Engineering 28University of CaliforniaLecture # 9Orthogonal projectionMulti-view presentationThird-angle projectionFirst-angle projection

Presentation for Fabrication

How About Pictorials?Features hiddenLengths distortedAngles distorted Hard to drawHard to scale

Problems with PictorialsCircles distortedCurves distortedHard to visualize curvature in a plane, e.g. for tool pathsHard to draw curves

Orthographic ProjectionProjection of a 3-D object on a plane by rays perpendicular to that plane

Fault (Benefit) of Orthogonal Projection

Part Placement

View Interpretation

Multi-view PresentationPresents more than one view of an object on the same viewing planeCan see features from different directionsWith enough views, can see and characterize all featuresGlass Box approach

Glass Boxinterpretation

Third-AngleProjection

Note alignment andorientation of views

ANSI Standards (Y14.5)Adapted by drafters and engineers to expedite the transfer of information.Maximum information with the minimum drawing.Too many, and to boring, to go though all in class, check reference if necessary.Some highlights...

ANSI Standards (Y14.5)Orthographic views usedAs many lines in true length and as many planes in true shape as possibleMultiple views from the glass boxDon't show the intersection lines of the orthographic planes.Section views used for clarification of internal geometries

ANSI Standards (Y14.5)Shapes are simpleExtended from basic machine toolsPlanes and holes (shafts) easy to makeLines assumed to be intersections of planesCircles assumed to be intersections of cylinders and orthogonal planes

Preferred Presentation

ANSI Standards (Y14.5)Add more views as required so the dimensions of the object can be defined entirely in true length measurementsAdd more views as necessary for presentation clarityTangent edges are usually not shown

ANSI Standards (Y14.5)Use hidden lines to add information, clarity.Do not use overuse hidden lines (not wrong, just poor practice)Use centerlines to mark the centers of holes, or cylindrical surfaces 180

How Many Views?

How Many Views?Two views fine

How Many Views?

How Many Views?

How Many Views?

How About Hidden Lines?

Preferred Presentation

Guidelines for PresentationStart with showing the object in the preferred configuration, i.e. the top, front and right side views. Orient the object such that as many edges as possible are shown in their true length in these views. Add more of the standard orthogonal views, e.g. left side, bottom, and/or back view, as necessary such that dimensioning can be applied to visible edges or features only.

Guidelines for PresentationAdd all the hidden lines from the exterior edges and interior detail that are not visible. If there are too many hidden lines, and the views are confusing, remove the hidden lines that are not necessary for fully defining the geometry or features of the object.

Guidelines for PresentationIf there are still too many hidden lines, and the views are still confusing, add more of the standard orthogonal views as necessary to reduce the number of hidden lines and maintain full definition of the objects geometry.

First-Angle ProjectionUsed in parts of Europe and Asia

First-Angle ProjectionNote alignment andorientation of views

1st vs. 3rd Angle Projection

Correct, even though its wrong

ANSI Standards (Y14.5)Small radii, intersections of blended planar surfaces shown as a line

ANSI Standards (Y14.5)Schematics used, i.e. for screws

ANSI Standards (Y14.5)

ANSI Standards (Y14.5)Small cuts on curved surfaces

ANSI Standards (Y14.5)Small protrusions from curved surfaces

Parts with Odd Rotational Symmetry

EndQuestions?