1. Introduction
In modern industrial automation, seamless communication between heterogeneous devices is essential. This case study explores the successful integration of a Mettler Toledo weighing scale (Modbus ASCII over RS232) with a Siemens HMI (Profibus-based PLC network) using the Anybus Communicator ABC3000-A.
The application is focused on an Armature Varnishing Machine, where varnish application depends on the precise weight of the armature core. Accurate and real-time communication between the weighing scale and HMI was critical to ensure process reliability and quality.
2. Application Background: Armature Varnishing Machine
- Process Requirement:
o The armature core of electric machines must be varnished by hot dipping.
o The amount of varnish applied depends directly on the measured weight of the armature core.
o Accurate weight data must be visible on the Siemens HMI for the operator to validate before varnishing.
- Challenge:
o The Mettler Toledo weighing scale communicates only via Modbus ASCII over RS232.
o The Siemens HMI and PLC environment runs on Profibus DP.
o Direct communication was not possible due to protocol mismatch.
3. Problem Statement
The weighing scale could not directly transfer the measured weight to the Siemens HMI. Without this integration:
- Operators had to manually read the weight from the scale display.
- Risk of human error increased during varnish application.
- The process lacked automation and efficiency.
A protocol bridging solution was required to integrate Modbus ASCII (RS232) data into the Profibus PLC network.
4. Solution: Anybus Communicator ABC3000-A
The Anybus Communicator ABC3000-A was introduced as the bridging device.
- Functionality:
o Acts as a protocol converter between Modbus ASCII (RS232) and Profibus DP.
o Configured to poll the weight data from the Mettler Toledo scale (Slave ID = 1).
o Transmits this data cyclically over Profibus DP to the Siemens PLC.
o The Siemens HMI, connected to the PLC, displays the weight in real time.
- Configuration Steps:
1. Transaction Mapping:
- Defined Modbus ASCII request/response frames for weight registers in the Anybus configuration.
2. Cyclic I/O Mapping:
- Weight value mapped to Profibus input data.
3. Siemens PLC Integration:
- GSD file of ABC3000-A imported into Siemens TIA Portal / STEP7.
- Profibus node assigned and I/O addresses mapped.
4. HMI Display:
- PLC tags linked to the HMI screen to visualize armature weight.
5. Results Achieved
- Seamless Integration: The Mettler Toledo scale was successfully integrated with Siemens HMI.
- Real-time Weight Display: Armature weights are now continuously visible on the HMI.
- Process Efficiency: Automated varnish application based on actual weight reduced manual intervention.
- Error Reduction: Elimination of manual reading improved accuracy and reliability.
Scalability: The solution can be extended to multiple weighing scales and machines.
6. Business Impact
- Increased Productivity: Faster varnishing cycle with automated decision-making.
- Improved Quality: Consistent varnish application ensured better motor performance and durability.
- Cost Savings: Reduction in varnish wastage and minimized rework.
- Future-Ready Communication: The plant floor can integrate more Modbus devices into Profibus/Ethernet-based networks using the same approach.
7. Conclusion
The integration of Anybus Communicator ABC3000-A with the Mettler Toledo weighing scale and Siemens HMI successfully solved the protocol incompatibility challenge in the armature varnishing process. This case demonstrates how protocol converters enable legacy devices to communicate seamlessly within modern industrial networks, ensuring efficiency, accuracy, and long-term scalability.