Tool Condition Monitoring Using Image Processing Techniques

Abstract

Tool wear and tool life are important criteria affecting the part quality. Traditionally there are two methods followed in the industry to determine the end of tool life and to change it. In one case, where the cost of work piece is significant, than the tool is discarded prematurely before its useful life has completed. This saves the costly part from getting damaged. In other case, where cost of the part in not significant, the tool is used till the end of the useful life. Once the tool reaches end of tool life and part quality affected, the tool is changed and the part is either discarded or rework is carried out. Generally industry utilizes past data to determine useful life of tool. There are two ways to know tool wear: Direct and Indirect. Traditionally, tool wear is measured directly using optical microscope which is an offline and time consuming technique. In indirect technique, parameter that is affected by tool wear is measured. Many researchers have selected the parameter like current, force, surface finish, temperature etc. and correlated it with tool wear and tool life.

After carryout literature review, it has been observed that optimization of critical parameters affecting tool life using image processing techniques has lot of scope. Digital image processing techniques automates the task of measurement and monitoring of tool wear. Also machining of hardened steel has gain lot of interest by researchers. The machining of hardened steel by advanced tool materials like ceramics, PCBN, CBN has been studied by many authors. But there is scope of machining of this hardened steel using coated carbide tools. It has also been found that researchers have mainly focused in optimization of parameters for getting good surface finish. Equally important is studying the effect of parameters on tool wear and tool life. This work is focused on implementing digital image processing techniques to automate the task of flank wear measurement and using it to optimize parameters for tool life in machining of hardened steel by coated carbide tools. The coated carbide tools were used during machining of hardened steel. Three most influential parameters: speed, feed and depth of cut were studied. The relationship between tool life and cutting parameters are established using Response Surface Method. Significant parameters were determined using Analysis of Variance (ANNOVA). It was observed that cutting speed and depth of cut are the most significant variables affecting the tool life.