{"id":"wpc-tech100-article-086-en","slug":"process-capability-for-a-qualified-wpc-tolerance","locale":"en","url":"https://woodplasticcomposite.net/guides/process-capability-for-a-qualified-wpc-tolerance/","title":"Process capability for a qualified WPC tolerance","answer":"A capability index is meaningful only when its assumptions and data basis are appropriate. It should not be used as a decorative quality score without checking the process being summarised.","author":"NFC & WPC Knowledge Reference","faqIds":["wpc-tech100-faq-086-en"],"tagIds":[],"noindex":false,"related":["wpc-tech100-article-087-en"],"version":1,"modified":"2026-10-15","reviewer":"","sections":[{"id":"technical-context","text":"The relationship between process variation and specification limits depends on stability, measurement quality and the distribution of results. Combining unrelated production states can produce a misleading single index.","heading":"Technical context","references":[],"url":"https://woodplasticcomposite.net/guides/process-capability-for-a-qualified-wpc-tolerance/#technical-context"},{"id":"verification-plan","text":"Define the characteristic, sampling period and product revision. Establish that the measurement system is suitable and examine process behaviour before interpreting capability. State the calculation method and any assumptions rather than publishing an unexplained number.","heading":"What to measure and document","references":[],"url":"https://woodplasticcomposite.net/guides/process-capability-for-a-qualified-wpc-tolerance/#verification-plan"},{"id":"practical-decision","text":"Use capability evidence to improve production and inform realistic tolerances. It is not a replacement for agreed acceptance procedures or finished-product qualification. Buyers should ask what the reported figure covers and whether it represents the material they will receive.","heading":"Implications for development and specification","references":[],"url":"https://woodplasticcomposite.net/guides/process-capability-for-a-qualified-wpc-tolerance/#practical-decision"},{"id":"reading-scope","text":"General engineering-statistics guidance; not a WPC product standard. Use the linked work as related reading. The practical checks above are editorial recommendations, not reported test results or a substitute for product qualification.","heading":"Related reading and evidence limits","references":[1],"url":"https://woodplasticcomposite.net/guides/process-capability-for-a-qualified-wpc-tolerance/#reading-scope"}],"seoTitle":"Process capability for a qualified WPC tolerance | WPC Reference","topicIds":[],"published":"2026-10-15","tableText":"Review step | Evidence to retain\nMaterial and geometry | Exact specimen or product identity\nVerification | Method, conditions and individual observations\nDecision | Approved scope and documented limitations","takeaways":"The relationship between process variation and specification limits depends on stability, measurement quality and the distribution of results.\nDefine the characteristic, sampling period and product revision.\nUse capability evidence to improve production and inform realistic tolerances.","aiAssisted":true,"categoryId":"wpc-tech100-category-4","reviewedAt":"","change_note":"New focused technical draft; not a product certification or production recipe.","description":"A capability index is meaningful only when its assumptions and data basis are appropriate.","heroImageId":"","referenceIds":["wpc-tech100-ref-statistics"],"review_status":"AI-assisted English editorial draft. Human technical review has not been recorded.","table_caption":"Evidence checklist for process capability for a qualified wpc tolerance","seoDescription":"A capability index is meaningful only when its assumptions and data basis are appropriate.","translationGroup":"wpc-tech100-086-2026","references":[{"url":"https://www.itl.nist.gov/div898/handbook/","type":"web","title":"NIST engineering statistics handbook","noindex":false,"accessed":"2026-10-14","seoTitle":"NIST engineering statistics handbook","publisher":"NIST","description":"Related reading; scope and limitations are identified in each article.","seoDescription":"Related reading; scope and limitations are identified in each article."}],"faqs":[{"question":"What evidence is needed for process capability for a qualified WPC tolerance?","answer":"Define the characteristic, sampling period and product revision. Establish that the measurement system is suitable and examine process behaviour before interpreting capability. State the calculation method and any assumptions rather than publishing an unexplained number."}]}