Locating Principle and Locators

8/20/2019 Locating Principle and Locators

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LOCATING PRINCIPLES

and LOCATORS


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Referencing andRepeatability"Referencing" is a dual process of

positioning te !orpiece relati#e to te!orolder$ and te !orolder relati#eto te cutting tool%

If a part is incorrectly placed in a!orolder$ proper location of te!orpiece is not acie#ed and te part!ill be &acined incorrectly%

If a cutter is i&properly positionedrelati#e to te '(ture$ te &acineddetail is also i&properly located%


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Locators

To perfor& properly$ !orolders&ust accurately and consistentlyposition te !orpiece relati#e to

te cutting tool$ part after part% To acco&plis tis$ te locators&ust ensure tat te !orpiece

is properly referenced and teprocess is repeatable%


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Te )ecanics of Locating

A !orpiece free in space can&o#e in an in'nite nu&ber ofdirections% *or analysis$ tis

&otion can be broen do!n intot!el#e directional &o#e&ents$ or"degrees of freedo&%"


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Locators and cla&ps

Te de#ices tat restrict a!orpiece+s &o#e&ent are telocators% Te locators$ terefore$

&ust be strong enoug to &aintainte position of te !orpiece and toresist te cutting forces% Tis factalso points out a crucial ele&ent in

!orolder design, locators$ notcla&ps$ &ust old te !orpieceagainst te cutting forces%


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Locators and cla&ps

Locators pro#ide a positi#e stop for te!orpiece% Placed against te stop$ te

!orpiece cannot &o#e% Cla&ps$ onte oter and$ rely only upon frictionbet!een te cla&p and te cla&pedsurface to old te !orpiece%

Su-cient force could &o#e te!orpiece% Cla&ps are only intendedto old te !orpiece against telocators%


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*or&s of Location

.% Plane Location/% Concentric Location

0% Radial Location


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*or&s of Location

Plane locators locate a !orpiece fro& any surface% Te surface &ay be 1at$ cur#ed$ or a#e an irregularcontour% In &ost applications$ plane2locating de#iceslocate a part by its e(ternal surfaces$

Concentric locators$ for te &ost part$ locate a!orpiece fro& a central a(is% Tis a(is &ay or &aynot be in te center of te !orpiece% Te &ost2co&&on type of concentric location is a locating pinplaced in a ole%

Radial locators restrict te &o#e&ent of a!orpiece around a concentric locator


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Locating fro& E(ternal Surfaces2Supports

Supports are teprincipal de#icesused for tis

location in 1atsurfaces%

solid$ ad3ustable$

and e4uali5ing$


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Locating fro& E(ternal Surfaces2SupportsSolid supports are '(ed2eigt locators% Tey precisely

locate a surface in one a(is% Toug solid supports &aybe &acined directly into a tool body$ a &ore2econo&ical&etod is using installed supports$ suc as rest buttons%

Ad3ustable supports are #ariable2eigt locators% Tesesupports are used !ere !orpiece #ariations re4uiread3ustable support to suit di6erent eigts% Tesesupports are used &ainly for cast or forged !orpiecestat a#e une#en or irregular &ounting surfaces%

E4uali5ing supports are a for& of ad3ustable support used!en a co&pensating support is re4uired% As one side ofte e4uali5ing support is depressed$ te oter side raiseste sa&e a&ount to &aintain part contact%


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Locating fro& InternalSurfacesLocating a !orpiece fro& an internal

dia&eter is te &ost2e-cient for& oflocation% Te pri&ary features used for tisfor& of location are indi#idual oles or ole

patterns%

Te t!o for&s of locators used for internallocation are locating pins and locating plugs%

Te only di6erence bet!een tese locators isteir si5e, locating pins are used for s&alleroles and locating plugs are used for largeroles%


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Locating fro& InternalSurfaces


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Analy5ing )acining*orces Te &ost2i&portant factors to consider in

'(ture layout are te direction and&agnitude of &acining forces e(ertedduring te operation%


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Analy5ing )acining*orces

"ea#iest2cut orsepo!er" is not total &acine orsepo!er7 rater it is t&a(i&u& orsepo!er actually used during te &acining cycle% Typical &acine e-ciency is rougly 89: ;%89


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Analy5ing )acining*orces


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LOCATING G>I?ELINES

position te locators suc tattey contact te !orpiece on a&acined surface% Te &acined

surface not only pro#idesrepeatability but usually o6ers a&ore2stable for& of location%

Te best &acined surfaces touse for location$ !en a#ailable$are &acined oles%

Proper spacing of locator is


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LOCATING G>I?ELINES


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LOCATING G>I?ELINES

In te part so!n at ;b


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LOCATING G>I?ELINES


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LOCATING G>I?ELINES

Te e(a&ples in *igure so! conditions tat&ay occur !en locators are placed too closetogeter if te center positions of te locatorsare &isaligned by %==."%

@it te spacing so!n at ;a


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02/2. Locating Principle

3-2-1 principle &ay be statedas,

To locate an ob3ect fully$ placeand

old it against three points in abase

plane$ two points in a vertical plane$

and one oint in a lane


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A !orolding rule de'ning te&ini&u& nu&ber of contactpoints necessary to properly

locate a rectangular part in treeplanes% Te pri&ary datu&re4uires tree points$ te

secondary datu& t!o points$ andte tertiary datu& one point%


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Tats all for

Today

Locating Principle and Locators

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