Post on 08-Nov-2015
description
transcript
3Datums
Permission granted to reproduce for educational use only.
Explain the purpose of datums Define common terms related to datum features Interpret information provided by datum feature
symbols Describe methods for representing datum
surfaces on drawings Explain how to establish datum reference
frames
Permission granted to reproduce for educational use only.
Identify the degrees of freedom of a part Explain how to establish datum targets Identify datum target points, areas, and lines Describe methods for representing datum axes
on drawings Describe methods for representing datum
center planes on drawings
Permission granted to reproduce for educational use only.
Datums
Represent true geometric counterpart of a datum feature
Reference features of an object Establish location and size dimensions
Permission granted to reproduce for educational use only.
Datum Feature Simulator
Opposite shape of datum feature Two types:
Theoretical datum feature simulator Physical datum feature simulator
Manufacturing examples: Machine tables Surface plates Gauge surfaces Surface tables Specially designed rotation devices
Permission granted to reproduce for educational use only.
Datum Feature Symbol Do not apply to centerlines, center planes,
or axes Draw using thin lines Use any letter to identify a datum feature
except I, O, or Q Use double letters when number of datums
exceeds number of letters in alphabet
Permission granted to reproduce for educational use only.
Datum Feature Symbol
Permission granted to reproduce for educational use only.
Datum Feature
Datum plane
Simulated datum plane
Datum feature
Part
Physical datum feature simulator
Surface of manufacturing or verification equipment
Permission granted to reproduce for educational use only.
Datum Feature Terms
Actual mating envelopeSimulated datumTangent plane
Permission granted to reproduce for educational use only.
Datum Feature Symbol Placement for Surfaces
Permission granted to reproduce for educational use only.
Datum Surface Can be controlled by geometric tolerance Datum plane measurements do not take
variations in datum surface from datum plane into account
Permission granted to reproduce for educational use only.
Geometric Control of Datum Surface
Permission granted to reproduce for educational use only.
Datum Reference Frame (DRF) Concept
Select three perpendicular datum features based on their importance to part design
Assign precedence and datum reference order Primary datum Secondary datum Tertiary datum
Permission granted to reproduce for educational use only.
Datum Reference Frame Concept
Permission granted to reproduce for educational use only.
Datum Reference Frame Concept: Inspecting the Part
All parts have six degrees of freedomThree degrees of translationThree degrees of rotation
Movement is either translational or rotational
Permission granted to reproduce for educational use only.
Degrees of Freedom
Permission granted to reproduce for educational use only.
Establishing Multiple Datum Reference Frames
Datums X, Y, and Z establish one datum reference frame
Datums L and M establish second datum reference frame
Permission granted to reproduce for educational use only.
Datum Features Specified Individually
Place a note next to datum feature symbols indicating how many datum features to consider separately
Place the note 2X INDIVIDUALLY next to datum feature symbols of two separate datum features identified by same letter
Permission granted to reproduce for educational use only.
Datum Target Symbols
Identify datum targets Useful on parts with surface or contour
irregularities Connect to datum target point, line, or area
with a leader
Permission granted to reproduce for educational use only.
Datum Target Symbols
Permission granted to reproduce for educational use only.
Datum Target Points Establish primary datum plane by locating at least
three points on primary datum surface Establish secondary datum plane by locating at
least two points on related secondary datum surface
Establish tertiary datum plane by locating at least one point on related tertiary datum surface
Dimension using baseline or chain dimensioning Location dimensions originate from datums
Permission granted to reproduce for educational use only.
Datum Target Points
Permission granted to reproduce for educational use only.
Datum Target Points
Datum plane established by locating pins at datum target points
Permission granted to reproduce for educational use only.
Datum Target Areas
Used to establish datums using areas of contact
Locating pins are flat end tooling pins with pin diameter equal to specified size of target area
Top half of the datum target symbol identifies size of target area
Use datum target point at center location when area is too small to accurately or clearly display on drawing
Permission granted to reproduce for educational use only.
Datum Target Areas
Permission granted to reproduce for educational use only.
Datum Target Lines
Indicated by a target point on edge view of surface and a phantom line on surface view
Locating pins are cylindrical or knife-edged with datum target line along tangency where pins meet the part
Surface is often placed 90 to the pin to create datum reference frame
Permission granted to reproduce for educational use only.
Datum Target Lines
Permission granted to reproduce for educational use only.
Partial Datum Surface
Permission granted to reproduce for educational use only.
Coplanar Surface Datums
Used to establish coplanar surfaces as one datum plane
Specify number of surfaces with a note such as: "2 SURFACES" below related feature control frame
Permission granted to reproduce for educational use only.
Coplanar Surface Datums
Permission granted to reproduce for educational use only.
Datum Axis
Represents two theoretical planes intersecting at 90
Represented in drawings with centerlines Pitch cylinder for screw threads establishes
datum axis unless otherwise specified When not using pitch cylinder for screw threads,
place note such as "MAJOR DIA" or "MINOR DIA" next to datum feature symbol
Simulated datum axis established by inspection equipment
Permission granted to reproduce for educational use only.
Datum Axis
Permission granted to reproduce for educational use only.
Datum Feature Symbol Placement for a Datum Axis
Permission granted to reproduce for educational use only.
Coaxial Datum Features
Separate datum reference letters by a dash in one compartment of the feature control frame
Permission granted to reproduce for educational use only.
Datum Axis Established with Datum Target Symbols
Primary datum axis established by two sets of three equally spaced targets
Identify datum target points in correlation to adjacent cylindrical datum feature when two cylindrical features of different diameters establish a datum axis
Permission granted to reproduce for educational use only.
Datum Axis Established with Datum Target Symbols
Cylindrical datum target areas and circular datum target lines can be used to establish datum axis Target area represented by two phantom lines
with section lines between Datum target line represented by phantom line all
around part Establish secondary datum axis by placing
three equally spaced targets on cylindrical surface
Permission granted to reproduce for educational use only.
Movable Datum Target Symbols and Datum Target Points
When datum targets establish a center point, axis, or center plane on a RMB basis, datum feature simulator movement is normal to true profile
Permission granted to reproduce for educational use only.
Movable Datum Target Symbols and Datum Target Spheres
Circular phantom line represents spherical datum feature simulator to establish datum axis
Permission granted to reproduce for educational use only.
Datum Center Plane
Axis and center plane datum feature symbols align with/replace dimension line arrowhead or appear on feature, leader shoulder, dimension line, or feature control frame
Permission granted to reproduce for educational use only.
Datum Center Plane
Permission granted to reproduce for educational use only.
Translation Modifier
Added to feature control frame following datum feature reference and any other applicable modifiers
Specifies that basic location of datum feature simulator is unlocked and free to translate within specified geometric tolerance
Permission granted to reproduce for educational use only.
Translation Modifier
Permission granted to reproduce for educational use only.
Using Contoured Surface as Datum Feature
3D mathematical coordinate system defines compound surface feature on a part
Datum simulator results from mathematical data Common when design copies contour of an
actual object that has few or no flat surfaces to use as datums
Permission granted to reproduce for educational use only.
Identify the datum feature, part, simulated datum plane, physical datum feature simulator, and datum plane.
A)Datum featureB) Datum planeC) Part
D) Simulated datum planeE) Physical datum feature simulator
Permission granted to reproduce for educational use only.
Fill in blanks for Part I A and B and Part II A, B, C, and D. Provide dimensions for Part II B, C, and D.
Part I:A) Datum feature symbolB) Feature control frame
Part II:A) Datum plane AB) 12.2 minimumC) 12.8 minimumD) 0.1 geometric tolerance
Permission granted to reproduce for educational use only.
A) Basic dimension
Identify items AF.
B) Datum feature symbolC) Target pointD) Datum target symbolE) Datum referenceF) Target numberG) Datum target line
Permission granted to reproduce for educational use only.
Identify items AC.
A)Datum targetarea
B) Datum target symbol
C) Target area size
Permission granted to reproduce for educational use only.
A) Datum surface
Identify whether the datum reference symbol represents a datum surface, datum axis, or datum center plane in items AC.
B) Datum center planeC) Datum axis
Permission granted to reproduce for educational use only.
Actual mating envelope The smallest size that can be contracted about an
external feature or the largest size that can be expanded within an internal feature.
Coaxial datum features Exist when a single datum axis is established by
two datum features that are coaxial. Coplanar surfaces
Two or more surfaces that are on the same plane.
Permission granted to reproduce for educational use only.
Datum axis The center axis established when a cylindrical
datum feature is used. Datum center plane
The plane that splits a symmetrical feature, such as a slot or tab.
Datum feature An actual feature on a part that is used to
establish the datum.
Permission granted to reproduce for educational use only.
Datum feature simulator A perfect theoretical boundary or a physical
boundary used to establish a datum or simulated datum from a specified datum feature.
Datum feature symbol A symbol used to identify an object feature
specified as a datum and referred to as a datum feature.
Datum plane The theoretically exact plane established by the
simulated datum of the datum feature.
Permission granted to reproduce for educational use only.
Datum reference frame (DRF) The "frame" created by three datum features that
are perpendicular to each other and used for layout purposes.
Datum target lines Datum targets indicated by the target point
symbol "X" on the edge view of the surface and by a phantom line on the surface view.
Datum target A point, line, or area of contact on a part used to
establish a datum when it is not possible to use a surface.
Permission granted to reproduce for educational use only.
Datums A surface, plane, point, or axis considered
theoretically perfect. A datum is assumed to be exact.
Degrees of freedom The number of coordinates it takes to exclusively
control the position of a part.
Permission granted to reproduce for educational use only.
Normal Term used to describe a feature that is
perpendicular to a plane surface and radial to a curved surface.
Order of precedence The order in which the datums appear in the last
three compartments of the feature control frame. The primary datum is given first, followed by the secondary datum and then the tertiary datum.
Primary datum The primary datum reference established in the
datum reference frame. The primary datum is first in the order of precedence.
Permission granted to reproduce for educational use only.
Primary datum plane A datum plane established by at least three points
on the primary datum surface. These points are used to provide stability on the primary plane.
Rotational Movement around an axis.
Secondary datum The secondary datum reference established in
the datum reference frame. The secondary datum is second in the order of precedence.
Permission granted to reproduce for educational use only.
Secondary datum plane A datum plane established by at least two points
on the related secondary datum surface. Two points provide the required stability for the secondary plane.
Simulated datum A point, axis, line, or plane consistent with or
resulting from processing or inspection equipment, such as a surface plate, inspection table, gage surface, or a mandrel.
Permission granted to reproduce for educational use only.
Simulated datum axis The axis of a perfectly cylindrical inspection
device that contacts the datum feature surface. Simulated datum center plane
The center plane of a perfectly rectangular inspection device that contacts the datum feature surface.
Simulated datum plane The plane derived from the physical datum
feature simulator. It coincides with the datum plane when the datum plane is in contact with the simulated datum plane.
Permission granted to reproduce for educational use only.
Tangent plane A plane that contacts the high points of the
specified feature surface. Tertiary datum
The tertiary datum reference established in the datum reference frame. The tertiary datum is third in the order of precedence.
Tertiary datum plane A datum plane established by at least one point
on the related tertiary datum surface. One point of contact at the tertiary datum plane is all that is required to complete the datum reference frame and provide stability.
Permission granted to reproduce for educational use only.
Three degrees of rotation Occurs when a part can rotate about each axis in
the datum reference frame. Three degrees of translation
Occurs when a part can move without rotation in each of the three directions from the mutually perpendicular planes.
Translational Refers to uniform movement without rotation.
Slide 13Slide 3Slide 4DatumsDatum Feature SimulatorDatum Feature SymbolSlide 8Datum FeatureDatum Feature TermsDatum Feature Symbol Placement for SurfacesDatum SurfaceGeometric Control of Datum SurfaceDatum Reference Frame (DRF) ConceptDatum Reference Frame ConceptDatum Reference Frame Concept: Inspecting the PartDegrees of FreedomEstablishing Multiple Datum Reference FramesDatum Features Specified IndividuallyDatum Target SymbolsSlide 21Datum Target PointsSlide 23Slide 24Datum Target AreasSlide 26Datum Target LinesSlide 28Partial Datum SurfaceCoplanar Surface DatumsSlide 31Datum AxisSlide 33Datum Feature Symbol Placement for a Datum AxisCoaxial Datum FeaturesDatum Axis Established with Datum Target SymbolsSlide 37Movable Datum Target Symbols and Datum Target PointsMovable Datum Target Symbols and Datum Target SpheresDatum Center PlaneSlide 41Translation ModifierSlide 43Using Contoured Surface as Datum FeatureSlide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Slide 53Slide 54Slide 55Slide 56Slide 57Slide 58Slide 59Slide 60