Vibration of Thin Walls during Cutting Process of 7075 T651 Aluminium Alloy

Abstract

The subject of this study is the analysis of vibrations induced during milling of a thin-walled element. The milling was performed with a 2-flute custom end mill for machining Al alloys (FENES, 12x22x80-45°W-Z2), diameter d=12 mm. The rectangular 7075-T651 aluminium alloy workpiece of the following original dimensions: 120x60x12, was machined in a DMG MORI DMU 65 MonoBLOCK 5-axis milling machine. The vibrations of the aluminium alloy test plate were identified with Siemens LMS Scadas Mobile system and LMS Test Lab software. A PCB Piezotronics triaxial ICP accelerometer (model 356B21), offering sensitivity of 10mV/g, was employed. The sampling frequency was 11.5 kHz. The first stage consisted in measuring the vibration levels of the sample, in the function of its thickness and federate vf, at constant technological parameters of machining. The feed vf was set to 1500, 2000, 2500 and 3000mm/min, the depth of cut ap =2mm, the cutting speed was constant and equal to vc = 150.7 m/min (n=4000rev/min). The wall thickness b of samples was equal to: 30mm - reference sample and 11, 9, 7, 5, 3mm - test samples. The vibration signal was measured by two sensors attached to the surface of the sample in two extreme positions on the sample: point P1 and point P2.