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
–
–

Isometric (a type of axonometric drawing) & Perspective
–
–

Advantage: easy to visualize the object
Disadvantage: no true face
Multi-View (orthographic)
–
–

Advantage: one true face
Disadvantage: not “photorealistic”
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.