{"id":"epei","model_id":"EPEI","name":"Every Product Every Interval (EPEI)","summary":"EPEI (written EPEx in the text) is the frequency with which the different part numbers assigned to a machine or process are produced. If every part number assigned to a machine is produced once every three days, then EPEx is three days. A small EPEx lets each part number be made in small lots, which minimises inventories in the system.","study_notes":["EPEx is stated to be the frequency with which different part numbers are produced in a production process or system.","Example given: if a machine is changed over in a sequence so that every part number assigned to it is produced every three days, EPEx is three days.","In general it is good for EPEx to be as small as possible, so that small lots of each part number are produced and inventories in the system are minimised.","A machine's EPEx depends on its changeover times and on the number of part numbers assigned to it.","A machine with long changeovers (and large minimum batch sizes) running many part numbers will inevitably have a large EPEx unless changeover times or the number of part numbers can be reduced.","The document cross-references Heijunka; no entry for Heijunka is available in the reference list."],"safety_notes":[],"sources":[{"url":"https://www.lean.org/lexicon-terms/every-product-every-interval/","title":"Every Product Every Interval - Lean Enterprise Institute","accessed":"2026-10-25"}],"verification":{"status":"source_checked","checked_at":"2026-10-25","values":1,"method":"llm_source_check"},"updated_at":"2026-10-25","type":"operational","spec":{"kind":"metric","related":[]},"url":"https://machineschema.com/operational/epei","license":"https://creativecommons.org/licenses/by/4.0/"}