PSI - Issue 13

Peter Monka et al. / Procedia Structural Integrity 13 (2018) 959–964 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

964

6

It is clear from the figure above that the important changes occur at frequencies ranges 750 – 1000 Hz. There are also peaks at 6000 and 6250 Hz, however these peaks appear at the both new and worn tool and they are in relation with natural frequency of the magnet and with control system of the machine. The same situation has been observed at taps with helix angle of ω = 15° at both cutting speeds, where also the changes in values of amplitude at 750 and 1000 Hz have been recorded. It means that frequencies in the range 750 Hz - 1000 Hz are related to the wear of tap what will be used as a base of on-line diagnostics during next experiments and also at the threads making in real practice. During machining process, it occurs to the tool wear. Except the abrasion on the tool flank and the plastic deformation, it begins to appear also the built-up edge on the face of the cutting tool that is a reason of the worse quality of machined surface and deformed threads. The tests have shown that a short time after these phenomena, it occurs to the cutting-edge cleavage or the tool body breaks in "brittle fracture" way. It is not only dangerous from a worker health point of view, but also from a possibility of machine damage point of view. No less important aspect of this problem is that the thread making operation is one of the last operations in component manufacturing. A poor-quality thread can degrade the entire production process, and the product can be classified as a faulty piece, which affects economic efficiency of a company. (Turisova et al., 2012) Experiments presented in the article have proved that tool life of all tested taps corresponds to the supplier statement, when cutting speed 10 ms -1 is used at the machining based on the supplier recommendations and company catalogues. Next findings confirmed that it is possible to identify a tap wear by means of vibrodiagnostics. It has been found that resonance frequencies 750 and 1000 Hz are related to the tool wear, if the same specific machining and measuring equipment are used, and also it has been found that they are not dependent on the cutting speed and helix angle of a tap. 5. Conclusion

Acknowledgements

The present contribution has been prepared with direct support of Ministry of Education, Science, Research and Sport of Slovak Republic through the projects KEGA 007TUKE-4/2018, VEGA 1/0795/19 and APVV-17-0380, as well as under the project CZ.02.1.01/0.0/0.0/16_019/0000867.

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