The transport system thus optimally implements different product variations within a PLC recipe change. The mechatronic concept of the system was validated in advance on the basis of the digital twin from Siemens.

Partnership and flexibility - this is how the Swiss company Paro AG has been successful since 1986. In order to combine a high cycle rate with maximum flexibility in the process, Paro today only uses linear technology in its machines and systems, from the transfer systems to the pick & place units through to the completely flexible assembly automation. The automatic assembly machines operate in a performance range of 5 to 60 parts (single-lane) per minute and are advancing into the performance range of cam-controlled systems thanks to optimum coordination of all components and a well thought-out, modular system concept.

Diverse types, short cycle times
"As a partner for automation and robotics, Paro implements completely individual special solutions in its assembly systems," explains Gregory Kyd, Technical Manager at Paro. "Flexibility or batch size 1 has always been a reality for us: we build machines and systems for specific applications.

We typically develop over 50 percent of the functionality according to customer requirements. This high degree of individuality is a real added value for Paro AG's customers, but always a challenge for the company itself. The time required for machine and system development is a particular focus for Kyd. In order to shorten the project duration in special machine construction, he and his team must above all minimize the uncertainties and risks that the development process can entail. To achieve this, the developers must quickly identify the critical path in design and engineering and verify the functionality of the concept. After extensive comparisons of various solutions, Paro recently started using the Multi-Carrier System (MCS) from Siemens for this task (see box).

Mr. Kyd says: "In general, the time that the workpiece carrier needs to move in and out of the station is an important factor for the performance of the entire system in our special machines and systems, so we were looking for a way to position the workpiece carriers flexibly directly in the conveyor system - and we found it with the Multi-Carrier System (MCS)."

Verification of the concept using the behavioral model
It was important for Mr. Gregory Kyd to clarify possible risks and problems at an early stage during the development of the system. Siemens therefore supported the project with a digital twin of the feeding system, which was created using the NX Mechatronic Concept Designer. This allowed the behavior of the system to be tested virtually using the model and the functionality of the sequence program and the library blocks for the Simatic controller to be verified: "For me, a real highlight of the digital twin was that the first hurdles of the PLC user program could already be discussed two months before the real commissioning. From then on, it was clear that we were using a technology with great potential," recalls Mr. Kyd.

The digital twin was also helpful in implementing the new concept beyond the concept verification. This made it possible to parallelize the development of the MCS and the "PARO-Motion" so that the machine could be implemented faster than usual. Last but not least, the virtual commissioning of the MCS also helped to optimally prepare the integration and commissioning of the MCS on site at Paro: In just two days, the MCS was installed on site and ready for the first test run - "that was then the second highlight of the project: seeing that the transport also works in the real machine," says Kyd.

Flexible product changes with the multi-carrier system now also based on SIMATIC S7-1500T
The multi-carrier system is a transport solution that enables quick product or type changes without long changeover times. The system makes it possible to position or move trolleys or carriers individually and flexibly within a line. The system consists of a basic profile, guide system and linear motor. The carrier itself has no motor or active electronics and therefore moves without vibration or wear. As a modular system, the MCS can be easily adapted to the respective requirements with scalable motion control systems such as Simotion and Sinamics as well as various motors, carriers and guides. At the end of this year, the MCS library for the Simatic S7-1500 T-CPU will be officially available as a motion control system. A correspondingly scalable modular system of software tools is also available.