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:
- 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.