Using the Torquemeter TVD by example

March 23, 2022

What is a torque screwdriver? Thanks to this tool, the watchmaker is able to ensure very precise torque settings for the many screws in a watch. At the end of the screwing process, when the preset torque is reached, a click is felt to indicate the passage from one notch to another. The final quality of the timepiece depends on the precision and regularity of these releases. Vincent Nardella, who is in charge of the product assembly and customer service group, reveals to us what goes on behind the scenes of torque measurement, in particular that of VOH’s TVD torque meter.

Vincent Nardella has been working at VOH since 2018. He holds a CFC in automation and two years of higher technical education in Biel, which gives him the status of ES technician in automation. Within the company, the young man is responsible for the product assembly group and also travels to customers to ensure installation and maintenance. As an expert in mechatronics, he is responsible for explaining the concept of torque measurement at VOH. “Very simply, this measurement consists of detecting and measuring the effort required to rotate a concentric element in relation to another.

Let’s take a closer look at the TVD Torquemeter, the motorized electronic torque measurement device for torque screwdrivers developed by VOH. First, a torque screwdriver is scanned via the QR code on its handle to identify it and load the pre-defined measurement program.  It is then placed in the TVD Torque Meter and held in position by dedicated clamping means.

The motor, which is attached to the measuring gauge, drives the moving part of the screwdriver, which allows us to detect and measure each release point. It is these points that we analyze, with precision”, explains Vincent Nardella.

In short, the objective is to measure the effort required to pass each notch, one after the other, at a controlled speed. During the measurement, four values, expressed for example in milli newtons (named after the famous Isaac Newton) per meter (mNm), are displayed on the screen: the highest value, the average value, the instantaneous value and the lowest value.
The Torquemeter’s motor controls the speed of rotation with a regularity that cannot be reproduced manually. “At the end of the test, the graph allows the user to visualize the result obtained for each of the screwdriver’s notches and to see the state of wear of the instrument. If the values do not comply with the criteria defined in the program, the result is declared KO. If only the average is out of tolerance, but the dispersion is correct, an adjustment is necessary and can be done in “adjustment” mode directly at the end of the test. But if the dispersion is too great, the screwdriver must be removed from production and overhauled. The technician explains: “After a change in the screwdriver setting, it is necessary to carry out a few lapping runs beforehand in order to obtain a stabilized measurement and, ultimately, reliable results.

A MUCH FINER ANALYSIS OF THE DATA

To find out what goes on behind the scenes in torque measurement, and more particularly the software aspects, Vincent Nardella directs us to the Research and Development department under the responsibility of Bastien Paratte, a HES engineer. He goes back over the way in which the TVD torque meter is parameterized. The measuring sequence and parameters are defined via programmable sequences that can be assigned to each type or group of screwdriver [screen capture possible? authorized?]: the running-in, the direction of rotation, the speed of rotation, the number of notches, the OK/KO criteria, etc… everything can be configured! With the new TVD 4.0 Torque Meter, traceability data and programs can be collected, transferred, managed and visualized and parameterized through the LINKiX smart production ecosystem developed by the company.

A 100% VOH TORQUE SENSOR

Back to the assembly part of the VOH factory. The torque sensor is produced in-house,” explains Vincent Nardella. It exists in two versions: for torques < 50 mNm and one for torques > 50 mNm. This is done on a table mounted on a pneumatic cylinder, which avoids any parasitic vibrations such as movement in the workshop. A pulley system is mounted on the Torquemeter and certified weights are placed on either side of the device. Calibration begins. “For a 20g load, I calculate what torque I should be at using a computer file.
It takes two to three hours to calibrate a Torquemeter and deliver a full calibration report. It is imperative that this step is done without interruption. To be sure of the results, the technician will measure each value three times.

As can be seen, all the stages in the production of VOH metrology equipment are subject to precise procedures, whether it be software development or the manufacture of the device itself. All the VOH teams are mobilized in such a way as to consolidate our company’s status as an essential reference in the world of watchmaking equipment manufacturers.

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