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Tolerance Stack-ups
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Problems due to tolerancestack-ups include:
Failure to assemble
Interference between parts Failure of parts to engage
Failure to function as intended
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Overview:
Tolerance stack-ups areaccumulations of variations
on drawings or in part
assemblies.
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3.000.0!
".000.0!
#$ample: %ccumulation of tolerances ona drawing.
&'at is t'e e(ective dimension and tolerance between t'e
two 'oles)
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In t'is case t'e tolerances add directl*
T'e furt'est apart t'e two centers can be is
".0!-+.,,.0+
T'e closest is
/.,,-3.0!3.,
T'us1 t'e e(ective dimension and tolerance
is
.000.0+
T'is addition of tolerances ma* make it 'ard
to 2oin wit' a mating part t'at 'as two pins
t'at t in t'ose 'oles.
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&'at can we do as designersto improve t'is)
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T'e logical t'ing is to put t'e dimension and
tolerance directl* on t'e 'ole spacing if t'at is t'elocation
most important to function.
".000.0!
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#$ample: %ssembl* ofindividual parts
4uppose we 'ave two blocks1 % and 5 t'at are to t
into a slot in 61 all wit' tolerances s'own.
7ap
6c
%a5b
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8et9s look at t'e largest and smallest gap t'at
we could 'ave.
8argest 7ap 6;c< = %-a< = 5-b
