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Injection Molding Cycle Time Estimator

This Injection Molding Cycle Time Estimator adds the main recurring phases of a molding cycle to estimate total seconds per shot and cycles per hour. It is designed for process engineers, estimators, and production planners who need a transparent first-pass cycle estimate from mold-close, injection/pack, cooling, and mold-open/ejection time.

Cooling often dominates molding cycle time, but every recurring phase contributes to machine capacity. By changing one component at a time, you can see which improvement would have the largest effect on hourly cycle rate. The estimator is intentionally process-level and does not predict resin-specific cooling behavior or validate a molding window.

Cycle phases

sec
sec
sec
sec
Result
—
estimated cycle time per shot
Theoretical cycles/hour—
Cooling share—
Non-cooling time—

1. Enter mold-close time
Use the recurring time from the start of closing until the mold is ready for injection.

2. Add injection and pack time
Enter the combined fill and packing/holding portion you want included in each cycle.

3. Enter cooling time
Use the planned in-mold cooling duration before opening the tool.

4. Add opening and ejection
Include the recurring time to open the mold, eject or remove parts, and reach the next close sequence.

5. Review cycle rate
Compare total cycle time, cycles per hour, and cooling share to identify which phase dominates the cycle.

Cycle time = Mold close + Injection/pack + Cooling + Mold open/ejection
Cycles per hour = 3,600 ÷ Cycle time in seconds

What the result means

The main result is the estimated recurring time required to complete one full molding shot based on the entered phase durations.

This simplified model excludes non-recurring events such as mold changeovers, material purging, maintenance, and unexpected stops.

Given: 2.8 s close, 4.7 s injection/pack, 16.5 s cooling, and 4.0 s open/eject.

Calculation: Cycle time = 2.8 + 4.7 + 16.5 + 4.0 = 28.0 s. Cycles/hour = 3,600 ÷ 28.0 = 128.57.

Result: 28.0 seconds per shot, or about 128.6 theoretical cycles per hour.

Cooling accounts for 58.9% of the modeled cycle, making it the largest time component in this example.

Does the cycle time include setup and mold change time?

No. The model adds recurring per-shot phases. One-time changeover and startup losses should be handled separately in capacity planning.

Should pack and hold be combined with injection time?

They can be combined for this simplified estimator as long as the total reflects the recurring phase before cooling or overlapping time is not double-counted.

Can some phases overlap?

Yes, real molding sequences can overlap auxiliary actions. If times overlap, enter only the net time that contributes to the total cycle rather than summing duplicated time.

How do cavities affect cycle time?

Cavity count does not directly change the time formula here. It changes the number of parts produced per shot and is more relevant to throughput.

Why is theoretical cycles per hour higher than actual production?

The hourly value assumes continuous cycling with no stops. Actual output is reduced by downtime, speed variation, startup loss, and quality loss.