Examining the Influence of Cutting Parameters on Tool Life for Tungsten and Molybdenum During CNC Lathe Turning of Mild Carbon Steel When Flank Wear is Present
Abstract
This study investigates the effects of cutting parameters on the tool life of two grades of high-speed steel tools, Tungsten (T1) and Molybdenum (T2), during the turning of mild carbon steel on a CNC lathe. Experiments were conducted on mild steel rods (200 mm length, 30 mm diameter) at three feed rates (0.1, 0.2, and 0.3 mm/rev), with a constant depth of cut (0.4 mm) using an 18-spindle rotational speed CNC lathe. Power and linear regression models were employed in MATLAB to determine and validate R² values. Analysis of variance (ANOVA) was performed to identify the best-fit model for experimental tool lives. Furthermore, chip-tool interface temperatures were modeled and compared with established literature to ensure accuracy and reliability.
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Introduction
Lathe turning operation is probably the most used of all the machining processes. About one third of the machines in production are employed in turning. In a turning operation, the work piece, held in the chuck is rotated and a cutting tool removes the work material strip by strip and then layer by layer as the latter is being turned [11].
Computer-controlled (numerically controlled, NC, CNC) lathes incorporate a computer system to control the movements of machine components by inserting coded instructions in the form of numerical data. A CNC lathe is especially useful in turning operations and precise machining
Some of the cutting conditions that influence tool life and tool wear include the cutting speed, the feed rate and the depth of cut. Much effort has been done to establish the relationship between cutting speed, tool wear and tool life [2]. The cutting speed influences the tool life such that at low cutting speeds, the tool lasts long and the tooling cost is low [3]. But the metal removal rate will be low and hence the cutting cost and the total costs are high. However, at high cutting speeds, the metal removal rate will be high resulting in low cutting cost, shortened tool life and giving high tooling cost [12]. The life of a cutting tool can be terminated by a number of means, although they fall broadly into two main categories;
a) Gradual wearing of certain regions of the face and flank of the cutting tool and
b) Abrupt tool failure.
Conclusion
Two Tungsten grades of High-speed steel tools were used to machine mild steel rods at various combinations of cutting speeds and feed rates to determine their influence on tool life. The conclusions drawn are as follows
1) The effect of feed rate and cutting speed on tool life was studied successfully. The power and linear regression models were developed for each tool. The power regression model gave the closest fit compared with the experimental tool lives. The R 2 values for the T1 grade are 0.96 for power model and 0.60 for the linear model. For T2, the R 2 values of 0.95 and 0.70 were found for power and linear model respectively. It is therefore adequate to predict the tool life with power regression model.
2) The power model gave the highest R 2 values throughout the prediction of flank wear. It is, therefore, the best to use for prediction of tool life. All the other regression models are also adequate for prediction of flank wear.