Condition monitoring of drill process using a telemetry system
TL;DR: In this article, a non-contract telemetry has been developed to monitor the status of the drilling process, which helps in preventing the drill point from such failures, and the details of the telemetry are presented in this paper.
Abstract: Drilling is a complicated process Where-in the drillpoint is exposed to combined Thrust and Torque. This causes heating of the drilling point and subsequent sieizure into the work material resulting in chipping of point material. A non-contract telemetry has been developed to monitor the status of drilling process. This helps in preventing the drill point from such failures. The details of the telemetry are presented in this paper.
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01 Jan 2014
5 citations
Cites background from "Condition monitoring of drill proce..."
...the signals to a frequency modulated (FM) signal to be transmitted to a data acquisition unit on a computer [52], [13]....
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TL;DR: In this article, the frequency composition of the signal and the changes of its pattern during tool wearing process were experimentally investigated and a micro-breakage stage was first discovered, then a new approach of in-process monitoring tool wear stage, the frequency band-energy method, was proposed.
Abstract: Summary In metal cutting, there is plenty of information about cutting process within the vibration signal. The frequency composition of the signal and the changes of its pattern during tool wearing process were experimentally investigated and a “micro-breakage stage” was first discovered, then a new approach of in-process monitoring tool wear stage, the frequency band-energy method, was proposed. In this method, the problem in frequency domain was changed into that in time domain. It is shown by experiments that the rapid tool wear stage can be predicted correctly, therefore adequate measures can be taken to prevent workpiece and tool from damage.
89 citations
TL;DR: In this article, a diffusion threshold model for tool wear is proposed, which allows the machining economics problem to be formulated as a stochastic optimal control problem incorporating measurement feedback of tool wear.
Abstract: A machining economics problem is considered where feed rate selection and tool replacement policies are to be determined. A new stochastic model for tool wear, called a diffusion-threshold model, is proposed. This tool wear model allows the machining economics problem to be formulated as a stochastic optimal control problem incorporating measurement feedback of tool wear. Two types of control policies are described. One is a traditional machining economics policy and the other utilizes tool wear feedback and allows on-line decision making. The optimal policy is described for both types. An example problem based on actual data is worked out that compares the two approaches and demonstrates the utility of information feedback and on-line control.
46 citations
TL;DR: In this paper, a microcomputer-based feedback control system was used to predict failure due to excessive wear commonly encountered with 5 and 8 mm drill heads, which led to very high temperatures (>600°C), causing local welding of the drill material to the peripheral surface of the hole being drilled.
Abstract: Real-time control of drilling was carried out by measuring the thrust force and determining its gradient. Using a microcomputer-based feedback control system, experiments were carried out under different cutting conditions to test the effectiveness of the thrust force gradient in predicting failure. The system was able to predict failure due to excessive wear commonly encountered with 5 and 8 mm drills. With such drills, excessive weat at the outer corner led to an increase in the local temperature which in turn increased the wear. This led to very high temperatures (>600°C), causing local welding of the drill material to the peripheral surface of the hole being drilled. Furthermore, the high temperatures reduced the compressive yield strength of the drill material, causing sub-surface fracture to occur under the influence of the cutting loads. This cyclic phenomenon of “seizure” due to local welding and “release” due to shear fracture (i.e. “stick-slip”) caused sharp fluctuations in the thrust force under constant feed. This paper discusses the effectiveness of the control system described above in predicting failure due to the excessive wear common to large drills. This system is also contrasted with another based on vibration measurements which has been successfully used to predict failure due to fracture common with small drills. This paper also presents other experimental sensor schemes in the literature. Finally, this paper proposes a framework for an “intelligent” machining process control system driven by multiple sensors, which would facilitate untended machining.
22 citations