The news of TRAXX

Today, let's dive into a major client case with one of the first and most loyal TRAXX clients, #STELLANTIS !(formerly PSA)

Here is the feedback from Pascal Zych, Process Tightening Manager at STELLANTIS (formerly PSA) in the validation sector.

Pascal Zych has been working for several years on preparing vehicles for industrial production, supporting vehicle development from the perspective of tightening processes. He is responsible for all torque-angle tightening processes in the factories. In this context, he is supported by the TRAXX-M2 devices:

• During the launch of a new vehicle, to validate the torque-angle tightening characteristics of new assemblies.
• To validate the quality of serial bolts. In other words, he can check if the evolution of serial bolts impacts the quality and repeatability of torque-angle tightening.
• In case of a quality issue or product failure, the TRAXX-M2 allows for measuring the installed tension between parts to diagnose the problem.

 

Pascal Zych is particularly satisfied with the TRAXX-M2, which has perfectly integrated into the company's quality process and allows for synthesizing and maintaining great consistency between laboratory data and the measurements taken.

Pascal Zych is also very pleased with TRAXX's customer service, which is very responsive and always attentive. This service also enabled one of his teams to be trained in the use of the TRAXX-M2 remotely during the lockdown periods.

To date, Stellantis (formerly PSA) is our largest client, with a fleet of over 50 devices. We would like to thank them for their loyalty and the trust they have placed in us over so many years.

This article aims to list various applications made possible by bolt tension measurement, covering design, assembly, maintenance, and detection of tightening-related anomalies.

New Perspectives in Industry

The concept of tension tightening, already adopted by major global industry players, is rapidly expanding. It has already proven its worth in sectors such as automotive, aerospace, energy, and transportation. Besides obvious improvements in performance and precision, this method opens up new possibilities in the field of tightening. For example, it is now possible to track the evolution of an assembly’s tightening over time and monitor in real-time the behavior of bolted assemblies. In the long term, maintenance becomes easier as it is possible to check the condition of a bolted assembly over several years. This conceptual advancement is driving the emergence of innovative applications and transforming how assemblies are designed and executed in factories.

During the Design Phase 1- Perfecting Assembly Design

In design offices, engineers adopt a tension-based approach (expressed in kN) when designing bolted assemblies. However, during assembly, operators use torque (expressed in N.m). This disparity between design and implementation creates a gap in the product development and industrialization process. To address this discrepancy, designers typically increase safety margins on all designed parts and recommended screws as a precaution. The consequences of this divergence are significant: assemblies become oversized and heavier, the assembly process becomes more complex and time-consuming, and operational and maintenance costs increase. Mastering tension tightening helps mitigate these issues by restoring consistency across the process: all departments take tightening tension into account.

During the design phase, using a bolt tension meter allows engineers to evaluate the strength of assemblies and analyze their mechanical properties. Ultimately, this improves the design.

During assembly, these same systems can verify whether the tension applied between parts matches the one defined by the design teams.

2- Reducing Prototyping Time

Designing a prototype assembly often requires many trials and errors. Take, for example, the study of a new cylinder head gasket: its behavior is closely tied to the tension of the cylinder head studs. When tightening by torque, it is difficult to differentiate between the effects of tightening and those of the gasket itself. Multiple tests are necessary to characterize the gasket’s behavior, statistically eliminating variations caused by tightening.

On the other hand, controlling tightening tension allows studying the behavior of the gasket independently of tightening variations. By controlling tension, it becomes possible to separate these two variables, simplifying the study by reducing the number of parameters to consider.

During Assembly 1- Controlling the Installed Tension Between Parts

A bolted assembly is held together by a cohesive force between its components, which corresponds to the tension applied to the bolts uniting the assembly. Bolt tension measurement devices work independently of the tool used to tighten the bolts (whether a screwdriver, torque wrench, or hydraulic tensioner). Users of these devices synchronize the tightening they perform with the tension measurement: during tightening, regardless of the tool used, they can directly track the tension’s progress on the measurement device.

2- Ensuring Optimal Sealing of Joints and Applying Uniform Tension Between Parts

Since joints play a crucial role in sealing assemblies, the screws used to maintain pressure on the joint can either ensure a tight seal or compromise it if the tension is not evenly distributed across the joint’s surface. As joints are sensitive to pressure, using a tension measurement system to apply uniform tension between parts ensures proper assembly sealing.

During Maintenance 1- Controlling the Quality of Assemblies by Monitoring the Tension Installed by Tightening Robots

How can you determine if screwdrivers on a production line achieve the predefined tightening tension and whether that tension remains constant over time? With a bolt tension meter it becomes possible to statistically verify whether the screwdriver’s settings (torque/angle) lead to controlled tensions. It also becomes possible to adjust the settings to achieve "acceptable" tightening tensions in production, as is done at Stellantis, for example.

2- Monitoring the Behavior of an Assembly Over the Long Term

In industry, maintaining bolted assemblies often involves fully disassembling and reassembling all assemblies, as is done in refineries, or a portion of installations, representing about 20% of bolted assemblies in the wind sector annually. This process is laborious, repetitive, and outdated.

Another method, known as the torque re-tightening method, involves slightly loosening the assembly before re-tightening it. However, during this re-tightening, the operator may sometimes apply more tension than initially intended, risking exceeding the bolt’s elastic limit and deforming it.
 

Anomaly Detection 1- Investigating a Tightening Incident Through Controlled Disassembly

It is common to suspect a loss of tension in one or more bolts. A common method to check this is to measure the bolt tightening tension of the suspected bolts before disassembling them to determine their residual tension. By comparing this tension with the theoretically expected one, it is possible to determine if there has been any loosening and to what extent. This information then allows the investigation to begin, identifying the causes of the loosening.

 

Conclusion

Regardless of the method used, maintenance is considerably more reliable and simplified with a bolt tension measurement device. With these systems, disassembling the assemblies is unnecessary. This non-intrusive method allows measuring the tension between two parts by simply taking a measurement on the assembly’s screws. This makes it possible to track the evolution of tightening tension over time (over a month, five years, or twenty years…). By comparing the initial tightening data with those recorded at different points, such as during the first maintenance cycle, it becomes easy to detect loosening or anomalies in the assembly. This is a highly effective method for long-term control, monitoring, and surveillance of assemblies.