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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

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### 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!

- Straight edges, templates, compasses etc.

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

- 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

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.

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