# CHAPTER 4: ISOMETRIC AND OBLIQUE - UniMAP Notes... · PDF fileOblique Projection In oblique projections the front view is drawn true size, and the receding surfaces are drawn on an

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• CHAPTER4:ISOMETRICANDOBLIQUE

• Studentsareable: To construct isometric objects from twodimensionalorthographicprojections.

To draw isometric object and nonisometricobject

Toconstructisometricellipseondifferentplane

Todeterminethebestisometricpositions

Objectives:

• Introduction:

Isometric illustration is the method of depiction ideaswhichformedinactual3Dobjects.

Thismethodcandescribetheobjectshapeeasily.

This construction could be done based on theobjects shape which viewed from certaindirections.

• Isometricobjectviewedfromdifferentdirection

• IsometricSketches

Isometricprojectionisproducedusing3axes:verticalaxisleftaxisrightaxis

Theleftandrightaxesareproducedattheangleof30tothehorizontallines

• Figure below shows the main axis of isometricdevelopedwith30setsquare

30 30120

• Figureshowsaboxinisometricdrawing

• Isometricsketchingfrommultiviewdrawing

• SelectionofIsometricaxes View (a) is preferred as it reveals moredetailthantheothers.

• Isometricdrawing:objecthasinclinedsurfaces

• DrawingofCirclesandArcs

In isometric drawing, a circle appears as an

ellipse.

Sketchingsteps:

1.Locatethecenterofanellipse

2.Constructanisometricsquare

3.Sketcharcsthatconnectthetangentpoints.

• Fourcentremethodisusuallyusedwhendrawnan

isometricellipsewithdrawinginstrument.

SketchingSteps

1.Locatethecenterofanellipse2.Constructanisometricsquare.3. Construct a perpendicular bisector from eachtangentpoint.4.Locatethefourcenters.5.Drawthearcswiththesecentersandtangenttoisometricsquare.

• Exampleofisometricellipse

• DrawingofIrregularcurvesinIsometricdrawing

Steps:

1. Construct points along the curve in multiview

drawing.

2.Locatethesepointsintheisometricview.

3.Sketchtheconnectinglines.

• ObliqueProjection

Inobliqueprojectionsthefrontviewisdrawntruesize,and the recedingsurfacesaredrawnonanangle togive it a pictorial appearance.This formof projection has the advantage of showing oneface (the front face) of the object withoutdistortion. Generally, the face with the greatestdetailfacesthefront.

Therearetwotypesofobliqueprojectionused inengineeringdesign.

• CavalierOblique

In cavalier oblique drawings, all lines (includingrecedinglines)aremadetotheirtruelength.

• CabinetOblique

Incabinetobliquedrawings,therecedinglinesareshortened by onehalf their true length tocompensate for distortion and to approximatemorecloselywhatthehumaneyewouldsee.Itisfor this reason that cabinet oblique drawings arethemostusedformofobliquedrawings.

• TypicalAnglesofProjection

In oblique drawings, the three axes of projectionare vertical, horizontal, and receding. The frontview (vertical & horizontal axis) is parallel to thefrontalplaneand theother two facesareoblique(receding).Thedirectionofprojectioncanbetopleft, topright, bottomleft, or bottomright. Thereceding axis is typically drawn at 60, 45, or 30degrees.

• Typicalanglesofprojection

TopLeft

BottomLeft BottomRight

TopRight

• CenterlinesinIsometricdrawingCenterlines are drawn only for showingsymmetry or for dimensioning. Normally,centerlines are not shown, because manyisometric drawings are used to communicate tonontechnical people and not for engineeringpurposes.

• Exercise:1.Drawinfullsizeanisometricviewoftheobject.Thegridsizeis10mmx10mm.

• 2.Drawinfullsizeanisometricviewoftheobject.Thegridsizeis10mmx10mm.

• 3.Drawinfullsizeanisometricviewoftheobject.Thegridsizeis10mmx10mm.

• 4.Draw in full sizeacavalierobliqueviewof theobject. Choose the proper orientation. The gridsizeis10mmx10mm.

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