Customized connection of a pick-by-light system

Various types of customer-specific connection of pick-by-light

Pick-by-light, as a subordinate system, must control the compartment displays in accordance with the specifications of the warehouse management system. If the warehouse management system software is too slow or not flexible enough, the standard interface cannot be used. In this case, the complete picking orders must be transferred to the pick-by-light system. The requirements for the interface vary greatly here.

The indicator lights illuminate in a standard process as soon as the order is activated. There are various methods for starting a picking order. These must also be taken into account for customer-specific connections, because in this case the pick-by-light system is responsible for activating the picking order.

There are various options for customer-specific connections.

Connection via a database table

For simple systems that do not require any special functions, a shared database table is sufficient as a customer-specific interface. Both the warehouse management system and the pick-by-light system access the same tables and thus exchange data and status values. One or more tables can be used.

The higher-level system enters the order data into the table and sets the order status to "unprocessed." The lower-level pick-by-light system can read the open orders and start them accordingly.

Once the picks have been made and confirmed with the acknowledgment button, the pick-by-light software enters the corresponding pick quantities and status values into the table. The warehouse management system then takes over the values and immediately performs a stock correction and order posting. Here is an example with two separate tables:

• Order header:
  • order number
  • Type of packaging unit (cardboard box type, pallet, container, etc.)
  • Number of picking items
  • status
• Order item (multiple records per picking order)
  • order number
  • item number
  • Removal storage location (storage location)
  • Withdrawal quantity (target number of items)
  • Quantity removed (actual number of items for confirmation)
  • [Optional: serial number, batch, weight, etc.]
  • status

Advantages of the connection method: A simple type of customer-specific connection where the data structures are mapped directly in the database table.

Disadvantages: No optimal communication in special cases, such as correction of the withdrawal quantity and alternative storage locations. No possibility for batch changes or feedback of zero-crossing messages (container has become empty). The providers of warehouse management systems often refuse to provide the tables.

Customized online software connection via TCP/IP socket or REST interface.

To achieve greater flexibility and high performance for customer-specific online connections, special connections are implemented via TCP/IP socket or REST interface.

In both variants, these are telegrams that are integrated into the software of both systems. In addition to the user data, the TCP/IP socket interface also integrates the simple and secure transmission protocol. The data content can be connections in both methods.

Advantages of direct online connection: Very fast and direct communication with any content for special applications with complex processes.

Disadvantages: Relatively complex implementation and commissioning.

SAP interface with special formats

For several years now, the RFC (Remote Functions Call) method has been the standard for customer-specific connections between the pick-by-light system and SAP. Once the data structures have been coordinated, the functions are registered and the calls are started.

Data exchange takes place via internal SAP connection mechanisms (libraries). In our experience, the best results are achieved with two asynchronous connections. One for transferring the picking list and the second for feedback on the withdrawals.

Advantages of the customized RFC connection: The software automatically establishes connections and works directly online without requiring a great deal of implementation effort. Data content is transferred quickly and securely.

Disadvantages: Relatively complex configuration and commissioning, including simulation of orders. Test systems are often used, which makes commissioning very complex.

Conclusion

Customized connections for a pick-by-light system are used when the standard interface cannot be operated directly by the warehouse management system. In some cases, the response speed and complexity of the process flows are also decisive factors. The picker must not have to wait during picking. Thanks to the very fast LUCA communication server, our software guarantees very short response times.