The poka-yoke process
The poka-yoke process

Functions as poka-yoke

Possible vulnerabilities are already eliminated during the development of a production line. Nevertheless, unforeseeable difficulties often come up during operation. They must be identified, a detection method must be implemented and a procedure for monitoring them must be developed.

Maintaining high quality standards is a prerequisite for optimum production. This is guaranteed in the ongoing process using targeted error management with poka-yoke from Balluff.

Typical weak points can be identified early and countermeasures taken, increasing production security and enablingfast correction runs and prompt adjustments when requirements change.

This necessary transparency and flexibility is guaranteed by sensor technology from Balluff.

Steps one and two: Identifying and detecting

  • Identifying problem areas

    Ensure quality standards with poka-yoke checks

    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
    Visual inspection and adjustment of the inclination of car seats

    In this application the angle of automobile seats is set and optically checked.

  • Implementing error recognition

    Checking of process steps using sensors and vision systems for error prevention

    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. The variant that is to be used is determined by the respective task.
    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 such as BVS vision sensor from Balluff are excellent for error prevention. They are simple, efficient and flexible.

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

    Implementing error recognition

    Passive and active error prevention: a comparison