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International Interdisciplinary Journal of Scientific Research Vol. 1 No. 3 December, 2014
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DESIGN AND FABRICATION OF A CNC MACHINE FOR
ENGRAVING AND DRILLING
Khan LA 1, Mehtab U
2, Hasan EU
3, Hussain Z
4
1Associate Professor/Associate Dean University of Lahore Islamabad Campus
2,3,4 Department of Mechatronics Engineering, Air University, Pakistan
Abstract
The paper is focused on the research of On-machine measurement system for a CNC multi-axis milling
machine. This research is aimed at the suitable selection of measuring parameters for On-machine
measurement system in order to reach an accurate and reliable quality control of the mechanical part.
Theoretical information and overall concept of research are also presented.
Keywords— CNC multi axis milling machine, on-machine measurement, quality control
Introduction
The importance of improving machine accuracy is well recognized due to increasing demand of reducing the
product dimensional tolerance. Quality control is one of the important parts of production process which can
be performed through many possible ways with different measuring gauges and equipment. New products
following trends of designers and requirements of industrial applications with free form surfaces demand
instruments with high ability of measuring. Regarding many advantages of On-machine measurement
system, the utilization of the system has become a subject of many researchers. These systems allow
controlling the parts directly on the machine tool, and also the process can be integrated directly to the
machining process, whereas the delays from transportation and measuring process performed on coordinated
machine are omitted.
System Overview
The CNC Engraving Machine consists of an X-axis, Y axis (gantry, Cutting table, Spindle, Base & Frame),
and Z-axis linear drive system (plunge arm, frame etc). However, CNC Control card and Computer are the
typical parts of a CNC machine and together formed the complete control unit of the machine. A standard
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system configuration is shown in Fig
mechanism is used for 3 axis drive sys
mechanism has a high mechanical effici
stepper motors as accurate rotation was
without any compromise at torque.
F
Mechanical Modeling
� � � � �� ��� + ��� = �net (1)
Electrical Modeling
Using Kirchoff’s Voltage Law
V Input = � � �����
� � � � ���
� ������� (2)
The net torque of stepper motor is
� � �m sin � ∆�� (3)
�m = �hold on/rated = 1.5 Nm/A
Substituting (1) in (3)
��� + ��� = �m sin� ∆��
Now, Substituting (2) in (4)
��� + ���= �m sin� ∆�� " �������
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ig 1, showing the essential parts of a CNC m
ystems as it provides reliability and durability of
iciency and a very low cost of maintenance. The
as required in the process and stepper motor pro
Fig 1 System Flow diagram
1)
2)
3)
(4)
33 www.iijsr.org
machine. Ball screw
of to the system. This
he actuators used were
rovides such accuracy
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Taking Laplace
��#�$�#% � &#' � �m sin� ∆�� (�) � � �#�*(5)
� → ,-./0/1-23 4.5 �27-#
� � 8% �9%� � 9%
� � 0.318 �0.0179�% " �6.28�% � 4.01 " 10BCDE
Substituting values in (5)
��#�$4.01 " 10BC#% � 1.5 #' � 1.55�60 " 2� F4.5# �3.21 � 0.05�G
So,
��-� � 0.17 − 0.209.�BI.JK�� � 0.034.�BI.CLM�� (6)
S.No Parameter Value
1. ∆� 2
2. 60
3. M 0.32 kg
4. R 0.0179 m
5. Fc 9.81 N
6. b 1.56 N/s
Table 1 Parameters used for the solution of equations from 1 through 5
Spindle Motor Power Calculations
Input Power = VI
Efficiency = 80%
POutput = 80" � MJNII� W = 7.68 W
P required = �required " 9
�required → Required Torque for routing PCB (Copper + Bakelite or Fiber)
�required = 0.012 Nm
9 = 628.3 OP�)QR
P required = 7.54 W
P required < P Output
Motor can be used.
S.No Parameter Value
1.
RPM
628.3 OP�)QR
2. Input Voltage 12 V
3. Current 0.8 A
4. PInput 9.6 W
Table 2 Parameters used to calculate spindle motor power
International Interdisciplinary Journal of Scientific Research ISSN: 2200-9833 www.iijsr.org
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Spindle Motor Modeling
RPM = 6000
9 = 628.3 OP�)QR
tm = K Im (7)
E = k 9m (8)
K = N%
J%L.C = 0.019 V/s
G = 1
Ro = G Ed / Im = 15 Ohms
Using Newton’s 2nd
Law of Motion
∑ � � � �� = �M - b9m – �L (3)
IM = �M / K
Using Kirchoff’s Voltage Law
EM = G ED - Ro IM
EF = h 9m
e = ED - EF
EM = Ge + Ro IM (9)
G = 1
So,
�M = K " (ED - h 9m - k 9m) Ro (10)
Substituting equation (5) in equation (3)
�9m + b9m = k/ Ro [Ed - h9m - k 9m] – �L (11)
9m = [JD + (B+K2/ Ro + K h/ Ro) = – �L + K Ed / Ro (12)
B= FC/9 = 0.02/628.3 = �L max / Imax = 0.012 / 0.8 = 0.015
By using the values given in table 3and solving equation (7), we get
9m [(1.28 D +1)] =17 Ed – 6.6 x 104 �L
T, = Static Gain = 17
�, = Disturbance Sensitivity = -6.6 x 104
V , = Time Constant = 1.28 seconds
Natural time constant = J / B = M.WK "NIXYC.NL "NIXY = 3 seconds
Homogenous complimentary solution is
9m (1.28 D + 1) = (17" 2) - 6.6 " 104
(6 " 10-5
)
9m (1.28 D + 1) = 200 (13)
9m (1.28 D + 1) = 0
D = -0.78
9mh = A e-0.78t
Complimentary solution is
9mc = %II
�N.%L ��N�
9m (t) = A e-0.78t
+200
Initial conditions at 9m = 0 and t=0
9m = 0
0 = A +200
A = -200
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So,
9m (t) = 200 (1 – e-0.78t
)
S.No Parameter Value
1. J
9.54 x 10-5
Nm
2. FC
0.02 (2000
RPM)
3. 9mc
200
Table 3 Parameters used for spindle motor modeling
Ball Screw Calculations
Required Accuracy = 0.0254 mm
Step of motor = 2O
L "(%
CJI) = 0.0254
L = 4.572 mm (Pitch of Lead Screw)
Percentage of Error = 1.57 %
Can be neglected. OK to use
Conclusion
The project started with a machine capable of only point to point motion with many drawbacks (accuracy,
jerks etc).The existing machine features are compared with the professional CNC machine.
After comparison and making the required improvements, the machine is in a position to mill complex
contours on PCB, soft wood and soft metals with considerable accuracy and speed. Achieving this primary
goal is the result of improvements in both electrical and mechanical design. Exploring new software with
better capabilities also helped us in achieving this goal. The workspace and job clamping system is also
improved.
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Fig 2 Fabricated working model of CN
Fig 3 PCB board engraved by the deve
X-axis
Y-axis
Z-axis
PCB sit-in for engraving and d
Tool
l of Scientific Research ISSN: 2200-9833
CNC engraving and drilling machine
eveloped CNC machine
axis
ing and drilling
33 www.iijsr.org
International Interdisciplinary Journal of Scientific Research Vol. 1 No. 3 December, 2014
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References
[1] Katsuhiko Ogata, Modern Control Engineering, 4th Edition, Prentice Hall Of India, New Delhi, 2004
[2] Kelly James Floyd, Patrick Hood-Daniel, Build Your Own CNC Machine, 1st Edition, Springer-
Verlag, New York, 2009.
[3] Geoff Williams, CNC Robotics: Build Your Own Shop Bot, 1st Edition, McGraw Hill, New York,
2003.
[4] Seames, S. Warren, Computer Numerical Control, 4th
Edition, Thomson Learning Inc., New York,
2002.
[5] Overby Alan, CNC Machining Handbook: Building, Programming, and Implementation, 1st Edition,
McGraw Hill, New York, 2010.
[6] Madison James, CNC Machining Handbook, 1st Edition, Industrial Press Inc., New York, 1996.
[7] Albert Alan, Understanding CNC Routers, 1st Edition, FPInnovations, Ottawa, 2011.
[8] Valentino James , Goldenberg Joseph, Introduction to Computer Numerical Control, 5th
Edition,
Prentice Hall, New York, 2012