location & location devices

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LOCATION & LOCATION

DEVICES

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Degree of Freedom

• Degrees of Freedom (DOF) are the set of independent

displacements and/or rotations that specify completely thedisplaced or deformed position and orientation of the bodyor system.

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Purpose of locating system

The locating system must, in conjunctionwith the clamping system, completely

constrain the workpiece, or eliminate asmany of the six degrees of freedom as

necessary for the operation to becompleted with the required accuracy 

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The choice of locating system

• The requirements of the locating system depend upon the

operation being performed, and upon the workpiece beforethe operation

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The choice of locating system

• When there is a choice of location points the most effective locationsystem must be selected

• The cylinder is the best location shape• The ease of loading and unloading the workpiece must also be

considered

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Redundant Location

• A redundant location is said to exist when two locators are attempting to

constrain one freedom from two location points• It must be avoided

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The Six Point (3-2-1) Location Principle

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The Six Point (3-2-1) Location Principle

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Locators

• For the best possible accuracy, locators should contact theworkpiece on its most accurate surfaces (versus unmachined,

rough surfaces).• Although point contact would yield best positioning accuracy,

most locators have planar contact surfaces, in order tominimize damage to the workpiece due to potentially high-

 pressure contact points.

• Locators are manufactured separately from the main body ofthe workholding device (e.g., a mounting plate) using tool-quality-hardness steel for minimum wear.

• They are normally fabricated to exact specifications as fixeddimension components or as adjustable height locators

• Locators may be placed on the periphery of the object orunderneath it and, occasionally, fitted into existing holes onthe workpiece.

• Locators should not be mounted directly on the machine tool’stable but on the workholding device’s body, which is

subsequently secured onto the machine tool’s table 

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Types of Locators

• Locators may be classified as:

a) Flat

 b) Cylindrical

c) Conical

d) Vee

• They may be fixed or adjustable according to thecircumstances

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Flat Locators

• Flat locators control the workpiece from flat surfaces or from

its profile by means of pads or pins

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Flat Locators

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Flat Locators

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Cylindrical Locators

• Cylindrical location is the most common method because it is

most effective.

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Cylindrical Locators

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Conical Locators

• Conical locators are used to locate the workpiece from a

tapered hole or shaft, and when applied in this manner aresimilar to location posts and pots.

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Vee Locators

• Vee locators are used to locate from cylindrical or part cylindrical profiles

• They may be fixed or sliding

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Vee Locators

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Vee Locators

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Vee Locators