2. Computer Aided design¶
This week I worked with three types of programs:
2D Vector Design (Inkscape)¶
I have very little experience with Inkscape, basically I limited myself to drawing shapes and changing them using editing tools (zoom in and out, changing a straight line to a curve). But in the future, it was not used for laser cutting or CNC cutting.
Inkscape for me was a vinyl cutter program, not a drawing program.
Since I wanted to create a drone I thought it would be a good idea to draw a sketch of my drone with this software.
I started to draw ovals and then end up with this arrangement looking like a propeller.
Next I changed it’s fill and stroke settings to have only the outline of the shape. I also used the boolian operation to join several shapes into one.
Here’s the result of the union operation.
After some back and forts I finally got this result that reminds a toroidal propeller I want to have on my drone.
I used a new tool I discovered from path effect section
It’s called Rotate Copies as you might notice there are bunch of cool tools here that might be handy like the mirror symmetry tool.
Here you see the resulting 6 copies of my propeller which you can controll from the right side by changing the number of copies.
I changed it to 4 since I’m going to need 4 propellers and moved the center accordingly.
After finishing this step I realized I can add the arm of the drone to the prop and copy that instead of doing it separately.
So i modelled the arm and deleted the other three propellers
and performed the Rotate copies operation again.
after chnign the number to 4 again and moving the center
I got this result
And then finished my drawing by adding a basic body for my drone.
Raster 2D design (GIMP)¶
I’ve been doing simple things in Photoshop 10 years ago, and the only thing I know is that it was a powerful tool.
I opened the program and imported my drawing of the drone.
With the help of the Fuzzy Select Tool I mark the areas that I want to paint over in the future.
Now that the areas are selected, I select the Bucket Fill Tool and click on the areas I want to fill.
If FG color fill is active in the Fill Type settings, then the area is painted in the color that is currently active.
Thus, I select areas, choose colors and paint over the parts I need. And that results in the following.
And now I want to change the background of the drone, in the same way that I choose the area above. Then I select the Bucket Fill Tool, and in its settings Fill Type, make active Pattern fill and select Sky, I want to choose as cloud background.
Now clicking in the selected area will change the background
I did not really like the result, it would be desirable to change it.
Let’s try to make a gradient. To do this, instead of the Bucket Fill Tool, you must select the Gradient Tool. In the settings field in Shape select the value Radial. We also choose colors.
The gradient is characterized by a line, because I’m working with a Radial gradient, the starting point of the line characterizes the center of the gradient, and the line characterizes the radius. For this reason, I will choose the starting point in the center of the drone and the second one somewhere along the edge of the picture.
The result will be the following:
I did not really like the result, for this reason I still remove the background.
Now let’s add some text that characterizes my drone. Text is added using the Text Tool. When we select this tool, the first step is to select a rectangular area in which we want to add text. You can then change the font, font size, font color, and so on.
Now you can write text.
After adding the texts, the final result will be as follows
I know I could do this in inkscape too but It was interesting to try to do it in raster software.
3D Design (FreeCAD)¶
I will try to model my toroidal propeller using FreeCad, with the only difference that it will already be a three-dimensional object and it will be parametric.
- And so we start. When we open the program, we need to click on Create new ….
- Then we go to the Part Design tab
- create the body Create body
- Then select Create sketch
- We need to select the plane in which we want to make a 2D drawing (in my case it will be the XZ_Plane plane).
- And the sketcher tools will open up.
- Using the ellipse tool I created an ellipse
But before continuing, there is one point, I want my model to be parametric. To do this, I need to store the parameters in a special table. Let’s create such a table.
- Go to the Spreadsheet section and select Create a new spreadsheet
- A table opens in which you must enter the name of the parameter and its value.
- If you right-click on the value of a parameter that has just been written and click on Properties…, a pop-up window will open. In the Alias tab, you must enter short name, by which this parameter will be recalled in the future.
- Then, if in the Display unit tab you can enter the value mm (I entered the value mm, because later on it will help to get a 3D model of the size I want).
If an Alias is entered, the cell is shaded yellow, which means that the cell value can be used as global variables in the program. This implies that cells that are not shaded have no effect. In this case, cells in column A are auxiliary cells that organize the creation of parameters. To simplify the writing of parameter aliases and their further use, I will write them in column C.
And then I will enter for all values Alias and Display unit.
Now we move to Sketcher and draw two concentric ellipses. The right side of the outer ellipse is located at the origin of the coordinate system. We mark two points on the outer ellipse and choose the tool to fix the distance between these two points (Shift + D). A pop-up window appears (Insert length) where we can enter the value manually or click on the circle on the right side of the Length field to open the Formula Editor dialog box. There, we can enter the parametric value. The name of the variable table is Spreadsheet, and the parameter to select is by. Therefore, we need to enter Spreadsheet.by.
After clicking OK and closing all pop-up windows, the distance between the two selected points will be parametric, which means that if you change the value of the parameter in the Spreadsheet table to another one, the distance between the points on the drawing will change to the changed value.
After setting all the parameters, the sketch will change color to green, indicating that it is fully parametric.
After that, you need to create a new Sketcher. You need to have two similar sketches that will be eccentric and located on different planes, which will allow you to get a volumetric detail that we need.
This means that since we did not hide the previously made Sketcher, it is visible to us, but it is not involved in the current sketch. In order for us to use constraints to the first sketch, we need to use the tool Create an edge linked to an external geometry (X) (when this tool is active, clicking on parts of another sketch makes its parts available for constraint).
To use the “Create a parallel constraint between two lines (Shift+P)” tool, select the axis of the ellipse and the “X” coordinate. This will make the axis of the ellipse parallel to the “X” coordinate.
Next, draw a line starting from the center of the ellipses in the other sketch and parallel to the Y axis. Then, using the tool Fix a point onto an object (Shift+O) and selecting the center of the ellipse and the line parallel to the Y axis, ensure that the center of the ellipse belongs to this line. Then select the central point of the ellipse and the starting point of the line which is located in the center of the ellipses from the other sketch, and set a parametric length.
After applying several constraints and parameters, the second sketch will also turn green, which will mean that it is also fully constrained.
To lift the second sketch to the level of “blade thickness” indicated in the “Spreadsheet”, select the second sketch and in its parameters, change the “Z” value in the “Position” section to “Spreadsheet.bz”.
Then select two sketches and use the tool Loft a selected profile through other profile sections.
After applying this tool, you will get a three-dimensional body.
It’s time to get the mounting location to the motor. I have two parameters characterizing this assembly: center R and center hole R. Based on these two parameters, we need to create a new sketch that will contain two concentric circles located in the center of the XY plane.
To create a solid object from the sketch, select the sketch and use the tool Pad a selected sketch. Set the length to be equal to the value of the parameter bz from the Spreadsheet table.
There is an extra part of the blade that is present in the hole intended for the motor shaft.
To subtract this part from the hole, you need to select the inner circle of the hole and use the “Pocket” tool. In the “Type” parameter, choose the “Through all” option to subtract it throughout the entire body.
At the moment, the propeller has one blade, but I need it to be two-bladed.
To make the propeller with two blades, we can use the “Polar array” tool in the “Draft” workbench. First, select the propeller, then click on the “Polar array” tool.
In the Polar array dialog box, set the number of elements to 2 and set the Polar angle to 360 degrees. Finally, click “OK” to create the new two-bladed propeller.
You will end up with a two-blade toroidal propeller.
Here is the resulting propeller that can be parametrically edited. For example I can change the diameter, angle of attack, center hole diameter, blade thickness etc.
Conclusion¶
In conclusion, this week I had the opportunity to work with three different types of programs: raster, vector, and 3D. I explored Inkscape for vector design and learned how to create shapes, combine them, and use various editing tools to design a drone. In GIMP, I explored raster design and learned how to use the Fuzzy Select Tool, Bucket Fill Tool, and Gradient Tool to add colors, patterns, and backgrounds. Finally, in FreeCad, I worked with 3D design and learned how to create a simple model by adding shapes, extruding them, and manipulating in 3D space. These experiences gave me a taste of the capabilities of each program and the various possibilities they offer in the design process.
