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Dynamic simulation of machine spindles
2002 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Tool and spindle monitoring is one feature that users of modern tool machines ask for more and more frequently when they plan to purchase a new machine. Therefore it is obvious that SKF is looking into this issue to be able to supply their customers with a monitoring system if they ask for it. The system shall be able to predict failures of the spindle bearings and detect unbalances that may ruin the spindle unit. The purpose of this Master Thesis is to see how the accelerometer signal can be used to estimate dynamic cutting and bearing forces. A sub purpose is to find an optimum accelerometer placement on an existing tool spindle made by SKF. This thesis consists of two main parts, theoretical analysis and verification by practical experiments. The first step to obtain the optimum placement of the accelerometers was to construct a mathematical model of a spindle and its housing in order to theoretically determine where the sensors should be mounted. This resulted in a program written in MATLAB. The program is called VAMS3D, which stands for Vibration Analysis of Multi Shaft systems. The software can as the name implies perform rotor dynamic analysis on systems containing multiple shafts. The practical test was conducted as a so called "modal hammer test". The results were then used to properly calibrate the mathematical model. The chosen sensor position is located 52.8 mm from the front face of the mounting flange, which is straight above the front end ACBB (Axial Contact Ball Bearing). The reason is firstly the lack of space and secondly the close vicinity to the vibration transmitting source, the bearing. It is only the bearings that can transmit vibrations from shaft 1 to shaft 2 due to the construction of the spindle. The reason that the sensor placement is above the first ACBB is that this bearing takes up the heaviest load. This bearing also has the largest deflection and has therefore the highest amplitude on the accelerometer signal. A 'bearing force divided by the sensor signal' function in VAMS3D is used to translate the sensor signal into a force, which acts on each bearing in the frequency spectrum. The force graphs are made by multiply the simulated force/sensor signal function with the measured signal. If the real- and calculated transfer functions are matching each other in a satisfying manner one can expect a good estimate value of the forces.

Place, publisher, year, edition, pages
Keyword [en]
Technology, rotor dynamic, machine spindle, vibration analysis, monitoring system, accelerometer, sensor
Keyword [sv]
URN: urn:nbn:se:ltu:diva-43223ISRN: LTU-EX--02/104--SELocal ID: 11b8ea9a-fdde-49ff-bef8-1103758f51e0OAI: diva2:1016452
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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