Value Stream Mapping Metrics and Abbreviations: C/T, C/O, EPEI, L/T

Data boxes and textbooks are full of abbreviations. This glossary lists each metric with its abbreviation, definition, formula and unit, the way the app calculates it. Where German maps (Erlach) use other short forms, they are noted for reference.

Times per process

• Cycle time (C/T), seconds: the time between two finished parts at the process exit. German maps: ZZ.
• Work content (process time), seconds: the pure working time on the part. When several operators work in parallel, it is larger than the cycle time (2 operators × 30 s cycle time = 60 s work content).
• Processing time (P/T): on the timeline, the sum of the cycle times along the main path, i.e. the time the part is being worked on; the counterpart to lead time.
• Changeover time (C/O), minutes: from the last good part of the old product to the first good part of the new one. German maps: RZ.
• Effective cycle time: C/T ÷ uptime ÷ performance rate ÷ (1 − scrap rate) + changeover time ÷ batch size; comparable with takt time.

Performance and quality

• Uptime, %: the share of working time in which the process is not stopped by breakdowns. In the data box, changeovers count separately through changeover time and batch size (unlike availability in OEE).
• Performance rate, %: actual speed relative to rated speed.
• Scrap and rework rate, %: the share of parts that are not good the first time; quality = 1 − scrap rate.
• OEE (Overall Equipment Effectiveness), %: availability × performance rate × quality.
• Utilization, %: occupied time relative to available time.

Takt, inventory, lead time

• Takt time, seconds: available working time per day ÷ customer demand per day. The planned cycle time of a line is set slightly below it.
• Days of inventory, days: inventory ÷ daily demand.
• Production lead time (L/T): Σ days of inventory + Σ cycle times along the main path. German maps: DLZ.
• Value-added ratio (Process Cycle Efficiency, PCE), %: processing time ÷ lead time.
• Flow factor (Erlach): lead time ÷ processing time, the inverse of the value-added ratio.
• WIP (work in process): the sum of all inventories between the processes.

Batches, product mix, control

• Batch size, pcs: the quantity made in a row without a changeover.
• EPEI (Every Part Every Interval), days: the interval in which every product in the family is made once; Σ changeover times ÷ changeover capacity per day.
• Pitch: the release unit at the pacemaker process, takt time × pack-out quantity.
• Kanban: a card or signal that triggers production (production kanban) or withdrawal (withdrawal kanban).
• Supermarket: a controlled pull inventory with a set quantity per product.
• FIFO (First In, First Out): a lane with a limited number of pieces in a fixed sequence.
• Pacemaker process: the one process that receives the customer schedule.
• Heijunka: leveling mix and volume over the day.
• VSM: value stream mapping; VSD: value stream design, the design of the future state.
• %C&A (percent complete and accurate) and RTY (rolled throughput yield): quality metrics mainly used in office value stream maps.

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