3-2-1 Method of Location:
3-2-1
method of location is the fundamental arrangement of locating system. A work
piece may be positively and properly located by means of six pins,so positioned
that collectively they restrict the work piece in nine of it’s degree of
freedom.For this purpose a definite arrangement is used.This arrangement is called 3-2-1 method of
location.
Cause of using three locating pins
in base plane:
A minimum of three points or pins or
locators are generally used in base plane to locate the work piece, although
four or more may be used to provide adequate support. It should be noted that a
minimum of three pins will always theoritically establish the same location of
the work piece. four or more pins(locators)don’t establish this type of
theoritical location because if the work piece surface is not geometrically
true, the position is still determined by three pins.
Three pining system create one surface
which is geometrically true and this surface is parallel to the locating base
surface whereas four or more pining system create surface more than one having
non-parallel relation with the base surface. So the use of more than three pins
or points causes surface deviation frequently.That’s why three pins are used in
base plane.
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