Mold Filling Time Calculator

Calculator

Pick a method, enter values, then calculate.

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Advanced options

Method

Choose how you want to define flow.

Part volume (per cavity) *

cm³

Use net part volume only.

Cavities

Total cavities in the mold.

Runner volume

cm³

Enter 0 for hot runner.

Sprue volume

cm³

Include cold sprue if present.

Gates per cavity

Used for gate-based method.

Flow rate *

cm³/s

From machine data or trials.

Mass flow *

g/s

If you measure mass per second.

Density *

g/cm³

Use melt density if available.

Gate area (per gate) *

mm²

For one gate; multiplied by gates and cavities.

Melt velocity *

m/s

Average velocity through the gate.

Discharge coefficient

Typical range 0.7–1.0.

Packing time

s

Optional hold/pack duration.

Safety factor

%

Adds margin to the fill time.

Gate thickness (optional)

mm

Used for shear-rate estimate.

Gate length (optional)

mm

Used in rough pressure estimate.

Viscosity (optional)

Pa·s

Provide to estimate gate pressure drop.

Reset

Notes: Results are estimates. Validate with trials and material data.

Example data table

Sample values and typical outputs for quick testing.

Scenario	Part (cm³)	Cavities	Runner (cm³)	Sprue (cm³)	Flow (cm³/s)	Fill time (s)
Baseline trial	35	2	6	3	55	(35×2+6+3)/55 ≈ 1.45
Higher throughput	35	2	6	3	75	≈ 1.06
More cavities	22	4	8	4	65	≈ 1.48

Formula used

Total shot volume: V_total = V_part×N + V_runner + V_sprue
Filling time: t_fill = V_total / Q
Safety adjustment: t_adj = t_fill × (1 + SF/100)
Mass method flow: Q = \dot{m} / ρ
Gate method flow: Q = C_d × A × v (scaled by gates and cavities)
Optional segment: t_segment = t_adj + t_pack

Gate shear and pressure values are rough screening estimates, not design guarantees.

How to use this calculator

Select a flow definition method that matches your data.
Enter part volume, cavities, and any runner or sprue volume.
Provide the required flow inputs for the chosen method.
Add packing time and a safety factor if you need margin.
Click Calculate to view results above the form.
Use the download buttons to save CSV or PDF outputs.

FAQs

1) What is mold filling time?

It is the time required to push material from the gate into the cavity until the target volume is filled. It excludes cooling, ejection, and often excludes packing unless you add it.

2) Should I include runner and sprue volumes?

Yes for cold runner systems, because that material must also be filled during the shot. For hot runners, runner volume may be near zero, depending on the design.

3) Which method is best?

Use volumetric flow if you know the machine’s delivered flow at your settings. Use mass flow if you measure weight per second. Use gate area and velocity for early-stage screening.

4) What safety factor should I use?

A small margin like 3–10% is common for planning and comparisons. If viscosity, temperature, or venting varies a lot, increase the margin and confirm with trials.

5) Why does the gate method include a discharge coefficient?

Real flow differs from the ideal area×velocity product due to losses and nonuniform profiles. The coefficient provides a practical correction when detailed rheology data is unavailable.

6) Are shear rate and pressure results accurate?

They are quick estimates for comparison only. Actual values depend on rheology, temperature, gate geometry, and non-Newtonian effects. Use simulation or testing for final decisions.

7) Can I use this for casting as well?

Yes, if your flow rate reflects the casting system and material. Enter cavity volume plus runners, then provide a realistic volumetric flow or a gate-based estimate for your process.