Why Does Classification Matter?
In industrial engineering, an activity is not just a name; it has attributes. A task may be "Welding" (an activity), but it is vital to know whether it is:
- Value-Added (VA) – Transforms the product
- Non-Value-Added (NVA) – Eliminatable waste
- Delay – Interruption outside the worker's control
Generalist tools only offer "Project" and "Label". They do not allow qualifying categories or associating multiple attributes with an observation.
The MECE Principle
Categories must be MECE (Mutually Exclusive, Collectively Exhaustive):
Mutually Exclusive
Each observation belongs to only one category.
Collectively Exhaustive
Every possible activity is covered.
The 3 Main Categories
PRODUCTIVE (Value-Added)
Activities that transform the product or service, adding value that the customer would be willing to pay for.
Examples:
- • Assembling components
- • Welding parts
- • Machining material
- • Inspecting quality
Key question:
"Would the customer pay more for this?"
NON-PRODUCTIVE (Non-Value-Added)
Activities that add no value and are the worker's responsibility (not caused by the system).
Examples:
- • Chatting (non-work)
- • Using personal phone
- • Absent from station
- • Working slowly without cause
Action:
Supervision, training, motivation
DELAY (NVA-Necessary or System)
Interruptions outside the worker's control, caused by system failures (logistics, machinery, planning).
Examples:
- • Waiting for material
- • Machine breakdown
- • Waiting for instructions
- • Missing tools
Action:
Improve logistics, maintenance, planning
💡 Why separate Non-productive from Delay?
Delays are problems that management must resolve (improve the system). Non-productive time requires actions toward the worker. Distinguishing them allows taking the right actions with the right people.
Hierarchical Structure (Tree)
Instead of flat lists, a hierarchical taxonomy is recommended that allows root-cause analysis. Our software can handle up to 3 levels of depth:
📂 PRODUCTIVE
├── Assembling
├── Welding
├── Inspecting
├── Preparing material
└── Packing
📂 DELAY
├── 📁 Waiting for material
├── Due to supplier failure
└── Due to warehouse failure
├── 📁 Machine breakdown
├── Electrical failure
├── Mechanical failure
└── Calibration
├── Waiting for instructions
└── Authorised break
📂 NON-PRODUCTIVE
├── Chatting
├── Using phone
├── Absent without permission
└── Distraction
Taxonomy Design: Guiding Questions
Before starting the study, answer these questions:
1. What are the 3-5 main operations?
E.g.: Assemble, Weld, Inspect, Pack
2. What are the most common delays?
E.g.: Missing material, Machine stopped, Waiting for supervisor
3. What non-productive activities are observed?
E.g.: Conversations, Absences, Distractions
4. Do I need to distinguish sub-causes? (Level 3)
E.g.: "Machine stopped" → Electrical vs Mechanical vs Calibration
The "Other" Category
Always include an "Other" or "Unclassified" category for unexpected activities. Rules:
- If "Other" exceeds 5% → Review and create specific new categories
- When logging "Other" → Add a mandatory descriptive note
- After the study → Analyse notes and reclassify if possible
💡 Tip
Start with 8-15 well-defined tasks. You can add more during the study if you discover activities not contemplated. The app lets you manage tasks dynamically.
How Our App Implements It
In the study configuration section:
- You create tasks with a descriptive name
- You assign a category (Productive / Non-productive / Delay)
- Optionally, you link them to specific stations
- Reports automatically group by category
When registering an observation, you just tap the task and the system already knows which category it belongs to for the calculations.