In the world of precision engineering, accurate measurements are essential to ensure that machinery operates within required parameters. A recent use case with one of our clients in the defense and automotive sectors sheds light on the importance of precise torque monitoring in gearbox testing.
The client, a manufacturer of military-grade gearboxes for steering systems, faced a challenge in measuring the running torque (also known as prevailing torque) of their gearboxes. Historically, they relied on a manual and less accurate method for testing torque, which involved using a spline drive and a manual torque reader. This traditional setup was time-consuming and prone to inaccuracies, particularly when measuring running torque at low speeds (in this case 50 RPM).
Their specification required the gearboxes to run at 75 cNm of torque at 50 RPM, a target that was difficult to achieve using their existing testing method.
Note: running torque, also known as prevailing torque, is defined by NASA as “the torque required to overcome kinetic friction of the mating threads plus the torque required to overcome any locking feature when 100% of the locking feature is engaged and the fastener is unseated”.
The Solution: Kolver's K-DUCER running torque monitoring feature
To address this challenge, we introduced the Kolver K-DUCER smart fastening system, a KDU-1A control unit paired with an MT1.5 inline screwdriver. This system provides advanced running torque (also known as prevailing torque) features, which is exactly what the client needed to ensure proper assembly and precise measurement and traceability.
Setting up the K-DUCER
The test setup was customized to meet the client's specific requirements for measuring running torque. The parameters were carefully configured to ensure accurate data collection and analysis:
- Target Angle and Speed: A target angle of 1000 degrees was set to monitor the full rotation of the gearbox, while a speed of 50 RPM was chosen to closely match the operational conditions of the gearbox.
- Torque Limits: In the Advanced Torque screen, PV/running torque was set to monitoring mode. A max (peak) torque value of 1 Nm was set to ensure that the test would not exceed the desired torque range. The running torque was then monitored within a window of 100–950 degrees. This approach allowed for dynamic torque measurement while excluding static friction or “breakaway” torque, ensuring that the data captured was solely reflective of the gearbox's performance in motion.
- Data Collection and Traceability: The Kolver K-DUCER system enabled the inclusion of a unique serial number for each gearbox, allowing the client to track and store data with full traceability for each unit tested. With a barcode associated with the serial number of each gearbox, they can track each piece by enabling the serial barcode mode "On SN" (using any USB barcode scanner plus Kolver 's USB barcode adapter) in the KDU-1A's general settings. This feature allows easy tracking of which component each recorded fastening operation is associated with.
Insights and Improvements
Through testing with the Kolver system, the client discovered that their gearboxes were not meeting the expected 75 cNm at 50 RPM. The running torque averaged 0.88 Nm, higher than initially expected. This insight allowed the client to identify performance gaps and make necessary adjustments to their manufacturing process.
The system provided flexibility in how results were assessed. The client could choose to evaluate the data based on either the "average" or "peak" running torque value. This customization enabled them to set precise pass/fail limits for gearbox performance, improving the overall accuracy of the tests. Test data was saved in CSV format, allowing for easy analysis via K-Graph software.
Additional Setup Optimization for Greater Accuracy
In addition to the Kolver K-DUCER system, we recommended incorporating a torque reaction arm to improve test accuracy. A torque reaction arm is designed to absorb and transfer the reaction force generated at the power tool or nutrunner during fastening. By balancing the weight and preventing any significant movement or misalignment, the reaction arm ensures that the tool maintains stable orientation. This stability prevents issues like cross-threading and contributes to more precise and consistent fastening, ultimately improving both test reliability and the overall quality of the gearboxes.
In this case, an appropriate reaction arm for the application was Kolver's LINAR1 linear torque arm, which was specifically chosen to meet the requirements of the test. Moreover, mounting the KDS screwdriver on a linear arm and securing the gearbox in a fixture would ensure that both the tool and the gearbox remain parallel throughout the test. This setup minimizes any potential misalignment or stress on the system, further enhancing the accuracy and consistency of the measurements.
Where Precision Matters, the K-DUCER is the answer
This use case illustrates the significant benefits of using modern torque measurement systems like the Kolver K-DUCER for gearbox testing. By automating the process and enabling precise running torque monitoring, manufacturers can improve operational efficiency, ensure product quality, and extend equipment life.
For the client, adopting an automated torque measurement system has resulted in a far superior testing process, clearer data for decision-making, and a more accurate assessment of gearbox assembly quality. The ability to monitor and track running torque in real-time, coupled with enhanced traceability, ensures that their gearboxes meet the rigorous standards required for critical applications in the defense and automotive sectors.
If your company is facing similar challenges with torque measurement or gearbox testing, consider implementing a precise and automated system like the Kolver K-DUCER to enhance both accuracy and operational efficiency.
