Using spindle noise to monitor tool wear in a turning process

A tool condition monitoring system can increase the competitiveness of a machining process by increasing the utilised tool life and decreasing instances of part damage from excessive tool wear or tool breakage. This article describes an inexpensive and non-intrusive method of inferring tool condition by measuring the audible sound emitted during machining. The audio signature recorded can be used to develop an effective in-process tool wear monitoring system where digital filters retain the signal associated with the cutting process but remove audio characteristics associated with the operation of the machine spindle. This study used a microphone to record the machining sound of EN24 steel being face turned by a CNC lathe in a wet cutting condition using constant surface speed control. The audio signal is compared to the flank wear development on the cutting inserts for several different surface speed and cutting feed combinations. The results show that there is no relationship between the frequency of spindle noise and tool wear, but varying cutting speed and feed rate have an influence on the magnitude of spindle noise and this could be used to indicate the tool wear state during the process

Using Barkhausen Noise to Measure Coating Depth of Coated High-Speed Steel

Coated high-speed steel tools are widely used in machining processes as they offer an excellent tool life to cost ratio, but they quickly need replacing once the coated layer is worn away. It would be therefore useful to be able to measure the tool life remaining non-destructively and cheaply. To achieve this, the work presented here aims to measure the thickness of the coated layer of high-speed cutting tools by using Barkhausen noise (BHN) techniques. Coated high-speed steel specimens coated with two different materials (chromium nitride (CrN), titanium nitride (TiN)) were tested using a cost-effective measuring system developed for this study. Sensory features were extracted from the signal received from a pick-up coil and the signal features, Root mean square, peak count, and signal energy, were successfully correlated with the thickness of the coating layer on high-speed steel (HSS) specimens. The results suggest that the Barkhausen noise measuring system developed in this study can successfully indicate the different thickness of the coating layer on CrN/TiN coated HSS specimens

Monitoring Tool Wear in Drilling Process Using Spindle Noise Features

The use of worn cutting tools has a detrimental effect on the surface finish of a workpiece, tool precision and internal machine stress. Worn tools also decrease productivity through unplanned stops, tool changes and increase the production of scrap material. This study investigates an inexpensive and non-intrusive method of inferring tool wear by measuring the audible sounds emitted during a drilling process. A microphone was used to record the machining operation sound of S50C steel, which was drilled using a computer numerical control (CNC) milling machine in wet conditions. The audio signature was examined using a spectrogram, and the extracted sound features of the rotating spindle motor in the frequency domain were used to correlate with tool wear. The results indicated that the frequency of spindle noise was unrelated to tool wear, but although the magnitude of spindle noise significantly increased in accordance with tool wear progression

Crack Initiation Detection in JAC780Y during Tensile Loading by Using Direct Current Potential Drop and Acoustic Emission Techniques

In this work, the non-destructive and fracture test techniques were studied for micro-crack detection in the advanced high strength steel (AHSS) notched sheets. Crack initiation of JAC780Y during tensile loading was investigated by Direct Current Potential Drop (DCPD) and Acoustic Emission (AE) techniques. The results confirm for the first time that both techniques can be induced to indicate micro-crack from fracture behavior of AHSS sheet in forming and AE technique can detect the crack initiation faster and more effective than DCPD

Bendability evaluation of sheet metals in three-point bending test by using acoustic emission features

In this work, bendability evaluation of three sheet metals, a galvanized steel (JAC780Y), a stainless steel (SUS304) and a cold rolled steel (SPCC) was precisely investigated using an acoustic emission (AE) technique. A three-point bending test, with three different punch plate radii, was performed to evaluate the formability of the metal sheets in bending and hemming processes. Bending force–displacement curves were derived from the results of the tests and were correlated with AE features (Root Mean Square and Peak-to-Peak) that were extracted from data obtained during those tests. These correlations showed for the first time that AE techniques could be used to detect an intercrystalline fracture from bending behavior and also to evaluate the bendability of the given materials

Influence of Backfat Thickness and the Interval from Altrenogest Withdrawal to Estrus on Reproductive Performance of Gilts

Estrus synchronization of gilts can be achieved by feeding the orally active progestogen altrenogest (AT) to cycling gilts at 20 mg/day for 14 to 18 days with gilts usually returning to estrus 4 to 8 days after the last feeding. In practice, gilts failing to exhibit estrus by 6 days after AT withdrawal may compromise weekly breeding targets. The cause of prolonged intervals to estrus are unknown but may involve prolonged suppression due to the release of progesterone (P4), and by extension AT, from adipose tissues. The present study examined relationships between gilt P2 backfat depth (<13.5 mm, 14–16.5 mm, >17 mm groups), the AT withdrawal to estrus interval, and subsequent reproductive performance in gilts. We noted longer intervals to estrus in gilts with greater P2 backfat depths (p < 0.0001), and higher serum P4 concentrations on the last day of AT feeding and at estrus detection (p < 0.05). Total born litter sizes were unaffected by backfat depth, but pigs born alive progressively decreased with increasing backfat depth with the fattest gilts producing the fewest liveborn pigs (p < 0.05). Taken together, these data suggest that adipose tissues may provide a reservoir of steroid, with its release from fatter gilts having potential negative effects on their subsequent reproductive performance