Each bearing or tolerance ring is designed uniquely for your specific application – and not simply chosen from a catalogue. Our design engineers work with yours to develop the ideal material configuration, shape and dimensions to meet your needs. We then rigorously test our product, both separately and as part of your system, to confirm that the solution works perfectly.
Our thorough testing regime for products and systems is without equal. It involves a variety of stages but, most importantly, it culminates in application tests which closely simulate real-life conditions. As a result, you can move to production with full confidence.
The number, range and accuracy of our testing machines is unparalleled, and our collection even includes unique equipment created specifically for us.
Crucially, our testing facilities are not available for hire. Only Saint-Gobain customers, working with our design engineers, can benefit from these capabilities and enjoy this level of certainty in the bearing-related performance of their systems.
We test our products both individually and in combination with the system and product in which they are to be applied. Our main products, which can be customised and optimised in many different ways, are:
NORGLIDE® sliding bearings (rotating and linear), whose layer of self-lubricated, low-friction PTFE enables smooth interaction with contact surfaces. Their layered structure can be reinforced by selecting metals and PTFE filler materials in application-tailored configurations.
RENCOL® Tolerance Rings, used primarily for effective frictional fastening of cylindrical mating components. In addition to firm mounting of bearing and other assemblies, their functions can include torque transfer in pulley or gear mounts for example. They can also act as slip clutches, disengaging components in the event of a potentially damaging overload.
SPRINGLIDE™ Spring Energised Bearings, which combine steel spring elements with a soft, low-friction polymer layer. They eliminate the need for clearance and address issues like rattle noise dampening, misalignment and tolerance compensation. In effect, they roll NORGLIDE® and RENCOL® technology into one simple solution.
There are currently nine dedicated Saint-Gobain bearing testing facilities, spread worldwide, which bring specialised equipment, expertise and understanding of local needs close to our main customer and manufacturing bases. (See Figure 1.) Their test engineers, prototype engineers and other experts communicate with each other globally, sharing knowledge, advice and access to testing machines.
Figure 1. Testing worldwide.
Our facilities are designated, according to their key activities, into one of three categories:
The ATCs have a particularly important role in accelerating the development of bearing solutions for customers’ new applications. They can quickly assess the feasibility of a product and test its mechanism before it proceeds to prototyping and full application testing.
Clearly it makes sense to test a product thoroughly in its application before introducing it into the market, to minimise the risk of failure. Application testing in the field is very time-consuming and expensive. Expense can be saved, and products can be brought to the market faster, by using application testing machinery. This accelerates processes and gives an early indication of any problems. If an issue arises, it can be addressed before the new product goes on sale. If the application testing equipment confirms that the product works well, you can go to market with increased confidence and reduced risk.
Friction and wear are the most crucial considerations in bearing-related engineering. Wear limits the lifetime of a bearing. Knowledge of our sliding materials wear rate means we can develop bearings that perform to match the product lifetime across a range of diverse applications. Friction is the force resisting the motion of surfaces sliding against each other. Depending on the application high or low friction in a bearing point can be desired. A friction level, matched to an application need will help qualify the material selection. Using the right material in this situation is key to adjusting a force or torque to a specified level. It can also reduce the friction losses in a highly loaded bearing keeping this loss to a minimum and avoiding unnecessarily high heat generation. This is especially important for compact modules to prevent impairment of adjacent components.
Our linear friction testing (LFT) machines measure friction and wear resulting from linear movement relating to bearings. They include ‘yoke testers’ (Figure 2), uniquely built for Saint-Gobain for the initial purpose of testing automotive steering yokes. The same machines can be used for brake systems, head restraints and many other applications in the automotive industry and beyond. Wherever different materials slide against each other in a linear motion, our LFT machines can determine their friction levels and durability. Tests can be carried out under varying conditions, including load, sliding speed, stroke, lubrication and temperature, to reflect real-life application circumstances.
Figure 2. ‘Yoke tester’ (for linear friction and wear testing)
Figure 3. Torque tester (for rotational friction and hysteresis measurement)
Torque testers (Figure 3) look instead at rotational (or torsional) friction. In addition to overall torsional friction, they can measure hysteresis (deformation) in materials as they move against each other, change direction, for example turning clockwise or anti clockwise or between loading and unloading. Examples of applications in the automotive sector include hinges, sensor assemblies in steering systems and input pinion assemblies in head-up displays, but there are uses in many other systems and industries. Again, factors such as input torque, rotation speed and temperature can be varied.
For tolerance rings, torque levels can vary greatly depending on application. Thus, several torque testers are needed to cover that range. Our torque testers allow us to measure torque from 10-5 Nm to 500Nm. Should you need to test torque over 500Nm we have testing facilities in Bristol and Willich that can support this.
Figure 4. M15 torque tester
Figure 5. Mcmesin torque tester
Figure 6. TL500 Torque tester
Our flexible test beds (Figure 7) measure friction and efficiency for whole systems, which they can subject to a complex combination of simultaneous linear, rotating and oscillating forces. Movements are typically applied in two linear axes and one rotational. They may involve, for example, a repeated pattern of rotating several times in one direction, stopping, and then doing the same in reverse. Aside from automotive door, seat and steering mechanisms, flexible test beds are used for applications including bicycle steering set-ups and solar power equipment. Along with their almost infinite variety of movement combinations, they can be used to test the effects of changing factors like input torque and load, sliding and rotating speeds, and stroke.
Figure 7. Flexible test bed (for multi-factor friction and efficiency testing)
Figure 8. Pneumatic pulser (for lifetime testing)
A further application testing option involves use of a pneumatic pulser (Figure 8). Our Pneumatic Pulser test machines allow oscillating linear motion test up to 35Hz. These testers are used for both fundamental and application related testing. Fundamental tests such as three-point bending are conducted to identify material properties related to fatigue. On application level the PP tester is used for tests on finished products for fatigue testing and to validate required endurance strength.
In addition to determining the behaviour and resilience of products and systems under varying application conditions, we carry out accelerated lifetime testing. The range of machines described above can be programmed to simulate a lifetime’s movements, cycles and harsh conditions in a matter of days. By periodically examining a product’s condition, or even testing it to destruction, we can calculate its likely lifespan and benchmark it against alternative solutions.
The application testing machines described here contribute to our understanding of tribology in relation to the materials, products and systems we test and we investigate further using advanced microscopy. Tribology is the science and technology of interacting surfaces in relative motion. It deals in particular with their friction, wear and lubrication. Wherever there is friction contact between two substrates, in a bearing or tolerance ring set-up for instance, we study its tribology.
Using high-precision microscopes, we can closely examine surfaces before and after application tests to see what has changed. For example, we might find areas of scouring damage, or transfer of material from one surface to another. Our equipment includes scanning electron microscopes (SEMs) with energy-dispersive X-ray spectroscopy (EDS) – see Figure 9. This not only gives extremely detailed images but enables analysis of the chemical make-up of transferred material, so we can determine its origin in a system.
Figure 9. Scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS) uses focused beams of electrons to identify surface topography and composition
Depending on the required precision or the desired scope, our microscope range offers geometry, surface and material analyzes. The telecentric digital 3D microscope - Figure 10 - enables geometry, shape and position characterization through structured light scanning for geometry analysis on a macro scale (mm range). For analyzes on a microscale (µm scale), our confocal 3D laser scanning microscope - Figure 11 - is preferably used to characterize the technical surfaces. This includes roughness and texture analysis. For example, one use case could be to determine the difference between worn and fresh surfaces. A SEM is used for high-resolution microscopy - with a magnification range of x30 to a maximum of x10,000. In combination with the integrated EDS, material analyzes are possible. With the move to ever smaller systems, the requirements for testing on the nanoscale are growing.
Figure 10. Digital 3D microscope
Figure 11. 3D laser scanning confocal microscope
Another aspect of our analytical work is quality control. For example, we need to be certain that all dimensions of a product are exactly as they should be – before and after application, and throughout production runs. We can use a three-dimensional co-ordinate measuring machine (CMM) – see Figure 12 – to measure anything from a single point location to the whole 3D shape of a product.
Figure 12. 3D co-ordinate measuring machine (CMM)
Figure 13. Hommel Nanoscan tester (for creating 3D surface maps)
There are times when obtaining more data points from a surface apart from roughness and contour is needed. The Hommel Nanoscan (Figure 13) can obtain roughness, contours and create 3D Maps from different components, using a wide range of probes depending on specimen characteristics, down to the micro scale.
When physical probes are not an option to measure features, an optical measurement system can be used. On our site in Bristol we have a OGP CNC 670 (Figure 14). It features a bed and programming function where geometric characteristics can be measured and checked against drawings. It is used to measure tolerance rings, jigs, customer components and assemblies.
Figure 14. OGP CNC 670 optical measurement tester
Figure 15. Mitutoyo roundness tester for concentricity testing
Our custom-made RENCOL® Tolerance Rings are used in and with round and cylindrical systems, where roundness, concentricity and circular run out are parameters that can define assembly performance. The Mitutoyo Roundness Tester (Figure 15) allows us to measure concentricity, cylindricity and roundness of different assemblies and components.
We test bearings, tolerance rings (if required), assemblies and other components for corrosion resistance using salt spray chambers (Figure 16). These accelerated tests normally involve a 5% sodium chloride solution, with a pH between 6.5 and 7.2, at 35⁰C, according to DIN EN ISO 9227. A check for rust is made once every 24 hours, and between checks the specimen is sprayed constantly. Most commonly, testers are looking for the number of hours taken for red rust to appear. Results may be stated as 24, 48, 72, 96, 120, 240, 480 or 960 hours without red rust.
In addition to red rust, there are more than 50 different classes of corrosion – named according to their appearance or their cause. The main categories affecting bearings are surface, galvanic and crevice corrosion.
To reflect the changeability of real-life conditions, we can make the ‘climate’ in the chamber vary over a cycle of several days – with periods of salt spraying (rain), dryness (sun) and high humidity (fog), for instance according to OEM specs. This testing typically lasts 6 or 12 weeks. We can also combine it with factors such as mud and mechanical stress to test the overall effect.
For more detailed corrosion test and to characterize the electrochemical systems - with less complexity - we also have the possibility to use potentiostat in combination with electrochemical impedance spectroscopy (EIS). This allows us as well to change the electrolytes easily, that specific investigation can be conducted with acids, bases or alkalines.
Figure 16. Salt spray chamber.
Figure 17. Semi-anechoic chamber for NVH testing and development
Noise, vibration and harshness (NVH) can be tested and accurately measured for components, systems and entire products – including whole vehicles – in our semi-anechoic chamber (Figure 17). In addition to relatively simple noise and vibration measurement, we can investigate and assess complex interactions and effects – and identify solutions to improve sound performance. Products tested range from household electrical appliances to automotive seat frames, electric vehicle motors and drones.
At Saint-Gobain, Finite Element Analysis (FEA) is used to support the design and development of our products, considering the processing, assembly and performance in representative sub-assemblies across a range of tolerance and operating conditions.
FEA complements testing by virtualising physical processes, providing a predictive capability to understand a much wider range of parameters than would otherwise be possible. It can also reveal hidden behaviours and mechanisms that allow insights to be drawn which may not be possible from physical tests alone.
Figure 18 shows a visualisation of a RENCOL® Tolerance Ring assembly, with a precise representation of a tolerance ring assembled into the mating components. This type of analysis can help predict the impact of the assembly process on the final performance before any parts are made and can be routinely undertaken by our tolerance ring Application Engineers utilising a unique democratised FEA tool based upon ABAQUS.
As well as the FEA embedded in the design process, a specialist in-house team is constantly developing new, bespoke methods to help our customers with specific project requirements as well as supporting the development of new products including SPRINGLIDE™ and certain NORGLIDE® developments.
A simple example of the kind of prediction made possible by FEA for some rotating bearings which have been used in a press-fit assembly. The NORGLIDE® Bearing, in this test, has a layer of PTFE backed by a layer of steel. Its competitor has an all-plastic construction. Pressure from the metal link into which the bearing is inserted is transmitted right through the plastic product, producing broad line contact stress on both its inner and its outer surfaces. In the NORGLIDE® product, PTFE spreads the pressure out evenly. The result is line contact stress on the steel outside surface but none on the PTFE inner surface.
Figure 18. FEA of a Tolerance Ring assembly showing Von-Mises Stresses
Our advanced testing, as summarised in the sections above, builds on the essential knowledge gained through fundamental test processes. Moving into material testing and characterisation we have a number of universal tensile / compression test machines available that are used (Figure 20) to determine stiffness and strength characteristics of our materials. We also have equipment for determining material density, hardness and surface roughness.
Figure 20. Tensile tester
Figure 21. Tribometer/rheometer
A tribometer (Figure 21), for example, is used to measure friction and wear in a very fundamental contact. The benefit of tribometer testing of our materials is that it is quick and highly reproducible and provides controlled variation of the main operating parameter e.g. load, speed, temperature. Contact surfaces can be analyzed optically easily after testing. Therefore, tribometer tests are used in early development stages, as well as in application tests.
Although direct transfer from tribometer results to system level is not always possible (as friction and wear are system values) tribometer tests help to understand material behavior. This way, findings can be used for system optimization questions.
Alongside tribometer testing fundamental investigations are done using our journal bearing tester (JBT) (Figure 22). These tests are used to determine coefficient of friction (COF) and wear performance of our sliding bearings. Tests are carried-out at different loading conditions representing the wide range of the operating conditions of our different markets.
Figure 22. Journal bearing tester (JBT)
Figure 23. Zwick Z100 (for material testing)
When a higher level of force is demanded, the Zwick Z100 (Figure 23) allows to test tensile specimens up to 20KN or to compress specimens up to 100KN. Yield point, stiffness and deformation can be measured and used as quality control or to test and check new materials and prototypes. Our Zwick Z200 can test components, systems and sub-assemblies up to 600mm in width.
Our test engineers and facilities are uniquely equipped to solve your testing challenges and allow you to develop and launch your products with confidence. To get in touch and talk to us, engineer to engineer, use our contact form or email us at: firstname.lastname@example.org.