Non-constraint resources have by definition over-capacity. We should always remember that the utilization of a non-constraint resource is determined by the need to subordinate its activity to the decisions regarding the exploitation of a constraint. Between constraints and non-constraints there is an interaction. This means, that we can not always forecast when a non-constraint resource will be used.

What if you need a non constraint resource for only 5 hours per week, but you need those hours only Friday from 15:00 till 15:30. Is this not a huge constraint?

This new constraint, caused by the interaction between constraints and non-constraints, is one of the reasons for the existence of so called Interactive Constraint. Their impact might be much worse on the T(hroughput) then the real constraint.

The existence of interactive constraints is also depending on the use of the capacity. We can divide the operative capacity of a non-constraint into 3 parts:

• Productive capacity: needed for set ups and processing
• Protective capacity: to protect the proper functioning of the constraint
• Excess capacity: free capacity of the resource.

Especially the availability of the protective capacity is essential to avoid Interactive Constraints.

If you want any more knowledge on interactive constraints, read 'the Haystack Syndrome' of E. Goldratt and ask for additional education. Interactive constraints are solved by so called Red Lane Peaks and First Day Loads. A unique concept for a complex problem.