Freehand sketching
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Transcript of Freehand sketching
Freehand Sketching
Introduction to Mechanical Engineering
Fall 2004
Created by:
P.M. Larochelle & J.S. Ketchel
Freehand Sketching
Ideation – Integral to the design process– Generation of design concepts to solve a design problem
Usually freehand sketching is used to explore, study and communicate these design concepts
Even today, and for the foreseeable future, many great design ideas are communicated via freehand sketching
The “BEST” design engineers can immediately communicate an idea via a freehand sketch
Freehand Sketching
Required– Pencil, Paper and Eraser
Do not use– Straight edges, templates, compasses etc.
They slow down the process and defeat the purpose of fast communication of ideas!
Freehand Sketching
Sketches are planned Visualize the sketch
– Size of paper & scale– Orientation of the object– Minimum detail to communicate the idea– Type of sketch
Oblique Isometric Orthographic
Types of Sketches
Types of Sketches Oblique
– Advantage: one true face– Disadvantage: not “photorealistic”
Isometric (a type of axonometric drawing) & Perspective– Advantage: easy to visualize the object– Disadvantage: no true face
Multi-View (orthographic)– Advantage: true faces– Disadvantage: hard to visualize
Isometric, oblique, and perspective sketches are methods of showing the object in a single view.
Freehand Sketching Freehand sketches are not sloppy!
Freehand Sketching When possible use the grid on your engineering paper!
Freehand Sketching
Outline the sketch– Use light lines– Show major edges and boundaries and then add
small details
Freehand Sketching
Shape the sketches– Add appropriate details– Darken object lines
Freehand Sketching
Fundamental Rule of Sketching– Maintain Proportion
Hints: use standard techniques to draw lines and arcs
Lines– Locate a start “dot”– Locate an end “dot”– Put pencil on start dot, look at the end dot and smoothly
move pencil toward the end dot
Freehand Sketching
Circles (arcs)– Draw light horizontal and vertical lines that
intersect at the center– Lightly mark the radius on the lines– Connect the radius marks with arcs to complete
the circle– See Step-by-Step 3.1& 3.3 on pages 60 & 62.
Construction Lines
Light and thin lines Serve as path for final straight lines Intersection of construction lines specify the
length of the final lines Points marked by the intersection of
construction lines serve as guides for sketching of arcs and circles
Guide the proportion of the sketch
Linetypes
Examples of Good Freehand Sketching Technique
Oblique Sketching
Step 1 – Draw the horizontal and vertical construction lines which outline the basic shape of the main face - “Blocking in”
Step 2 – Sketch the face of the part Step 3 – Sketch receding construction lines
at 30 or 45 degrees Step 4 – Sketch- in and darken the lines
outlining the part – Done!
Isometric Sketching
Step 1 – Construct a horizontal line, two lines at 30 degrees above the horizontal and a vertical line through their intersection– This defines the isometric axes used to draw the
sketch
Isometric Sketching
Step 2 – Sketch in a box to “block-in” the front face and the other faces follow
Step 3 – Sketch the outline of the front face in it’s “block” and the other faces follow– Work parallel to the isometric axes
References
Chapter 3 of Modern Graphics Communication by Giesecke, Mitchell, Spencer, Hill, Dygdon, Novak, and Lockhard, 3rd edition. Prentice-Hall, 2004.
Technical Drawing by Giesecke, Mitchell, Spencer, Hill, Dygdon, and Novak, 9th edition. Macmillan, 1991.