The usual process flow of a P2L assembly control system is as follows::
- Selection of an assembly sequence from the order management
- manual picking by the worker
- correct picking: PLC sends the next pick command according to the assembly recipe (continue with 2.)
- PLC sends pick command to the sensor of the first/next picking compartment
- Incorrect picking: consequence e.g. signal tone, acknowledgement, ejection of the assembly
- End of the assembly procedure (continue with 1.)
Automatic teaching function
The sensor range must be adapted to the corresponding container geometry and to the level of the material in the container. This process of automatic range adjustment is called teaching.
Teaching allows the sensor to detect only one removing hand and not the piled up material. The sensor has an automatic teaching function that permanently monitors the fill levels of the containers.
Immediately after the switch-on sequence, the sensor starts recording the fill levels (automatic teaching function). During teaching, a reference value is formed which builds the reference for detecting picks (= outliers). This is necessary, as the sensor would otherwise report incorrect picks all the time, for example, as soon as the material is filled:
The initial teaching takes place directly after the sensors are connected to the power supply. In addition, permanent teaching happens automatically so that the sensor range is continuously adjusted. A refilling process on a material container will be considered as a false move for a short time, but after approx. 10 seconds the sensor automatically adapts to the changed conditions.
Advantages of CAN bus model
With the P2L C002 sensor, the LEDs can be controlled variably via the CAN bus according to individual process requirements. For large assembly systems with many sensors, we recommended using the P2L with CAN bus, because the electrical wiring is much less complex: all P2L C002 are connected in series and only one supply line to the PLC is required.
Both the CAN bus and the digital version of our P2L sensors are also available as ESD variants.
General advantages of the Pick-to-Light system
With a pick-to-light system, production times can be minimized considerably. The order of the picking processes comes from the material flow computer, which manages the assembly lists or translates the picking orders from the ERP system. Particularly in the case of highly varied products, this allows workers to concentrate fully on the process without having to study order slips, parts lists or assembly drawings before starting. Both hands remain free and any assembly instructions that may be required are displayed on a monitor.
Furthermore, pick-to-light systems enable high process reliability. According to the Poka Yoke method, as many sources of error as possible are eliminated. Assemblies with many variants in small batch sizes are particularly prone to errors, and process reliability is of great importance, especially for safety-relevant components, and can be permanently monitored and documented with a pick-to-light system.
A Pick-to-Light system can thus make a difference in optimizig manual assemblies in terms of costs and quality and to maintain long-term competitiveness.
Example Exhibition Setup – Video
In this video, we show the functionality of the pick-to-light sensors on a small exhibition setup. A simple sequence is shown as well as grabbing into the wrong container and teaching.