The requirements for speed and flexibility of automation solutions are increasing. As a specialist for automated manufacturing processes and as a second-generation family business, the Tünkers Group's solutions originate from its own production facilities and decades of experience. Tünkers is known worldwide among engineers and designers for solutions in the robot environment such as clamping, processing and transporting. The robust, low-maintenance components are designed for extreme operating conditions in high-volume production in the automotive and supplier industries.

Innovation, reliability and precision in automation technology are also of central importance for the subsidiary EXPERT-TÜNKERS. Also operating worldwide, the focus of the portfolio is on rotary tables and transport technology, whereby customer-specific solutions are increasingly being developed. One product that combines the tried and tested with the new is the seventh axis of the company from Lorsch in Hesse. This is an additional traversing axis. The seventh axis increases mobility and reach in robotics. The solution not only enables the robots to move quickly to the respective work area, but also to guide them precisely to parallel path-controlled work processes. This means that a robot can carry out several work steps at different locations, resulting in faster processes, more economical operation and the conservation of resources.

The seventh axle of EXPERT-TÜNKERS GmbH is driven by a rack and pinion system. Safety dampers from ACE protect the construction in the end positions © EXPERT-TÜNKERS GmbH

Requirement: Current-independent end position safety device
EXPERT-TÜNKERS relies on a torsion-resistant modular design for the fast, precise traversing axes, which enables high process accuracy even with a length of 30 meters. They are driven by a helical toothed rack with hardened flanks, a robust, adjustable guide system and a servo geared motor integrated into the robot's carriage. In addition to applications close to the floor, moving geo-tools are also conceivable and, thanks to the expertise in roller turning tables, the seventh axis can also be designed as a curve. Whether with or without a curve, a crash in the end positions must be avoided in any case. Otherwise, in addition to repairs to robots and the overall design, there is a risk of costly downtime. For this reason, during the development phase, the design team of the traversing axis was looking for protection that works independently of electricity. For the EXPERT-TÜNKERS team, only a company that met their own high quality standards could be considered as a supplier for the safety elements. At the same time, the solution had to be inexpensive. The design engineers found that ACE Stoßdämpfer GmbH from Langenfeld met these requirements: "We knew from past collaborations that, in addition to product quality, service is often the deciding factor with ACE. This was confirmed during the course of the project," says Nuno Martins, International Engineering Coordinator at EXPERT-TÜNKERS. The design revealed that different key data had to be taken into account at the two ends of the travel path. For example, with a maximum drive torque of around 400 Nm, 2,500 kg had to be decelerated once at 2 m/s and 4,000 kg once at 1 m/s. TUBUS safety dampers of type TC134-146-S were installed in both end positions at the start of the project.

The reversible TUBUS safety dampers in the TC-S design achieve the spring rates with high restoring force required for crane systems and secured the robot linear traversing axis from EXPERT-TÜNKERS, which is manufactured in a torsion-resistant modular design, in the first design phase © ACE Shock absorber GmbH

Solution 1: Reversible and irreversible solid-state dampers
All TC-S types from ACE combine high force absorption with an attractive price-performance ratio. They also have a compact shape with diameters from 64 mm to 176 mm and a variety that covers energy absorption in the range from 450 Nm to 17,810 Nm. This type is designed to absorb kinetic energy from 7,310 Nm to 10,230 Nm. EXPERT-TÜNKERS was very satisfied with the work of these safety dampers. The design team was even more satisfied with the high operational safety of the seventh axle during the course of the project. This led to the desire to make the end position safety device even more economical. From ACE's wide range of solutions, the initial decision was made in favor of a damper designed for use in crane systems. This is characterized by its unique dual concept, in which two reversible solid-state dampers are combined in one component. As a result, high spring rates and the aforementioned values can be achieved. After the design engineers shared their experience of operating the seventh axis with ACE in terms of securing the end positions, TUBUS Product Manager Thorsten Kohnen and his team in Langenfeld took another close look at the design data. They calculated the TUBUS TI30-75-3 safety dampers as another suitable solution for the application with the higher speed of 2 m/s. For case 2 with a travel speed of 1 m/s, they recommended type TI24-33-1. A comparison of the values of these components for the emergency stop with the aforementioned TC-S type shows that they have been tailored even more precisely to the respective requirements at 7,683 Nm/stroke and 2,701 Nm/stroke. The biggest difference, however, is that the TUBUS TI types are equipped with bellows and a metal guide sleeve. This means that, unlike the reversible TC-S safety dampers from ACE, which are made of co-polyester elastomer, they work without rebound. With an energy absorption of up to 96 percent, these TI components are irreversible and therefore intended for single use. A circumstance that was accepted based on the experience that the emergency almost never occurs.

In the final design phase, EXPERT-TÜNKERS opted for ACE crash absorbers made of either aluminum or steel. The irreversible components fold up like a crumple zone in the event of an accident and dissipate the energy of inertial forces in one fell swoop with virtually no rebound © ACE © GW St. Pölten

Solution 2: New one-way crash dampers for the emergency stop
Following the delivery of these components, the protagonists remained in contact. Nuno Martins from EXPERT-TÜNKERS reports: "ACE informed us early on that a new product series was about to be launched, which promised an even more interesting price-performance ratio for our case." We are talking about ACE crash dampers. Like the TI dampers, these machine elements from ACE are also irreversible. The machine elements made of special aluminum or steel tubing are folded into a designated shape in the event of a crash. As a result, they protect structures like a crumple zone with a uniform energy dissipation of 98 percent. Available in ten basic types with external diameters of 87.5 mm in the aluminum and 63 mm and 38 mm in the steel versions, the suitable components for the end positions of the seventh axle were quickly found. Depending on the type, their maximum stroke is between 45 mm and 160 mm. Low support forces of 13,000 N to 70,000 N make a decisive contribution to securing the structures.

Another decisive advantage for users of machine tools, conveyor systems or, as in this case, robotics is the range of possible energy absorption between 670 Nm/stroke and 11,200 Nm/stroke. Secondly, after an accident, the crash event can be reconstructed from the deformation of the one-way element and, in the best case, can be avoided in the future. As they can be replaced very quickly and easily, this application illustrates how the expansion of ACE Stoßdämpfer GmbH's range of products and services enables specific customer requirements to be realized to the point. "Thanks to the cooperation with ACE, we have created an end position safety solution for the seventh axle that is truly suitable in all respects," says EXPERT-TÜNKERS, drawing a positive conclusion.