ACE Stoßdämpfer GmbH and Burat & Klein Datentechnik GmbH have been cooperating for many years in the field of measurement technology in order to be able to precisely test industrial damping technology in the area of dynamic parameters for customer-specific projects.

Here they give an insight into their successful cooperation.

Different types of dampers are used in many automated manufacturing processes. Small and industrial shock absorbers as well as safety shock absorbers are particularly suitable as efficient, currentless hydraulic components for deceleration or for the precise braking of mass forces in order to increase productivity and safety. ACE provides a wide range of these machine elements in the form of self-adjusting and adjustable types for a wide variety of applications, enabling designers to cover the most common force ranges with the company's standard components. ACE also offers components made of reversible and irreversible solid-state materials for emergency stops as overrun protection or as stop dampers.

First simulate damping behavior, then validate on drop testers

Sensors and simulations play a role when engineers want to test the products before market launch or, in the case of sensitive applications, want to determine the actual damping behavior of the respective damper types for their specific application in advance. This applies in special cases in automation, handling or the deceleration of extraordinarily high mass forces on machine tools or rotary tables. If the damping curves specified by the manufacturer are not sufficient for the application and for the customer's project team, ACE's consulting engineers use in-house testing facilities to check the theoretical simulations from the designs with standard components in practice and validate them.

Two drop testers are used in Langenfeld, the German headquarters of the expert brand ACE, which is part of the Stabilus Group. The first covers mass forces from 130 kg to 500 kg with a maximum drop height of 1500 mm. The drop tests carried out according to the laws of gravity result in maximum impact velocities of 4.8 m/s (v = √2*g*h) and kinetic energies of approx. 6000 Nm (m*g*h). The second drop tester is suitable for masses from 3 kg to 350 kg with a maximum drop height of up to 1500 mm, whereby impact velocities of up to approx. 5.5 m/s and energies of up to approx. 5150 Nm are measured. In addition to the aforementioned hydraulic dampers from the company's damping technology division, ACE also uses both drop testers to test the company's safety products, which include reversible fixed bodies in addition to the safety shock absorbers, which also operate hydraulically.in addition to the hydraulic safety shock absorbers, these also include reversible solid-state shock absorbers such as those from the TUBUS product families and irreversible solid-state shock absorbers made of aluminum and steel.

Focus on maximum possible energy absorption

The latter generation of safety dampers from ACE is referred to as crash dampers. Designed as emergency stop components for single use, the engineers in Langenfeld carry out extensive series of tests on the respective types on drop testers before their market launch. They examine the dampers, which are made of special aluminum or steel tubing, primarily with regard to the maximum possible energy absorption in the event of an accident. They pay particular attention to recording the specific damping characteristics of the individual types of each new series using drop testers. This enables them to check and validate the catalog values and approve the respective product series for sale. For example, the engineers there examined the maximum energy absorption of four new, smaller crash dampers. These have external diameters of approx. 20 mm and are launched on the market with different strokes. Since the successful completion of the validations, ACE has expanded the range of energy absorbers in the lower range from 100 to approx. 400 Nm and can also offer the crash dampers for systems in smaller formats as an inexpensive and effective emergency stop solution. Because the task of these solid-state dampers in an industrial environment is similar to that of crumple zones in vehicle technology, they have been tested for the toughest loads. After all, in the event of a crash, the components absorb the impacting energy immediately and are deformed and folded in a manner defined in advance in computer simulations in order to convert the impacting kinetic energy into heat and dissipate it to the outside environment. In this way, the single-use dampers protect structures in the event of an accident through high, uniform energy dissipation of 98 percent. Due to the requirement for these safety elements to offer high long-term stability in everyday operation and maximum protection in the event of an emergency stop, the tests and simulations were carried out under conditions that were as close to reality as possible.

Small shock absorbers examined in horizontal linear tests

In addition to these gravity-based test options, which examine dampers and their deceleration performance at the end of the travel of vertical linear axes, for example, another test bench from ACE also enables horizontal linear tests. Here, the drive accelerates mass forces of 20 kg to 100 kg on a horizontal axis to speeds of up to approx. 3.5 m/s.

In a practical example in which high-precision, friction-free axles are installed in a handling system that is secured in the end positions in three axles (X, Y, center pole) by small shock absorbers, the engineers at ACE first select the appropriate damper types for the respective axle from the standard range. Because the highly sensitive axles may only be loaded with defined maximum forces in the event of a crash, ACE carries out specific theoretical designs for each of the selected small shock absorbers using simulation software in the second step. Each individual hole pattern, i.e. the number and size of the throttle holes inside the damper, is simulated on the computer in order to optimize the force progression, i.e. the force-displacement curve. The engineers can then validate the theoretical simulations by taking measurements on the linear axis using appropriately prepared test specimens in the linear tests on the test bench. In such a test application, the moving mass can be adjusted down to a few grams and the impact speed can be matched almost one-to-one with a tolerance of 0.02 m/s for each specific case. If the test specimens pass the tests, the measurement results are used for the production of the required small series.

Measurement technology validates simulation and test results

Whether ACE components are tested in vertical or horizontal linear axes, the damping travel is determined using a laser displacement measuring system and the actual support force using force sensors on all test benches. The company cooperates with Burat & Klein Datentechnik GmbH, based in Meckenbeuren in the Lake Constance district. While the sensors and displacement transducers are connected to a measuring system called MultiMessBOX, which is precisely adapted to the respective test point, the data determined in each test run can be evaluated using the MessMax® software programmed by Burat & Klein. As described in the small shock absorber case, MessMax® makes it possible to superimpose the curve measured in the real test with the theoretical curve determined on the computer and thus validate the theory in practice. Jörg Küchmann, engineer from ACE's research and development department, comments: "In the application cited, Burat & Klein was able to offer us special evaluation software with which we can compare three parameters and automatically export the results to Excel as required. In this case, the maximum support force, the maximum damping distance and also the energy, i.e. the area under the force-displacement curve, are evaluated and checked."

Over the past few years, ACE has gained extensive experience in this area of measurement technology and the evaluation of the results obtained thanks to the increasing number of validations requested by customers. It is remarkable that the simulations show only very small percentage deviations compared to the actual measurement results in practice. ACE's simulations are therefore also very accurate thanks to Burat & Klein's measurement technology.