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ACOUSTIC EMISSION FOR PROCESS MONITORING DURING METAL CUTTING

Objective


Within the scope of this research, a new approach for tool wear monitoring during turning was tested successfully. It was demonstrated, that the beginnings of tool wear can be detected with relative sensitivity using a broadband acoustic emission (AE) detection, short transmission paths and the extraction of disturbance signals caused by collisions between the chips and the tool.

An essential result of this research concerns the sources of AE during the turning process. The examination of the signal transmission from the workpiece to the tool suggests that the interactions at the contact area between the workpiece and the tool are the most important AE sources, ie the sources within the workpiece itself can be neglected. Furthermore, a new theoretical approach to the general of AE during turning has been evolved. This approach starts from the assumption that the essential AE sources during turning result from the friction at the contact area between the workpiece and the tool. The present experimental results prove this model, ie the model makes correct predictions on the AE behaviour, where other theories fall (eg independence of AE from the feed per revolution).

In the examined case, tool wear monitoring during drilling could be performed relatively simply by an evaluation of the average signal level (ASL value). It has to be ascertained, if this result can be generalised.

A new measuring technique for tool wear monitoring during turning has been developed. The technique makes possible the early detection of tool wear (flank or crater wear as well as cutting edge chippings) during the machining process and before tool breakage. The use of this monitoring technique makes better utilization of tool life and can lead to the avoidance of tool breakage by accurately predicting when a tool change is necessary. The measuring technique is based on the analysis of acoustic emission (AE) signals generated by machining processes. The new method of analysis is based on a physical model, which correlates quantitatively AE and tool wear parameters.
THE OBJECTIVE IS TO APPLY ACOUSTIC EMISSION (AE) TECHNIQUES TO THE AUTOMATIC TOOL MONITORING FOR TURNING, DRILLING AND GRINDING. MOREOVER THE NEW AE-SYSTEM HAS TO BE INTEGRATED IN A COMPUTER AIDED ON-LINE TESTING SYSTEM. STEPS ARE:- TO DEVELOP AE AS A TESTING METHOD WHICH IS ABLE TO GAIN ON-LINE INFORMATION ON THE EXTEND OF TOOL WEAR, CHIP-FORMATION AND MICRO-FRACTURE ON THE CUTTING-EDGE
- TO SEPARATE THESE PARAMETERS
- FIRST FOR TURNING, SECOND FOR DRILLING AND GRINDING
- AT LAST EXPERIMENTS UNDER REAL INDUSTRIAL CONDITIONS TO DEMONSTRATE AND TO PROVE THE CAPABILITY OF THE DEVELOPED AE-SYSTEM.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

ROBERT BOSCH GMBH.
Address
Robert-bosch Platz 1
70049 Stuttgart
Germany

Participants (2)

Danfoss A/S
Denmark
Address

6430 Nordborg
FRAUNHOFER-GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG E.V.
Germany
Address
Universitaet, Gebaeude 37
66123 Saarbruecken