2. Computer-Aided Design

Designing a 3D object using Autodesk Fusion

I started by testing the use of Autodesk Fusion software to design a simple object, that I could use in my final project (this design was for the old final project, I changed the final project topic later).

Figure: CAD design exercise.

First I draw a sketch with polyline and line tools.

Figure: CAD design exercise first step.

I added a circle for an eye to the design.

Figure: CAD design exercise second step.

I extruded the fish shape to obtain 3D structure. I measured the center of the mass usign a tool in the Fusion software, and added a hole above the center of mass, so I could hang the fish with a string that would be attached to this hole. I used the hole tool to add the hole.

Figure: CAD design exercise third step.

Figure: Menu selection for hole.

Figure: Menu selection for hole, to get it to the other surface.

Figure: Menu selection for calculating center of mass.

I also added some rounding to the edges of the final 3d design.

Figure: CAD design exercise third step.

The 3d design file, made with Autodesk Fusion.

Basic editing of raster images with Gimp software

To test basic editing with Gimp software, I took a photo of a suitable object.

Cropping

To crop an image, I first select the region with the select tool. Then I choose: Image -> Crop to Selection.

Figure: cropping an image with Gimp.

Figure: cropped image.

Drawing ellipse on an image

To draw an ellipse on an image, I choose: Tools -> Selection Tools -> Ellipse Select.

Figure: drawing an ellipse to an image to highlight a region.

Then using the ellipse selection tool, I draw the ellipse at desired location on the image, and choose Edit -> Stroke Selection.

Figure: drawing an ellipse to an image to highlight a region.

There appears a menu to control line properties, click -> Stroke

Figure: drawing an ellipse to an image to highlight a region.

An ellipse is created to the image.

Figure: drawing an ellipse to an image to highlight a region.

Transforming color image to grayscale

To transform a color image to grayscale image I choose: Colors -> Components -> Decompose.

Figure: transforming a color figure to grayscale image.

Then I accept the suggested color model RGB, and click -> OK.

Figure: transforming a color figure to grayscale image.

This yields the RGB colors as grayscale image layers.

Figure: transforming a color figure to grayscale image.

The final image is here.

Designing a 2D line (vector) and raster object using Inkscape

Basic inkscape usage: drawing Bezier curves for laser cutting

In inkscape, it is convenient to draw smooth paths for laser cutting. This is achieved by using Bezier curves. They can be created easily using menu selection:

Figure: Selection for creating a Bezier curve.

After selecting the Bezier curve tool, the path can be created on the drawing screen. Holding the left mouse button down allows to chnange orientation of the line, and this way the line can be made smooth.

Figure: Drawing a Bezier curve.

For laser cutting, it is necessary to modify the line thickness. The lines that are sufficiently thin will be cutted with laser, and thicker lines will be engraved. To change the line thickness, I select the line, and then object -> fill and stroke. In the side panel, which opens, the width can be changed.

Figure: Modifying line thickness of a selected curve.

From Pixabay, I downloaded an image of bird symbolizing peace, (image by Clker-Free-Vector-Images from Pixabay)

I opened the file using Inkscape, and drew a spline around the bird, set the line thickness to 0.02 mm, and saved the file to a pdf file.

Figure: Making a design using inkscape.

Then I printed the file, which sent it to the laser cutter. I choose 3 mm plywood material with cut and engrave.

Figure: Laser cut and engrave an image.

The final result turned out fine and peaceful.

Figure: Laser cutted and engraved object.

I tested some additional vector and raster cutting jobs. For a second test, I made a raster image of a horse created by Sponchia, which I downloaded from pixabay, where I created a surrounding line for cutting.

Figure: An image of a horse

The raster was engraved nicely on the painted material. In the lower side, there appeared some brown color near to the cut line.

Figure: Horse image after laser engraving and cutting.

I asked the lab instructor for the reason for the brown color, and he explained that it is because of the air, which is blown to the material from that direction, and that it can be easily wiped away with a wet paper. I wiped the edges, and got rid of the brown color.

Figure: Horse image after cleaning with wet paper.

Parametric design with FreeCAD

I tested parametric design using FreeCAD software. First, I drew an object using polyline, constrained horizontal and vertical lines, and made a length constraint for few sides.

Figure: Using FreeCAD to create a sketch with constraints

Then I used spreadsheet tool to create parameters for the design, so that I can easily change the geometr using those parameters. I named the parameters h1, h2, w1 and w2. I then used these parameters in the sketch to determine the geometry, which would be applied when I recalculated the object.

Figure: Using parameters defined in the spreadsheet.

Figure: Parameter definition in the spreadsheet.

Changing the parameter values in the spreadsheet change the parameters in the sketch.

Figure: Sketch with a set of parameters.

Figure: Sketch with changed parameter.

I tested to add 3rd dimension to the object by using pad tool.

Figure: Adding 3rd dimension.

The end result was a 3D object, where the parameters could be used to control the geometry.

Figure: 3D object with parametric design.

The FreeCAD files for the first parametric design:

The parametric sketch designed with FreeCAD.

The .svg file that could be used for laser cutting (after changing the line width to 0.02 with Inkscape).

The 3d object designed with FreeCAD.

Designing a post card stand

I wanted to do another design, that would have some application purpose. I decided to make a stand that could be used for postcards. In the same way as in the previous example, I used FreeCAD to design the parts, and took kerf in to account using the spreadsheet tool. I used helper lines to make certain parts to be aligned in the correct way.

Figure: Designing parts for the postcard stand using FreeCAD. This stage applied helper lines to keep parts aligned.

When I was ready with the design, I wanted to export the result to svg file and transfer it to inkscape, so I could prepare it for laser cutting. At this stage I removed the helper lines from the design.

Figure: Designing parts for the postcard stand using FreeCAD. Helper lines removed.

Then I exported the design to svg (I selected the parts in Sketch mode, choose File -> export -> Flattened svg).

Figure: SVG file exported from FreeCAD. The left part would be cut twice.

The FreeCAD files for the postcard stand:

The design of the postcard stand made with FreeCAD, FreeCAD file.

The postcard stand design after removing the helper lines, FreeCAD file.

Then I opened the svg file with inkscape, set the line thickness to 0.02 mm and exported to pdf, and proceeded to cut the parts in the same way as explained above. The cut parts fit together well, as shown in the documentation of Computer Controlled Cutting week.

Rigid body simulation with Blender

I wanted to try to use Blender to make a simple rigid body simulation. I found a good tutorial written by Ryan Bury, that explained the basic steps but here I used torus instead of a ball.

The most important commands for navigating and adding/removing items are:

Press mouse wheel: grab and rotate scene.

Press mouse wheel and shift: grab the scene and translate it laterally.

Scroll mouse wheel: zoom in/out.

Select object: Right click.

Object manipulation: Translate: g, Rotate: r, Scale: s

Hotkey for adding object: shift-a. (Can be done from menu as well).

Hotkey for deleting object: x. (Can be done from menu as well).

I started blender and deleted the initial cube. Then I added a plane to the geometry

Figure: Using blender to create plane

Then I re-sized the plane.

Figure: Resizing the plane

Then I added Torus to the scene using menu.

Figure: Adding torus by using menu.

Figure: The scene with the torus and plane.

I set the plane as passive from the rigid body menu, so it would not drop down when the simulation is started.

Figure: Making the plane passive rigid body.

I checked that the torus is active in the rigid body menu, so it would drop down when the simulation is started.

Figure: Checking that the torus is active rigid body.

In the simulation, the torus dropped and collided with the plane.

Video: Simulation of torus dropping on a plane.

The Blender file of the dropping torus simulation.