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3. Computer Aided design

This week we started with various drafting softwares.

Raster and Vector

A raster graphics or bit map image is type of media format in computers where an image is represented by array of pixels in a rectangular grid. Each pixel’s colour is reperesented by bits. The images are represented in JPG,PNG,GIF format. A vector graphics is one in which the images are represented using 2D points. Lines or curves join these points to make images. Other properties like stroke color, type of curve, thickness etc are represented in the vector drawings. Formats like SVG,EPS and PDF are examples for vector image formats.

Difference between Raster and Vector Credits :https://www.ratermanis.com/blog/2017/12/28/vector-vs-raster A raster image Each pixel is having bit information which is the combination of Red, Green and Blue.
Credits: https://en.wikipedia.org/wiki/Raster_graphics#/media/File:Rgb-raster-image.svg

GIMP (GNU Image Manipulation Program)

GIMP is a free and opensource raster based image editing software. Images can be modified and edited by creating layers and editing them.

GIMP image working The logo can be selected using Fuzzy select tool

GIMP image working New layer added and the logo pasted upon it GIMP image working Copying the selected logo
File here

Inkscape

Inkscape is an opensource vector based image processing software.
One of the uses of inkscape is that you can convert a raster image to a vector one. trace bit map from the path.

image working Various scanning options image working Scanned picture

Another option is that we can create interesting polygons. image working

image working Two poygons placed over each other. image working The Difference tab under path can yield interesting shapes. The blue square was placed under by Move Selection to layer below in the Layer tab. image working This time with Intersection in the Layer tab.
File here

3D-Parametric modelling

Parametric modelling enables us to use computer to create models that can simulate almost real world like geometry and other functional attributes. Parametric models are based on mathematical equations.

There are two parametric representations
1) Constructive Solid Geometry (CSG)
Development of basic primitive models like sphere, cylinder, cube etc. Operations like extrude,boolean etc. are performed to alter/ build the model.
2) Boundary Representation (BR)
Model is built my surfaces. These surfaces are inturn made by connecting spatial points. Finite Element based softwares mainly work this way. So many softwares are used for example Solid Works, Fusion 360, FreeCAD, Oneshape etc.

FreeCAD

In this one week I tried my hands on FreeCAD. FreeCAD is an opensource parametric modelling software. Ver .17 was used.

FreeCAD necessarily has workbenches. Workbenches can be described as a set of tools designed specific for sepererate modelling applications. FEM ,Part , Part Design, Sketcher etc.. are some of the work benches.

Constraint Sketching- Unlike traditional drafting the models are first drafted unconstrained. These can be extruded, rotated or scaled according to the constraint conditions. I started by working in Sketcher workbench.

I started by making a circle in the part workbench and extruded it to get the required thickness. The groove of this pattern was made by Holecommand in `part design’ . In the sketcher workbench various restraints can be used both geometrical as well as dimensional. FreeCAD shape Various restraints in the Sketcher workbench FreeCAD shape Restraints shown in red as inside angles of the polygon FreeCAD shape Centre of the polygon aligned with the centre of the extruded solid.

FreeCAD shape Hole extruded using hole in the part design
File here

Though I started with FreeCAD I understood only in the later weeks that the Fusion 360 suits me better. The dating part was not complete in this week. Frankly I was too slow to experiment with different softwares in a week. But after selecting Fusion 360, I got acquanited with it over the time and during the final project week the tool came so handy that I could use it without external help. The links to the other week’s work in CAD design in Fusion 360 is below.
(This part was documented during the evaluation)

Week 4-Press Fit Design
Week 6- 3D printing CAD Design

References

  • [Parametric Modelling] (https://www.designtechsys.com/articles/parametric-modelling)
  • FreeCAD WIKI