Thermal validations of the linear actuator at VDL-ETG

Madhar, M.C. (2015) Thermal validations of the linear actuator at VDL-ETG.

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Abstract:This internship report reflects the work performed at VDL-ETG at Almelo. The assignment consisted of validating the thermal behavior of the Drift Motor NXE, which is one of the linear actuators produced at VDL-ETG. Linear actuators are used in semiconductor manufacturing equipment for the fabrication of integrated circuits. At VDL-ETG a roadmap has been set for future development of the motors in which life-time testing is important for gaining more knowledge. To gather enough information about the actuators, different types of tests and measurements need to be performed. The thermal resistance test (RTH) and the Highly Accelerated Life Time test (HALT) are tests that characterize certain behaviors of the actuator. The resulting failure modes are then used to understand the behavior of the actuator. During this assignment the RTH test was used to determine the thermal resistance from the coils inside the actuator to the cooling channels. During the test, thermal inspections were done by using an infra-red camera to inspect the surface temperatures of the actuator. The obtained thermal images were then compared with the results of the NTCs of the actuator. The NTCs are the temperature sensors which are placed at different positions inside the actuator for temperature readings during testing. Due to the small widths of the cooling channels, the selection of an appropriate IR-camera with good resolution was crucial. Another important factor for the IR-camera, was the viewing distance and Field of View. The camera will also be used with the HALT test, which is performed in a vacuum environment. This vacuum environment is created inside a vacuum box which will impose certain restrictions in the minimum viewing distance of the camera to obtain clear enough images. Other limitations as the temperature measurement range, sensitivity etc. have also been considered. To gain preliminary insights in heating behaviours of the actuator for future (damage) scenarios, a thermal model of the actuator was also constructed in SolidWorks and analysed using the Flow Simulation toolbox, where the settings of the RTH test were applied to the model. The obtained heating results were then compared with the measurements from the IR-camera to validate the model. From the infra-red measurements could be seen that the heating temperatures were close to the NTCs near the coils, instead of the NTCs right underneath the cooling plate. The rate of heating also followed the coils behaviour. Because it was expected that the surface temperatures followed the NTC underneath it, it can be concluded that the top surface heats up in a different way than from the inside. Concerning the thermal model, the surface temperature stays 293 K and the NTC of the coil showed readings far less than the reality. This suggested too poorly heating inside the actuator, which was not enough to heat the top surface. Further improvement of the model is then required. As mentioned before, the HALT test is also used for characterizing the behaviour of the actuator. In the assignment a vacuum box was also designed according to the vacuum regime restrictions for ‘Rough Vacuum’. The box should be able to contain the actuator without the magnet yoke, have the appropriate mountings for the vacuum pump and the possibility for a viewing window to perform the thermal inspections with the IR-camera. Finally, a complete design and cost estimate was prepared for a complete vacuum box ready to be used with the HALT test.
Item Type:Internship Report (Master)
VDL-etg, the Netherlands
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:Thermal validations, vacuum, HALT, linear actuators
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