The Effect of Cutting Speed on the Ploughing Forces

The ploughing forces (PFs) are one of the important parameters for calculating the tool life. They directly affect the stress on the tool ank face and are responsible for wear and tear conditions of the cutting tool as well. In this study we attempted to nd the impact of cutting speed on PFs, that is, the relation between cutting speed and PFs. In this paper, the ploughing forces were estimated by a new comparison method in which forces at different point of contact areas are added (sum of forces) to get the PFs accurately. The accuracy of PFs estimated with this method will be better than previously used methods. This paper presents the measurement results of the PFs when turning stainless steel, structural steel and aluminum alloy materials. The results of experimental studies showed that an increase in cutting speed ranging from 50 to 200 m/min resulted in increase in PFs by 1.4–3.2 times when turning with different ank wears.


Introduction
Currently, numerous wear models that relate stresses and temperature at the tool ank face to the wear rate are used to calculate the tool life in various technological operations. Several studies focused on the tool wear mechanisms use ank face stress and temperature to predict the tool life in diamond turning [1], to model fretting wear in partial slip regime [2] or to study the computational modelling of 3D turning process [3].
The ploughing forces (PFs) directly affect the stress on the tool ank face and thereby determine the wear and tear conditions of the cutting tool. Because of this reason, wear models created for calculating the tool life cannot be used without determining the PFs [4][5][6][7].
An analysis of the scienti c literature has revealed the lack of information about the PFs dependence on cutting speed, an important parameter of cutting conditions, which signi cantly in uence the tool life.
Moreover, there is no information about this PFs dependence on cutting speed even in the new "comparison method of total forces at different contact areas" (Popov-Dugin's method) [8,9]. But PFs estimated using this method increased the accuracy by 23%-84% compared with the previously used "comparison method of total forces at different ank wears" (Zorev's method) [10].
This study is aimed at solving this important and practical problem, by determining the effect of cutting speed, Vc, on the PFs using the Popov-Dugin's method.

Experimental Procedure
The turning process was conducted on a lathe TOS SU 50/1500. The workpieces with a diameter of 70 mm and thickness of 5 mm from three different materials were used, namely stainless steel 1.4571, structural steel 1.0301, and aluminum alloy AlMgSi. The cutting plate TPUN 160308 of hard alloy ISO P30 was xed in the PRAMET TOOLS cutter CTCPN 2514 M16. The cutting tool had the front angle of γ = Page 3/14 5° and the ank angle of α = 6°. The turning experiments have been performed with the cutting speed V c ranged from 50 to 200 m/min, and with the uncut chip thickness a p of 0.05 mm for all experiments.
Measuring the rounding radius of the new cutting insert with the KEYENCE Laser Scanning Confocal Microscope has revealed that the new insert has a radius of 0.03 mm. The ank wear VB was produced arti cially by grinding against a diamond grinding wheel in an EBN-2C machine. VB was measured by the KEYENCE Laser Scanning Confocal Microscope with a measuring accuracy of approximately 1 µm.
PFs were measured by a three-component piezo-electric KISTLER dynamometer, model 9265B-9441B using the Popov-Dugin's method described in previous studies [11][12][13][14]. The expansion scheme of the total active force F a , which was used to determine the cutting forces (CFs), is shown in Figure 1   shows that, when processing structural steel, an increase in the V c from 50 to 200 m/min has led to an increase in the F pl,c by 2.4 times, but at the same time the F ch,c is reduced by 16%, and the F c is reduced by 11%.
When processing structural steel, an increase in the V c from 50 to 200 m/min has resulted in an increase in the F pl,f by 2.7 times, but at the same time a decrease by 30% in the F ch,f and by 20% in the F f [ Figure   3(b)] is observed.
When processing structural steel, an increase in the V c from 50 to 200 m/min has resulted in an increase in the F pl by 2.6 times, but at the same time a decrease by 20% in the F ch and by the 13% in the F a [ Figure   3(c)] is observed.
Notably, Figure 3    It is a well-known fact that F a decreases as V c increases in the process of cutting with different materials and is re ected in a large number of studies [11][12][13][14][15]. At the same time, an increase in PFs with an increase in V c was established for the rst time.

Measurement results of the effect of V c on the PFs when turning different materials using a cutting insert with different VB
The measurement results of the effect of V c on the PFs when turning stainless steel, structural steel, and aluminum alloy using a cutting insert with different VB are shown in Figures 5-7. Figure 5(a) shows that, when processing stainless steel, an increase in the V c from 50 to 200 m/min has led to an increase in F pl,c by 2.4 times when turning using a cutting insert with VB = 0.03 mm, by 1.8 times when using a cutting insert with VB = 0.1 mm and by 2.6 times when using a cutting insert with VB = 0.2 mm.
When processing stainless steel, an increase in the V c from 50 to 200 m/min has led to an increase in F pl,f by 1.6 times when turning using a cutting insert with VB = 0.03 mm, by 1.7 times when using a cutting insert with VB = 0.1 mm and by 2 times when using a cutting insert with VB = 0.2 mm [ Figure 5(b)].
When processing stainless steel, an increase in the V c from 50 to 200 m/min has led to an increase in F pl by 1.9 times when turning using a cutting insert with VB = 0.03 mm, by 1.8 times when using a cutting insert with VB = 0.1 mm and by 2.     It was established for the rst time that an increase in cutting speed leads to an increase in PFs -when turning with VB from 0.03 mm to 0.2 mm and with an increase in cutting speed ranging from 50 to 200 m/min, an increase in. In the operations performed in this article, it is observed PFs were increased (1) 2.1-3.2 times when turning structural steel, (2) 1.9-2.2 times when turning stainless steel, and (3) 1.4-1.5 times when turning aluminum alloy.
Such an increase in PFs in the studied range does not contradict the well-known fact of a decrease in the active force F a decreases with an increase in cutting speed in the studied range. This phenomenon is explained by the fact that with an increase in the cutting speed, the forces on the front surface, which signi cantly exceed the forces on the rear surface, and decrease simultaneously. The decrease in CFs on the front surface in absolute value exceeds the increase in forces on the rear surface, which ultimately leads to a decrease in the active force F a.

Declarations
Funding Not applicable  The scheme of the active force Fa, expanded into the chip-forming force FCh and PF FPl and into the components in feed and cutting directions