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2.4 Line Restraint Time

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2.4.1 Definition
Line Restraint Time: The machine is fully functional but cannot run due to receiving no input from the former process or being not able to get rid of its output due to a problem somewhere downstream.
Would there be ‘flow’ at input and output side, no Line Restraint would occur.
This category shows unbalanced capacities and problems in the line, even though the machine it selves could be perfectly OK.
2.4.2 Line Restraint Categories
No Time Usage Max. recommended Time Type
50 No Input (in Line process) 5 P F w L -
  • Empty input buffer
  • No input due to pre-heater
  • No input due to depalletizer
The machine stands still due to no input from a preceding process that has a technical link, e.g. a conveyer.
In lines it can be useful to get an overview in the Pareto to show what process decreases the effectiveness from this machine the most. In that case the time usage is split in two or more items like;
[no input due to process x].
51 No Output (in Line process) 5 P F w L -
  • Output buffer full
  • Stop at palletizer
  • Stop at tray packer
  • Conveyer blocked
The machine stands still due to the fact it cannot get rid of its output; mostly due to a stop in a succeeding process that has a technical link, e.g. a conveyer. Also see block [No Input].
2.4.3 Extended use
The Line Restraint categories are used to reveal unbalanced capacities and/or timing in line processes.
  1. A line can be thought of literally: several machines tied together with conveyors, pipes etc.
  2. However, applying Lean-Principles, those categories can be very well used to detect unbalanced situations between machines not technically tied together, e.g. in a cell or between several departments.
  3. It can also being used to detect flaws in the supply-chain.
The [L] category therefore can be seen as a strict [L]ine Restraint but also as
a [L]ean or [L]ogistic restraint.
2.4.4 OEE Solitaire
To detect how well the machine would have performed would it not be restraint by the rest of the line, it is possible to calculate the “OEE Solitaire” (See 1. Scope). In OEE Solitaire, all Line Restraint time is excluded from the total time.
2.4.5 Warning
Remember: Every product on a machine has a certain theoretical maximum speed, regardless the fact this might be too high for the line it is in.
  1. The machine has a structural over-capacity while it is not a bottleneck. Do not try to ‘mathematically’ balance the line by reducing the Standard (the maximum speed for a product on a machine). By doing so you will hide a potential loss (the unused over-capacity of the machine).
  2. Do not try to run a line restrained machine as fast as possible! Although the performance rate would go up, the availability will go down due to line restraints and worse: it will de-stabilize the flow in the line! Slowing down this machine will NOT reduce the OEE, however it will run smoother and as result the OEE might even raise!
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