Abstract
This article focuses on the development of a mathematical model of a cutting force that is applicable for coated and uncoated cutting tool inserts and aims to enable more accurate calculation of the cutting force. Two common PVD coatings, AlTiN and TiAlCrN, were used. Firstly, a mathematical model of the cutting force based on the specific cutting force and cutting area is proposed. This mathematical model considers the cutting speed and coating correction factor as well as the real cutting edge geometry, i.e., it includes both the straight and rounded parts of the cutting edge. For this proposed model, material constants for C45 steel, which was machined with uncoated inserts, were obtained. Before determining an equation for a coating correction factor and implementing it into the model, experimental cutting force data for coated and uncoated inserts were compared using a paired t-test. The result was that the difference between them was statistically significant. Their percentage difference was found to be up to 4%. The correction factor equation that was obtained and implemented into the mathematical model was applied to compare the calculated and experimental data of the coated inserts, also using a paired t-test. The result was that the difference between them was insignificant. Moreover, their percentage difference was found to be up to 0.6%.
Highlights
A coating provides a physical barrier between a cutting tool and the workpiece material, which protects the cutting tool against heat, abrasion, adhesion and the chemical effects of the close environment [1]
This study proposed a mathematical cutting force model that is applicable for cutting workpiece materials made of C45 steel and for coated and uncoated cutting tool inserts to enable more accurate calculation of the cutting force
In the comparison of the experimental cutting force data for the uncoated and coated inserts, there was a statistically significant difference resulting from the paired t-test p-values, which were below the confidence level (α = 0.05); see Table 9
Summary
A coating provides a physical barrier between a cutting tool and the workpiece material, which protects the cutting tool against heat, abrasion, adhesion and the chemical effects of the close environment [1]. Sivam measured the non-zero effect of coatings on the forces, tool wear and quality of machined surfaces during titanium alloy machining through grey relational analysis [3]. Jindal investigated various coatings made through physical vapour deposition (PVD) [5] He focused on the turning of an Inconel 718 sample and proved that the cutting tool composition had a significant influence on cutting tool wear. Wang researched the difference in cutting force when turning an AISI S1020 steel bar using uncoated and CVD-coated inserts [8]. Kulkarni investigated this issue when turning an AISI 314 steel bar In this case, the coating change caused a difference in the cutting force in the range of approximately 30–100 N depending on the cutting velocity for PVD coatings. Instability can be observed by force measurement and needs to be avoided during machining for comparison of different coatings in terms of the forces [11]
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