ISO 22514-8:2014

Overview

ISO 22514-8:2014 - Statistical methods in process management: Machine performance of a multi-state production process defines how to quantify the short-term capability (machine performance) of a production tool when the process generates multiple distinct states. The standard targets situations where the characteristic distribution is multi-modal because different intrinsic factors (e.g., cavities, fixtures, furnace positions) create systematic differences in outputs. ISO 22514-8:2014 specifies principles and statistical methods - not long-term process capability metrics - to evaluate whether a machine or tool can reliably produce parts that meet toleranced product characteristics.

Key topics and technical requirements

• Multi-state process definition: Identification of intrinsic factors and the process states created by combinations of those factors (cavity, fixture, batch position, etc.).
• Assumption of multi-modal distributions: Guidance for treating distributions that arise from different states and may show distinct locations or dispersions.
• Preliminary technical analysis: Identification of intrinsic factors, determination of process-specific states, and assessment of measurement systems.
• Sampling plan: Requirements for designing sampling to estimate global intrinsic dispersion when pooling data across states.
• Statistical verifications: Tests for outliers and guidance on state-by-state analysis (Annex B contains statistical tests).
• Estimation methods: Procedures to determine widths and locations of local intrinsic dispersions, pool them into a global intrinsic dispersion, and estimate capability.
• Capability indices and acceptance: Calculation of machine performance (capability) indices (short-term indices) and discussion of acceptance thresholds.
• Informative and normative annexes: Annex A (states qualifying a process) and Annex B (statistical tests) support practical implementation.

Practical applications and users

ISO 22514-8 is practical for manufacturing contexts where multiple simultaneous sub-processes produce systematic differences:

• Multi-cavity casting (each cavity = a state)
• Multi-fixture machining
• Batch load treatments (heat-treat furnaces with positional effects) Primary users:
• Quality and process engineers
• Metrology and measurement-system analysts
• Production managers and continuous improvement teams (Six Sigma, SPC)
• Auditors and conformity assessment specialists

The standard is especially useful to develop in-process sampling, predict batch variation ranges, and support machine-level capability decisions when no sorting systems are used.

Related standards

• ISO 22514 series (Parts 1, 2, 3, 4, 6, 7)
• ISO 22514-3 (machine performance for discrete parts)
• ISO 3534 (Statistics - vocabulary)
• ISO 5725 (Accuracy of measurement)
• ISO/IEC Guide 98-3 (GUM: uncertainty of measurement)
• ISO/IEC Guide 99 (VIM)

Keywords: ISO 22514-8, machine performance, multi-state production process, capability index, intrinsic dispersion, multi-modal distribution, process capability, sampling plan, measurement system.