Thiết kế flash - Multiview projections 3

Multiview Projections 3Third-Angle ProjectionUsed in the United States to determine arrangement of multiviewsViews projected onto projection plane in front of objectFirst-Angle ProjectionUsed in Europe and Asia to determine arrangement of multiviewsViews projected onto projection plane behind objectThird and First-Angle ProjectionIIIIIIIVView SelectionMost descriptive view selected as the front viewLongest dimension should appear in front view as a horizontal dimensionUse minimum number of views that completely describe objectChoose views to minimize number of hidden linesLine PrecedenceVisibleHiddenCenterWhen lines coincide with each other, more important lines take precedence over other lines. The order of precedence is: Intersections and TangencyPlanar surface tangent to contoured surface  no line drawnPlanar surface intersects a contoured surface  line (edge) drawnShow edgeNo edgeFillets and RoundsFillet – inside rounding on a cast, forged or plastic partRound – outside rounding on a cast, forged or plastic partTypically 3 - 5 mm radiusIn multiview drawings, fillets/rounds only represented in views where you see curved shape Fillets and Rounds - ConventionsNo true change in planes when surfaces are related by a fillet/roundMultiview convention - add lines as if fillets/rounds were absent Revolution ConventionsTrue multiview projections can be confusing when showing radially distributed featuresBy convention, these views are typically simplified by rotating the radial features along horizontal and vertical centerlinesMachined HolesThrough HoleA hole that goes all the way through the objectBlind HoleA hole that does not pass all the way through the object Counterbore Hole Used to allow bolt heads to be flush with or below the surface Spotface HoleProvides smooth surface for fastener heads to rest on a cast partCountersink HoleUsed for flat-head fasteners Multiview Projections - 3