Mistake-Proofing Resource Center

Forced Control Devices

Forced control effects are preferred over other forms of mistake-proofing effects.

  • Wherever possible, use mistake-proofing techniques that lead to a forced control effect.
  • With forced control, the action or trigger that leads to the effect is both automatically triggered and compulsory.

There are four families of devices or methods used to achieve a forced control effect:

  • Elimination
  • Combination
  • Use of Guides
  • Process Control Systems

These devices do not have to be “high-tech” to work. In fact, many “low-tech” solutions are more elegant and robust than their “high-tech” counterparts.

To use Elimination techniques:

  • Eliminate decisions
  • Eliminate steps

To use Combination techniques:

  • Combine components
  • Combine steps

To create forced control effects via the Use of Guides:

  • Take advantage of different shapes in the part.
  • First, study the size, weight, and shape of the part. Then, use one of those characteristics to develop the guide.
  • Keep the shapes simple.
  • Check that the guide can only be used one way.
  • Leverage asymmetry.
  • Use built-in, asymmetrical features.
  • Add a new feature or shift/modify existing features to create asymmetry.
  • Trade off aesthetics for functionality if needed.

Words of caution

  • Make sure the guides are robust.
  • They need to be strong, rigid, and wear resistant.
  • Guides should be added to the PM (preventive maintenance) schedule.

If using Process Control Systems

  • Keep the control system simple.
  • The control system does not always need to be electronic.
  • Mechanical process control systems can be highly effective.
  • Make sure that if the control system fails, that it fails in a “Fail-Safe” mode.
  • Allow for expandability to accommodate future process changes.
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