How much output do I lose when I block a cavity?

One cavity's share at the same cycle: blocking one of eight cavities cuts parts per hour by 12.5%. Enter the cavities still running to see whether the target still holds and what cycle would restore it.

Should I enter the standard cycle or the measured one?

The measured one from the press monitor. Uptime and scrap here do not cover slow cycles, so a cycle that has drifted two seconds past standard only shows up if you enter the real cycle.

How does this relate to OEE?

OEE multiplies availability, performance and quality. Uptime here is availability and one minus scrap rate is quality; performance is carried by entering the measured cycle rather than the ideal one.

How many press hours will a 50,000-part order take?

Divide the order by good parts per hour. At the default 423 good parts an hour, 50,000 parts take about 118 press hours, before the changeover to hang the mold.

Injection Molding calculator

Mold Parts per Hour Calculator

Turn the cycle on the press monitor and the cavities running into good parts per hour, and check it against the rate your schedule needs. You need the cycle, cavity count, uptime, scrap rate and target.

What this calculator does

Good parts per hour a mold makes after uptime and scrap, and whether that covers the rate you need.

Formula used

Shots per hour = 3,600 ÷ cycle time; gross parts per hour = shots per hour × cavities running
Good parts per hour = gross parts per hour × uptime % ÷ 100 × (1 − scrap % ÷ 100)
Load against target = parts needed per hour ÷ good parts per hour × 100; margin = good parts per hour − parts needed
Longest cycle that meets target = 3,600 × cavities running × uptime % ÷ 100 × (1 − scrap % ÷ 100) ÷ parts needed per hour

Inputs explained

Cycle Time per Shot: Mold close to mold close, measured on the press monitor.
Cavities Running: Cavities in the mold minus any blocked off.
Uptime: Share of scheduled time the press is cycling, from downtime logs.
Scrap Rate: Rejects as a share of parts molded, from the reject count.
Parts Needed per Hour: Good parts per hour the schedule or customer release requires.

How to use the result

Best suited to loading a press against a customer release, replanning output after blocking a damaged cavity.
An hourly average: startup scrap and purging at the start of a short run lower real output further. Treats every cavity as equally good; a single bad cavity needs its own reject count.

Current U.S. benchmarks

The producer price index for plastic resins and materials stands at 280.569 (BLS, Aug 2026), up 6.6% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 9,635 plastics product manufacturing establishments employing about 677,302 workers (Census County Business Patterns, 2023).

Common questions

How much output do I lose when I block a cavity? One cavity's share at the same cycle: blocking one of eight cavities cuts parts per hour by 12.5%. Enter the cavities still running to see whether the target still holds and what cycle would restore it.
Should I enter the standard cycle or the measured one? The measured one from the press monitor. Uptime and scrap here do not cover slow cycles, so a cycle that has drifted two seconds past standard only shows up if you enter the real cycle.
How does this relate to OEE? OEE multiplies availability, performance and quality. Uptime here is availability and one minus scrap rate is quality; performance is carried by entering the measured cycle rather than the ideal one.
How many press hours will a 50,000-part order take? Divide the order by good parts per hour. At the default 423 good parts an hour, 50,000 parts take about 118 press hours, before the changeover to hang the mold.

Related guides

Last reviewed 2026-10-01.