<s>
A	O
ball	B-Algorithm
screw	I-Algorithm
(	O
or	O
ballscrew	B-Algorithm
)	O
is	O
a	O
mechanical	O
linear	B-Algorithm
actuator	I-Algorithm
that	O
translates	O
rotational	O
motion	O
to	O
linear	O
motion	O
with	O
little	O
friction	O
.	O
</s>
<s>
In	O
contrast	O
to	O
conventional	O
leadscrews	O
,	O
ball	B-Algorithm
screws	I-Algorithm
tend	O
to	O
be	O
rather	O
bulky	O
,	O
due	O
to	O
the	O
need	O
to	O
have	O
a	O
mechanism	O
to	O
recirculate	O
the	O
balls	O
.	O
</s>
<s>
The	O
ball	B-Algorithm
screw	I-Algorithm
was	O
invented	O
independently	O
by	O
H.M.	O
Stevenson	O
and	O
D	O
.	O
Glenn	O
who	O
were	O
issued	O
in	O
1898	O
patents	O
601,451	O
and	O
610,044	O
respectively	O
.	O
</s>
<s>
Low	O
friction	O
in	O
ball	B-Algorithm
screws	I-Algorithm
yields	O
high	O
mechanical	O
efficiency	O
compared	O
to	O
alternatives	O
.	O
</s>
<s>
A	O
typical	O
ball	B-Algorithm
screw	I-Algorithm
may	O
be	O
90	O
percent	O
efficient	O
,	O
versus	O
20	O
to	O
25	O
percent	O
efficiency	O
of	O
an	O
Acme	O
lead	O
screw	O
of	O
equal	O
size	O
.	O
</s>
<s>
This	O
,	O
combined	O
with	O
their	O
overall	O
performance	O
benefits	O
and	O
reduced	O
power	O
requirements	O
,	O
may	O
offset	O
the	O
initial	O
costs	O
of	O
using	O
ball	B-Algorithm
screws	I-Algorithm
.	O
</s>
<s>
Ball	B-Algorithm
screws	I-Algorithm
may	O
also	O
reduce	O
or	O
eliminate	O
backlash	O
common	O
in	O
lead	O
screw	O
and	O
nut	O
combinations	O
.	O
</s>
<s>
The	O
balls	O
may	O
be	O
preloaded	O
so	O
that	O
there	O
is	O
no	O
"	O
wiggle	O
"	O
between	O
the	O
ball	B-Algorithm
screw	I-Algorithm
and	O
ball	B-Algorithm
nut	I-Algorithm
.	O
</s>
<s>
Because	O
of	O
their	O
very	O
high	O
mechanical	O
efficiency	O
,	O
especially	O
compared	O
to	O
traditional	O
lead	O
screws	O
,	O
ball	B-Algorithm
screws	I-Algorithm
can	O
potentially	O
be	O
back-driven	O
(	O
i.e.	O
,	O
a	O
linear	O
force	O
applied	O
directly	O
to	O
the	O
nut	O
can	O
induce	O
a	O
rotation	O
of	O
the	O
shaft	O
,	O
an	O
effect	O
counterproductive	O
to	O
most	O
uses	O
)	O
.	O
</s>
<s>
The	O
static	O
torque	O
and	O
digital	O
control	O
of	O
an	O
appropriate	O
servomotor	B-Algorithm
can	O
be	O
made	O
to	O
resist	O
and	O
compensate	O
,	O
but	O
hand	O
cranked	O
mechanisms	O
would	O
require	O
additional	O
mechanisms	O
to	O
prevent	O
undesirable	O
behaviors	O
.	O
</s>
<s>
If	O
the	O
ball	B-Algorithm
nut	I-Algorithm
did	O
not	O
have	O
a	O
return	O
mechanism	O
the	O
balls	O
would	O
fall	O
out	O
of	O
the	O
end	O
of	O
the	O
ball	B-Algorithm
nut	I-Algorithm
when	O
they	O
reached	O
the	O
end	O
of	O
the	O
nut	O
.	O
</s>
<s>
An	O
endcap	O
return	O
ball	B-Algorithm
nut	I-Algorithm
employs	O
a	O
cap	O
on	O
the	O
end	O
of	O
the	O
ball	B-Algorithm
nut	I-Algorithm
.	O
</s>
<s>
A	O
ball	B-Algorithm
screw	I-Algorithm
involves	O
significantly	O
more	O
parts	O
and	O
surface	O
interactions	O
than	O
many	O
similar	O
systems	O
.	O
</s>
<s>
While	O
a	O
basic	O
lead	O
screw	O
is	O
composed	O
of	O
only	O
a	O
solid	O
shaft	O
and	O
a	O
solid	O
nut	O
with	O
simple	O
mating	O
geometries	O
,	O
a	O
ball	B-Algorithm
screw	I-Algorithm
requires	O
precisely	O
formed	O
curved	O
contours	O
and	O
multi-part	O
assemblies	O
to	O
facilitate	O
the	O
action	O
of	O
the	O
bearing	O
balls	O
.	O
</s>
<s>
Where	O
is	O
torque	O
applied	O
to	O
screw	O
or	O
nut	O
,	O
is	O
linear	O
force	O
applied	O
,	O
is	O
ball	B-Algorithm
screw	I-Algorithm
lead	O
,	O
and	O
is	O
ball	B-Algorithm
screw	I-Algorithm
efficiency	O
.	O
</s>
<s>
In	O
the	O
United	O
States	O
,	O
ASME	O
has	O
developed	O
the	O
B5.48-1977	O
Standard	O
entitled	O
"	O
Ball	B-Algorithm
Screws	I-Algorithm
"	O
.	O
</s>
<s>
The	O
correct	O
evaluation	O
of	O
the	O
curvatures	O
of	O
ball	B-Algorithm
screw	I-Algorithm
grooves	O
allows	O
to	O
accurately	O
design	O
the	O
constructive	O
parameters	O
of	O
this	O
mechanism	O
and	O
to	O
enhance	O
its	O
performance	O
.	O
</s>
<s>
This	O
may	O
be	O
achieved	O
by	O
using	O
rubber	O
or	O
leather	O
bellows	B-Algorithm
to	O
completely	O
or	O
partially	O
enclose	O
the	O
working	O
surfaces	O
.	O
</s>
<s>
While	O
reducing	O
friction	O
,	O
ball	B-Algorithm
screws	I-Algorithm
can	O
operate	O
with	O
some	O
preload	O
,	O
effectively	O
eliminating	O
backlash	O
(	O
slop	O
)	O
between	O
input	O
(	O
rotation	O
)	O
and	O
output	O
(	O
linear	O
motion	O
)	O
.	O
</s>
<s>
This	O
feature	O
is	O
essential	O
when	O
they	O
are	O
used	O
in	O
computer-controlled	O
motion-control	O
systems	O
,	O
e.g.	O
,	O
CNC	O
machine	O
tools	O
and	O
high	O
precision	O
motion	O
applications	O
(	O
e.g.	O
,	O
wire	B-Algorithm
bonding	I-Algorithm
)	O
.	O
</s>
<s>
In	O
practice	O
,	O
most	O
ball	B-Algorithm
screws	I-Algorithm
are	O
designed	O
to	O
be	O
lightly	O
preloaded	O
,	O
so	O
that	O
there	O
is	O
at	O
least	O
a	O
slight	O
load	O
on	O
the	O
ball	O
at	O
four	O
points	O
,	O
two	O
in	O
contact	O
with	O
the	O
nut	O
and	O
two	O
in	O
contact	O
with	O
the	O
screw	O
.	O
</s>
<s>
It	O
is	O
more	O
common	O
to	O
design	O
the	O
ball	B-Algorithm
nut	I-Algorithm
as	O
effectively	O
two	O
separate	O
nuts	O
which	O
are	O
tightly	O
coupled	O
mechanically	O
,	O
with	O
adjustment	O
by	O
either	O
rotating	O
one	O
nut	O
with	O
respect	O
to	O
the	O
other	O
,	O
so	O
creating	O
a	O
relative	O
axial	O
displacement	O
,	O
or	O
by	O
retaining	O
both	O
nuts	O
tightly	O
together	O
axially	O
and	O
rotating	O
one	O
with	O
respect	O
to	O
the	O
other	O
,	O
so	O
that	O
its	O
set	O
of	O
balls	O
is	O
displaced	O
axially	O
to	O
create	O
the	O
preload	O
.	O
</s>
<s>
Ball	B-Algorithm
screw	I-Algorithm
shafts	O
may	O
be	O
fabricated	O
by	O
rolling	O
,	O
yielding	O
a	O
less	O
precise	O
,	O
but	O
inexpensive	O
and	O
mechanically	O
efficient	O
product	O
.	O
</s>
<s>
Rolled	O
ball	B-Algorithm
screws	I-Algorithm
have	O
a	O
positional	O
precision	O
of	O
several	O
thousandths	O
of	O
an	O
inch	O
per	O
foot	O
.	O
</s>
<s>
Ball	B-Algorithm
screw	I-Algorithm
are	O
classified	O
using	O
"	O
accuracy	O
grades	O
"	O
from	O
C0	O
(	O
most	O
precise	O
)	O
to	O
C10	O
.	O
</s>
<s>
Ball	B-Algorithm
screws	I-Algorithm
are	O
used	O
in	O
aircraft	O
and	O
missiles	O
to	O
move	O
control	O
surfaces	O
,	O
especially	O
for	O
electric	O
fly	O
by	O
wire	O
,	O
and	O
in	O
automobile	O
power	O
steering	O
to	O
translate	O
rotary	O
motion	O
from	O
an	O
electric	O
motor	O
to	O
axial	O
motion	O
of	O
the	O
steering	O
rack	O
.	O
</s>
<s>
They	O
are	O
also	O
used	O
in	O
machine	O
tools	O
,	O
robots	B-Algorithm
,	O
and	O
precision	O
assembly	O
equipment	O
.	O
</s>
<s>
High	O
precision	O
ball	B-Algorithm
screws	I-Algorithm
are	O
used	O
in	O
steppers	B-Algorithm
for	O
semiconductor	B-Architecture
manufacturing	I-Architecture
.	O
</s>
<s>
A	O
ball	B-Algorithm
screw	I-Algorithm
is	O
used	O
to	O
expand	O
the	O
Deployable	O
Tower	O
Assembly	O
(	O
DTA	O
)	O
structure	O
on	O
the	O
James	O
Webb	O
Space	O
Telescope	O
.	O
</s>
<s>
Another	O
form	O
of	O
linear	B-Algorithm
actuator	I-Algorithm
based	O
on	O
a	O
rotating	O
rod	O
is	O
the	O
threadless	O
ballscrew	B-Algorithm
,	O
a.k.a.	O
</s>
<s>
An	O
advantage	O
of	O
this	O
design	O
over	O
the	O
conventional	O
ballscrew	B-Algorithm
or	O
leadscrew	O
is	O
the	O
practical	O
elimination	O
of	O
backlash	O
and	O
loading	O
caused	O
by	O
preload	O
nuts	O
.	O
</s>
