Whether it's the automotive industry or aviation, medical technology or microelectronics - the number of applications in which very low torques have to be controlled, monitored and documented is growing steadily.
The Nano Driver ERXS with integrated transmitter from Desoutter is the tool of choice in these areas. A new range of static torque transducers now enables these electric screwdrivers to be tested inhouse as well.
Desoutter is launching on the market a range of static torque transducers for its Nano Driver ERXS miniature screwdriver. “With the DSTxs, it is now possible to carry out a machine capability study in the area of the lowest torques", explains Lukas Kois, Product Manager at the screw technology specialist Desoutter GmbH, based in Maintal. "For every nano driver model there is a suitable static transducer in line with its torque range. We also offer the user a simulator set, the so-called DJS set box, with which the four test conditions - hard and soft screw joints with minimum or maximum torque - are covered on metal, whereas in the case of assembly in plastic, with seals or washers, "soft" screw joints predominate. Different tightening strategies are also required for these different conditions.
With the sensors and the simulator set, users can now check all electric and pneumatic screwdrivers that work in the area of very low torques in terms of their accuracy and suitability for the respective installation task (a so-called "machine capability study", MCS). Desoutter recommends measurement on a guided test station in order to ensure perfect alignment of the tool or connection simulator and torque transducer. The scope of delivery of the DSTxs 20 also includes an adapter that achieves high accuracy with MCSs under 0.2 Newton metres (Nm).
Increasing requirements for process reliability in micro assembly
“The reason for the new development was the realisation that even with delicate assembly processes, the requirements regarding quality control and process monitoring are becoming more stringent”, says Lukas Kois. “In addition, the global market for automotive electronics in the areas of driver assistance systems, body electronics, entertainment, power train and security systems will grow significantly in the coming years”. This will also increase the demand for printed circuit boards, which in many cases are mounted with micro screws. “There is also a revolution in the field of results data collection”, says Kois. “Both have the consequence that the manufacturers will use more and more electrical tools with very low torque instead of manual screwdrivers and pneumatic tools - whether hand-held, attached to a tool stand or automated”.
Desoutter had already launched the Nano Driver ERXS with integrated sensor for such screw connections. The electric screwdriver can be used wherever screws with very low torques are tightened and the installation has to be monitored and documented. Desoutter is exhibiting the Nano Driver, including 2nd to 4th April at the Aircraft Interiors Expo, the international trade fair for aircraft interiors in Hamburg (Hall B1, Stand 1A50). The handy tool is available in three versions, which cover a total torque range from 0.06 to 0.8 Nm. All models work at a maximum speed of 1,000 revolutions per minute (rpm) and have pressure and lever starters. With a length of just 216 mm, their low weight of 300 g and their soft, non-slip grip, they offer a high level of ergonomic comfort. The tools are also suitable for the so-called KoALa procedure. This procedure describes a special strategy for screw connections in different materials, in which the clamp force control of the screw is an important parameter for programming. In such cases, the KoALa procedure leads to a higher installation quality than a simple torque or angle control.
Machine capability study for the lowest torques
Users can now further increase process reliability in their installations by regularly checking their nano driver screwdrivers with the DSTxs. For this purpose, the sensor can be connected to mobile measuring devices from the Desoutter Delta range. In addition to the minimum, maximum and mean values, it also provides the standard deviation as well as Cm and Cmk values. The measurement uncertainty of the DSTx is ± 0.5% over the entire measuring range. “All relevant data for the report, such as sensor type, serial number, sensitivity, nominal load and test date, can be called up via the built-in smart chip memory”, explains Product Manager Lukas Kois. “And on request, our Project Department can also integrate the DSTx into a test station or robot cell”.
15 cycles and 50 sets of parameters can be programmed
The nano driver models themselves are equipped with an M20 connection thread for easy integration into the assembly line. They offer a maximum torque tolerance of ± 5% above 6 sigma, very good repeatability and reliable feedback with a total of four LEDs, two of which can be programmed flexibly. In combination with the vacuum suction integrated into the ERXS screwdriver, 4 mm wing or crescent bits allow the insertion of the smallest screws in accordance with the pick ’n’ place principle. “Apart from Desoutter, I can't think of a manufacturer that currently offers a measurement-controlled screwdriver with an integrated vacuum suction", Kois emphasises. The vacuum pump can be controlled directly via the Desoutter CVIXS control unit, with which the screwdrivers also work. Up to 50 sets of parameters with a maximum of 15 phases each can be programmed and saved.
