Computer Simulation of Dynamic Axial Force and Torque of Three Section Vibration Drilling

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1 Introduction

The vibration drilling process is a dynamic cutting process. During the vibration drilling process, the axial vibration and feed rate of the drill bit have dynamic characteristics such as rake angle, back angle, blade inclination angle, cutting speed, cutting thickness, shear angle, friction angle and chip angle. This produces dynamic axial forces and torques that are characteristic of the vibration drilling process.
According to the bevel cutting theory, it is assumed that the deformation process on the main cutting edge and the chisel edge of the drill bit is processed into a series of small vibration cutting units with dynamic characteristics, which can be constructed by mechanical analysis of the dynamic cutting mechanism of each unit. A predictive model of the dynamic axial force and torque of the entire drill bit.

1
Figure 1 Three-section division of the drilling process

Based on the previous research work, this paper divides the drilling process into three sections, namely drilling, drilling and drilling sections, as shown in Figure 1. The drilling section is a drilling process from when the chisel edge contacts the workpiece until the main cutting edge just enters the workpiece completely; the drilling section is the moment from the moment the workpiece is drilled from the chisel edge to the moment the main cutting edge just drills the workpiece. The cutting process; the mid-drilling section is the drilling process between the drilling and drilling sections.

2 Establishment of forecasting model

The dynamic axial force and torque prediction model of the entire drill bit is established by considering the action of the main cutting edge and the chisel edge of the drill bit in three sections.
  1. Drilling section
    2. In the mid-drilling section of the drilling process, the dynamic axial forces and torques should be considered taking into account the effects of the main cutting edge and the chisel edge, and the dynamic axial forces generated by the main cutting edge and the chisel edge in the mid-drill section. The torque is superimposed separately, that is, the dynamic axial force P and the torque M generated by the middle section of the drill, that is,
    (1)
    (2)
    Where, P l , P c ( M l , M c ) are the axial forces (torques) produced by the main cutting edge and the chisel edge, respectively, D P lj , D P ck ( D M lj , D M ck ) are The elemental axial force (torque) produced by the main cutting edge and the chisel edge, and the number of elements are N l and N c , respectively, F′ c , F′ T are the cutting force components in the normal plane of the bevel cutting, F f is The frictional component perpendicular to the normal plane, l sd , K rd , h d ( h ′ d ) are the dynamic blade inclination angle, the main declination angle and the feed angle, respectively, r j and r k are the main cutting edge and the chisel edge of the unit respectively. The radius at the midpoint.
  2. Drilling section
    The analysis of the dynamic axial force and torque of the drilling section during the drilling process is similar to that of the drill section, and the dynamic axial force and torque generated by the main cutting edge and the chisel edge in the drilling section are respectively superimposed, ie The dynamic axial force P i and the torque M i generated for drilling the section, ie
    (3)
    (4)
  3. Drilling section
    Since the chiseling section of the drilling section does not participate in the cutting, the dynamic axial force and torque of the drilling section are the dynamic axial forces P o and the torque M o produced by the main cutting edge in the drilling section. ,which is
    (5)
    (6)

1
(a) A = 5 μm, F = 200 Hz, f = 60 mm / min, m = 4

1
(b) A = 5 μm, F = 500 Hz, f = 60 mm / min, m = 3

1
(c) A = 4 μm, F = 300 Hz, f = 60 mm/min, m = 3

1
(d) A = 8 μm, F = 300 Hz, f = 60 mm / min, m = 5

1
(e) A = 6 μm, F = 300 Hz, f = 40 mm / min, m = 5

1
(f) A = 6 μm, F = 300 Hz, f = 80 mm / min, m = 3

Fig. 2 Computer simulation of dynamic axial force and torque in the section of vibratory drilling

3 Computer simulation of three-section dynamic axial force and torque

According to the three-section forecasting model established above, the C-language simulation program was developed, and the dynamic axial force of the mid-drill section during the drilling of brass (H62) for the drill with diameter D=0.5mm under several different cutting conditions The torque was computer simulated as shown in Figure 2. In the figure, ab, cd, and ef represent the effects of the vibration frequency F, the amplitude A, and the feed amount f on the axial force P and the torque M, respectively. It can be seen from the figure that the axial force and torque during vibration drilling exhibit pulse characteristics, and the drilling process is intermittent. According to the pulse energy and stress concentration theory, this is a reasonable processing method. It can also be seen from the figure that the axial force and torque during vibration drilling vary with the parameters F, A, and f. Therefore, the drilling process can be optimized by rationally selecting the machining parameters, thereby reducing the drilling force. Improve the life of the drill bit.
In addition, comparing equations (1) to (6), the dynamic characteristics of the axial force and torque of the drilling and drilling sections are compared with the dynamic characteristics of the section in the drill, only in the axial force and torque amplitude. There are differences, limited to the length, the simulation of the dynamic axial force and torque of the drilled and drilled sections is not given here.

4 Conclusion

Due to the existence of axial vibration, a series of parameters such as rake angle and blade inclination angle during vibration drilling have dynamic characteristics, which in turn produces dynamic axial force and torque unique to the vibration drilling process. Vibration drilling changes the cutting process mechanism, transforming the continuous cutting process of ordinary drilling into a pulse cutting process, thus conforming to the pulse energy and stress concentration theory, so it is a reasonable processing method.

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