Pilz PNOZmulti 2 and PSENslock ensure safety of test rig

SAR Grpler GmbH specialises in the development and construction of high-performance simulation and test rigs for shock absorbers used in the automotive industry.

Single- or dual-tube shock absorbers essentially consist of the absorber tube, piston, piston rod, gaskets, valves and rubber-mounted fixing points. Before they are manufactured in series and installed in vehicles in their thousands, the automotive manufacturer needs to be absolutely sure that the shock absorber will satisfy real-life demands over many years.

New models are therefore tested comprehensively on special simulation and test rigs. Almost all conceivable applications and loads that are likely to arise in rugged, everyday use are simulated with regard to the respective vehicle model, its weight and special features. Various road surface conditions are included, as are temperature fluctuations and operation in different climate zones.

Summarising the task, Gnter Grpler, the company's founder, says: "It is our job to develop and construct a rig in such a way that the performance requirements specified by the vehicle manufacturer can be simulated efficiently and reliably."

A recently completed test rig that is now installed at a well-known German car manufacturer measures around 2x2m at ground level and is approximately 3m tall. The shock absorber to be tested is initially clamped vertically to the upper and lower lugs between retaining pins.

Once the safety gates are closed, a multi-stage test and simulation programme begins, in accordance with on the customer's requirements. Two motor-driven spindles compress the shock absorber; the massive eccentric on the lower part of the rig is then set in motion. Controlled by proprietary software, the rig now simulates on-road use with a variety of speeds, hubs, gas pressures, vibration forces and frequencies. This is where it gets hard and fast: forces of up to 40kN are exerted; sensors regularly measure the absorber's reaction, the gas pressure and other relevant parameters.

The shock absorber under test must meet the stipulated performance features even under extreme conditions; obviously it must neither squeak nor creak. The software displays progress clearly on the central operator panel; at the end of the test series, all measured data - such as speed, load, friction and absorption - are also displayed. Jan Grpler explains: "Based on these results, the manufacturer makes corrections and fine adjustments to the valves, for example, or changes the oil pressure."

Manipulation-proof safety gate system

Automation and safety technology from Pilz is used to ensure that set-up, operation and maintenance of the test rig is simple, efficient and, above all, safe. Timo Lurf, head of the technical office at Pilz in Reutlingen, says: "The risk assessment in accordance with EN ISO 12100 showed that risks emanate in particular from the eccentric and that a risk of crushing and injury in the event of a power failure cannot be ruled out, so that safety functions up to PL e of EN ISO 13849-1 are required."

The focus was therefore on finding reliable, safety-related systems for the two safety gates in the upper area and for the safety gate in the eccentric area. That is why the Pilz PSENslock safety gate system is used on all three gates. The non-contact, low-wearing and fully coded system with an electromagnetic holding force of up to 1000N offers manipulation protection thanks to RFID transponder technology. Whether connected separately or in series, PSENslock devices are suitable for safety gate monitoring up to PL e.

Thanks to flexible connection options (M12 connectors with five or eight pins), wiring is simple and quick. The safety gate system combines safety, automation and diagnostic functions in one device; thanks to IP67 protection it is also suitable for rugged environments.

The versatile Pilz PNOZmulti 2 configurable control system fulfils its role as the central safety component in the SAR Grpler test rigs; it monitors all the sensors and the installed emergency stop pushbuttons, as well as controlling the stroke movements. The housing width of the base unit is only 45mm; on the left-hand side it is possible to connect communication modules with serial or Ethernet interfaces, or fieldbus protocols such as Profibus-DP, CANopen, EtherCAT or Powerlink. This leaves 20 safe inputs available, up to eight of which can be configured as non-safety-related outputs, plus four safe semiconductor outputs (each with PL e). With the new illuminated display users can save time and costs during configuration and diagnostics and reduce the engineering work significantly.

With the PNOZmulti Configurator utility, configuration is simple and intuitive via drag-and-drop actions. Furthermore, in conjunction with PNOZmulti 2 as a contact expansion module, PNOZsigma safety relays provide multiple shutdown paths. Finally, Pilz PITestop emergency stop pushbuttons are fitted to all relevant parts of the rig, the control cabinet and the operator terminal. As a result, the rig can be brought to a safe standstill within fractions of a second.

One-stop automation technology and safety

SAR Grpler's customers benefit from the security of knowing that the shock absorbers tested on its rigs meet the required quality features. Jan Grpler, the Junior Manager, says: "Thanks to our test rigs, customers can be certain that the type of shock absorber subsequently installed in the vehicle satisfies everyday demands."

With wide-ranging industry expertise, competence in the field of risk analysis and CE certification, as well as an extensive portfolio of sensor and control technologies, Pilz is a complete safe automation supplier able to offer customers like SAR Grpler one-stop, economical and tailor-made systems for automation and safety tasks.

Follow the link to learn more about PNOZmulti 2 configurable control systems and PSENslock interlocks from Pilz.