Injection Moulding OEE: Cycles, Cavities and Reject Counts

Download the cycle and cavity worksheet

Download the injection moulding cycle-and-cavity worksheet. It includes an explicitly hypothetical worked example and a blank row for a real production segment. Record the mould, active cavities, cycle count, reference cycle time, running time and first-pass rejects for each segment, with the source of every adjustment.

The OEE management service provides the broader project scope. The production-environments guide explains why different machines need different counting boundaries, while manufacturing services connects the measurement to the plant's operating decision.

Establish what one recorded cycle means

Confirm the controller event used as the cycle count and compare it with the observed machine sequence. A completed moulding cycle, a controller counter increment and a transferred batch quantity may use different definitions. Identify resets, aborted cycles and manual counter changes before treating the value as a production total.

Record the mould and product configuration with an effective time or cycle boundary. A cavity setting entered after the shift should not be assumed to have applied throughout the shift. Keep the original event and the authorised correction so a reviewer can reconstruct the sequence.

Agree how trials and setup cycles are treated. Their inclusion in planned production time, running time and quantity should follow a documented plant policy. The chosen rule needs to remain consistent across reporting periods so an apparent improvement is not simply a change in classification.

Split the record when active cavities change

A nominal eight-cavity mould may operate with fewer cavities active for part of a period. Multiplying every cycle by eight would then overstate the quantity that could have emerged from the actual configuration. Create separate segments whenever the active count changes and retain the reason and authorised owner.

The effective active count should describe cavities producing the included part type. For a family mould or a tool producing different items together, establish the product relationship before reducing everything to one total-parts figure. The reporting unit should remain useful for planning and quality reconciliation.

Keep nominal capability visible even when the operational count uses active cavities. The plant may want to understand the capacity lost through a disabled cavity. That question is distinct from reconciling how many parts were actually produced, and both should be available without silently changing the performance reference.

Work through an explicit hypothetical example

The following figures are invented for calculation practice; they are not a customer result or a recommended production target. Suppose the selected period has 60 planned minutes and 50 running minutes. During the first segment, 100 cycles run with eight active cavities; during the second, 50 cycles run with six active cavities.

The calculation is 100 × 8 + 50 × 6 = 1,100 total parts. Good parts are 1,100 − 30 = 1,070. Using the nominal eight cavities for every cycle would produce 1,200, overstating this example's actual configured output by 100 parts.

This arithmetic assumes each included cycle produced one counted part from every active cavity before first-pass rejection. If short shots, missing parts or another condition breaks that assumption, reconcile the count with an independent reference and use a more suitable quantity source. The worksheet is a model whose inputs must be verified.

Keep the performance reference explicit

Suppose the approved ideal cycle time is 18 seconds and the plant's declared policy measures machine-cycle performance using the active configuration. The hypothetical 150 cycles represent 2,700 ideal seconds, or 45 minutes, against 50 running minutes. Performance on that stated basis is 90%.

Availability is 50 ÷ 60 = 83.3333%, and quality is 1,070 ÷ 1,100 = 97.2727%. Their product is approximately 72.95%. Calculate with the unrounded inputs and round only the final displayed result.

This example does not treat disabled-cavity capacity as a separate performance loss. A plant using a nominal-tool output reference would obtain a different performance result. Record the selected policy and retain cavity-utilisation information alongside the metric; changing the denominator without documenting it prevents a fair comparison between shifts.

Reconcile rejects at the first-pass boundary

Define where and when a part becomes a reject for the selected quality calculation. Inspection at the press, a downstream check and a later customer return describe different events. Keep the first-pass quantity and subsequent disposition distinguishable even when the business ultimately needs all of them.

Link rejects to the relevant batch or segment where the evidence supports it. If a shift-end reject total cannot be allocated reliably across cavity configurations, preserve that limitation rather than inventing a precise distribution. The combined result may be valid while segment-level quality remains unresolved.

Record rework and regrind according to the plant's approved quantity rules. A reprocessed item should not silently become additional first-pass good output in the original period. Retain the relationship between the original production, quality decision and later movement so the report can be explained to both production and quality teams.

Choose a practical source for each field

The controller may supply cycles, recipe and running state, while quality provides rejects and the tool setter records cavity changes. Identify those responsibilities explicitly. A field that can be collected automatically still needs a documented meaning and a response when it is missing or inconsistent.

The EUROMAP 77 interface overview is a useful reference when assessing available injection-moulding data interfaces. Confirm the actual machine implementation, permissions and fields before including an interface in the project. The calculation method does not depend on assuming universal machine compatibility.

At acceptance, compare the chosen cycle source with observation, verify a cavity-change boundary and reconcile a representative reject event. Retain the independent counts, timestamps and configuration used in the comparison. A correct formula cannot compensate for an unverified input definition.

Review anomalies before publishing the shift result

Flag impossible or inconsistent combinations for review: good quantity above total quantity, rejects above the included output, missing cavity settings or a performance result above the expected range. An anomaly may reflect a valid unusual condition or a data-definition problem; it needs evidence before correction.

Preserve the submitted result, the correction and the reason for change. Assign ownership of cycle resets, product mappings, rate references and late quality adjustments. The shift supervisor should be able to identify which figures are final and which remain provisional.

Use the calculation boundaries described in Vorne's OEE guidance as a reference for availability, performance and quality. The factory's approved cycle, cavity and quality policies make those definitions operational for its machines. Discuss an injection-moulding measurement scope using one tool, one shift and the actual records required to reproduce the result.

Frequently asked questions