters in mold design.
Input Parameters
Results
Fill in the data and click Calculate
ARGUS automatically analyzes the flow path and selects gate locations
Flow path determines injection feasibility — ARGUS combines this analysis with filling pressure, material viscosity, and machine parameters.
How do we calculate flow path?
The flow path is the maximum distance the polymer melt must travel from the injection point to the farthest point of the cavity. It is a critical feasibility parameter — if the flow path is too long relative to wall thickness, the mold will not fill correctly.
The calculator determines the flow path to wall thickness ratio (L/T) — a dimensionless feasibility index. Every material has a maximum permissible L/T ratio, above which injection requires special conditions (high speed, high temperature, additional gates).
L/T = Lmax / s
Lmax — max. flow path [mm]
s — wall thickness [mm]
L/T — flow path to thickness ratio [-]
The L/T ratio is the fundamental criterion for assessing injection feasibility. Typical maximum L/T values: PP 250–300, ABS 150–200, PC 100–150, PA6 150–250, POM 100–150. Low-viscosity materials (PP, PA) permit a longer flow path than high-viscosity materials (PC, PMMA). Fillers (GF, mineral) reduce the permissible L/T by 20–40%.
Optimizing the number and position of gates
When the L/T ratio exceeds the permissible value for the material, you have several options:
Center gate — minimizes flow path but restricts ejector pin positions
Thicker wall — improves L/T but extends cycle time
Higher temperature — reduces viscosity but risk of degradation
A center gate position reduces the maximum flow path by ~50% compared with an edge gate. For rectangular parts a center gate gives Lmax = √(L²+W²)/2, while an edge gate gives Lmax ≈ √(L²+W²). Weld lines form where two flow fronts meet — their position should be controlled.
When simulation is essential
This calculator provides a good approximation for simple geometries. For parts with variable wall thickness, complex geometry, or requiring control of weld line positions, flow simulation (Moldflow, Moldex3D) is necessary. In the ARGUS system, flow path analysis is integrated with the full process model.
ARGUS connects flow path analysis with flow simulation and injection parameter selection
See it for yourself — book a presentation and discover how ARGUS integrates flow analysis with the full project context.