orthographic convention
TRANSCRIPT
Chapter 8Convention Practice
in Orthographic Writing
TOPICS Definition Purposes Types of conventions
- Alternate position of side view- Incompleted view- Aligned view- Enlarged view- Non-existing intersection line- Cylinder intersection
DEFINITION
Convention is a commonly accepted practices which disregard some strict rules of orthographic projection.
Projection’ srules
ObjectMore readable
multiviewrepresentation
Multiviewrepresentation
Conventionpractices
Disregardsome rules
Using a dash line for representing the hidden edge.
EXAMPLE : Already met convention practice
Front view
CONVENTIONPRACTICE
PURPOSES
To improve the clarity of a drawing.
To reduce the drafting effort.
To save or efficiently use a drawingspace.
To facilitate the dimensioning.
1. Alternate position of side view
2. Incompleted view
TYPES OFCONVENTION PRACTICE
2.1 Incompleted side view
2.4 Local view
2.3 Half view
2.2 Partial view
3. Aligned view
4. Enlarged view
6. Intersection : Hole on a cylinder
5. Non-existing intersection line
TYPES OFCONVENTION PRACTICE
ALTERNATE POSITION OF SIDE VIEW
Whenever the height of an object is small and thedepth is relatively large, places the side view besidethe top view.
To save drawing space.
To improve the clarity of a drawing.
Purposes
Conventional practice
ALTERNATE POSITION OF SIDE VIEW
Front
Top
Right
Example
Example
Slot becomesmore readable.
Hole becomesmore readable.
New orientation of views stillagree with 3rd angle system.
INCOMPLETED SIDE VIEW
Incompleted side views are side views thatare eliminated a feature that can not clearlyseen from a selected viewing direction.
DEFINITION
Principal view
Difficult to read and to dimension.
Left-side view Right-side view
Details are interfered by thoseon the opposite view.
Example : Strictly orthographic projection.
Example : Incompleted side views
Incompletedleft-side view
Incompletedright-side viewPrincipal view
Better describe an object andfacilitate dimensioning.
Principal view
Example : Incompleted side views representation
PARTIAL VIEW HALF VIEW
LOCAL VIEW
Partial view is a view that represents portionsof the part that have a features need to clarify.
DEFINITION
Half view is a partial view that is illustrated only half of the part.
Local view is a view that shows only featuresneed to clarify.
Clearly seena shape.
Example : Partial views
Symmetry symbol
Left half Right half
Thin line (4H)
Center line acts as aline of symmetry.
No continuous line !
Example : Half view
Half view can be made by drawing the viewsslightly beyond the line of symmetry.
No symmetry symbol.
It is allow for writinga break line.
In this course, we omit the break line.
Example : Half view : alternative representation
Thin line (4H)
Example : Half view : two symmetry axes
Example : Local view
Shape of theslot is completelyshown.
R67
Easy fordimensioning
ALIGNED VIEW
DEFINITION
Align view is a view that is drawn by imaginarilyrotating the object’s features, appeared in aprinciple view about symmetry axis.
Example : Necessity of align view
Waste of time
Confuse
Apply convention
Clear
Strictly Projection
CONVENTION PRACTICE
For an object that has symmetrical positionedfeatures, it is advisable to show them on adjacentview in true size at true radial distance fromthe symmetry axis.
Example : Align view of holes
Gives the impression that thereis a hole at the center of the plate.
Given
Apply aligned
convention
Example : Align view of holes
Given
Gives the impression that holesare at unsymmetrical position.
Apply aligned
convention
Example : Align view of holes
Apply aligned
convention
Example :Example : Align view of ribs
Apply aligned
convention
Example : Align view of ribs & holes
Apply aligned
convention
Example : Align view of ribs & holes & keyway
Make Orthographic Projection
Apply Convention
Example : Align view
ENLARGED VIEW
Enlarged view is a view partly selected fromfull view and is drawn with a larger scale.
DEFINITION
At full view, the selected portion is framed bycontinuous thin line and having a name.
For an enlarged view, it must be specified bothname and scale used.
Conventional practice
Example : Enlarged view
Full view
A
A (3:1)
Enlarged view
A (3:1)
or
Referenceposition
Scale
NON-EXISTING LINE OF INTERSECTION
Non-existing line of intersection is the line ofintersecting surfaces that are eliminated by filletsand rounds.
When true projection mislead the representationof an object, it is necessary to show the additionallines that are projected from the actual intersectionof the surfaces as if the fillets and rounds werenot present.
DEFINITION
Conventional practice
Example : Non-existing line of intersection
Object does not hasrounds and fillets
Edges of the surfacesare shown as lines inthe top view.
Example : Non-existing line of intersection
The view looks like a platewith a hole !!
Object hasrounds and fillets
No edge !(No intersection between surfaces)
Convention practice required !
Construct a non-existing line of intersection.
Example : Non-existing line of intersection
INTERSECTION BETWEENFILLET AND ROUND
Runout
INTERSECTION BETWEENFILLET AND ROUND
Tangent point
TO DRAW A RUNOUT
about 1/8 of circle
RR/3
R = radius of fillet or round
R
INTERSECTION BETWEENROUND PLANE SURFACE
INTERSECTION
HOLE IN CYLINDERLarge hole : True projection
HOLE IN CYLINDERLarge hole : True projection Small hole : Convention