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Joint research project with Fraunhofer IPA

 2 June 2021
Automated DIN Rail Mounting with Robots

Robots with intelligent programming instead of a costly system for automated DIN-rail mounting: The “pitasc” software tool from Fraunhofer IPA makes this possible, allowing robot programming with force regulation by means of individual program modules. A joint research project between the institute and WAGO shows how an application for DIN-rail assembly is possible.


A lightweight robot picks up a plastic part with its two-finger gripper, guides it to the component to which it is to be attached and can snap it firmly into place using a tilting motion with force regulation. If the mounting application ever needs to be reconfigured, there is no need to reprogram the movements. Programming is workpiece-specific, and the force regulation allows intelligent compensation for component and position tolerances. The application just described has been implemented by researchers at the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA). The institute has been working on solutions for fully or partially automated assembly for many years. After all, this production step is notoriously still largely carried out by hand: In 2020, only about one in ten of all robots sold worldwide worked in assembly. Challenges such as small batch sizes, a high number of variants and numerous individual processes often make it difficult to implement cost-effective assembly automation.

The Benefits for You:

  • Innovative: Automated DIN-rail mounting with robots in practice

  • Unrivaled: TOPJOB® S Rail-Mount Terminal Blocks used for automated control cabinet component placement

  • Easy: Completely eliminates manual work steps, saving time

  • Versatile: Thanks to the wide range of rail-mount terminal block variants, robots can perform assembly in a structured way

Standard robots can place components on DIN-rails – even terminal blocks with complex designs.

Michael Dörbaum, Team Leader for Product Management of Control Cabinet Components at WAGO

Is Full Automation the Solution?

Many control cabinet manufacturers face similar challenges. As a solution partner in control cabinet manufacturing, WAGO has experts familiar with these problems from many discussions within customers. One example is the assembly of control cabinets with rails, components and wires, as this process is characterized by many manual work steps. These processes are often time-consuming, expensive and error-prone. In a standard control cabinet, 500 connections are required for the control technology alone, and this includes cables of various colors, cross-sections, and assemblies.

To optimize existing processes, full automation is not always the right solution for every requirement. There are various points to consider here.
Although automation offers clear processes and a workload reduction for skilled assemblers, it associated with higher costs and only pays off for large quantities. In addition, specialized assembly machines do not always fit the specific requirements. However, as WAGO knows from experience, it is often sufficient to simplify or digitize processes in order to shift some of the workload away from skilled assemblers.

If automation is still necessary, using standard, commercially available robotic arms can be a solution. The advantages of standard robotic arms are obvious: They are comparatively inexpensive and allow flexible use and expansion One question that obviously needs to be addressed: Can standard robots even handle component placement on DIN-rails? “My answer to that: Yes, they can, and even for terminal blocks with complex designs,” says Michael Dörbaum, Team Leader for Product Management of Control Cabinet Components at WAGO.

In order to determine the extent to which such standard robot hardware and sophisticated software allow automated mounting of rail-mount terminal blocks, WAGO and Fraunhofer IPA set up a test scenario for DIN-rail mounting in a joint project. The aim was for a robot to attach various WAGO TOPJOB® S Rail-Mount Terminal Blocks to DIN-rails via snap-on mounting. TOPJOB® S Rail-Mount Terminal Blocks of various sizes were used (with nominal cross-sections ranging from 1 mm² to 16 mm²), some of which, such as multi-level terminal blocks or building installation terminal blocks, involved complex designs. They also tested terminal blocks with a conductive DIN-rail contact; for these, the PE foot makes snap-on mounting somewhat more difficult. Another criterion in the test was the wiring density of the mounted terminal blocks, since automated assembly needs to achieve the same density as manual assembly in order to allow subsequent marking, for example with WAGO continuous marking strips.

In a joint research project, WAGO and Fraunhofer IPA tested standard robot hardware to explore how suitable it is for snap-on mounting of rail-mount terminal blocks.

Source: Fraunhofer IPA/Photo: Rainer Bez.

Structured Programming of Assembly Tasks/Software as a Modular System

The Fraunhofer IPA offers its “pitasc” software module for assembly tasks of this type, which present challenges due both to the variety of terminal blocks and to the demanding plugging process. It allows structured programming of assembly applications. “It used to be necessary to set up a robot system largely from scratch for each application. With our software, once tasks have been modeled, they can be quickly transferred to new product variants – in this case the terminal blocks – to new products and even to robots from other manufacturers,” says Lorenz Halt, a researcher at Fraunhofer IPA and one of the developers of pitasc. The software a modular structure: It contains many ready-to-use, reusable program modules that allow tailored combination, parameterization and use for setting up a robot system.

Pitasc also uses sensors for active process control regulation. For the WAGO test, a UR10e robot was used, with force sensors already integrated. “This allows the robot system to compensate for component and position tolerances and avoid exerting excessive forces,” explains Halt. “That protects sensitive components.” Since the process is programmed from the point of view of the workpieces, once the program is created, it can be easily adaptable to variants – only certain parameters such as process forces and gripping positions need to be modified. Last but not least, the software is independent of the specific robot manufacturer.

With our software, once tasks have been modeled, they can be quickly transferred to new product variants – in this case the terminal blocks – to new products and even to robots from other manufacturers.

Lorenz Halt, Researcher at Fraunhofer IPA and One of the Developers of Pitasc

Successful Assembly with Robots

The tests conducted with the WAGO rail-mount terminal blocks were successful. The robot used was able to successfully plug in all the terminal blocks with pitasc. The project partners were able to easily adapt the software to the different terminal block variants, including more complex designs such as double-deck or ground terminal blocks, via the program parameters. No time-consuming reprogramming was required. Furthermore, even with ground terminal blocks, it was possible to also achieve high wiring density by having the robot press, with force regulation, against the unit that had already been mounted.

These test results show that assembly automation for DIN-rails with robots and “off-the-shelf” terminal blocks is also a technical post, as long as the software used can meet the challenges of the application. “Our experience with customers makes clear that many specific requirements have to be taken into account when automating control cabinet manufacturing. The results show that a simple solution is possible if standard hardware can be used,” Dörbaum explains.
The advantage of such a solution is that the investment costs for the application remain manageable, and the solution offers flexibility at the same time. The software can also help manage the large number of variants. Nevertheless, industrial use of such an application still requires further work, since experience has shown that the requirements differ considerably among control cabinet manufacturers with regard to the number of different components, the throughput times and the integration of different process steps.
These remarks show: There is no one way to automate control cabinet manufacturing. Building on the approach shown here with “standard robots and terminal blocks,” there are still many more questions to answer. For example, is it possible to place components directly within small distribution boards and then wire them? What’s the best way to supply the terminal blocks? “Based on the success of these tests, robot-based mounting on DIN-rails with the IPA software is a good starting point for further collaboration in this industrial research field and for further developments in the direction of productive use,” says Dörbaum.

Author Information:

Frank Nägele is the head of the Robot Programming and Control Group at the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA); frank.naegele@ipa.fraunhofer.de, +49 711 9701063

WAGO Contacts:
Burkhard Niemann is Product Manager for Control Cabinet Components, and Lena Wilkening is Communication Manager

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