Injection Molding OEE Calculator
OEE tells you what share of the planned time your molding press produced good parts at the ideal speed. This calculator handles the multi-cavity math that trips up many spreadsheets and gives availability, performance, quality and the overall figure.
Your numbers
Breakdowns, mold changes, material waits and warm-up.
Count only cavities that are actually running.
The best demonstrated or standard cycle for this mold and resin.
Good plus rejected, not counting startup purge.
Your results
Results depend on how you define ideal cycle and which stops you count as planned. Agree the definitions before comparing machines or plants.
Automate OEE from your MES or ERP
Optional: we can review which production counts and downtime codes you already capture and how they could feed OEE.
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How to use it
Enter the planned production hours for the shift, the hours lost to unplanned stops and setups, active cavities, the ideal cycle, total parts and rejects. Performance compares the parts you produced with what the press would have made in the run time at the ideal cycle. The important detail for molding is to multiply shots by active cavities so a blocked cavity shows up as a performance loss.
The formula
Availability is run time divided by planned time. Performance is total parts divided by (run time in seconds divided by ideal cycle, times cavities). Quality is good parts divided by total parts. OEE is the product of the three. A press that runs 85 percent of planned time, at 90 percent of ideal speed, with 97 percent good parts has an OEE near 74 percent.
- Availability losses: breakdowns, mold changes, no material, no operator
- Performance losses: slow cycles, blocked cavities, short stops
- Quality losses: scrap, startup rejects, rework
Reading the result
Look at the lowest of the three factors first. Low availability points to changeover and maintenance work. Low performance often means cycle times drifted above standard or cavities are shut off. Low quality points to process stability, material drying or mold condition. Track OEE per mold and per press, not just per plant, or the averages hide the poor performers.
Common mistakes
Setting the ideal cycle to whatever the machine currently runs, which hides performance loss. Ignoring cavities in the formula. Counting startup purge as good production. Mixing planned and unplanned stops so the figure cannot be compared over time. Decide your rules once and apply them to every press.
Frequently Asked Questions
What is a good OEE for injection molding?
Many plants run between 60 and 85 percent depending on changeover frequency and part mix. Plants with long dedicated runs can be higher. Compare against your own trend and similar machines rather than a single target.
Why do cavities matter in the OEE calculation?
Each shot makes one part per active cavity. If a cavity is shut off for a defect, parts per shot fall even though cycle time is normal. Including cavities makes that loss visible as a performance loss.
How should I treat mold changes?
Count them either as planned downtime excluded from the planned time, or as availability loss. Both are valid but you must choose one and use it consistently, or OEE will not be comparable between plants.
What if performance comes out above 100 percent?
The ideal cycle is probably slower than what the press achieves, or the counts include something extra. Reset the ideal cycle to the best proven cycle and check the part counter.
Netray can feed shop floor counts from your MES or ERP into an OEE view per press, mold and shift, so the figure is calculated automatically instead of copied from paper.
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