Showing papers on "Tool wear published in 2001"

Tool wear condition monitoring in drilling operations using hidden Markov models (HMMs)

Abstract: Monitoring of tool wear condition for drilling is a very important economical consideration in automated manufacturing. Two techniques are proposed in this paper for the on-line identification of tool wear based on the measurement of cutting forces and power signals. These techniques use hidden Markov models (HMMs), commonly used in speech recognition. In the first method, bargraph monitoring of the HMM probabilities is used to track the progress of tool wear during the drilling operation. In the second method, sensor signals that correspond to various types of wear status, e.g., sharp, workable and dull, are classified using a multiple modeling method. Experimental results demonstrate the effectiveness of the proposed methods. Although this work focuses on on-line tool wear condition monitoring for drilling operations, the HMM monitoring techniques introduced in this paper can be applied to other cutting processes.

Experimental Investigation of Thermo-Mechanical Characteristics in Laser-Assisted Machining of Silicon Nitride Ceramics

Abstract: Laser-assisted machining (LAM) of silicon nitride (Si 3 N 4 ) is evaluated for its potential to become an economically viable process in fabricating precision ceramic parts. On-line measurements of cutting force and workpiece temperature are performed, and tool wear and surface integrity are examined. Tool wear characteristics are determined as a function of workpiece temperature, which is measured on-line using a laser pyrometer Tool wear/failure mechanisms are characterized using optical microscopy while application of scanning electron microscopy to heated and machined surfaces, as well as to chips, is used to infer material removal mechanisms and the extent of damage caused by LAM. The sub-surface damage of parts produced by LAM is compared with that of typical ground parts.

Economical and Ecological Cryogenic Machining

Abstract: To eliminate health and environmental problems caused by using conventional cutting fluid in the machining industry, a new economical and practical approach to cryogenic machining technology was developed. Using micro nozzle jetting to the cutting point locally, this approach minimizes the amount of liquid consumption to levels at which nitrogen costs less than conventional cutting fluid. It reduces tool wear and lengthens tool life up to five times, thereby allowing for high-speed cutting, improving productivity and reducing overall production cost. In addition, this approach reduces the frictional force, improves chip breaking, eliminates build-up edge, and improves surface quality. This paper discloses the new cryogenic machining approach, and assesses the economics of the process in comparison with state-of-the-art conventional emulsion cooling.

Evaluation of Minimal of Lubricant in End Milling

Abstract: When considering machinability parameters, the use of coolant is indispensable in metal cutting operations. However, stricter environmental regulations are making the use of an ample amount of conventional coolant impossible because of its negative impact on the environment. Consequently, the use of minimal quantities of lubricant (MQL) can be regarded as an alternative solution in which the functionality of cooling and lubrication can be achieved by a tiny amount of cutting oil. In this study, flood coolant (421 min -1 ) was used compared to the MQL amount of 8.5 ml h -1 and the comparative effectiveness was investigated in terms of cutting force, tool wear, surface roughness, and chip shape. Unlike the catastrophic tool failure in flood cooling, the use of MQL resulted in the cutting edge remaining intact, in spite of a higher flank width. The findings of this study show that MQL may be considered to be an economical and environmentally compatible lubrication technique.

Optimal drilling of particulate metal matrix composites based on experimental and numerical procedures

Abstract: An experimental and numerical study of the evolution of cutting forces, tool wear and surface finish, measured when drilling the particulate metal matrix composite A356/20/SiCp-T6 is presented The experimental work was developed through the continuous measurement of the cutting forces with an appropriate piezoelectric dynamometer The wear type was identified and its evolution with cutting time was measured Drills with polycrystalline diamond were tested The surface finish of the holes was evaluated with a profilometer Using the experimental results, a numerical search of optimal drilling conditions was performed Since there are contradictory objectives, such as maximisation of tool life and minimisation of tool wear, the concept of the Pareto optimum solution is considered in the optimisation procedure An evolution strategy is adopted to obtain the optimal solution for cutting speed, feed rate and tool life prediction with industrial interest

A decision fusion algorithm for tool wear condition monitoring in drilling

Abstract: Tool wear monitoring of cutting tools is important for the automation of modern manufacturing systems. In this paper, several innovative monitoring methods for on-line tool wear condition monitoring in drilling operations are presented. Drilling is one of the most widely used manufacturing operations and monitoring techniques using measurements of force signals (thrust and torque) and power signals (spindle and servo) are developed in this paper. Two methods using Hidden Markov models, as well as several other methods that directly use force and power data are used to establish the health of a drilling tool in order to avoid catastrophic failure of the drill. In order to increase the reliability of these methods, a decision fusion center algorithm (DFCA) is proposed which combines the outputs of the individual methods to make a global decision about the wear status of the drill. Experimental results demonstrate the effectiveness of the proposed monitoring methods and the DFCA.