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LEAN GLOSSARY

Lean, Six Sigma & VSM terms

Plain-English definitions of every term used in VeSiMy and across Lean, TPS, and Six Sigma practice. No jargon required.

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C
Cycle Time (CT)
The time it takes to complete one unit of work at a process step, from when work starts to when work ends at that step. Measured in seconds, minutes, or hours.
Changeover Time
The time required to switch a process from making one product or service to another. Reducing changeover time is the goal of SMED (Single-Minute Exchange of Die).
Continuous Improvement (CI)
An ongoing effort to improve products, services, or processes. In Lean, CI is often called Kaizen, small, incremental changes made frequently.
Current State Map
A VSM that documents how a process works today, including cycle times, wait times, WIP, and information flows. The starting point for improvement.
D
Defect Rate
The percentage of units that come out of a process step with errors, rework, or quality failures. A key driver of waste. Measured as 0–100%.
DMAIC
Define, Measure, Analyse, Improve, Control. A structured Six Sigma problem-solving framework used for improving existing processes.
Demand Rate
How many units of output a customer requires per time period (e.g. 40 orders per day). Used to calculate takt time.
F
Fishbone Diagram (Ishikawa)
A visual tool for identifying root causes. Causes are grouped into categories (6M: Man, Machine, Method, Material, Measurement, Mother Nature). Used before 5 Why.
5 Why Analysis
A root cause technique: ask "why" five times to drill through symptoms to the underlying systemic cause. Developed by Taiichi Ohno at Toyota.
Future State Map
A VSM showing how the process should work after improvement. Defines targets for cycle time, WIP, wait time, and PCE. The output of a kaizen event.
Flow
The smooth, uninterrupted movement of work through a process without stopping, queuing, or batching unnecessarily. One of Lean's five principles.
K
Kaizen
Japanese for "change for the better." A structured improvement event (1–5 days) where a team maps, analyses, and improves a process together.
Kanban
A visual signalling system that controls the flow of work between steps. Originally physical cards; now also used in digital project management.
L
Lead Time (LT)
Total time from when a customer request enters the system to when it is fulfilled, including all waiting time and process time. Always longer than total cycle time.
Lean
A management philosophy derived from the Toyota Production System (TPS) focused on creating value and eliminating the 8 wastes: overproduction, waiting, transport, over-processing, inventory, motion, defects, and unused talent.
Little's Law
A queuing theory principle: Average queue size = Arrival rate × Average wait time. Used in VeSiMy's simulation engine to model demand changes.
M
Muda
Japanese for "waste", any activity that consumes resources without creating value for the customer. The 8 types: overproduction, waiting, transport, over-processing, excess inventory, motion, defects, unused talent.
Mura
Unevenness or variability in a process. Causes stop-and-start flow, queue build-up, and worker stress. Smoothed by levelling (heijunka).
Muri
Overburden, pushing workers or equipment beyond their natural capacity. Causes defects, breakdowns, and burnout.
O
OEE (Overall Equipment Effectiveness)
A manufacturing metric: Availability × Performance × Quality. World-class OEE is 85%. Most plants run at 40–60%. VeSiMy calculates OEE when uptime, cycle time, and defect data are entered.
Operators
The number of people required to run a process step. Used in VeSiMy to calculate line balance efficiency and operator utilization.
P
PCE (Process Cycle Efficiency)
Value-added time ÷ Lead time × 100%. Shows what percentage of the total lead time is actually productive work. World-class PCE varies by industry: 25%+ is good for manufacturing, 50%+ for services.
PDCA
Plan, Do, Check, Act. A four-stage iterative improvement cycle originated by W. Edwards Deming. The foundation of all continuous improvement frameworks.
Pull System
Work is only produced when the downstream customer signals demand (via kanban). Prevents overproduction. The opposite of a push system.
Push System
Work is produced and pushed downstream regardless of whether the next step is ready. Creates inventory, queues, and WIP build-up.
S
SMED (Single-Minute Exchange of Die)
A method to reduce changeover time to under 10 minutes. Works by separating internal activities (machine must be stopped) from external ones (can be done while running).
Standard Work
The documented, current best method for performing a task safely and efficiently. Forms the baseline for further improvement.
Six Sigma
A data-driven methodology targeting near-zero defects (3.4 defects per million opportunities). Uses DMAIC for improvement and statistical tools including Cp/Cpk, control charts, and hypothesis testing.
T
Takt Time
Available production time ÷ Customer demand rate. The "heartbeat" of the process, how fast you need to produce one unit to meet demand. If any step's cycle time exceeds takt, you have a bottleneck.
TPS (Toyota Production System)
The original Lean system developed by Toyota. The foundation of all modern Lean and continuous improvement frameworks. Based on Jidoka (stop and fix problems) and Just-in-Time flow.
V
Value
Anything a customer is willing to pay for. In VSM, steps are classified as VA (Value-Added), NNVA (Necessary Non-Value-Added, required but wasteful), or NVA (Non-Value-Added, pure waste to eliminate).
VSM (Value Stream Mapping)
A Lean tool that visualises every step in a process, from supplier to customer, along with cycle times, wait times, WIP, information flows, and quality data. Used to identify improvement opportunities.
W
Wait Time (WT)
Time a unit spends waiting between process steps, not being worked on. Part of lead time but not cycle time. Reducing wait time directly improves PCE and lead time.
WIP (Work In Progress)
Units that have started being processed but have not yet been completed and delivered. High WIP indicates poor flow, bottlenecks, or batch processing.
Y
Yamazumi Chart
A bar chart showing cycle times for each operator or station relative to takt time. Used to identify imbalanced workloads and rebalance the line.

All definitions are based on published Lean, TPS, and Six Sigma literature. Primary sources: Toyota Production System (Ohno), Learning to See (Rother & Shook), The Machine That Changed the World (Womack, Jones, Roos). Suggest a missing term →