In brief
Flexibility describes a corridor thought out in advance within a given structure. Changeability means the ability to alter the structure itself. Wiendahl, Reichardt and Nyhuis draw the distinction explicitly in order to make changeability assessable — through properties that can be built into buildings, technology and organisation.
The difference in one sentence
Flexibility uses a corridor that was thought out when the system was built. Changeability alters the structure itself. A machine with a broad part spectrum is flexible; that does not make it a changeable factory.
In the Handbuch Fabrikplanung, Wiendahl, Reichardt and Nyhuis state that changeability has to be delimited from related terms — convertibility, flexibility, reconfigurability, transformability and agility — and give the reason: to make it assessable. The distinction is not a definitional quarrel but the precondition for making any statement at all.
Side by side
| Feature | Flexibility | Changeability |
|---|---|---|
| Reference | Corridor within the structure | The structure itself |
| When it is fixed | Thought out during design | Built in as a property, activated later |
| Limit | Ends at the edge of the corridor | Moves the corridor |
| Typical question | Which variants run on the system? | What can be changed in three years — and how fast? |
| Cost effect | At procurement | In buildings, utilities and interfaces |
The problem changeability answers
Grundig names it precisely in his Fabrikplanung: planning results have a (quasi-)static character and can later be altered only to a limited degree, or at high financial cost — whereas the use of the factory has a dynamic character, marked by the constant mutual adjustment of factory and production task.
A static result therefore has to carry a dynamic operation. Flexibility softens that contradiction within a corridor. Changeability moves the corridor.
Changeability can be built in — and it costs
The handbook calls the required properties change enablers: an inherent property that can be activated within a given period and brings about a desired change. They are derived from three system properties — system dynamics, complexity and connectivity — and lead to mobility, scalability, modularity and connectivity, among others.
Each has a price: mobility costs foundations and utility connections, modularity costs interfaces, scalability costs floor space that initially stands empty. The aim is therefore not the maximally changeable factory but the one whose enablers match the expected change drivers.
Four questions for the direction
- Which change is likely — volume, variant, technology or site?
- Does the corridor thought out in advance cover it, or must the structure change?
- Which enabler solves exactly that case — and what does it cost today?
- How quickly must the change take effect once it occurs?
Basis
Wiendahl, H.-P.; Reichardt, J.; Nyhuis, P. (2014): Handbuch Fabrikplanung, 2nd edition, Hanser, section 5; the systematics of change enablers goes back to Hernández Morales (2003) there. Grundig, C.-G. (2018): Fabrikplanung, 6th edition, Hanser, section 1.