week_02 Computer Aided Design

Objectives

1) - understanding the method of modeling and the thought of 2D modeling or 3D modeling.
2) - understanding the technique of the software of 2D modeling and 3D modeling.

Assignments

1) - model (raster, vector, 2D, 3D, render, animate, simulate, …) a possible final project, and post it on your class page.

Software

There are many open-source and paid CAD software options on the market today. As a process engineer, I have used some of professional CAD/CAM software, such as AutoCAD, Corel Draw, NX UG, hyperCAD-S, and so on. I prefer AutoCAD and Corel Draw for 2D modeling and NX UG for 3D modeling. For this week, I also tried to use the software of blender, FreeCAD, Inkscape, GIMP.

2D Modeling

There are two ways to make 2D CAD modeling:

1) - Raster graphics (graphical techniques using arrays of pixel values).

① Raster graphics are resolution dependent, meaning they cannot scale up to an arbitrary resolution without loss of apparent quality.
② Raster-based image editors, such as PaintShop Pro, Painter, Photoshop, Paint.NET, MS Paint, and GIMP.
2) - Vector graphics (images defined by geometric primitives as opposed to bitmaps).

① Vector graphics are computer graphics images that are defined in terms of 2D points, which are connected by lines and curves to form polygons and other shapes. Each of these points has a definite position on the x- and y-axis of the work plane and determines the direction of the path; further, each path may have various properties including values for stroke color, shape, curve, thickness, and fill.
② vector-based image editors, such as Xfig, CorelDRAW, Adobe Illustrator, or Inkscape.

GIMP

GIMP is a free and open-source raster graphics editor used for image retouching and editing; free-form drawing, converting between different image formats, and more specialized tasks. I find that this software is similar to Photoshop, which can handle graphics.

Inkscape

nkscape is a free and open-source vector graphics editor. Inkscape can render primitive vector shapes (e.g. rectangles, ellipses, polygons, arcs, spirals, stars and 3D boxes) and text. These objects may be filled with solid colors, patterns, radial or linear color gradients and their borders may be stroked, both with adjustable transparency. Embedding and optional tracing of raster graphics is also supported, enabling the editor to create vector graphics from photos and other raster sources. Created shapes can be further manipulated with transformations, such as moving, rotating, scaling and skewing.

This week, I tried to use Inkscape as well, at first I drew a cup, which can drink coffee. I used a lot of features, such as drawing Bézier curves, editing text, drawing starts and polygons and so on.

Then I drew a USB flash disk, which used grid features. First, I set up the relevant environment and created the "axial side grid".

Then I Used the line tool to draw the outline of the U disk. Finally, I used the filling tool to fill the color for the U disk, so that it has a stereo effect.

AutoCAD

I have been using this software for more than three years. AutoCAD is a commercial computer-aided design (CAD), drafting software application and is not free software, but have 36-month renewable license for students and educators. I think it is one of the best software for engineers, architects to make 2D modeling. Inkscape and GIMP are fit for designer to design.
AutoCAD main tools I used, such as trim, extend, move, rotate, line, rectangle, mirror, scale and others.

3Dmodeling

FreeCAD

FreeCAD is a free and open-source general-purpose parametric 3D CAD modeler and a building information modeling (BIM) software with finite-element-method (FEM) support. FreeCAD features tools similar to CATIA, Creo, SolidWorks, Solid Edge, NX, Inventor, Revit, and therefore also falls into the category of Building Info Modeling (BIM), Mechanical computer-aided design (MCAD), PLM, CAx and CAE. It is intended to be a feature-based parametric modeler with a modular software architecture, which makes it easy to provide additional functionality without modifying the core system.

Through this process, I have learned commands in part design module and part module.

UG NX

I also have been using this software for more than three years. NX, formerly known as "UG", is an advanced high-end CAD/CAM/CAE. It is used Design (parametric and direct solid/surface modelling), Engineering analysis (static; dynamic; electro-magnetic; thermal, using the finite element method; and fluid, using the finite volume method), Manufacturing finished design by using included machining modules.

① Basic study
About design and CAD in NX UG, I divide a design of 3D model as four steps (not include the CAD and product management process, just for a fun design or maker do).
Step1: The first is to make a plan.
Step2: Then do sketch base on this plane and add correct constrain to line and curve. I summarized the process of build sketch as shown in the following figure.

Then I used the drawings in the book to practice the sketch module.

Step3: Convert to 3D components by using stretch or rotate tools or use the voxel feature tools (such as cuboids tools and cylinders tools) for 3D modeling directly.

Step4: Make this model by real physics process such as laser cutting,3D printing, NC or hand made.
② Parametrization design: five-pointed star
First, I enter the sketch screen and draw the sketch of the five-pointed star.

Then convert to 3D components by using stretch tools.

Notably, I used expressions to control the length and height of the pentacle in the sketch modeling and stretch instructions.

③ Assembly
Assembly is the assembly of multiple parts together to form a complete assembly, which is generally the final state of the market. Assembly in NX is the assembly of parts using "assembly constraints", which are similar to the geometric constraints on curves or points in sketches, with the end result that the parts are placed in the specified position.
I'm going to use the "bottom to up" assembly method to practices.

④ 3C sample
Finally, based on my previous work experience, I integrated many machining features of many 3C industries into one part, as shown in the following figure.

OpenSCAD

OpenSCAD is software for creating three-dimensional CAD objects. It is free software available for GNU/Linux, Microsoft Windows and apple OSX. OpenSCAD unlike most free software used to create 3D models (such as the famous Blender application), all the design is done by writting code.
I think it is funny. Because of I have no basis in computer programming, I can only design some simple products. So, it can be really difficult to model complex surfaces for me. First, I learned the basic instructions of from OpenSCAD . Then, I mainly use cubes, spheres and Boolean operations.