3. Computer Aided design¶
This weeks assignement deals with CAD programs. The learning outcome is to select a CAD program and draw something in it.
Research¶
In the past I have used Inkscape, Gimp, Photoshop and Fusion 360.
Inkscape¶
According to Inkscape manual,
Inkscape is an open source, SVG-based vector drawing program. It is useful for drawing:
- Illustrations for the Web
- Graphics for mobile phones
- Simple line drawings
- Cartoons
- Complex works of art
- Figures for articles and books
- Organization charts
There are two basic types of graphic images: bitmap (or raster) images and vector images. In the first case, the image is defined in terms of rows and columns of individual pixels, each with its own color. In the second case, the image is defined in terms of lines, both straight and curved. A single straight line is described in terms of its two end points. The difference in these types of graphic images becomes readily apparent when a drawing is enlarged. When the bitmap resolution of a drawing matches the display resolution, the objects in the drawing look smooth. If the bitmap resolution is significantly less than the display resolution, the display will show jagged lines.
Vector Design¶
In the past, I have used Inkscape to draw outline for tabbed boxes which I used to cut via the laser printer. I have used the tabbed box maker plugin. Besides the dimensions of the box, the most important setting is the Kerf setting which basically tells the plugin that how much material will be taken away by the laser cutter. Kerf larger than the actual kerf will result in a tight fitted box. I have used 0.22mm kerf when I was working with acrylic. Power was set to 100% and speed was set to 5%.
The finished file can be downloaded from here
Raster Design¶
According to Wikipedia:
In computer graphics, a raster graphics or bitmap image is a dot matrix data structure that represents a generally rectangular grid of pixels (points of color), viewable via a monitor, paper, or other display medium. Raster images are stored in image files with varying formats.
Inkscape can also be used for raster designs. One example of raster design is tracing bitmaps, in which an image can be converted into a black and white bitmap which then can be used for vinyl cutting or can be used with laser cutter to emboss. A nice tutorial of bitmap tracing can be found from here.
I used the Inkscape to draw a pixelated image of a cat for the raster design. I used a 3mmx3mm solid rectangle and just stacked them up like legos to create a cat like image.
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Fusion 360¶
I have only recently started playing with Fusion 360. I have been following the following tutorial on youtube.
Below is the first model I ever created in Fusion 360.
To model the lego block, which is quite small in dimension, it is important to model it in mm instead of inches. The default unit for the design in changed in the preference settings.
First we will create a sketch - a 2D image which we build into a 3D model. We’ll create a rectangle as shown in the first top left image. This 2D image is now made into a 3D cube by extruding it by giving it a specific height.
Then select the top of the rectangle, which creates another sketch, and on this creates a circular pattern as shown in the second-top left image. Then we extrude the circles, and this creates the Lego studs. Next, we want to make the rectangle hollow by shelling it.
Next we create the three columns on the bottom of the lego, that snaps to the studs. This is also done by creating three circles and them extruding them. Lastly, the edges are filleted or rounded to make sure they are not sharp. This completes the lego model.
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