Wire-frame models – It is created by connecting each edge of the physical object where two mathematically continuous smooth surfaces meet, or connecting an object's vertices using straight lines or curves. They create skeleton like models with lines and arcs. Since they appear to be made of wires, and everything in the background is visible, they are called wire-frame models.

Surface models – These models are created by joining 3D surfaces. Since nothing in the background is visible. It is created by connecting each plane or a series of planes. Surface model lacks internal features.

Solid models – They are considered to be the most useful CAD models. Although they appear to be the same as surface models, they also have additional properties like weight, volume and density, just like actual physical objects. These models are commonly used as prototypes to study engineering designs. All the internal features are embedded in the model itself.

GIMP image editor

GIMP for Editing PCB schematics

Vector softwares

Inkscape

Inkscape is professional quality vector graphics software which runs on Windows and Linux. It is used by design professionals and hobbyists worldwide, for creating a wide variety of graphic such as illustrations, icons, logos, diagrams, maps and web graphics. Inkscape uses the W3C open standard SVG (Scalable Vector Graphics) as its native format, and is free and open-source software. Inkscape has sophisticated drawing tools with capabilities comparable to Adobe Illustrator, CorelDRAW . It can import and export various file formats, including SVG, AI, EPS, PDF, PS and PNG. It has a comprehensive feature set, a simple interface, and is designed to be extensible; users can customize Inkscape's functionality with add-ons.

AutoCAD

AutoCAD software is used for mechanical product design and drafting applications that cater to the various needs of the mechanical engineering companies , It comes with a complete set of powerful drafting and detailing tools for drafting. It is a simple enough software with friendly interface , It is easy to grasp and have simple tools. AutoCAD supports most of the standard CAD files while importing. It also have specific drafting tools for generating the standards Industry based geometric dimensions, the surface texture symbols, the mechanical symbols and the weld symbols.AutoCAD automatically redraw the geometry to illustrate the dashes and the hidden lines of parts which are blocked by the other parts in the mechanical design, and drawings can be created in 2D or 3D and rotated. This software contains standards and allow the designer to check if the design is within the specification or tolerance limit. The fits and tolerance details are available on Autocad.

The control features are very important in fabrication drawings along with tolerance. Fabrication drawing of a pipe holder have been created in AutoCAD using Feature controlled frame and datum features. While generating these types of fabrication drawings, the type of machines and its limits are also considered.

I have been working with AutoCAD for quite somelong and just created drawing of Corner shelf in AutoCAD using the following commands.

3D CAD software

Autodesk Inventor software

Autodesk Inventor is a 3D mechanical engineering, design, visualization, and simulation software. Autodesk Inventor is a parametric and feature-based solid modeling tool. It allows you to convert the basic 2D sketch into a solid model using very simple modeling options. In my personal opinion this is a good software for beginners. Exploded views and presentationscan be easily created and connected with inventor. The updating feature easily updates in models without altering other parameters..

NX software

NX, formerly known as NX Unigraphics or usually just UG, is an advanced high-end CAD/CAM/CAE software package originally developed by Unigraphics, but since 2007 by Siemens PLM Software. It is used, among other tasks, for:

Ansys

Ansys have engineering analysis software across a range of disciplines including finite element analysis, structural analysis, computational fluid dynamics, explicit and implicit methods and heat transfer analysis. ANSYS Fluent, CFD, CFX, and related software are Computational Fluid Dynamics software tools used by engineers for design and analysis. These tools can simulate fluid flows in a virtual environment — for example, the fluid dynamics of ship hulls; gas turbine engines (including the compressors, combustion chamber, turbines and afterburners); aircraft aerodynamics; pumps, fans, HVAC systems, mixing vessels, hydrocyclones, vacuum cleaners, etc.

CFD Analysis

Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to solve and analyze problems that involve fluid flows. The above model of a CD nozzle can be analysed with CFD. A simple CFD analysis consists of the followoing process.

A thin layer of the above model (CD nozzle) is considered for CFD anlysis. The outline of the model is drawn using modeller followed by meshing.

All the boundary conditions are verified in the setup and calculations are done. The progression is monitored, the number of the iteration is set to 500. After the post processing the gas velocity through the nozzle is shown below. The gas is chocked at the throat and is ejected out at a supersonic velocity of 609m/s (indicated by red color). The 'mach diamond' is also visible just after the throat.