The Bocholt-based company Benning is a supplier of chargers for electric vehicles such as forklift trucks. In the current generation of traction chargers in the Belatron series, the high-efficiency charging process is monitored electronically. The devices and in particular the charging cycles can be configured individually if the customer so wishes. The traction chargers are available for voltages from 24 to 120 V. Comprehensive connectivity enables integration into energy management systems, among other things. The test system at the end of the production line was designed and implemented using 'on-board resources'. The aim in developing the test system was that the operator only has to connect the charger and all other processes run automatically.

One robot for many testing tasks

To achieve this goal, a low-cost robot from Igus was mounted on the ceiling of the test cell, which plays a central role in the test. As it has many tasks to perform, the tool on the 'Robolink' robot arm is versatile: in addition to a camera for image recognition and a laser distance sensor for measuring the device, an electrically conductive test needle is integrated for housing contacting and for actuating the operating elements.

When searching for the right robot for the test cell, Benning's design engineers were able to use their existing expertise, as collaborative robots were already being used in production. Ultimately, the choice fell on an Igus 5-axis articulated arm robot of the type 'Robolink RL-DP-5'. The robot, which is largely made of tribologically optimized (for friction and wear) and lubricant-free plastics, can move payloads of up to 3 kg and achieves cycle times of less than 7 seconds. Its arm has a reach of 790 mm and the positioning accuracy is 1 mm.

The engineers involved broke new ground when planning and commissioning the test cell. The tool is fully integrated into the robotics software. Image processing is performed by a standard camera, for which a separate program was written on an open source basis and integrated into the inspection system. The LED light in the cell changes with each camera position. Documentation is also generated automatically. Overall, Benning was able to carry out the majority of the design and project planning itself; Igus was involved in the design of the tool in that different variants were developed, one of which Benning decided on after testing.

The author: Alexander Mühlens is Head of the Low-Cost Automation division at Igus in Cologne.

© Igus

After a good year of experience with the self-developed test cell and the robot, those responsible at Benning have come to an all-round positive conclusion: after contacting the test specimen, the operator can take over other tasks for the entire test cycle, which lasts several minutes. This optimizes costs - keyword ROI. The quality of the test is also improved, as the results are evaluated objectively. Another positive side effect: comprehensive statistics and evaluations are generated, which can be used as a basis for further process improvements. Thanks to the individual documentation of the complex testing process, a 'digital twin' of each individual traction charger is created almost automatically.