The poka-yoke process

Typical vulnerabilities

Typical error sources include missing or incorrect parts, insufficient evaluation of colors, a defective assembly process or even manual data entries and machine configurations.

Further problem areas

Threads are a frequent production problem. Missing or incomplete threads can occur in screw, bolts and threaded holes.

It is also very difficult to find the right screw for a certain torque, as well as the tightening sequence. Electrical torque controls are a step in the right direction, but cannot prevent problems. The positioning of torque tools has proven successful.

Errors can also occur wherever markings or labels are made manually. Such errors can be avoided with a simple traceability system.

The solution

When it comes to error prevention: Every production step done by hand can lead to an error. This includes all assembly procedures and machine configurations. In these areas, an evaluation must be carried out to ensure that suitable quality standards, such as those of Total Quality Management (TQM), are met. In general, at least two poka-yoke checks should be made for each assembly procedure.

The features

• Ensuring suitable quality standards through poka-yoke checks
• Simple traceability system for preventing typical errors

Sensors and vision systems from Balluff check whether all process steps have been carried out correctly. On this basis, errors can be prevented.

Passive and active error prevention

There are two methods for preventing errors in production: Passive and active error prevention.

Passive error prevention ensures that a process cannot be carried out incorrectly using mechanical coding. This is extremely effective and efficient.

In active error prevention, sensors and vision systems check whether a process step was carried out properly. This is more flexible and can provide more data than a passive device. Moreover, methods for tracing are easy to integrate. For the implementation of active error prevention, a discrete or analog sensor, a color sensor or a vision-based system are used.

Implementing sensors

Sensors have standardized outputs that have either discrete (yes/no) or analog (measurement) designs. Every output can be processed as desired. For example, it is possible to control simple indicator lights, measuring instruments or even discharge functions for rejection or reworking.

Implementing vision systems

Vision-based systems are used wherever conventional sensors reach their limits. A distinction must be made between vision systems and vision sensors.

Vision sensors like the BVS vision sensor from Balluff are excellent for error prevention. They are simple, efficient and flexible.

Vision systems offer many advantages for complex procedures such as robot control, image analysis, image capture and image storage.