The guide block structure design of boring and trepanning association

The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-018-2418-7

ORIGINAL ARTICLE

The guide block structure design of boring and trepanning association (BTA) deep hole drilling Shucai Yang 1 & Xin Tong 1 & Xuqing Ma 1 & Wei Ji 1,2 & Xianli Liu 1 & Yuhua Zhang 1 Received: 7 November 2017 / Accepted: 16 July 2018 # Springer-Verlag London Ltd., part of Springer Nature 2018

Abstract In the process of boring and trepanning association (BTA) deep hole drilling, the guide block plays the role of guiding, balancing the cutting force and extruding and polishing the machined surface. In this paper, the trapezoidal guide block and the spiral guide block are designed on the basis of ordinary guide block. With simulation and experiment, the cutting force, cutting vibration, and cutting temperature of guide blocks of different shapes during drilling process have been analyzed. When the spiral guide block deep hole drilling is compared with ordinary and trapezoidal guide blocks, it ensures effective cutting performance of BTA deep hole drilling. It also improves the quality of machined surface of the workpiece, reduces the tool wear, and forms stable chips. Keywords BTA deep hole drilling . Guide block . Structural design . Cutting performance . Workpiece surface quality

Deep hole drilling is a special case of drilling and the boring and trepanning association (BTA) deep hole drilling is a typical structure of inner chips removal deep hole drilling. The working principle of deep hole drilling is shown in Fig. 1 [1–3]. BTA drill is welded with carbide guide block, which is the main structural difference between BTA deep hole drilling tool and other deep hole machining tools. The guide block plays the role of guiding and supporting the tools, balancing the cutting force, and extruding and

* Shucai Yang [email protected] Xin Tong [email protected] Xuqing Ma [email protected] Wei Ji [email protected] Xianli Liu [email protected] Yuhua Zhang [email protected] 1

Harbin University of Science and Technology, Harbin 150080, China

2

KTH Royal Institute of Technology, 100 44 Stockholm, Sweden

polishing the machined surface during deep hole drilling process. Once the guide block is worn seriously and the phenomenon of bonding and tearing is occurred, it destroys the stability of the deep hole drilling system and affects the surface quality of the machined hole [4–6]. Since 1995, researchers have been improving the shape of the guide block. It has been found that better surface roughness can be obtained by changing the shape of the extrusion part of the guide block and thus the wear of the guide block at work can be reduced [7, 8]. It is also found that the guide block which uses the positive cone structure is easy to cause the wear of the guide block and hence reduce the tool life, while the inverted cone structure is difficult to wear and hence have no reduction in life [9–11]. Some experimental studies show that the twist deformation of the drill bit increases if the length of the guide block is too long. Some studies show that the coating of amorphous tetrahedral bonding (ta-C) on the surface of the guide block will improve the friction conditions [12–14]. There are few reports about the influence of the shape of the guide block on the drilling process. In this paper, we investigate different shapes of the guide block such as ordinary guide block, trapezoidal guide block, and the spiral guide block and provide detailed analysis of influence of these shapes on the cutting performance, quality of machined surface of the workpiece and the tool wear in the drilling process.

Int J Adv Manuf Technol

Hydraulic oil inlet

outlet

Workpiece

drill

Drill pipe

Fig. 1 Schematic diagram of BTA deep hole drilling

1 Design of guide block for BTA deep hole drilling

Fig. 2 The geometric parameters of guide block

The guide block on deep hole drilling is very important for the quality of deep hole drilling and its design must follow certain principles. First of all, make sure that the resultant force of the tool can play the supporting role effectively. Secondly, the force on per unit area of the guide block is as small as possible and the numerical value must be same to ensure the uniform wear. Finally, make sure the stability of the drilling process, so that the drill bit beating is reduced as much as possible [15, 16]. The geometric parameters of the guide block are shown in Fig. 2, where L is the length, l is the radian, h is the thickness, r is outer cambered surface radius of the guide block, and η is the amount of inverted cone.

to the hole wall. As shown in Fig. 4, the friction force of the guide block 1 is Ff1, the friction force of the guide block 2 is Ff2,the positive pressure of the guide block 1 is P1, the positive pressure of the guide block 2 is P2, and the F represents the component of cutting force of the cutter edge on the XOY plane. Fx and Fy are the components of F. The angle between F and positive x axis is λ and θ1 and θ2 are position angles of guide blocks 1 and 2 respectively. In case of hydrodynamic lubrication, since the two surfaces are completely separated by the fluid medium, therefore the value of friction Ff is independent of the positive pressure and it depends only on the value of the internal friction of the fluid. According to the Newton viscous resistance relationship:

1.1 Theoretical analysis

F f ¼ ηvAα =h

By considering the influence of the hydraulic oil between the guide block and the hole wall and according to the fluid friction theory, this paper designs the wedge-shaped guide block [17–18], as shown in Fig. 3. The outer cambered surface of radius r of the guide block is smaller than the machined surface of radius R of inner bore of the workpiece. In the cutting process, a wedge gap is formed between the outer surface of the guide block and the hole wall. This gap is filled with hydraulic oil which is adsorbed on the surface of the guide block and the hole wall. The relative motion between the guide block and the hole wall drives the hydraulic oil to move from the big end of the gap to the small end of the gap; therefore, the hydrodynamic lubrication oil film is formed. In Fig. 3, r is the outer cambered surface radius of the guide block, R is the machined surface radius of the inner bore of the workpiece, U is the rotary speed of deep hole drilling, and P is the dynamic pressure of the guide block.

In Eq. (1), η is a constant related to viscosity coefficients, ν is the relative motion or velocity, h is the thickness of oil film, and Aα is the area of friction surface.

ð1Þ

The hole wall R

U

the guide block

(a) The hydraulic oil flow schematic diagram between the guide block and the hole wall

P

U

1.2 Force analysis of guide block The acting force on the guide block includes the extrusion force between the guide block and the hole wall and the friction force generated by the rotation of the guide block relative

U

(b)

the guide block

The fluid dynamic pressure distribution diagram of the guide block

Fig. 3 The hydrodynamic lubrication oil film forming principle of the guide block. a The hydraulic oil flow schematic diagram between the guide block and the hole wall. b The fluid dynamic pressure distribution diagram of the guide block

Int J Adv Manuf Technol

P1

The guide block

Y

θ2 Ff 1

F

Fy

θ1 λ

Fx

X MB

The guide block 2

P2

(a) ordinary Ff 2

Fig. 4 The force analysis of the guide block

1.3 Design the shape of guide block According to the above discussion and related literatures, design the outer cambered surface radius of the guide block r = 0.99 R. Deep hole drilling is a particular case of drilling processes for machining holes with length-to-diameter ratio great than 5. So the chip is difficult to be removed from narrow space inside of BTA drill. The trapezoidal and spiral guide block has been designed for this question as shown in Fig. 5. The dimensions of the trapezoidal guide block are l1 = 0.9 l and l2 = 1.1 l. The dimensions of the spiral guide block are l3 = 0.2 l and l4 = 0.8 l; b is the halfway point of the spiral line, two points O and a on the same horizontal line, radius r1 is determined by O, a, and b, and the other sizes are the same as the ordinary guide block.

(b) Trapezoidal

(c) Spiral

Fig. 6 The model of BTA deep hole drilling. a Ordinary. b Trapezoidal. c Spiral

UG software. The parameters of the ordinary guide block are l = 3.2 mm, L = 7.8 mm, r = 8.1 mm, and h = 1.8 mm as shown in Fig. 6.

2.2 BTA drilling simulation based on deform-3D We use Deform-3D software to conduct drilling simulation. In simulations, we set the workpiece material to be 34MnR, the cutter material to be 42CrNiMo and the guide block material is to be YG8 cemented carbide. We set the cutting parameters to be n = 1500 r/min, f = 0.1 mm/r, and ap = 0.5 mm.

2.3 Simulation results and analysis 2.3.1 Cutting force and torque amplitude

2 Mechanical characteristics analysis of BTA deep hole drilling 2.1 Development of finite element model for BTA deep hole drilling In this paper, three kinds of BTA deep hole drilling 3D models with different guide block structures are established by using

The cutting force and the torque amplitudes of different shape guide blocks are shown in Figs. 7 and 8. In these figures, we show that the force in x, y, and z directions and the torque amplitude of ordinary guide block deep hole drilling are maximum, while the force in x, y, and z directions and the torque amplitude of spiral guide block deep hole drilling are minimum.

Fig. 5 The shape sketch diagram of the guide block. a Ordinary guide block. b Trapezoidal guide block. c Spiral guide block

(a) Ordinary guide block

(b) Trapezoidal guide block

(c) Spiral guide block

Int J Adv Manuf Technol

Ordinary Trapezoidal Spiral

Analysis step Fig. 9 Cutting temperature distribution of deep hole drilling Fig. 7 The cutting force amplitudes of different shape guide blocks

2.3.2 Cutting temperature distribution

3 BTA deep hole drilling test

In Fig. 9, we show the temperature field distribution of external edges of three kinds of deep hole drills against analysis step. The tool nose temperatures are 952 °C, 899 °C, and 708 °C of the ordinary guide block deep hole drilling, the trapezoidal guide block deep hole drilling, and the spiral guide block deep hole drilling respectively. The trapezoidal guide block and the spiral guide block can effectively reduce the drilling temperature. The drilling temperature of the trapezoidal guide block is 10% smaller than the drilling temperature of the ordinary guide block, while the drilling temperature of the spiral guide block is 25% smaller than the drilling temperature of the ordinary guide block. The results show that the trapezoidal guide block and the spiral guide block can effectively reduce the cutting force, the torque and the drilling temperature in the drilling process. We find the spiral guide block with the best characteristics among them.

3.1 Preparation of BTA deep hole drilling First of all, the trapezoidal guide block and the spiral guide block are prepared. The prepared guide block is welded on the cutter body with high frequency welding equipment. Then, we conduct the sand blasting and remove excess solder. The preparation process of cutting tool which is used in this experiment is shown in Fig. 10.

3.2 Drilling experiment arrangement We use Z3040 × 16/1 radial drilling machine for drilling experiments with the ordinary guide block, the trapezoidal guide block, and the spiral guide block [19]. The size of the rectangular workpiece is 150 mm × 150 mm × 80 mm. We set up the test platform as shown in Fig. 11. The selection of materials and cutting parameters are according to the simulation parameters.

3.3 Experimental results and analysis 3.3.1 Measurement and analysis of cutting force and cutting vibration

Fig. 8 The torque amplitudes of different shape guide blocks

The experimental results for the cutting force and the acceleration during drilling process are shown in Figs. 12 and 13. We can see that the amplitude of the force in x, y, and z directions of the ordinary guide block deep hole drilling is maximum, while the amplitude of the force in x, y, and z directions of the spiral guide block deep hole drilling is minimum. The resultant force amplitude of the ordinary guide block deep hole drilling is about 1200 N and its vibration acceleration is 65 m/s2. The resultant force amplitude of the trapezoidal guide

Int J Adv Manuf Technol Fig. 10 The preparation process of BTA deep hole drilling. a Guide block preparation. b Deep hole drilling after welding. c Deep hole drilling after grinding outer edge. d Deep hole drilling after sand blasting

(a) Guide block preparation (b) Deep hole drilling after welding

(c) Deep hole drilling after grinding outer edge

(d) Deep hole drilling after sand blasting

Fig. 11 The experiment platform Charge amplifier Spindle BTA deep hole drilling Dynam ic signal acquisition and analysis system Workpiece Dynamometer Calculator

block deep hole drilling is about 1000 N and its vibration acceleration is 53 m/s2. The resultant force amplitude of the spiral guide block deep hole drilling is about 750 N and its vibration acceleration is 46 m/s2. We can see that the cutting force of the trapezoidal guide block is 16% smaller than the cutting force of the ordinary guide block and its vibration acceleration is 18% smaller

than the vibration acceleration of the ordinary guide block. The cutting force of the spiral guide block is 37% smaller than the cutting force of the ordinary guide block and its vibration acceleration is 30% smaller than the vibration acceleration of the ordinary guide block. Therefore, the spiral guided block deep hole drilling has the highest stability.

Fig. 12 Cutting force for different shapes of guide block

Fig. 13 Acceleration for different shapes of guide block

Int J Adv Manuf Technol Table 1

Roughness value of cutter surface

The shape of the guide block

Ordinary shape

Trapezoidal shape

Spiral shape

The surface roughness Ra (μm)

9.85

8.14

8.08

3.3.2 Measurement and analysis of surface roughness We use the wire cutting machine to cut the machined material along the center. We measure the hole surface roughness with the CCI MP-HS high speed white optical interferometer and the roughness value is shown in Table 1. It can be seen from Table 1 that the surface roughness value of the inner hole wall is minimum for the spiral guide block. It

(a) Center edge

a) Chips of the ordinary guide block deep hole drilling

(b) Middle edge

b) Chips of the trapezoidal guide block deep hole drilling

(c) External edge c) Chips of the spiral guide block deep hole drilling Fig. 14 Comparison of chip morphology. a Chips of the ordinary guide block deep hole drilling. b Chips of the trapezoidal guide block deep hole drilling. c Chips of the spiral guide block deep hole drilling

Fig. 15 The wear of each cutter edge of the deep hole drilling. a Center edge. b Middle edge. c External edge

is mainly due to the smooth drilling, the change of relative position of the cutter edge, and the smaller size of the workpiece.

Int J Adv Manuf Technol Table 2

The wear value of each cutter edge of the deep hole drilling

The wear value of cutter edge (mm)

The shape of the guide block Ordinary guide block

Trapezoidal guide block

Spiral guide block

Center edge

0.19

0.14

0.098

Middle edge

0.21

0.16

0.15

External edge

0.24

0.22

0.19

3.3.3 Repeatability of chip shape If the drilling operation is smooth, then the repeatability of the chip shape should be higher. By comparing the collected chips, it is found that the chip shape of the spiral guide block is same and there are no large chips and debris. The repeatability of chips of the trapezoidal guide block deep hole drilling is worse than that of the spiral guide block deep hole drilling and there is a small amount of large chips. There are large chips and debris in the chips of ordinary guide block deep hole drilling. The experimental results are shown in Fig. 14.

The experimental results show that the spiral guide block deep hole drilling has the most remarkable effect on reducing the cutting force and vibration acceleration in drilling process. After machining, the surface roughness of the inner hole is the smallest and the repeatability of the chip shape is the highest. Therefore, the spiral guide block can improve the stability of drilling system. Funding information This work was supported by the National Science and Technology Major Project (2013ZX04009-021). Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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3.3.4 Measurement and analysis of tool wear Since the wear of BTA deep hole drilling rake face is more severe than its flank face, therefore this paper mainly addresses the wear of the rake face. We use super depth microscope to observe the wear of each cutter edge as shown in Fig. 15. The external edge wear is the most serious, then the middle edge wear, and then the central edge wear. We show the wear value of each cutter edge of the different guide block deep hole drilling in Table 2. The analysis shows that the wear value of each cutter edge of the spiral guide block and trapezoidal guide block deep hole drilling is smaller than that of the ordinary guide block deep hole drilling. And the wear value of each cutter edge of the spiral guide block deep hole drilling is minimum.

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4 Conclusions By considering the influence of the hydraulic oil on the force of the guide block, the interaction relationship between the outer diameter r of the guide block and the hole wall is studied to design the spiral guide block and the trapezoidal guide block. The finite element simulations show that the spiral and trapezoidal shape guide block have smaller cutting force, torque, and cutting temperature, and the effect of spiral guide block is the most significant.

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