Safe human-material differentiation on the assembly line: Progress through technology with Audi

How SICK sensors bring safety to human-material differentiation for car bodies

The goal? Implement an access protection solution on a newly developed inline measurement cell at Audi. The catch? Make sure it can handle complex vehicle geometries without muting sensors. So, how did SICK sensors help in the human-material differentiation practices for Audi?

In the giant manufacturing hall at Audi AG’s headquarters in Ingolstadt, representatives from Audi AG and SICK Vertriebs-GmbH worked to form an interdisciplinary team that includes members from the manufacturing planning, plant engineering, and maintenance departments on the Audi side, as well as the sales department and the technology division at SICK. This collaboration has been happening for several years now to guarantee the safety of the employees in the world's largest Audi factory while simultaneously ensuring the material flow processes run smoothly.

Creating a safe inline measurement cell for superior quality

Every vehicle manufactured in Ingolstadt passes through the final assembly hall for its final quality check, which includes checking for optimal gap dimensions. Previously, employees manually performed the final quality checks over and over again without electronic aids, posing quite a challenge for the human eye, not to mention limiting speed and efficiency. After a transition phase to handheld measuring devices, the task was then passed from employees to robots which means they now needed a human-materail differentiation procedure for these robots. The robots are equipped with sensors that measure the gaps and flushness on the vehicle.

“We constructed the inline measurement cell to sustainably support not only the quality process with its measurement values, but also the manufacturing process as a whole,” said Daniel Bartolic, Specialist Planner in Audi's Assembly Manufacturing Planning department and project manager.

The vehicles travel on the final assembly line into the inline measurement cell and are inspected for gaps and flushness, all done in a matter of seconds by two robots operating concurrently. Access protection is provided by means of the Safe Portal system from SICK, which utilizes the simultaneous protective field evaluation function of the microScan3 safety laser scanner. Two vertically aligned laser scanners are positioned at both the entry and exit of the inline measurement cell. They reliably and seamlessly protect the hazardous area through the intelligent evaluation of eight simultaneous protective fields.

The scanners use an infrared laser beam that is fanned out by means of a rotating mirror, thereby creating a virtual protective field at the left and right of the exit and entry point of the cell. A new TÜV-certified function block for the Siemens controller allows the simultaneous evaluation of both scanners. When a vehicle passes the suitably defined protective fields, the left and right scanners, which are operating in unison, recognize that it is a manufacturing material and not a person. The robots can perform their inspection task, as they now know a hazardous situation is not present.

This guarantees personal safety when using large industrial robots, but how did Audi get here?

From rigid mechanical systems to intelligent logic

Since several vehicle models with different geometries can be present on the same final assembly line, the requirements for a safe and productive solution for human-material differentiation are especially stringent.

“We were looking for a safety solution that would suit all our existing vehicle models and configurations, but would also allow us to implement new models as well,” Bartolic said.

The new solution needed to be flexible, productive, cost effective, space-saving, and not require safety gates or expensive muting sensors.

“We considered and investigated all safety-related perspectives and evaluated all relevant critical points with tests, trials, and naturally the requisite comprehensive documentation,” said Raphael Rotter, Strategic Product Manager at SICK.

An extensive one-off effort was implemented, an investment that paid off in the end.

“We now have a lean solution that provides exactly the level of flexibility to cope with future developments in the final assembly area,” Bartolic said about the outcome for Audi.

The Safe Portal safety system is TÜV-certified, comprises two safety laser scanners and a function block for the Siemens S7 controller, and fulfills the requirements of EN ISO 13849. This standard solution in the SICK portfolio offers a flexible and efficient means of access protection in automotive production. As a bespoke development, it demonstrates how important the systems approach is, which means combining hardware, software, and services from a single source.

More space, less complexity

Tobias Hacker, Technical Clerk in the Assembly Line Maintenance department at AUDI AG, said the space savings and reduced complexity on the final assembly line is the decisive advantage.

“The new compact solution dispenses with the previously used muting sensor – that saves up to a half a meter of space,” Hacker said. “We reduced the previously large number of variants of various hardware components—like photoelectric sensors and their cabling—to just two scanners. This saves time and money on maintenance and repairs, and we also benefit from the enormous reduction in complexity.”

Courage & collaboration = blazing new trails in technology

This success story was made possible by the intensive and trusting collaboration within the team and, in particular, the courage and preparedness of all those involved to blaze new trails. The black glossy surfaces of the car bodies really had the team stumped at the beginning, because highly reflective surfaces are difficult for opto-electronic sensors to detect. The safety experts countered this problem with continuous improvements in the logic.

For example, the restart procedure after a detected infringement in the protective field was made consistent with the standard procedure for the factory so that black glossy car bodies can now also be reliably identified by the Safe Portal system. A year and a half after the project commenced, the Safe Portal system has just been commissioned on the second assembly line and is performing its task safely and unobtrusively. Several crucial factors contributed to this success, according to Martin Demharter, Key Account Manager Automotive Industry at SICK Vertriebs-GmbH.

“Firstly the collaboration as equals, the long-standing cooperation between the companies, and most importantly, the common desire to find the truly best technical solution led to the good outcome,” Demharter said.

The word is already out at Audi about the positive experience with Safe Portal in the final assembly area; the people working in the car body construction area, the paint shop, and the press shop are also interested in technically mature, productive solutions for safe human-material differentiation. This is entirely consistent with the company’s primary motto: “Vorsprung durch Technik,” or, “progress through technology.”