Week 2:Computer Aided Design

CAD, or computer-aided design, is the use of computer technology for design and design documentation. CAD software replaces manual drafting with an automated process.

If you work in the architecture, MEP, or structural engineering fields, you’ve probably used 2D or 3D CAD programs. These programs can help you explore design ideas, visualize concepts through photorealistic renderings, and simulate how a design will perform in the real world.

2D Design

Raster and Vector Image

A raster image is made of up pixels, each a different color, arranged to display an image. A vector image is made up of paths, each with a mathematical formula (vector) that tells the path how it is shaped and what color it is bordered with or filled by. The major difference is that raster image pixels do not retain their appearance as size increases - when you blow a photograph up, it becomes blurry for this reason. Vector images do retain appearance regardless of size, since the mathematical formulas dictate how the image is rendered. Raster images are capable of displaying a myriad of colors in a single image and allow for color editing beyond that of a vector image. They can display finer nuances in light and shading at the right resolution. Vector images are scalable, so that the same image can be designed once and resized infinitely for any size application - from business card to billboard. Raster images cannot be made larger without sacrificing quality. Vector images cannot display the natural qualities of photographs. Raster images are often large files, while vector images are relatively lightweight. Raster images are used in web and print, vector images cannot as of this writing be used in electronic format - they must be converted to a raster first. Vectors display at the highest resolution allowed by the output device, while rasters blur when blown up.

When should I use a raster or a vector?

Raster images are primarily used with photos, which is why Photoshop is a raster editing program. Adobe Illustrator, on the other hand, is a vector drawing program that automatically creates your vector formulas as you draw. Logos, letterhead, and other graphic elements are typically best created as vectors; while photographs are best left for rasters. All vectors must be converted to raster for web use. Text is typically rendered in vector format.

CorelDraw (raster)

CorelDraw (styled CorelDRAW) is a vector graphics editor developed and marketed by Corel Corporation. It is also the name of Corel's Graphics Suite, which bundles CorelDraw with bitmap-image editor Corel Photo-Paint as well as other graphics-related programs (see below). The latest version is designated X8 (equivalent to version 18), and was released in March 2016.[1] CorelDraw is designed to edit two-dimensional images such as logos and posters.

I have designed a logo for my project using CorelDraw.

Fab Lab.cdr

InkScape

Inkscape is a free and open-source vector graphics editor; it can be used to create or edit vector graphics such as illustrations, diagrams, line arts, charts, logos and complex paintings. Inkscape's primary vector graphics format is Scalable Vector Graphics (SVG), however many other formats can be imported and exported.

I have converted the above logo to vector image. First I imported the image in Inkspace.

Then click on path>>Trace Bitmap and change the Brightness Cutoff threshold.

Fab Lab vectorised.svg

The resultant vector image will be like shown below

3D Design

The platforms which I have used for 3D modeling are FreeCad, Fusion 360 and SolidWorks.

FreeCad

FreeCAD is a parametric 3D modeler made primarily to design real-life objects of any size. Parametric modeling allows you to easily modify your design by going back into your model history and changing its parameters. FreeCAD is open-source and highly customizable, scriptable and extensible.Freecad's own main file format is FreeCAD Standard file format (.fcstd).

Click here to download excercise done by me on FreeCad.

Fusion 360

The plus point with fusion, is that it may be easier to get it download on your system as its trail version is free. Fusion 360 is a cloud-based 3D CAD, CAM, and CAE platform for product development. It combines industrial and mechanical design, simulation, collaboration, and machining in a single package. The tools in Fusion 360 enable fast and easy exploration of design ideas with an integrated concept-to-production toolset. Before starting Fusion 360 it is recommended to go through the user manual so that one can have basic idea of the shortcut keys. Then I learned how to navigate between the planes when modeling 3D design.

Click here to see the documentation done by me on Fusion 360.

SolidWorks

I have used the trail version of SolidWorks to create 3D designs for my project. SolidWorks is very similar to Fusion 360 which I have used earlier. Fusion is good, but it lacks many of the higher end capabilities of Solidworks. SolidWorks handle assemblies much better than Fusion. For simple part models they are all broadly comparable but beyond that Fusion falls behind fast. I started building scissor lift mechanism for my project as there is need to vary the height of the table.

First I created 2D link design as shown in the screen shot below. Then I created three circles of equal radius and equal distance. The shortcut menus and keys available in SolidWorks make the working environment comfortable.

After drawing the above sketch draw two circles at equal distance on the link then extrude it in particular direction.

Assembly

First step is to create part/parts in SolidWorks. The diagram shown in above screen shot is part of scissor ladder mechanism. An Assembly is comprised of one or more SolidWorks Parts or Assemblies, and is used to model relationships between these subcomponents or subassemblies using relationships called Mates.

In the above figure assembly is created using the link part along with different constraints. The constraints used are-concentric and co-incidents.