<s>
A	O
feature	O
,	O
in	O
computer-aided	B-Application
design	I-Application
(	O
CAD	B-Application
)	O
,	O
usually	O
refers	O
to	O
a	O
region	O
of	O
a	O
part	O
with	O
some	O
interesting	O
geometric	O
or	O
topological	O
properties	O
.	O
</s>
<s>
They	O
are	O
now	O
ubiquitous	O
in	O
most	O
current	O
CAD	B-Application
software	I-Application
,	O
where	O
they	O
are	O
used	O
as	O
the	O
primary	O
means	O
of	O
creating	O
3D	O
geometric	O
models	O
.	O
</s>
<s>
Form	O
feature	O
is	O
not	O
the	O
only	O
type	O
of	O
feature	O
that	O
is	O
discussed	O
in	O
CAD	B-Application
literature	O
.	O
</s>
<s>
Feature	O
data	O
in	O
CAD	B-Application
can	O
be	O
specified	O
either	O
as	O
a	O
collection	O
of	O
surfaces	O
or	O
as	O
volumes	O
.	O
</s>
<s>
Work	O
on	O
features	O
(	O
generally	O
called	O
feature	O
technology	O
)	O
can	O
be	O
divided	O
into	O
two	O
rough	O
categories	O
:	O
Design-by-features	O
and	O
Feature	B-Algorithm
recognition	I-Algorithm
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
the	O
goal	O
of	O
feature	B-Algorithm
recognition	I-Algorithm
(	O
FR	O
)	O
is	O
to	O
algorithmically	O
extract	O
higher	O
level	O
entities	O
(	O
e.g.	O
</s>
<s>
of	O
a	O
CAD	B-Application
model	I-Application
.	O
</s>
<s>
They	O
have	O
developed	O
a	O
feature	B-Algorithm
recognition	I-Algorithm
algorithm	O
based	O
on	O
the	O
concept	O
of	O
computing	O
dynamic	O
topological	O
status	O
of	O
faces	O
.	O
</s>
<s>
In	O
this	O
way	O
,	O
an	O
overall	O
CAD/CAM	O
system	O
can	O
be	O
fully	O
automated	O
,	O
however	O
,	O
the	O
idea	O
of	O
using	O
manufacturing	O
features	O
to	O
design	O
a	O
part	O
has	O
its	O
own	O
shortcomings	O
:	O
The	O
features	O
used	O
to	O
design	O
the	O
part	O
do	O
not	O
necessarily	O
represent	O
the	O
best	O
way	O
to	O
manufacture	O
it	O
.	O
</s>
<s>
Automatic	O
Feature	B-Algorithm
Recognition	I-Algorithm
(	O
AFR	O
)	O
is	O
regarded	O
as	O
an	O
ideal	O
solution	O
to	O
automate	O
design	O
and	O
manufacturing	O
processes	O
.	O
</s>
<s>
Successful	O
automation	O
of	O
CAD	B-Application
and	O
CAM	O
systems	O
is	O
a	O
vital	O
connection	O
in	O
building	O
Computer	O
Integrated	O
Manufacturing	O
(	O
CIM	O
)	O
systems	O
.	O
</s>
<s>
There	O
is	O
a	O
big	O
stockpile	O
of	O
different	O
AFR	O
techniques	O
that	O
has	O
been	O
proposed	O
for	O
CAD/CAM	O
integration	O
and	O
process	O
planning	O
.	O
</s>
<s>
In	O
the	O
graph-based	O
feature	B-Algorithm
recognition	I-Algorithm
,	O
a	O
graph	O
showing	O
the	O
topology	O
of	O
the	O
part	O
(	O
connection	O
of	O
faces	O
)	O
is	O
created	O
.	O
</s>
<s>
However	O
,	O
building	O
feature	B-Algorithm
recognition	I-Algorithm
systems	O
that	O
function	O
effectively	O
on	O
real	O
industrial	O
products	O
has	O
been	O
elusive	O
.	O
</s>
<s>
The	O
bulk	O
of	O
the	O
feature	B-Algorithm
recognition	I-Algorithm
literature	O
normally	O
deals	O
with	O
2.5D	O
features	O
(	O
those	O
made	O
by	O
sweeping	O
a	O
2D	O
profile	O
along	O
a	O
linear	O
axis	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
feature	B-Algorithm
recognition	I-Algorithm
algorithms	O
usually	O
assume	O
sharp	O
concave	O
edges	O
in	O
the	O
feature	O
geometry	O
.	O
</s>
<s>
Few	O
commercial	O
feature	B-Algorithm
recognition	I-Algorithm
systems	O
are	O
also	O
available	O
.	O
</s>
<s>
Though	O
feature	B-Algorithm
recognition	I-Algorithm
technology	O
can	O
be	O
applied	O
for	O
various	O
applications	O
,	O
commercial	O
software	O
have	O
effectively	O
adopted	O
feature	B-Algorithm
recognition	I-Algorithm
technology	O
for	O
recreating	O
the	O
feature	O
tree	O
from	O
imported	O
models	O
so	O
that	O
even	O
the	O
imported	O
models	O
can	O
be	O
edited	O
as	O
if	O
it	O
were	O
a	O
native	O
solid	O
model	O
.	O
</s>
<s>
Major	O
3D	O
CAD	B-Application
modelers	O
have	O
Feature	B-Algorithm
Recognition	I-Algorithm
to	O
convert	O
imported	O
3-D	O
models	O
into	O
native	O
feature	O
based	O
models	O
.	O
</s>
<s>
CAM	O
software	O
and	O
design	O
for	O
manufacturing	O
software	O
are	O
also	O
built	O
using	O
this	O
feature	B-Algorithm
recognition	I-Algorithm
technology	O
.	O
</s>
<s>
Few	O
CAD/CAM	O
software	O
have	O
used	O
commercially	O
available	O
third-party	O
feature	B-Algorithm
recognition	I-Algorithm
library	O
,	O
which	O
recognizes	O
various	O
features	O
from	O
3-D	O
B-Rep	O
models	O
.	O
</s>
<s>
Design	O
feature	B-Algorithm
recognition	I-Algorithm
library	O
can	O
identify	O
features	O
such	O
as	O
holes	O
of	O
various	O
types	O
,	O
split	O
holes	O
,	O
hole-chains	O
,	O
fillets	O
,	O
chamfers	O
,	O
cut	O
extrudes	O
,	O
boss	O
extrudes	O
,	O
drafted	O
extrudes	O
,	O
revolved	O
cuts	O
,	O
revolved	O
bosses	O
,	O
ribs	O
,	O
drafts	O
,	O
lofts	O
and	O
sweeps	O
are	O
identified	O
.	O
</s>
<s>
Manufacturing	O
feature	B-Algorithm
recognition	I-Algorithm
library	O
provides	O
recognition	O
of	O
manufacturing	O
features	O
such	O
as	O
simple	O
holes	O
,	O
tapered	O
holes	O
,	O
counter-bore	O
holes	O
,	O
counter-sunk	O
holes	O
,	O
counter-drilled	O
holes	O
,	O
hole-chains	O
,	O
hole	O
patterns	O
such	O
as	O
linear	O
,	O
rectangular	O
and	O
circular	O
patterns	O
,	O
fillets	O
,	O
chamfers	O
,	O
blind	O
pockets	O
,	O
through	O
pockets	O
,	O
drafted	O
pockets	O
,	O
filleted	O
and	O
chamfered	O
pockets	O
,	O
simple	O
slots	O
,	O
drafted	O
slots	O
,	O
filleted	O
and	O
chamfered	O
slots	O
,	O
islands	O
in	O
pockets	O
and	O
slots	O
,	O
machinable	O
volumes	O
,	O
machinable	O
slabs	O
,	O
multiple	O
intersecting	O
features	O
,	O
axi-symmetric	O
features	O
such	O
as	O
external	O
turned	O
profiles	O
,	O
internal	O
turned	O
profiles	O
,	O
turned	O
grooves	O
such	O
as	O
vee	O
and	O
dovetail	O
grooves	O
,	O
and	O
mill-turn	O
features	O
such	O
as	O
slots	O
and	O
pocket	O
in	O
turned	O
profiles	O
.	O
</s>
<s>
Sheet	O
metal	O
feature	B-Algorithm
recognition	I-Algorithm
library	O
extracts	O
features	O
from	O
a	O
sheet	O
metal	O
perspective	O
.	O
</s>
<s>
Manufacturing	O
features	O
such	O
as	O
3-axis	O
and	O
5-axis	O
feature	B-Algorithm
recognition	I-Algorithm
are	O
generally	O
not	O
available	O
in	O
such	O
commercial	O
systems	O
.	O
</s>
