ArticlePDF Available

Experimental Assessment of Hole Quality and Tool Condition in the Machining of an Aerospace Alloy

MDPI
Machines
Authors:
Muhammad Aamir at Edith Cowan University
Muhammad Aamir
Aamer Sharif at Edith Cowan University, Perth, Australia
Aamer Sharif
  • Edith Cowan University, Perth, Australia
Muhammad Zeeshan Zahir at University of Engineering and Technology, Peshawar
Muhammad Zeeshan Zahir
Khaled Giasin at University of Portsmouth
Khaled Giasin
Show all 5 authorsHide
Download full-text PDF
Read full-text
Download citation

Abstract and Figures

This paper deals with an experimental investigation of hole quality in Al2024-T3, which is one of the aerospace alloys used in aircraft fuselage skin due to its high level of resistance to fatigue crack propagation. The experiments are conducted with 6 mm uncoated carbide and HSS drill bits using a CNC machine under dry conditions and different drilling parameters. The characteristics of the hole quality are investigated in terms of its perpendicularity, cylindricity, circularity and hole size. An ANOVA (analysis of variance) and Pareto charts are used to analyze the effects of the drilling parameters on the hole quality. The hole quality is also assessed using a digital microscope to observe the formation of hole burrs. Moreover, scanning electron microscopy is also used to investigate the inside-hole surface defects. Further investigations are carried out using optical microscopy to inspect the post-drilling tool condition at high drilling parameters. The results show that hole quality reduces as the feed rate and spindle speed increase. However, from the ANOVA results and Pareto charts, the influence of the feed rate on the hole quality is found to be insignificant. At the same time, the type of drill bit material shows the highest percentage of contribution affecting the hole quality, following the spindle speed. The HSS drill bit shows more adhesion and built-up edges than the uncoated carbide drill bit. There were more burrs formed at the hole edges when the holes were drilled with uncoated HSS drill bits. In the same way, the SEM analysis reveals more surface deformation and damage defects inside the hole walls of holes drilled using the uncoated HSS drill bit.
Figures - available from: Machines
This content is subject to copyright.
Access to this full-text is provided by MDPI.
Content available from Machines 
This content is subject to copyright.
Citation: Aamir, M.; Sharif, A.; Zahir,
M.Z.; Giasin, K.; Tolouei-Rad, M.
Experimental Assessment of Hole
Quality and Tool Condition in the
Machining of an Aerospace Alloy.
Machines 2023,11, 726. https://
doi.org/10.3390/machines11070726
Academic Editors: Alessandro Greco,
Donato Perfetto and Mario Caterino
Received: 10 June 2023
Revised: 5 July 2023
Accepted: 7 July 2023
Published: 9 July 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
machines
Article
Experimental Assessment of Hole Quality and Tool Condition
in the Machining of an Aerospace Alloy
Muhammad Aamir 1, * , Aamer Sharif 2, Muhammad Zeeshan Zahir 3, Khaled Giasin 4
and Majid Tolouei-Rad 1
1School of Engineering, Edith Cowan University, Joondalup, WA 6027, Australia; m.rad@ecu.edu.au
2Department of Mechanical Engineering, CECOS University of Information Technology and Emerging
Sciences, Peshawar 25000, Pakistan; aamer@cecos.edu.pk
3
Department of Mechanical Engineering, University of Engineering and Technology, Peshawar 25000, Pakistan;
zeeshan.zahir@uetpeshawar.edu.pk
4School of Mechanical and Design Engineering, University of Portsmouth, Portsmouth PO1 3DJ, UK;
khaled.giasin@port.ac.uk
*Correspondence: m.aamir@ecu.edu.au
Abstract:
This paper deals with an experimental investigation of hole quality in Al2024-T3, which is
one of the aerospace alloys used in aircraft fuselage skin due to its high level of resistance to fatigue
crack propagation. The experiments are conducted with 6 mm uncoated carbide and HSS drill bits
using a CNC machine under dry conditions and different drilling parameters. The characteristics of
the hole quality are investigated in terms of its perpendicularity, cylindricity, circularity and hole size.
An ANOVA (analysis of variance) and Pareto charts are used to analyze the effects of the drilling
parameters on the hole quality. The hole quality is also assessed using a digital microscope to observe
the formation of hole burrs. Moreover, scanning electron microscopy is also used to investigate the
inside-hole surface defects. Further investigations are carried out using optical microscopy to inspect
the post-drilling tool condition at high drilling parameters. The results show that hole quality reduces
as the feed rate and spindle speed increase. However, from the ANOVA results and Pareto charts, the
influence of the feed rate on the hole quality is found to be insignificant. At the same time, the type of
drill bit material shows the highest percentage of contribution affecting the hole quality, following
the spindle speed. The HSS drill bit shows more adhesion and built-up edges than the uncoated
carbide drill bit. There were more burrs formed at the hole edges when the holes were drilled with
uncoated HSS drill bits. In the same way, the SEM analysis reveals more surface deformation and
damage defects inside the hole walls of holes drilled using the uncoated HSS drill bit.
Keywords: drilling; Al2024-T3; hole quality; ANOVA; tool condition
1. Introduction
There is no doubt about how important it is to perform drilling operations in vari-
ous industries to make a profit and survive in today’s very competitive market because
most industrial products in our daily lives incorporate holes generated via drilling oper-
ations. Figure 1shows the importance of drilling in all machining processes in various
industries [
1
]. However, the drilling process becomes challenging when many holes are
required, like in the aerospace industry [
2
]. For instance, in aircraft bodies, about 80%
of fatigue cracks are because of poor connecting holes, and 50–90% of fractures in aging
planes are due to fatigue fractures of fastener holes [
3
]. Hence, to ensure high-precision
structural integrity in aerospace alloys, the quality of holes drilled in aluminum is signif-
icantly important [
4
,
5
]. Furthermore, the major problems in the drilling process include
high cutting forces, low hole quality, tool wear, etc., which require selecting the appropriate
tool, increasing the cost for the manufacturing sectors [
6
,
7
]. The built-up edge is also
one of the problems associated with dry drilling that ultimately affects the tool and thus
Machines 2023,11, 726. https://doi.org/10.3390/machines11070726 https://www.mdpi.com/journal/machines
Machines 2023,11, 726 2 of 14
reduces the hole quality; however, drilling in dry conditions is environmentally friendly
as it reduces the environmental effect of coolants [
8
,
9
]. Hence, to achieve a long tool life
and high dimensional accuracy, drilling performance is therefore dependent on a variety of
variables, including tool geometry, tool materials, drilling parameters such as the spindle
speed (n) and feed rate (f), the type of drilling machine, and the absence or presence of
coolants [
10
,
11
]. Therefore, researchers are interested in optimizing/investigating these
important drilling parameters to maximize productivity.
Machines 2023, 11, x FOR PEER REVIEW 2 of 16
problems associated with dry drilling that ultimately affects the tool and thus reduces the
hole quality; however, drilling in dry conditions is environmentally friendly as it reduces
the environmental effect of coolants [8,9]. Hence, to achieve a long tool life and high di-
mensional accuracy, drilling performance is therefore dependent on a variety of variables,
including tool geometry, tool materials, drilling parameters such as the spindle speed (n)
and feed rate (f), the type of drilling machine, and the absence or presence of coolants
[10,11]. Therefore, researchers are interested in optimizing/investigating these important
drilling parameters to maximize productivity.
Figure 1. Machining processes.
Previously, Dahnel et al. [12] performed drilling experiments on the tool wear on
Al7075 using tungsten carbide tools with n values of 4000, 6000, and 8000 rpm and f values
from 0.01 to 0.10 mm/rev. It was concluded in their study that a lower spindle speed could
reduce heat generation; hence, the lower cuing speed was recommended for dry drilling
Al7075. Islam and Boswell [13] used high-speed steel (HSS) tools to determine the effect
of drilling parameters and cooling methods on the quality of holes drilled in Al6061. The
investigation was carried out by measuring the surface roughness, diameter error, and
circularity. The cooling methods included cryogenic drilling, flood drilling, and mini-
mum-quality lubrication (MQL). The study concluded that diameter error was highly af-
fected by the cooling method, followed by the surface roughness and circularity. MQL
drilling produced good surface roughness and dimensional accuracy. In contrast, the cir-
cularity was best achieved using cryogenic drilling. Khunt et al. [14] assessed the drilling
performance of AA6063. The experiments were performed using HSS drill bits. Different
cuing environments, including flood, MQL-sunflower, dry, flood cooling, and MQL-cas-
tor oil, were selected to measure torque, surface roughness, and axial thrust. The results
concluded that surface roughness was improved with vegetable MQL, while the torque
and axial thrust were reduced. Luo et al. [15] established a finite element model using
different spindle and feed speeds to drill Al7075-T6. They concluded that an increase in
the feed speed resulted in high axial force and torque. Similarly, the thickness of the uncut
chips also increased. Furthermore, the numerical simulation showed a higher tool tem-
perature field at the main cuing edge than at the cross edge. Pramanik et al. [16] worked
on drilling Al6061-T6 in three different conditions, including liquid nitrogen (LN2), com-
pressed air and MQL, to identify their impact on chip formation, the quality of holes, ac-
tive peak power, and surface roughness. The study concluded that cooling techniques had
a negligible impact on active power consumption. Additionally, the coolant’s impact on
Figure 1. Machining processes.
Previously, Dahnel et al. [
12
] performed drilling experiments on the tool wear on
Al7075 using tungsten carbide tools with nvalues of 4000, 6000, and 8000 rpm and fvalues
from 0.01 to 0.10 mm/rev. It was concluded in their study that a lower spindle speed
could reduce heat generation; hence, the lower cutting speed was recommended for dry
drilling Al7075. Islam and Boswell [
13
] used high-speed steel (HSS) tools to determine
the effect of drilling parameters and cooling methods on the quality of holes drilled in
Al6061. The investigation was carried out by measuring the surface roughness, diameter
error, and circularity. The cooling methods included cryogenic drilling, flood drilling,
and minimum-quality lubrication (MQL). The study concluded that diameter error was
highly affected by the cooling method, followed by the surface roughness and circularity.
MQL drilling produced good surface roughness and dimensional accuracy. In contrast,
the circularity was best achieved using cryogenic drilling. Khunt et al. [
14
] assessed the
drilling performance of AA6063. The experiments were performed using HSS drill bits.
Different cutting environments, including flood, MQL-sunflower, dry, flood cooling, and
MQL-castor oil, were selected to measure torque, surface roughness, and axial thrust. The
results concluded that surface roughness was improved with vegetable MQL, while the
torque and axial thrust were reduced. Luo et al. [
15
] established a finite element model
Machines 2023,11, 726 3 of 14
using different spindle and feed speeds to drill Al7075-T6. They concluded that an increase
in the feed speed resulted in high axial force and torque. Similarly, the thickness of the
uncut chips also increased. Furthermore, the numerical simulation showed a higher tool
temperature field at the main cutting edge than at the cross edge. Pramanik et al. [
16
]
worked on drilling Al6061-T6 in three different conditions, including liquid nitrogen (LN2),
compressed air and MQL, to identify their impact on chip formation, the quality of holes,
active peak power, and surface roughness. The study concluded that cooling techniques
had a negligible impact on active power consumption. Additionally, the coolant’s impact
on the chip thickness ratio and surface roughness was unclear. However, the surface
roughness increased as the speeds and feeds increased, while the chip thickness ratio
increased with speed and decreased with the feed. In a study by Banerjee et al. [
17
], 102
◦
and 115
◦
point angles were recommended for the minimum burr height and thickness
when drilling aluminum using high-speed steel (HSS) drill bits. Regarding the previous
studies on Al2024, the selection of various drilling parameters is provided in Table 1.
Table 1. Previous studies on drilling Al2024.
Material Spindle Speed/
Cutting Speed Feed Rate Drill Bits Areas Studied Ref.
Al2024 1000, 2000, and
3000 (rpm)
0.04, 0.08, and
0.14 (mm/rev)
Uncoated carbide,
6 mm and 10 mm
Thrust force, surface roughness,
burrs, hole surface damage analysis,
chips formation, and tool condition
[18]
AA2024 60, 120, and
180 (m/min)
0.05, 0.15, and
0.25 (mm/rev)
HSS twist drill
with cobalt, 6 mm
Surface roughness, thrust force, hole
diameter, and exit burr height [19]
Al2024 1000, 3000, 6000, and
9000 (rpm)
100, 300, 600,
900 (mm/min)
TiAlN-coated
carbide twist drill
Chip formation, surface roughness,
hole size, burrs, and circularity error [20]
Al2024 28 and 94 (m/min) 0.04 (mm/rev) HSS and HSS-Co Thrust force, torque, and
surface finish [21]
Al 2024 30, 45, and 60 (m/min) 0.15, 0.20, and
0.25 (mm/rev)
Uncoated HSS, TiN
and TiAlN-coated Surface finish and hole diameter [22]
Hence, studies in the literature are limited to other drilling process parameters, cool-
ing techniques, or materials. There is also a lack of studies investigating the significant
characteristics of hole quality. Therefore, this study evaluates important hole characteristics,
including circularity, hole size, perpendicularity, and cylindricity. The analysis was carried
out using different types of drill bit materials, spindle speeds, and feed rates. The results
were then evaluated using Pareto charts and an analysis of variance (ANOVA). The study
also included further experiments to examine the post-drilling tool conditions at high
drilling parameters and the burrs around the hole edges using optical microscopy. A fur-
ther examination of the quality of holes was performed using scanning electron microscopy
to investigate any defects inside the drilled hole surfaces.
2. Materials and Methods
Al2024-T3 and a CNC machine were used for drilling experiments. CNC machines are
high-volume production machines used for achieving high levels of productivity without
compromising quality. Uncoated HSS and uncoated carbide drill bits with a size of 6 mm
were mounted on the CNC machine to drill holes in the Al2024-T3. The drilling experiments
were repeated three times, and each time, a new drill bit was used for the accuracy of
the results. Hence, a total of 27 holes were drilled under dry conditions. The workpiece
material, drilling parameters, and experimental details are provided in Table 2.
Machines 2023,11, 726 4 of 14
Table 2. Experimental details.
Material Details
Material Al2024-T3
Dimension 150 ×200 mm2
Thickness 10 mm
Chemical composition Mg Cr Si Z Cu Mn Fe Ti Al
1.5 0.1 0.5 0.25 4.5 0.6 0.5 0.15
Balance
Ultimate tensile strength 445 MPa
Drilling parameters
Feed rate (mm/rev) 0.04, 0.08, 0.14
Spindle speed (rpm) 1500, 2500, 3500
Drilling condition Dry
Drill bit details
Type Twist drill
Material HSS, carbide
Coating None
Drill diameter 6 mm
Shank diameter 6 mm
Helix angle 30◦
Number of flutes 2 mm
Machines used
Machine tool CNC
Hole size, circularity, cylindricity,
and perpendicularity Coordinate measuring machine (Taichung, Taiwan)
Burrs USB digital microscope
Hole surface defects Scanning electron microscopy (Hitachi SU5000 Chiyoda, Japan)
Tool condition Optical microscope (LEICA M80)
The HSS and carbide drills are the most frequently used drill bits in industries, based
on the application. A likely explanation for selecting HSS drill bits is that they are less
expensive, commonly used, robust, and durable. They are also tough and heat-resistant.
In contrast, carbide drills are extremely hard, with a greater heat dissipation rate, and
are considered the toughest compared to other drill bits [
23
]. In addition, the 6 mm
size is a commonly used tool size range for aerospace alloys. At the same time, a high
helix angle was previously suggested to achieve high-quality holes during the drilling of
Al20254-T3 [
24
]. Furthermore, according to the machinery handbook [
25
], the feed rate
should be 0.05–0.15 mm/rev when a twist drill with a size of 3.175–6.35 mm is used. Finally,
Al2024-T3 was selected because it is a highly used aluminum alloy in the aerospace industry,
where millions of holes are required. Hence, the drilling process and geometric tolerances
are of great interest [26].
A coordinate measuring machine (CMM) was used to measure perpendicularity,
circularity, cylindricity, and hole size to investigate hole quality. It is worth noting that
CMMs are mostly used in the automotive, aerospace and defense industries to measure
geometric features of parts [
27
]. Afterwards, at a confidence interval of 95%, the impacts of
the drilling parameters on the hole quality characteristics were evaluated using an ANOVA.
The study also included additional experiments to examine the post-drilling tool
conditions for each drill bit at high spindle speed of 3500 rpm and feed rate of 0.14 mm/rev.
The investigation was carried out using optical microscopy after 9, 27, and 45 holes, and a
comparison was made between the built-up edges generated on each drill bit. Afterwards,
scanning electron microscopy (SEM) was used to examine the holes. The study also
included the examination of the burrs around the holes using a digital microscope. Further
Machines 2023,11, 726 5 of 14
examinations of the top and bottom hole edges and the inside surface defects of the holes
were performed via SEM.
3. Experimental Results and Analysis of Variance
3.1. Hole Deviation and Circularity
Figures 2and 3show the average hole size and circularity using the uncoated HSS
and uncoated carbide drill bits with different spindle speeds and feed rates. In general,
the results show that hole deviation and circularity increase as the spindle speed and feed
rate increase. At the same time, the uncoated carbide drills produced holes with lesser
deviations from the hole’s nominal size and fewer errors in circularity. The hole deviation
from the nominal size (6 mm) for the uncoated HSS drill bit ranged from 6.0581 mm to
6.0753 mm, while for the uncoated carbide drill bits, the minimum value obtained was
6.0086 mm, while the maximum was 6.0281 mm. Similarly, the circularity ranged from
0.0261 to 0.0541 mm for the uncoated HSS drill bits. In contrast, it ranged from 0.0193 to
0.0284 mm when the carbide drill bits were used. In the current study, the ANOVA was
used at a 95% confidence interval, so only those values with a p-value of less than 0.05 were
considered significant. Therefore, the results in Table 3indicate that the greatest impact
on hole size and circularity was achieved by the drill bit materials. The drill bit’s material
type affected the hole size by 94.10% and the circularity by 45.07%. The spindle speed’s
influence on the hole size was 3.75%, while none of the other parameters affected the hole
size and circularity in the 95% confidence interval.
Machines 2023, 11, x FOR PEER REVIEW 6 of 16
6.0753 mm, while for the uncoated carbide drill bits, the minimum value obtained was
6.0086 mm, while the maximum was 6.0281 mm. Similarly, the circularity ranged from
0.0261 to 0.0541 mm for the uncoated HSS drill bits. In contrast, it ranged from 0.0193 to
0.0284 mm when the carbide drill bits were used. In the current study, the ANOVA was
used at a 95% confidence interval, so only those values with a p-value of less than 0.05
were considered significant. Therefore, the results in Table 3 indicate that the greatest im-
pact on hole size and circularity was achieved by the drill bit materials. The drill bit’s
material type affected the hole size by 94.10% and the circularity by 45.07%. The spindle
speed’s influence on the hole size was 3.75%, while none of the other parameters affected
the hole size and circularity in the 95% confidence interval.
Figure 2. Hole size.
Figure 3. Circularity.
6.000
6.050
6.100
6.150
6.200
0.04 0.08 0.14 0.04 0.08 0.14 0.04 0.08 0.14
f (mm/rev) f (mm/rev) f (mm/rev)
1500 2500 3500
n (rpm) n (rpm) n (rpm)
Hole deviation (mm)
Uncoated carbide drill bit Uncoated HSS drill bit
0.000
0.020
0.040
0.060
0.080
0.04 0.08 0.14 0.04 0.08 0.14 0.04 0.08 0.14
f (mm/rev) f (mm/rev) f (mm/rev)
1500 2500 3500
n (rpm) n (rpm) n (rpm)
Circularity (mm)
Uncoated carbide drill bit Uncoated HSS drill bit
Figure 2. Hole size.
Machines 2023,11, 726 6 of 14
Machines 2023, 11, x FOR PEER REVIEW 6 of 16
6.0753 mm, while for the uncoated carbide drill bits, the minimum value obtained was
6.0086 mm, while the maximum was 6.0281 mm. Similarly, the circularity ranged from
0.0261 to 0.0541 mm for the uncoated HSS drill bits. In contrast, it ranged from 0.0193 to
0.0284 mm when the carbide drill bits were used. In the current study, the ANOVA was
used at a 95% confidence interval, so only those values with a p-value of less than 0.05
were considered significant. Therefore, the results in Table 3 indicate that the greatest im-
pact on hole size and circularity was achieved by the drill bit materials. The drill bit’s
material type affected the hole size by 94.10% and the circularity by 45.07%. The spindle
speed’s influence on the hole size was 3.75%, while none of the other parameters affected
the hole size and circularity in the 95% confidence interval.
Figure 2. Hole size.
Figure 3. Circularity.
6.000
6.050
6.100
6.150
6.200
0.04 0.08 0.14 0.04 0.08 0.14 0.04 0.08 0.14
f (mm/rev) f (mm/rev) f (mm/rev)
1500 2500 3500
n (rpm) n (rpm) n (rpm)
Hole deviation (mm)
Uncoated carbide drill bit Uncoated HSS drill bit
0.000
0.020
0.040
0.060
0.080
0.04 0.08 0.14 0.04 0.08 0.14 0.04 0.08 0.14
f (mm/rev) f (mm/rev) f (mm/rev)
1500 2500 3500
n (rpm) n (rpm) n (rpm)
Circularity (mm)
Uncoated carbide drill bit Uncoated HSS drill bit
Figure 3. Circularity.
Table 3. ANOVA for hole size and circularity.
Hole Size
Source DF Seq SS Adj SS Adj MS F-Value p-Value Contribution
Model 13 0.012127 0.012127 0.000933 33.73 0.002 99.10%
Linear 5 0.01198 0.01198 0.002396 86.63 0 97.89%
Drill bit material 1 0.011516 0.011516 0.011516 416.38 0 94.10%
Spindle speed 2 0.000459 0.000459 0.000229 8.29 0.038 3.75%
Feed rate 2 0.000006 0.000006 0.000003 0.11 0.9 0.05%
Two-way interactions 8 0.000147 0.000147 0.000018 0.66 0.712 1.20%
Drill bit material ×spindle speed 2 0.000041 0.000041 0.000021 0.74 0.532 0.34%
Drill bit material ×feed rate 2 0.000005 0.000005 0.000002 0.08 0.922 0.04%
Spindle speed ×feed rate 4 0.000101 0.000101 0.000025 0.92 0.533 0.83%
Error 4 0.000111 0.000111 0.000028 - - 0.90%
Total 17 0.012238 - - - - 100.00%
Circularity
Model 13 0.001579 0.001579 0.000121 3.24 0.133 91.33%
Linear 5 0.001282 0.001282 0.000256 6.84 0.043 74.19%
Drill bit material 1 0.000779 0.000779 0.000779 20.79 0.01 45.07%
Spindle speed 2 0.000107 0.000107 0.000054 1.43 0.34 6.21%
Feed rate 2 0.000396 0.000396 0.000198 5.28 0.075 22.91%
Two-way interactions 8 0.000296 0.000296 0.000037 0.99 0.544 17.14%
Drill bit material ×spindle speed 2 0.00005 0.00005 0.000025 0.67 0.563 2.89%
Drill bit material ×feed rate 2 0.000115 0.000115 0.000057 1.53 0.321 6.63%
Spindle speed ×feed rate 4 0.000132 0.000132 0.000033 0.88 0.548 7.63%
Error 4 0.00015 0.00015 0.000037 - - 8.67%
Total 17 0.001728 - - - - 100.00%
3.2. Cylindricity and Perpendicularity
In the current study, the cylindricity and perpendicularity increased with increases
in the drilling parameters. However, a significant impact on both cylindricity and perpen-
dicularity was found based on the type of drill bit material used, as shown
in Figures 4and 5. The uncoated HSS drill bit holes have greater cylindricity and per-
pendicularity than the uncoated carbide drill bit holes. Hence, when using the carbide
Machines 2023,11, 726 7 of 14
drill bits, the lowest cylindricity and perpendicularity values produced were 0.0271 mm
and 0.0120 mm. Likewise, the ANOVA result in Table 4indicates that the impact of drill
bit material on the cylindricity was 64.35%, while the impact on perpendicularity was
61.08%. Furthermore, the spindle speed had an impact of 16.17% on cylindricity and
8.92% on perpendicularity. However, the feed rate showed an insignificant contribution
in affecting the cylindricity and perpendicularity in this study at the confidence interval
of 95%. Moreover, in the two-way interactions, the combination of drill type and spindle
speed had an influence of 5.32% on the cylindricity. In comparison, the combined effect of
drill type and feed rate had an impact of 5.78% on the cylindricity. At the same time, in
the two-way interactions, only the drill type and spindle affected perpendicularity, with a
13.06% contribution. Hence, it is concluded that the drill bit material plays a significant
role during the drilling process in affecting the hole quality characteristics.
Machines 2023, 11, x FOR PEER REVIEW 9 of 16
Figure 4. Cylindricity.
Figure 5. Perpendicularity.
Table 4. ANOVA for cylindricity and perpendicularity.
Cylindricity
Source DF Seq SS Adj SS Adj MS F-Value p-Value Contribution
Model 13 0.014233 0.014233 0.001095 32.18 0.002 99.05%
Linear 5 0.011966 0.011966 0.002393 70.34 0.001 83.28%
Drill bit material 1 0.009246 0.009246 0.009246 271.76 0 64.35%
0.000
0.050
0.100
0.150
0.200
0.04 0.08 0.14 0.04 0.08 0.14 0.04 0.08 0.14
f (mm/rev) f (mm/rev) f (mm/rev)
1500 2500 3500
n (rpm) n (rpm) n (rpm)
Cylindricity (mm)
Uncoated carbide drill bit Uncoated HSS drill bit
0.000
0.015
0.030
0.045
0.060
0.04 0.08 0.14 0.04 0.08 0.14 0.04 0.08 0.14
f (mm/rev) f (mm/rev) f (mm/rev)
1500 2500 3500
n (rpm) n (rpm) n (rpm)
Perpendicularity (mm)
Uncoated carbide drill bit Uncoated HSS drill bit
Figure 4. Cylindricity.
Machines 2023, 11, x FOR PEER REVIEW 9 of 16
Figure 4. Cylindricity.
Figure 5. Perpendicularity.
Table 4. ANOVA for cylindricity and perpendicularity.
Cylindricity
Source DF Seq SS Adj SS Adj MS F-Value p-Value Contribution
Model 13 0.014233 0.014233 0.001095 32.18 0.002 99.05%
Linear 5 0.011966 0.011966 0.002393 70.34 0.001 83.28%
Drill bit material 1 0.009246 0.009246 0.009246 271.76 0 64.35%
0.000
0.050
0.100
0.150
0.200
0.04 0.08 0.14 0.04 0.08 0.14 0.04 0.08 0.14
f (mm/rev) f (mm/rev) f (mm/rev)
1500 2500 3500
n (rpm) n (rpm) n (rpm)
Cylindricity (mm)
Uncoated carbide drill bit Uncoated HSS drill bit
0.000
0.015
0.030
0.045
0.060
0.04 0.08 0.14 0.04 0.08 0.14 0.04 0.08 0.14
f (mm/rev) f (mm/rev) f (mm/rev)
1500 2500 3500
n (rpm) n (rpm) n (rpm)
Perpendicularity (mm)
Uncoated carbide drill bit Uncoated HSS drill bit
Figure 5. Perpendicularity.
Machines 2023,11, 726 8 of 14
Table 4. ANOVA for cylindricity and perpendicularity.
Cylindricity
Source DF Seq SS Adj SS Adj MS F-Value p-Value Contribution
Model 13 0.014233 0.014233 0.001095 32.18 0.002 99.05%
Linear 5 0.011966 0.011966 0.002393 70.34 0.001 83.28%
Drill bit material 1 0.009246 0.009246 0.009246 271.76 0 64.35%
Spindle speed 2 0.002323 0.002323 0.001162 34.14 0.003 16.17%
Feed rate 2 0.000396 0.000396 0.000198 5.82 0.065 2.76%
Two-Way Interactions 8 0.002267 0.002267 0.000283 8.33 0.029 15.78%
Drill bit material ×spindle speed 2 0.000765 0.000765 0.000382 11.24 0.023 5.32%
Drill bit material ×feed rate 2 0.000831 0.000831 0.000415 12.21 0.02 5.78%
Spindle speed ×feed rate 4 0.000671 0.000671 0.000168 4.93 0.076 4.67%
Error 4 0.000136 0.000136 0.000034 - - 0.95%
Total 17 0.014369 - - - - 100.00%
Perpendicularity
Model 13 0.00042 0.00042 0.000032 12.89 0.012 97.67%
Linear 5 0.000334 0.000334 0.000067 26.69 0.004 77.74%
Drill bit material 1 0.000262 0.000262 0.000262 104.83 0.001 61.08%
Spindle speed 2 0.000038 0.000038 0.000019 7.65 0.043 8.92%
Feed rate 2 0.000033 0.000033 0.000017 6.65 0.053 7.75%
Two-Way interactions 8 0.000086 0.000086 0.000011 4.27 0.088 19.93%
Drill bit material ×spindle speed 2 0.000056 0.000056 0.000028 11.21 0.023 13.06%
Drill bit material ×feed rate 2 0.00002 0.00002 0.00001 3.97 0.112 4.63%
Spindle speed ×feed rate 4 0.00001 0.00001 0.000002 0.96 0.516 2.23%
Error 4 0.00001 0.00001 0.000003 - - 2.33%
Total 17 0.00043 - - - - 100.00%
4. Discussion
In the current study, the quality of hole characteristics reduces with increases in the
spindle speed and feed rate. However, at a 95% confidence interval, the ANOVA results
concluded that the most influencing parameter affecting the hole quality was the type of
drill bit material, followed by the spindle speed. In contrast, the influence of the feed rate
on the quality of the holes was found to be insignificant. This could also be confirmed
by the Pareto chart, as provided in Figure 6. Additionally, the uncoated carbide drill bit
showed low perpendicularity, low circularity, low cylindricity, and a low level of deviation
of the hole from the nominal size compared to the results produced by the uncoated HSS
drill bits. One of the reasons for this might be the formation of fewer burrs around the entry
and exit sides of the holes produced by the uncoated carbide drill bits. Thus, the burrs
around the holes were observed using an optical microscope, as shown in Figure 7a, which
is an additional method apart from using the profile meters [
24
]. Hence, the formation
of burrs is provided in Figure 7b. Further details can be found in Appendix A. It is also
worth noting that in this study, the burrs at the edges of the holes were small and did
require further processing, such as de-burring. However, the burrs can affect the geometric
tolerances and might be affected by the drilling parameters. Hence, the material was further
examined using scanning electron microscopy at the entry and exit sides of the hole edges,
as shown in Figure 8. The SEM examination was also extended to the inside hole surface,
which revealed that the surface deformation, damage defects, and chip adhesion were more
visible in the holes drilled with uncoated HSS drill bits, as provided in Figure 9. It is also
worth mentioning that previously [
24
], the uncoated carbide drill bits also performed better
than the uncoated HSS drill bits in the process of drilling Al2023-T3. However, that study
was based on a multi-hole drilling approach to investigate thrust force, burr formation,
surface roughness, chips analysis, and tool conditions.
Machines 2023,11, 726 9 of 14
Machines 2023, 11, x FOR PEER REVIEW 11 of 16
(a) (b)
(c) (d)
Figure 6. (a). Pareto chart for hole size. (b). Pareto chart for circularity. (c). Pareto chart for cylin-
dricity. (d). Pareto chart for perpendicularity.
(a) (b)
Figure 7. (a) Burr investigation using digital microscope. (b) Burr formation at 3500 rpm and 0.14
mm/rev.
Figure 6.
(
a
). Pareto chart for hole size. (
b
). Pareto chart for circularity. (
c
). Pareto chart for
cylindricity. (d). Pareto chart for perpendicularity.
Machines 2023, 11, x FOR PEER REVIEW 11 of 16
(a) (b)
(c) (d)
Figure 6. (a). Pareto chart for hole size. (b). Pareto chart for circularity. (c). Pareto chart for cylin-
dricity. (d). Pareto chart for perpendicularity.
(a) (b)
Figure 7. (a) Burr investigation using digital microscope. (b) Burr formation at 3500 rpm and 0.14
mm/rev.
Figure 7.
(
a
) Burr investigation using digital microscope. (
b
) Burr formation at 3500 rpm and
0.14 mm/rev.
Machines 2023,11, 726 10 of 14
Figure 8. SEM images of hole top and bottom edge after drilling at 3500 rpm and 0.14 mm/rev.
Machines 2023, 11, x FOR PEER REVIEW 12 of 16
Figure 8. SEM images of hole top and boom edge after drilling at 3500 rpm and 0.14 mm/rev.
Figure 9. SEM hole analysis after drilling at 3500 rpm and 0.14 mm/rev.
Another reason for the beer hole quality was the formation of a lower built-up edge
(BUE) on the holes drilled with carbide drill bits. This was mainly due to the greater
strength, higher hardness, and lower coefficient of friction of the carbide drill bits when
compared to the uncoated HSS drill bits [24]. Furthermore, it has also been reported that
high machining parameters tend to increase the temperature at the drilling zone because
of the high friction and material removal rate. Hence, the material softens and undergoes
plastic deformation, which causes the material to accumulate at the cuing tool, resulting
in adhesion and built-up edges [28]. Previous studies have reported that high machining
parameters also contribute to increasing the tool wear, deformation effects, and the quality
of holes [29]. In addition, the Pareto chart in Figure 6 indicated that the second influencing
factor on the hole quality was the spindle speed in this study. Therefore, additional drill-
ing experiments were performed to compare the post-drilling tool conditions with respect
to the built-up edges. Hence, a high spindle speed of 3500 rpm and a high feed rate of 0.14
mm/rev in the current drilling parameters were selected, and post-drilling conditions
were investigated after 9, 27, and 45 holes were drilled. Figure 10 shows the optical mi-
croscopy images taken using each drill bit, which shows a high BUE generated on the
Figure 9. SEM hole analysis after drilling at 3500 rpm and 0.14 mm/rev.
Another reason for the better hole quality was the formation of a lower built-up edge
(BUE) on the holes drilled with carbide drill bits. This was mainly due to the greater
strength, higher hardness, and lower coefficient of friction of the carbide drill bits when
compared to the uncoated HSS drill bits [
24
]. Furthermore, it has also been reported that
high machining parameters tend to increase the temperature at the drilling zone because
of the high friction and material removal rate. Hence, the material softens and undergoes
plastic deformation, which causes the material to accumulate at the cutting tool, resulting
in adhesion and built-up edges [
28
]. Previous studies have reported that high machining
parameters also contribute to increasing the tool wear, deformation effects, and the quality
of holes [
29
]. In addition, the Pareto chart in Figure 6indicated that the second influencing
factor on the hole quality was the spindle speed in this study. Therefore, additional drilling
experiments were performed to compare the post-drilling tool conditions with respect
to the built-up edges. Hence, a high spindle speed of 3500 rpm and a high feed rate of
0.14 mm/rev in the current drilling parameters were selected, and post-drilling conditions
were investigated after 9, 27, and 45 holes were drilled. Figure 10 shows the optical
Machines 2023,11, 726 11 of 14
microscopy images taken using each drill bit, which shows a high BUE generated on the
uncoated HSS drills. It is worth mentioning that as the number of holes increases, there
might be high tool work friction, resulting in a high level of energy consumption and
generating higher thrust force [
30
]. Consequently, there are more chances of affecting the
hole dimensions due to a high BUE. Hence, the SEM mid-hole surface analysis was carried
out after 9, 27 and 45 holes were drilled with uncoated HSS and carbide drills, as shown in
Figure 11. It is also noteworthy that the hole quality might be affected by other parameters
like vibration, machine dynamics, the drilling temperature, etc. [
27
], which were not the
scope of this study.
Machines 2023, 11, x FOR PEER REVIEW 13 of 16
uncoated HSS drills. It is worth mentioning that as the number of holes increases, there
might be high tool work friction, resulting in a high level of energy consumption and gen-
erating higher thrust force [30]. Consequently, there are more chances of affecting the hole
dimensions due to a high BUE. Hence, the SEM mid-hole surface analysis was carried out
after 9, 27 and 45 holes were drilled with uncoated HSS and carbide drills, as shown in
Figure 11. It is also noteworthy that the hole quality might be affected by other parameters
like vibration, machine dynamics, the drilling temperature, etc. [27], which were not the
scope of this study.
Post-drilling
tool
condition
Unused drill bit After 09 drilled
holes
After 27 drilled
holes
After 45 drilled
holes
Uncoated
carbide
drill bit
Uncoated
HSS
drill bit
Figure 10. Post-drilling tool conditions after drilling at 3500 rpm and 0.14 mm/rev
SEM analysis at
middle of the hole
After 09 drilled holes After 27 drilled holes After 45 drilled holes
Uncoated carbide
drill bit
Uncoated HSS
drill bit
Figure 11. SEM mid-hole analyses after drilling at 3500 rpm and 0.14 mm/rev
5. Conclusions
In the current study, Al2024-T3 was used for drilling experiments, and a comparison
was made between uncoated HSS and carbide drill bits used with varying drilling process
parameters. The investigations were based on the hole quality; however, the study was
further extended to examine the tool conditions at high drilling parameters in combina-
tion with SEM analysis of the holes at the different locations. Hence, the results obtained
in this study can help the scientific community and industry in selecting high-quality
drilled holes. The following conclusions were made based on the above investigations.
The quality of holes with respect to hole size, cylindricity, circularity, and perpendic-
ularity increase as the spindle speed and feed rate increase. However, ANOVA results
Figure 10. Post-drilling tool conditions after drilling at 3500 rpm and 0.14 mm/rev.
Machines 2023, 11, x FOR PEER REVIEW 13 of 16
uncoated HSS drills. It is worth mentioning that as the number of holes increases, there
might be high tool work friction, resulting in a high level of energy consumption and gen-
erating higher thrust force [30]. Consequently, there are more chances of affecting the hole
dimensions due to a high BUE. Hence, the SEM mid-hole surface analysis was carried out
after 9, 27 and 45 holes were drilled with uncoated HSS and carbide drills, as shown in
Figure 11. It is also noteworthy that the hole quality might be affected by other parameters
like vibration, machine dynamics, the drilling temperature, etc. [27], which were not the
scope of this study.
Post-drilling
tool
condition
Unused drill bit After 09 drilled
holes
After 27 drilled
holes
After 45 drilled
holes
Uncoated
carbide
drill bit
Uncoated
HSS
drill bit
Figure 10. Post-drilling tool conditions after drilling at 3500 rpm and 0.14 mm/rev
SEM analysis at
middle of the hole
After 09 drilled holes After 27 drilled holes After 45 drilled holes
Uncoated carbide
drill bit
Uncoated HSS
drill bit
Figure 11. SEM mid-hole analyses after drilling at 3500 rpm and 0.14 mm/rev
5. Conclusions
In the current study, Al2024-T3 was used for drilling experiments, and a comparison
was made between uncoated HSS and carbide drill bits used with varying drilling process
parameters. The investigations were based on the hole quality; however, the study was
further extended to examine the tool conditions at high drilling parameters in combina-
tion with SEM analysis of the holes at the different locations. Hence, the results obtained
in this study can help the scientific community and industry in selecting high-quality
drilled holes. The following conclusions were made based on the above investigations.
The quality of holes with respect to hole size, cylindricity, circularity, and perpendic-
ularity increase as the spindle speed and feed rate increase. However, ANOVA results
Figure 11. SEM mid-hole analyses after drilling at 3500 rpm and 0.14 mm/rev.
5. Conclusions
In the current study, Al2024-T3 was used for drilling experiments, and a comparison
was made between uncoated HSS and carbide drill bits used with varying drilling process
parameters. The investigations were based on the hole quality; however, the study was
further extended to examine the tool conditions at high drilling parameters in combination
with SEM analysis of the holes at the different locations. Hence, the results obtained in
this study can help the scientific community and industry in selecting high-quality drilled
holes. The following conclusions were made based on the above investigations.
Machines 2023,11, 726 12 of 14
The quality of holes with respect to hole size, cylindricity, circularity, and perpendic-
ularity increase as the spindle speed and feed rate increase. However, ANOVA results
indicated that the type of drill bit material showed the highest influence on the hole quality.
The spindle speed was the second-most influencing factor affecting the hole quality. In
contrast, the feed rate showed an insignificant impact on the hole quality at the confidence
interval of 95% for the selected drilling parameters.
The burrs formed around the edges of holes produced by the uncoated carbide drill
bits at high drilling parameters were found to be fewer than those produced by the HSS
drill bits. Furthermore, the SEM images showed less surface deformation and damage
defects on the hole walls drilled by the uncoated carbide drill bits. The experimental results
also concluded that the uncoated carbide drill bits produced more high-quality holes than
the uncoated HSS drill bits because of their high strength and resistance to wear. Similarly,
the adhesion and built-up edges on the uncoated carbide drill bits were less than the
uncoated HSS drill bits at high drilling parameters. Therefore, it is concluded that the drill
bit materials play a significant role during the process of drilling Al2024-T3 in affecting
the hole quality characteristics. Hence, drill bits with excellent wear resistance and a high
degree of hardness are recommended for improving tool life.
Author Contributions:
Conceptualization, M.A., M.T.-R. and K.G.; methodology, M.A. and A.S.;
validation, M.A., M.T.-R. and K.G.; investigation, M.A. and K.G.; writing—original draft preparation,
M.A., M.Z.Z. and A.S.; writing—review and editing, M.A., M.Z.Z. and K.G. All authors have read
and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: The data presented in this study are available on request.
Conflicts of Interest: The authors declare no conflict of interest.
Appendix A. Entry and Exit Hole Burrs at Varying Drilling Parameters
Machines 2023, 11, x FOR PEER REVIEW 14 of 16
indicated that the type of drill bit material showed the highest influence on the hole qual-
ity. The spindle speed was the second-most influencing factor affecting the hole quality.
In contrast, the feed rate showed an insignificant impact on the hole quality at the confi-
dence interval of 95% for the selected drilling parameters.
The burrs formed around the edges of holes produced by the uncoated carbide drill
bits at high drilling parameters were found to be fewer than those produced by the HSS
drill bits. Furthermore, the SEM images showed less surface deformation and damage de-
fects on the hole walls drilled by the uncoated carbide drill bits. The experimental results
also concluded that the uncoated carbide drill bits produced more high-quality holes than
the uncoated HSS drill bits because of their high strength and resistance to wear. Similarly,
the adhesion and built-up edges on the uncoated carbide drill bits were less than the un-
coated HSS drill bits at high drilling parameters. Therefore, it is concluded that the drill
bit materials play a significant role during the process of drilling Al2024-T3 in affecting
the hole quality characteristics. Hence, drill bits with excellent wear resistance and a high
degree of hardness are recommended for improving tool life.
Author Contributions: Conceptualization, M.A., M.T.-R., and K.G.; methodology, M.A. and A.S.;
validation, M.A., M.T.-R., and K.G.; investigation, M.A. and K.G.; writing—original draft prepara-
tion, M.A. M.Z.Z., and A.S.; writing—review and editing, M.A. M.Z.Z., and K.G. All authors have
read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: The data presented in this study are available on request.
Conflicts of Interest: The authors declare no conflicts of interest.
Appendix A. Entry and Exit Hole Burrs at Varying Drilling Parameters
Entry holes Exit holes
Uncoated HSS drilled holes
Uncoated carbide drilled holes
Machines 2023,11, 726 13 of 14
References
1.
Rivero, A.; Aramendi, G.; Herranz, S.; de Lacalle, L.L. An experimental investigation of the effect of coatings and cutting
parameters on the dry drilling performance of aluminium alloys. Int. J. Adv. Manuf. Technol. 2006,28, 1–11. [CrossRef]
2.
Xu, J.; Kolesnyk, V.; Li, C.; Lysenko, B.; Peterka, J.; Gupta, M.K. A critical review addressing conventional twist drilling
mechanisms and quality of CFRP/Ti stacks. J. Mater. Res. Technol. 2023,24, 6614–6651. [CrossRef]
3.
Yuan, P.; Lai, T.; Li, Y.; Han, W.; Lin, M.; Zhu, Q.; Liu, Y.; Shi, Z. The attitude adjustment algorithm in drilling end-effector for
aviation. Adv. Mech. Eng. 2016,8, 1687814016629348. [CrossRef]
4.
Adin, M.¸S. Performances of cryo-treated and untreated cutting tools in machining of AA7075 aerospace aluminium alloy. Eur.
Mech. Sci. 2023,7, 70–81. [CrossRef]
5.
Selvakumar, S.J.; Muralidharan, S.M. Performance analysis of drills with structured surfaces when drilling CFRP/AA7075 stack
under MQL condition. J. Manuf. Process. 2023,89, 194–219. [CrossRef]
6.
Habib, N.; Sharif, A.; Hussain, A.; Aamir, M.; Giasin, K.; Pimenov, D.Y.; Ali, U. Analysis of Hole Quality and Chips Formation in
the Dry Drilling Process of Al7075-T6. Metals 2021,11, 891. [CrossRef]
7.
Habib, N.; Sharif, A.; Hussain, A.; Aamir, M.; Giasin, K.; Pimenov, D.Y. Assessment of Hole Quality, Thermal Analysis, and Chip
Formation during Dry Drilling Process of Gray Cast Iron ASTM A48. Eng 2022,3, 301–310. [CrossRef]
8.
Dahnel, A.N.; Fauzi, M.H.; Raof, N.A.; Mokhtar, S.; Khairussaleh, N.K.M. Tool wear and burr formation during drilling of
aluminum alloy 7075 in dry and with cutting fluid. Mater. Today Proc. 2022,59, 808–813. [CrossRef]
9.
Gupta, M.K.; Niesłony, P.; Korkmaz, M.E.; Kunto˘glu, M.; Królczyk, G.; Günay, M.; Sarikaya, M. Comparison of Tool Wear, Surface
Morphology, Specific Cutting Energy and Cutting Temperature in Machining of Titanium Alloys under Hybrid and Green
Cooling Strategies. Int. J. Precis. Eng. Manuf.-Green Technol. 2023, 1–14. [CrossRef]
10.
Ghasemian Fard, M.; Baseri, H.; Zolfaghari, A. Experimental investigation of the effective parameters and performance of
different types of structural tools in drilling CFRP/AL alloy stacks. J. Compos. Mater. 2022,56, 4461–4471. [CrossRef]
11.
Soori, M.; Arezoo, B. Cutting tool wear minimization in drilling operations of titanium alloy Ti-6Al-4V. Proc. Inst. Mech. Eng. Part
J J. Eng. Tribol. 2023,237, 1250–1263. [CrossRef]
12.
Dahnel, A.N.B.; Raof, N.A.; MK, N.K.; Mokhtar, S. The effect of cutting parameters on tool wear in drilling aluminium 7075. Test
Eng. Manag. 2020,83, 1274–1280.
13.
Islam, M.N.; Boswell, B. Effect of cooling methods on hole quality in drilling of aluminium 6061-6T. IOP Conf. Ser. Mater. Sci. Eng.
2016,114, 012022. [CrossRef]
14.
Khunt, C.P.; Makhesana, M.A.; Patel, K.M.; Mawandiya, B.K. Performance assessment of vegetable oil-based minimum quantity
lubrication (MQL) in drilling. Mater. Today Proc. 2021,44, 341–345. [CrossRef]
15.
Luo, H.; Fu, J.; Wu, T.; Chen, N.; Li, H. Numerical Simulation and Experimental Study on the Drilling Process of 7075-t6 Aerospace
Aluminum Alloy. Materials 2021,14, 553. [CrossRef] [PubMed]
16.
Pramanik, A.; Basak, A.K.; Prakash, C.; Shankar, S.; Chattopadhyaya, S. Sustainability in drilling of aluminum alloy. Clean. Mater.
2022,3, 100048. [CrossRef]
17.
Banerjee, B.; Dhar, A.K.; Bhattacharjee, S.; Mahato, N.K. Process Parameters Optimization in Drilling Using Taguchi Method. In
Proceedings of the Recent Trends in Product Design and Intelligent Manufacturing Systems, Singapore, 30–31 December 2021; pp.
701–708.
18.
Aamir, M.; Giasin, K.; Tolouei-Rad, M.; Ud Din, I.; Hanif, M.I.; Kuklu, U.; Pimenov, D.Y.; Ikhlaq, M. Effect of Cutting Parameters
and Tool Geometry on the Performance Analysis of One-Shot Drilling Process of AA2024-T3. Metals 2021,11, 854. [CrossRef]
19.
Kang, J.; Yao, E. Study On Burrs And Hole Quality Of Drilling AA2024 Plates Based On FEM And Experimental Investigation. J.
Appl. Sci. Eng. 2022,26, 911–921. [CrossRef]
20.
Giasin, K.; Hodzic, A.; Phadnis, V.; Ayvar-Soberanis, S. Assessment of cutting forces and hole quality in drilling Al2024 aluminium
alloy: Experimental and finite element study. Int. J. Adv. Manuf. Technol. 2016,87, 2041–2061. [CrossRef]
21.
Ashrafi, S.A.; Davoudinejad, A.; Barzani, M.M.; Salehi, P. Investigation into effect of tool wear on drilling force and surface finish
while dry drilling aluminum 2024. Adv. Mater. Res. 2012,548, 387–392. [CrossRef]
22.
Kurt, M.; Bagci, E.; Kaynak, Y. Application of Taguchi methods in the optimization of cutting parameters for surface finish and
hole diameter accuracy in dry drilling processes. Int. J. Adv. Manuf. Technol. 2009,40, 458–469. [CrossRef]
23.
Benchmarkabrasives. HSS VS Cobalt VS Carbide Drill Bits: What to Choose. Available online: https://benchmarkabrasives.com/
blogs/news/hss-vs-cobalt-vs-carbide-drill-bits-what-to-choose (accessed on 30 June 2023).
24.
Aamir, M.; Tolouei-Rad, M.; Giasin, K.; Vafadar, A. Feasibility of tool configuration and the effect of tool material, and tool
geometry in multi-hole simultaneous drilling of Al2024. Int. J. Adv. Manuf. Technol. 2020,111, 861–879. [CrossRef]
25. Oberg, E. Machinery’s Handbook 29th Edition-Full Book; Industrial Press: New York, NY, USA, 2012.
26.
Aamir, M.; Giasin, K.; Tolouei-Rad, M.; Vafadar, A. A review: Drilling performance and hole quality of aluminium alloys for
aerospace applications. J. Mater. Res. Technol. 2020,9, 12484–12500. [CrossRef]
27.
Mohammadi, F.; Mirhashemi, M.; Rashidzadeh, R. A Coordinate Measuring Machine with Error Compensation in Feature
Measurement: Model Development and Experimental Verification. Int. J. Adv. Manuf. Technol. 2022. [CrossRef]
28.
Mydin, N.M.M.; Dahnel, A.N.; Raof, N.A.; Khairussaleh, N.M.; Mokhtar, S. Comparison of Tool Wear Mechanisms During
Drilling of Aluminium Alloy 7075 in Dry and Chilled Air Conditions. J. Sci. Technol. 2022,14, 67–74. [CrossRef]
Machines 2023,11, 726 14 of 14
29.
Musavi, S.H.; Sepehrikia, M.; Davoodi, B.; Niknam, S.A. Performance analysis of developed micro-textured cutting tool in
machining aluminum alloy 7075-T6: Assessment of tool wear and surface roughness. Int. J. Adv. Manuf. Technol.
2022
,119,
3343–3362. [CrossRef]
30.
Ramulu, M.; Branson, T.; Kim, D. A study on the drilling of composite and titanium stacks. Compos. Struct.
2001
,54, 67–77.
[CrossRef]
Disclaimer/Publisher’s Note:
The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.
Content uploaded by Aamer Sharif
Author content
All content in this area was uploaded by Aamer Sharif on Jul 13, 2023
Content may be subject to copyright.
... In the automobile industry, it accounts for about 40 percent of all material removal procedures. In contrast, in the aerospace industry, millions of holes are essential in the fnal assembly of their products [4][5][6]. A typical aircraft requires nearly 2000 holes only for frame attachment with the main assembly [6,7]. ...
... In contrast, in the aerospace industry, millions of holes are essential in the fnal assembly of their products [4][5][6]. A typical aircraft requires nearly 2000 holes only for frame attachment with the main assembly [6,7]. Improper drilling operations, such as poor drilling conditions and rapid tool wear, can force additional fnishing operations and parts rejection, increasing the cost and time of the product [8,9]. ...
Deform 3D Simulation and Experimental Study in Machining of AISI 1020 Mild Steel
Article
Full-text available
  • May 2024
The drilling process plays a crucial role in the assembly process of modern-day manufactories. One of the major causes of component rejection during drilling operations is the incorrect selection of spindle speed and feed rate. Therefore, this study aimed to investigate the impact of process factors such as spindle speed and feed rate on torque, thrust force, temperature surface roughness, and chip formation during the drilling of AISI 1020 mild steel. A combination of finite element modeling and experimental investigation was employed to achieve the process. Specifically, the commercially available finite element software, Deform 3D, was used for simulation. The modeling results were then compared and validated with the experimental data. A high-speed steel drill bit was utilized during the modeling and experimentation. The spindle speed was varied at 330, 410, and 510 rpm, while the feed rates were set at 0.12, 0.2, and 0.3 mm/rev. The study’s findings suggest that the spindle speed has an inverse relationship with thrust force, torque, and surface roughness, whereas it has a direct relationship with temperature. Conversely, the feed rate directly correlates with thrust force, torque, temperature, and surface roughness. Additionally, an analysis of the chips produced during the experiments revealed the impact of the cutting conditions on chip formation. The study results showed a 2–10% discrepancy between the experimental and simulation data. The ANOVA results indicated that the feed rate contributes the most to thrust force and torque, with a percentage contribution of 61.73% and 59.87%, respectively, followed by spindle speed, with a percentage contribution of 37.09% and 38.89%, respectively. Furthermore, temperature influences spindle speed the most, followed by feed rate, with percentage contributions of 67.75% and 31.11%, respectively. Moreover, the feed rate’s percentage contribution to surface roughness is higher than the spindle speed, with a contribution of 66.20% and 32.18%, respectively.
View
... Perpendicularity is one of the important form tolerances in precision machining and widely used across a range of industries such as aerospace, automotive, and electronics, as evidenced by recent studies [16,17]. Drilling and deburring are essential machining processes and misaligned or non-perpendicular holes can lead to assembly difficulties, reduced load-bearing capacity, and increased stress concentrations which can lead to potential fatigue failure [18,19]. ...
Virtual prototyping of vision-based tactile sensors design for robotic-assisted precision machining
Article
Full-text available
  • May 2024
  • SENSOR ACTUAT A-PHYS
Vision-Based Tactile Sensors (VBTS) play a key role in enhancing the accuracy and efficiency of machining operations in robotic-assisted precision machining systems. Equipped with VBTS, these systems offer contact-based measurements, which are essential in machining accurate components for industries such as aerospace, automotive, medical devices, and electronics. This paper presents a novel approach to virtual prototyping of VBTS, specifically in perpendicularity measurements using Computer-Aided Design (CAD) generation of VBTS designs, Finite Element Analysis (FEA) simulations, and Sim2Real deep learning to achieve VBTS with high precision measurements. The virtual prototyping approach enables an understanding of the contact between VBTS with different designs and machined surfaces in terms of contact module shape, thickness, markers’ density. Additive manufacturing was employed to fabricate the molds of VBTS contact module, followed by experimental validation of the robotic arm to confirm the effectiveness of the optimized VBTS design. The results show that deviation from the hemispherical shape reduces the data quality captured by the camera, hence increasing the prediction errors. Additionally, reducing the thickness of the contact module enhances the precision of perpendicularity measurements. Importantly increasing markers’ distribution density significantly enhances the accuracy of up to 92 markers at which above it the rate of improvement becomes less pronounced. An VBTS with height of 20 mm, thickness of 2 mm, and 169 markers was found to be within the stringent perpendicularity standards of the aerospace manufacturing industry of 0.58◦ as a root mean square error, and 1.64◦ as a max absolute error around the roll and pitch axis of rotation. The established virtual prototyping methodology can be transferred to a wide variety of elastomer-based sensors.
View
... Drilling with a 5 mm drill bit reduced surface roughness compared to a 3 mm drill bit. Aamir and co-authors [33] conducted metrological studies related to the diameter and circularity of the hole during dry machining with respect to varying technological parameters of the drilling process (n = 1500; 2500; 3500 rpm and f n = 0.04; 0.08; 0.14 mm/rev) and two drills (HSS; carbide). They showed that spindle speed has a non-significant effect on the parameters studied. ...
Effect of Choice of Drilling Kinematic System on Cylindricity Deviation, Roundness Deviation, Diameter Error and Surface Roughness of Holes in Brass Alloy
Article
Full-text available
  • Jan 2024
This article presents the results of an experimental study on the effect of the selection of kinematic system for the drilling process on the cylindricity deviation, roundness deviation, diameter error and surface roughness of holes in brass alloy. Three different kinematic systems based on the dependence of the direction of rotation of the workpiece and the drill bit were used. The drill bit was mounted in an axially driven holder that allowed it to be put into motion. Cutting tests were conducted at three different spindle speeds and three different feed rates per revolution (27 tests in total). A static ANOVA analysis was used to evaluate the effect of each input parameter on each output parameter. The results of this work have practical applications in machining. The following input parameters of the drilling process should be used to obtain the smallest values of each output parameter: for CYL, n = 4775 rpm, fn = 0.14 mm/rev and KIN III; for RON, n = 4775 rpm, fn = 0.1 or 0.12 mm/rev and KIN II; for DE, n = 3979 rpm, fn = 0.1 mm/rev and KIN I; and for Rz, n = 4775 rpm, fn = 0.1 mm/rev and KIN II. This research work also used Grey Relational Analysis with which input parameter optimization was derived. The optimal drilling parameters are spindle speeds of 4775 rpm, a feed per revolution of 0.1 mm/rev and the use of the first kinematic system. This paper also includes equations for predicting each parameter that describes the dimensional and shape accuracy and roughness of the hole surface. Using the first kinematic system reduced the roughness of the hole surface by as much as 58%. The correct selection of kinematic system improved its dimensional accuracy by 15%. On the other hand, the roundness deviation of the hole improved by 33% and the cylindricity deviation of the hole by 6%.
View
... Drilling is one of the prominent machining process excessively used manufacturing industries such as aerospace and automotive industries [1][2][3]. The problems which are related to drilling process such that circularity error, deviation of the holes from the nominal size, burr formation and high surface roughness, which significantly affects the drilling operation [4][5][6][7].Therefore, parts are rejected due to rapid tool wear and low hole quality which may lead to increase in total manufacturing cost and time [8][9][10]. ...
Investigation of the effects of machining parameters on hole quality in drilling mild steel AISI 1045
Article
Full-text available
  • Dec 2023
The current study shows the effect of machining parameters such as feed rate and spindle speed on the hole quality such as hole size, circularity and surface roughness in drilling AISI 1045. The experiments were performed using high speed steel drill bits. The result indicated that hole size decreases with increasing feed rate and increases with increasing spindle speed. However, circularity decreases with increasing both feed rate and spindle speed. Furthermore, surface roughness increases with increasing feed rate and decreases with increasing spindle speed. Moreover, Analysis of variance deals that feed rate has higher influence on hole size with percentage contribution of 59.16% than spindle speed of 38.37 % on hole size. The percentage contribution of feed rate is greater than spindle speed on circularity 72.40 % and 25.57% respectively. Moreover, the percentage contribution of feed rate on surface roughness is 61.89% greater than spindle speed of 37.14 %.
View
... The 3D CAD model is shown in Figure 1 and design parameters are as shown in Table 1. Moreover, properties of gas turbine blade materials are as shown in Table 2. (Hussain, Sharif et al. , Habib, Sharif et al. 2022, Sharif 2022, Aamir, Sharif et al. 2023, Sharif, Hussain et al. 2023 ...
Investigation of Gas Turbine Blade Materials for Efficient Energy System
Article
Full-text available
  • Nov 2023
The present study aims to determine the best and most economical material for a gas turbine blade, which operates under high-temperature conditions and experiences high static structural and thermal loads. To achieve this objective, three different types of material alloys, namely Titanium alloy Ti6AL4V, Magnesium alloy AZ80, and Aluminum alloy 7075-T6, were selected for comparison. A turbine blade model was designed using Solid Works software, and structural and thermal analyses were performed using ANYAS 15.0 under steady-state conditions. The structural analysis aimed to determine the stress, strain, and deformation results on turbine blades by applying high pressure, while the thermal analysis aimed to determine the temperature distribution influences and heat flux generation by applying high temperatures. Based on the results obtained from both analyses of the three different materials, Titanium alloy Ti6AL4V is the best and most economical material. This material showed low stress, strain, and little deformation and the best material properties at high temperatures when compared to Magnesium alloy AZ80 and Aluminum alloy 7075-T6.
View
A critical review addressing conventional twist drilling mechanisms and quality of CFRP/Ti stacks
Article
Full-text available
  • Apr 2023
CFRP/Ti stacks have attracted considerable attention over the past decades as a promising alternative to individual fibrous composites and metallic alloys due to their improved properties and enhanced structural functions. Mechanical drilling is a compulsory but challenging process to shape these compound stacks to desired dimensions and target quality. Despite a large volume of studies already addressing the conventional twist drilling of CFRP/Ti stacks, a comprehensive understanding of their fundamental drilling mechanisms is still lacking. The present paper aims to report the state-of-the-art advances achieved in the fields of CFRP/Ti machining. Aspects including chip removal, damage formation, mechanical/thermal effects, influences of process conditions, hole quality attributes, and tool wear mechanisms are carefully reviewed. An emphasis is placed on the discussion of the interface drilling behaviors as well as the impacts of different drilling sequence strategies on the machining outputs of CFRP/Ti stacks. The current research limitations and future research perspectives are pointed out. The review paper could provide technical guidance for both scientific and industrial communities to achieve the damage-free drilling of CFRP/Ti stacks.
View
Performances of cryo-treated and untreated cutting tools in machining of AA7075 aerospace aluminium alloy
Article
Full-text available
  • Jun 2023
The quality of drilled holes in aluminium alloys used in the aerospace industry is vital to ensure high-precision structural integrity. For this reason, optimum selection of cost-effective cutting tools and cutting parameters is of great importance. Nowadays, due to their high cost and supply difficulties, there is a great interest in improving the performance of traditional HSS cutting tools as an alternative to ceramic, carbide and coated cutting tools. HSS cutting tools are widely used in different industries due to their cost-effectiveness and suitability to improve tool performance. In this research, the performances of cryo-treated (DC&T) and untreated (UT) HSS cutting tools used in dry machining of AA7075 aluminium alloys were investigated. Thanks to DC&T processes applied to HSS cutting tool, improvements have occurred in its microstructure. The hardness value of HSS cutting tool increased by 6.89% with the effect of DC&T processes applied. When the highest and lowest Ra values obtained using DC&T and UT HSS cutting tools were compared, it was seen that DC&T HSS cutting tool performed better by 11.05% and 25.91%, respectively. It has been determined that the hole surface quality of the aluminium workpiece machined with DC&T and UT HSS drills is negatively affected by the increase in spindle speed and feed rate. The highest S/N ratios calculated according to Ra values of holes drilled on aluminium workpieces using DC&T and UT HSS cutting tools were found to be -7.12 dB (2.27 μm) and -9.62 dB (3.03 μm), respectively. In the ANOVA analysis, it was determined that the most effective parameters on Ra values were spindle speed (70.62%), tools (18.19%) and feed rate (9.98%), respectively. In the regression analysis, R2 value for Ra values was calculated as 98.30%. High R2 value result shows that the model developed is quite successful in estimating Ra values.
View
Comparison of Tool Wear, Surface Morphology, Specific Cutting Energy and Cutting Temperature in Machining of Titanium Alloys Under Hybrid and Green Cooling Strategies
Article
Full-text available
  • Mar 2023
Cutting energy must be reduced in order to make machining processes more eco-friendly. More energy was expended for the same amount of material removed, hence a higher specific cutting energy (SCE) implies inefficient material removal. Usually, the type of coolants or lubricants affects the SCE, or the amount of energy needed to cut a given volume of material. Therefore, the present work deals with a study of SCE in the turning of Ti-3Al-2.5V alloy under green cooling strategies. In spite of this, the research effort is also focused on the mechanism of tool wear, surface roughness, and cutting temperature under hybrid cooling, i.e., minimum quantity lubrication (MQL) and cryogenic. The tool wear rate, were explored with tool mapping analysis, and the results were compared with dry, MQL, and liquid nitrogen (LN 2) conditions. The tool wear rate analysis claims that the dry condition causes more built up edge (BUE) formation. In addition, the hybrid cooling conditions are helpful in reducing the SCE while machining titanium alloys.
View
Cutting Tool Wear Minimization in Drilling Operations of Titanium alloy Ti6Al4V
Article
Full-text available
  • Feb 2023
Cutting tool wear during drilling operations can cause damage to cutting tools, machine tools, and workpieces which should be analyzed and minimized. Cutting tool wear impacts not just tool life but also the quality of the final product in terms of dimensional accuracy and surface integrity. High mechanical and thermal loads are generated during drilling operations of difficult-to-cut materials such as Ti-6Al-4V alloy which can reduce the performance and life of cutting tool during chip formation process. As a result, to increase accuracy of drilled parts from Titanium alloy Ti6Al4V, the cutting tool wear during drilling operations should be accurately predicted in order to be minimized. Application of virtual machining systems is developed in the study in order to predict and minimize the cutting tool wear during drilling operations of Titanium alloy Ti6Al4V. To predict the tool wear during drilling operations, cutting forces and temperature are calculated. Then, the finite element method is utilized to predict the tool wear by using the analytical model of Takeyama– Murata and updating the cutting tool geometry during chip formation process. In order to minimize the cutting tool wear during drilling operations, the optimum drilling parameters of feed rate and spindle speed are obtained by using the Taguchi method-based response surface analysis algorithm. As a result, optimized drilling parameters are used in order to minimize the cutting tool wear during drilling operations. To validate the study, the experimental works are implemented to the sample workpiece from Titanium alloy Ti6Al4V and the values of tool wear are then measured. To present the effectiveness of the proposed virtual machining system in minimization of cutting tool wear, the obtained results with and without optimized machining parameters are evaluated and compared. So, precision and productivity in drilling operations of Titanium alloy Ti6Al4V can be enhanced by using the developed virtual machining system in the study.
View
Comparison of Tool Wear Mechanisms During Drilling of Aluminium Alloy 7075 in Dry and Chilled Air Conditions
Article
Full-text available
  • Jun 2022
Aluminium alloys are widely used in manufacturing industry due to the need of lightweight components and low production cost. However, mechanical assembly of the alloy which requires drilling operations is challenging due to chip accumulation and heat at the cutting tool and workpiece interface. This often causes material adhesion on cutting edges, built-up edge, accelerated tool wear, shorter tool life and poor drilled hole quality. This paper investigates the effect drilling conditions (dry and chilled air at 10°C) on the wear mechanisms of tungsten carbide cutting tools during drilling Aluminium alloy 7075 (Al 7075) at two different feed rates. Chilled or cold air was used as a cooling medium in drilling Al 7075 to promote green manufacturing. Drilling operations of Al 7075 were performed at a constant cutting speed of 123 m/min with feed rates of 0.01 and 0.1 mm/rev. The cutting tools’ flank wear were measured using an optical microscope with Dino-Capture software and further examination on the tool wear (e.g., built-up edge, built-up layer, and crack) were conducted using Scanning Electron Microscopy (SEM). The results of this study indicate that at higher feed rate of 0.1 mm/rev, adhesive wear is dominant due to the presence of evident material adhesion and fractures on the cutting edges. The use of chilled air was found to cause less material adhesion, however more edge fracture occurred which could be due to workpiece hardening. Therefore, it is inferred that drilling Al 7075 with chilled air requires harder and stronger cutting tool in order prolong the tool life.
View
Assessment of Hole Quality, Thermal Analysis and Chip Formation during Dry Drilling Process of Gray Cast Iron ASTM A48
Article
Full-text available
  • Jun 2022
The cutting parameters in drilling operations are important for high-quality holes and productivity improvement in any manufacturing industry. This study investigates the effects of spindle speed and feed rate on temperature, surface roughness, hole size, circularity, and chip formation during dry drilling of gray cast iron ASTM A48. The results showed that the temperature increased as spindle speed and feed rate increased. The surface roughness had an inverse relationship with the spindle speed and direct relation with the feed rate. Furthermore, hole size increased with increased spindle speed and decreased as the feed rate increased, while hole circularity decreased with increasing both the spindle speed and feed rate. The analysis of variance (ANOVA) indicated that the spindle speed had the highest percentage contribution of 56.24% on temperature, followed by the feed rate with 42.35%. The surface roughness was highly influenced by the feed rate and the spindle speed with 55% and 44.12%, respectively. While the hole size was highly influenced by the feed rate with a 74.18% percentage contribution, and the contribution of spindle speed was 21.36%. In addition, the feed rate has a percentage contribution of 70.82% on circularity, which is higher than the spindle speed of 24.26% percentage contribution. The results also showed that thick and discontinuous chips were generated at higher feed rates, while long continuous chips were produced at high spindle speeds.
View
Sustainability in drilling of aluminum alloy
Article
Full-text available
  • Jan 2022
Drilling is an extremely crucial process and enormously used in manufacturing assembling components. On the other hand, the 6061-aluminum alloy is most used in modern industry. Therefore, sustainable drilling of this alloy to reduce the use of power and coolant without compromising the quality is promising for the modern industries. This study investigates the active peak power, burr formation, diameter error, circularity error, cylindricity and surface roughness for different cooling methods such as dry, minimum quantity lubrication (MQL), liquid nitrogen (LN2) and air cooling (AIR) under different speeds and feeds. It is found that cooling methods have negligible effect of active power consumption which increases with the increase of speed and feed. Clear trends of the dimensional errors are not noticed with the variation of parameters considered in this investigation. The influences of coolants on surface roughness and chip thickness ratio also don’t follow any trend. The surface roughness increases with the increase of feeds and speeds. The chip thickness ratio tends to increase with the increase of speed and decrease of feed. It is noted that a specific coolant is required at certain speed and feed to obtain a desired outcome. The balance of hardening and softening effects of workpiece materials at different cutting conditions and rigidity of machine tools controls the desired sustainable outcomes.
View
Tool wear and burr formation during drilling of aluminum alloy 7075 in dry and with cutting fluid
Article
Full-text available
  • Jan 2022
Aluminum alloy 7075 (Al 7075) has been widely used in aerospace and automotive industries to replace heavier alloys. This is because of its superior properties of high specific strength, high corrosion resistance, good formability, recyclability and low fabrication cost. However, the ductility and heat generation during drilling Al 7075 often produces a burr at the entrance and exit of the workpiece surface. This research investigates the effect of cutting speeds and drilling conditions on the burr formation of Al 7075. Drilling was performed in dry and with conventional cutting fluid using 6.0 mm high speed steel drills with cutting speeds of 22, 44 and 66 m/min at a constant feed rate of 0.15 mm/rev. The use of cutting fluid in drilling Al 7075 caused lower tool wear by 42%, 38% and 30%, respectively, at 22, 44 and 66 m/min, compared to dry drilling. As for burr formation, drilling with cutting fluid on average resulted in 20% lower burr root width and 10% lower burr height than dry drilling for all cutting speeds. This study indicated that drilling Al 7075 using the cutting speed of 44 m/min with cutting fluid is beneficial as it resulted in the least tool wear and minimum burr formation.
View
View
Experimental investigation of the effective parameters and performance of different types of structural tools in drilling CFRP/AL alloy stacks
Article
  • Oct 2022
In the modern aerospace industry, the application of hybrid multilayers (CFRP)/aluminum7075 stacks to manufacture various parts of modern aircraft fuselages is increasing in order to improve the quality of the structure. This study investigates the effective parameters when drilling carbon fiber composite (CFRP) and aluminum alloy 7075 stacks with different tool geometries/materials to compare dry machining with the cooling method and investigate the effect of cutting input variables of the drilling operation on machining results. With ANOVA analysis, the most influential parameter for the drilling operation of this kind of multilayer stack was determined as the feed rate. According to the experimental results, the surface roughness of the cooling system drilling was 38% lower than the average roughness of the other two tools (B and C). Moreover, the tool’s geometry and the cooling conditions (friction) have a greater influence on the drilling performance than the spindle speed and feed rate.
View