Circular profile while machined comes like a polygon.!!!

I have tried sketchucam which does the circular profile without any problem, when I generate tool path from fusion 360 it does not show any problem while simulation, but when I machine it circular profile comes like a polygon. Not able to identify the problem...!!! I am using grbl 0.9

 

Yes, I have drawn and generated the toolpath in fusion..I have attached the fusion file ..

This is the g code

%
(corner)
(T1 D=8 CR=0 - ZMIN=-18 - flat end mill)
G90 G94
G17
G21

(2D Contour1)
M9
T1 M6
S10000 M3
G54
M9
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Z15
Z5
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X179.588 Y48.346 Z-1.506
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X179.485 Y48.331 Z-1.687
X179.417 Y48.321 Z-1.766
X179.339 Y48.309 Z-1.835
X179.253 Y48.297 Z-1.893
X179.16 Y48.283 Z-1.939
X179.062 Y48.269 Z-1.973
X178.96 Y48.254 Z-1.993
X178.857 Y48.239 Z-2
X178.065 Y48.124
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G1 Y0
G2 X175 Y-4 I-4
G1 X0
G2 X-4 Y0 J4
G1 Y175
G2 X0 Y179 I4
G1 X25
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X179.773 Y46.756 Z-1.6
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X179.852 Y46.767 Z-1.407
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X179.879 Y46.771 Z-1.2
G0 Z5
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X179.852 Y46.767 Z-3.407
X179.873 Y46.77 Z-3.304
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X179.588 Y48.346 Z-5.506
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X179.485 Y48.331 Z-5.687
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X179.339 Y48.309 Z-5.835
X179.253 Y48.297 Z-5.893
X179.16 Y48.283 Z-5.939
X179.062 Y48.269 Z-5.973
X178.96 Y48.254 Z-5.993
X178.857 Y48.239 Z-6
X178.065 Y48.124
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G1 Y0
G2 X175 Y-4 I-4
G1 X0
G2 X-4 Y0 J4
G1 Y175
G2 X0 Y179 I4
G1 X25
G2 X177.389 Y47.217 J-154
G3 X178.296 Y46.54 I0.792 J0.115
G1 X179.088 Y46.656
X179.191 Y46.671 Z-5.993
X179.293 Y46.686 Z-5.973
X179.391 Y46.7 Z-5.939
X179.484 Y46.713 Z-5.893
X179.57 Y46.726 Z-5.835
X179.648 Y46.737 Z-5.766
X179.716 Y46.747 Z-5.687
X179.773 Y46.756 Z-5.6
X179.819 Y46.762 Z-5.506
X179.852 Y46.767 Z-5.407
X179.873 Y46.77 Z-5.304
X179.879 Y46.771 Z-5.2
G0 Z5
X179.649 Y48.354
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X179.622 Y48.35 Z-7.407
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X179.485 Y48.331 Z-7.687
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X179.062 Y48.269 Z-7.973
X178.96 Y48.254 Z-7.993
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X178.065 Y48.124
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X178.065 Y48.124
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G2 X-4 Y0 J4
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X179.57 Y46.726 Z-9.835
X179.648 Y46.737 Z-9.766
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X179.852 Y46.767 Z-9.407
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G0 Z5
X179.649 Y48.354
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X179.622 Y48.35 Z-11.407
X179.588 Y48.346 Z-11.506
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X179.485 Y48.331 Z-11.687
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X179.339 Y48.309 Z-11.835
X179.253 Y48.297 Z-11.893
X179.16 Y48.283 Z-11.939
X179.062 Y48.269 Z-11.973
X178.96 Y48.254 Z-11.993
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X178.065 Y48.124
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G2 X175 Y-4 I-4
G1 X0
G2 X-4 Y0 J4
G1 Y175
G2 X0 Y179 I4
G1 X25
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X179.191 Y46.671 Z-11.993
X179.293 Y46.686 Z-11.973
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X179.484 Y46.713 Z-11.893
X179.57 Y46.726 Z-11.835
X179.648 Y46.737 Z-11.766
X179.716 Y46.747 Z-11.687
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G2 X-4 Y0 J4
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X179.57 Y46.726 Z-13.835
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X179.716 Y46.747 Z-13.687
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X179.484 Y46.713 Z-15.893
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X179.716 Y46.747 Z-15.687
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X179.253 Y48.297 Z-17.893
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X178.065 Y48.124
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G2 X175 Y-4 I-4
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Z-16
X123.25
Z-18 F30
X51.75 F1920
Z-16
X35.75
Z-18 F30
X0 F1920
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Z-16
Y51.75
Z-18 F30
Y123.25 F1920
Z-16
Y139.25
Z-18 F30
Y175 F1920
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G3 X178.296 Y46.54 I0.792 J0.115
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X179.293 Y46.686 Z-17.973
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X179.484 Y46.713 Z-17.893
X179.57 Y46.726 Z-17.835
X179.648 Y46.737 Z-17.766
X179.716 Y46.747 Z-17.687
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X179.819 Y46.762 Z-17.506
X179.852 Y46.767 Z-17.407
X179.873 Y46.77 Z-17.304
X179.879 Y46.771 Z-17.2
G0 Z15
M9
M30
%

 

I'm using Universal G code sender....i'll give a try of what you suggested..