week 3: computer-aided design

assignment for the week

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

learning outcomes

1. Evaluate and select 2D and 3D software.
2. Demonstrate and describe processes used in modelling with 2D and 3D software.

have i

1. Modelled experimental objects/part of a possible project in 2D and 3D software.
2. Shown how I did it with words/images/screenshots.
3. Included original design files.

my goal for the week

To start with, I will focus on learning (by doing) some of the programs that Neil emphasized on and/or demonstrated during class viz. GIMP; Photoshop; FreeCAD; Fusion 360; and SolidWorks.

lecture notes

Here are some lecture notes from this week, written using Neil's lecture outline and recording.

programs installed

I installed the following programs on my computer:

1. 2D design:
1.1 GIMP; Photoshop: both are image/picture editing tools; freely available bitmap editing, GIMP is pixels, you can make an image, you can paint on it, and if you zoom in, at the bottom is just dots of intensity
1.2 Inkscape
1.3 FreeCAD
2. 3D design:
2.1 SketchUp: easy to use beginner design tool
2.2 Blender: for photorealistic animating and rendering, not a great CAD tool though
2.3 FreeCAD: the only freely available open-source 3D parametric industrial-scale CAD tool
2.4 Fusion 360: it's a CAD tool, with good simulation tools for modeling + also has very good CAM tools for planning + collaboration tools / overall, a really powerful tool that merges CAD with modeling of CAD, and then with planning how machines will make something; integration with Eagle is helpful in electronics design
2.5 SolidWorks: it can handle complex designs
2.6 OnShape: it's SolidWorks in the cloud
2.7 Antimony

learning the tools

I started out with learning SolidWorks with some help from another FabLAB student, Aditya, at the site, and an engineering student, ----------, also at the site. I used it to design some simple shapes, an equilateral triangle and a circle, to get a feel of the program. I then made slots in both, and since I wanted the slots to be parametric, I started putting constraints in the design. I also wanted the slots to be symmetric, meaning centered around the mid-point of each side of the triangle. To do so, I drew perpendicular bisectors of each side, drew one-half of a slot along one side, and then used the mirror tool around that side's bisector to complete the slot. This completed a slot on one side of the triangle. I then used perpendicular bisector of one of the adjacent sides as a mirror to create a slot on the third side, and repeated the process to create a slot on the remaining side.
To parametrize these 3 slots, I set an equality constraint for the 3 pairs of parallel sides of the slots, and a separate equality constraint for the non-parallel sides of the slots. I also set an equality constraint for the sides of the triangle.
I also created fillets at the 2 exterior vertices of each slot. I added this design feature to help guide press-fit parts into the slots. All 6 fillets were also parametrized by an equality constraint.
Design file for the equilateral triangle with features I created, as explained above, are appended. A screenshot of the design is shown in Figure 3.1 below. After designing, I decided to cut the design in cardboard on a laser cutter (Figure 3.2).
In the circle, I wanted to create 2 slots that are 150 degrees apart. I followed a similar approach as above. I created 2 radii, and set the angle between them to 150 degrees. I then created a third radius between the first 2, and set its angle with respect to each of the other 2 radii at 75 degrees. Then, I drew one-half of a slot along one of the first 2 radii, and then used the mirror tool along the same radius to complete the slot. This created a complete slot in the circle. I then used the mirror tool again, but this time around the middle radius, and created (or mirrored) a second slot centered around the third radius (one that is 150 degrees apart), and so the 2 slots are also 150 degrees apart. Using this approach we can create slots on a circle that are apart by any angle. Design file for the circle with features I created, as explained earlier in this paragraph, are attached, and a screenshot of the same is shown in Figure 3.3 below. Once again, I decided to cut this design in cardboard on a laser cutter (Figure 3.4).
By the computer controlled machining week, I got ambitious, and with my little CAD experience, decided to draw a bookcase in SolidWorks for the "make something big" assignment. Describe the process of creating the bookcase in SolidWorks here. Design files of all parts and of assembly are linked in documentation for the same week. A screenshot of the (in silico) assembled bookcase is shown in Figure 3.5.

Next, I tried SketchUp. Reason I started learning SketchUp is I wanted to make a chess set for the molding and casting week, and when I tried to look up some tutorials to do it, the first few I came across had modelled chess pieces in SketchUp. I first created a pawn following a tutorial, and it was not hard. I then created a king, a rook, a bishop, and a queen (Figure 3.6). All five are radially symmetric for the most part (except for special features in the king and the bishop), so the revolve tool was very helpful. The only piece I could not create was a knight. Anyway, it is a work in progress. Design file of all pieces (minus a knight) is appended.

From SketchUp I moved to Fusion 360, and used it to design a 2-part mold for a pawn (Figure 3.7) as part of molding and casting week's assignment. Design files of the mold are linked in documentation for the same week.

I also used Fusion 360 to design a hollow sphere during the 3D scanning and printing week. The sphere was designed as follows: Create a Center Diameter Circle with a diameter of 75 mm centered at the origin > Using the Line tool, draw a diameter splitting the circle in to 2 halves > Using the Trim tool, erase the circumfrence of one half of the circle > This leaves you with a closed semi-circle > Using this closed semi-circle as a planar face, Revolve it along the diameter (used as an axis) > This creates a hollow sphere centered at the origin, and with a diameter of 75 mm.

Another program I tried to learn is FreeCAD. It is not very intuitive, and it seems to me that it makes a difference whether you are using it on Windows or Mac. Another thing I found very unusual is that selecting, deleting, and moving something around is not very straightforward. I did, however, manage to do some of the things that Neil had demonstrated during class.

With help from several sources, I gradually learnt bits of a few programs. As is with most things in FAB Academy for me, learning CAD is also a work in progress.