engg graphics

Category: Education

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By: ngsirjal (83 month(s) ago)

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Introduction toEngineering Graphics : 

Introduction toEngineering Graphics

Topics : 

Topics Graphic Language & Design CAD Systems Sketching Techniques Lettering Geometric Constructions Multiview Projection Dimensioning Sectional Views Auxiliary Views Tolerancing Working Drawings

What is Engineering Graphic Communication? : 

What is Engineering Graphic Communication? A universal language Standards organizations like: ANSI (American National Standards Institute) ISO (International Standards Organization)

Engineering DesignUses Sketching & CAD : 

Engineering DesignUses Sketching & CAD Ideas are initially sketched and then more accurate CAD drawings are created

Terminology : 

Terminology CAD: Computer Aided Design CADD: Computer Aided Design & Drafting CAM: Computer Aided Manufacturing CIM: Computer Integrated Manufacturing CAE: Computer Assisted Engineering Reading Drawings: Interpreting drawings made by others Technical Drawing: Drawings used to express technical ideas Engineering Design Graphics: Technical Drawings representing designs & specifications for physical objects

Objective : 

Objective How to use sketching as an effective tool in the engineering design process

Freehand Sketching : 

Freehand Sketching Freehand sketching is used in engineering graphics to quickly communicate your ideas or designs. Drawing instruments and CAD are not always available, especially during field work Freehand sketching is not sloppy sketching! Your sketches need to be interpreted by others on your design team – use good lettering.

Slide 8: 

Example Freehand Sketch for Concept Development

Overview : 

Overview Sketching Review Pictorials Perspective Parallel projection

Sketching Allows for the Quick Translation of Thoughts to Paper : 

Sketching Allows for the Quick Translation of Thoughts to Paper Understand your audience Who is looking at the sketches? What details are they interested in? What type of sketch will they best understand? Sketches provide a log of ideas that were considered in a brainstorming session

Sketching (review) : 

Sketching (review) Definition A rough freehand drawing used to document, communicate, and refine ideas developed primarily in the ideation phase of the design process A developed skill Should be the first step of any CAD or mechanical drawing (including homework assignments)

Pictorial Sketches : 

Pictorial Sketches Definition: A sketch developed for ease of visualization that shows an objects height, width, and depth in a single view Particularly useful for non-technical audiences Assembly drawings Marketing Helpful in the ideation phase of the design process How we picture objects in our mind How we visualize spatial relationships

Pictorial Sketches : 

Pictorial Sketches Parallel Projection Parallel lines are always drawn parallel Easy to draw Two common types Oblique Pictorials Isometric Pictorials Perspective Projection Conveys information about distance and size Not as common as parallel projection

Parallel Projection Pictorials : 

Parallel Projection Pictorials Oblique Pictorials The simplest pictorial to sketch Surfaces which are parallel to the front face are undistorted as in a multiview drawing Circular features should be placed in the front view if possible Draw the front face first Lines which are perpendicular to the front face are drawn at an angle of 45o

Parallel Projection Pictorials : 

Parallel Projection Pictorials Oblique Pictorials Cavalier Oblique Depth is drawn full size Object looks distorted (depth is exaggerated) Cabinet Oblique Depth is drawn to 1/2 of full size Depth appears more accurate (2/3 is best) Circular features which are not parallel to the front plane appear elliptical

Axonometric Pictorials : 

Isometric Height drawn along vertical axis Width and depth drawn at 30o to horizontal axis Axonometric Pictorials

Parallel Projection Pictorials : 

Parallel Projection Pictorials Isometric Pictorials Begin drawing by blocking in height, width and depth of entire object. Continue to block in smaller features Add curved surfaces last circles appear as ellipses lines tangent to arcs locate the edge of curved surfaces Isometric grid paper is often helpful follow direction of axis and count intersections use tracing paper or grid paper with light lines

Tools : 

Tools Pencils Use a mechanical pencil (0.5mm lead) Practice using different pressure to produce desired linet ypes (construction lines) Paper Square grid and tracing paper is often useful Eraser A good eraser is worth the investment Do not overuse your eraser (save some mistakes)

Using Simple Instruments : 

Using Simple Instruments The use of mechanical instruments is recommended only for beginners. Break away from reliance on tools that slow you down. Helpful tools for beginners Compass Triangles Dividers Ruler

Mechanics of Sketching : 

Mechanics of Sketching Drawing straight lines Drawing curved lines Using a bounding box

Drawing straight lines : 

Drawing straight lines Mark starting and ending point Break long lines into short line segments by marking the midpoint Start with a light pass if necessary and then darken Use a loose comfortable grip Reorient the paper to your convenience test your skill with different orientations an awkward orientation may occasionally produce positive results

Drawing curved lines : 

Drawing curved lines Break large arcs/circles into small segments Make guide marks for each segment Circles and Ellipses Sketch a light square/rectangle Lightly sketch in diagonals Mark contact points on square/rectangle Rotate the paper for each segment

Bounding Box and Construction Lines : 

Bounding Box and Construction Lines Plan choose proper scale and orientation don’t crowd sketches Start with a bounding box Use light straight construction lines Draw boundary lines of internal features starting with the largest features Sketch dark object lines using light boundary lines as a guide

Summary : 

Summary Engineering drawing can be a universal language to communicate your ideas. The engineering design process uses sketching and CAD to communicate and record ideas.

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