Week 3:

Computer Aided Design

Parametric 3D-modelling using Antimony

Task

I worked with various Computer Assisted Design (CAD) and image manipulation software during this week. My work have included the use of:

  • GIMP for image resizing.

  • Inkscape for 2D-drawings to use for lasercutting.

  • Antimony for 3D-modelling my idea for a final project.

  • Fusion 360 to produce 3D-model as well as a parametric design for lasercutting.

Design files can be downloaded at the bottom of this page

Resize of Pictures

Image files on my website has been resized using either Apples bloatware Preview or the free open source GIMP (Short for GNU Image Manipulation Program). The GIF to the right show the process of using GIMP, further described below:

  • Select File > Open.. to open image file.
  • Select Image > Scale Image... to change size.
  • Set desired image size and press Scale.
  • Select File > Export As... to save the edited file.
  • Choose file name and press Export.
  • Select image quality (see note below).

Results:

I have resized a picture using GIMP from 3293 x 2848 px to 800 x 692 px, which resulted in the following changes of file sizes: The the original at: 3293 x 2848 px = 7,4 MB.

  • Original = 7,4 MB
  • Resized 100% = 756 kB
  • Resized 75% = 90 kB
  • Resized 50% = 57 kB
  • Resized 25% = 37 kB

Conclusion:

I think that there is a good cost-benefit ratio by reducing image size (to the largets size needend) and saving the image with a 75% image quality.

Resizing of images using GIMP
2D Modelling in Inkscape

Press-fit-test in Inkscape

I created a comb like sketch with different gap sizes ranging from 2.4 mm to 3.4 mm in increments of .1mm. This comb could hopefully be used to find the right spacing - allowing for the kerf - for a press fit construction.

I discovered - while messing around with Inkscape on a Mac - that copy-paste operations turned vector graphic into bitmap. This was caused by an faulty setup of XQuarts - a support software that is required to run Inkscape on a Mac. Make sure to follow the installation guide at the Inkscape website. Other settings that I found really usefull (read nessesary) is to:

  • Checkmark "Geometric Bounding Box" (Edit > Preferences > Tools), which makes a shape the same siz irrespectively of resizing of stroke thickness.
  • Uncheckmark "Scale Stroke Width" (Edit > Preferences > Behaviour > Transforms) to ensure that stroke width doesn't change when size of objects are changed.

2D-modelling in Inkscape

I used Inkscape to create a press fit box that could be used to subdivide the storage compartment in the table top. Inkscape is quite intuitive a fairly powerfull tool - I primarily used these operations:

  • Create rectangles: to make basic 2D-drawings.
  • Edit > Clone > Create Clone: to make repeat shapes.
  • Path > Union & Path > Difference: to combine to a final shapes.
  • Edit > Clone > Create Tiled Clone: to create multiple final shapes.

3D Modelling in Fusion 360
Parametric Design in Fusion 360

3D-modelling

It soon became evident that it can be tedious work to make manual adjustmenst of the size of the design or to account for changes in either material thicknes or kerf. I thus tried Antimony and Fusion 360 to develop a parametric CAD.

Antimony

Antimony seams like a really powerfull CAD. Drawing is based on pure matematical input (in the Graph Window). The Graph Window is used to connect parameters from on shape to another (ie. width of a table) but also to connect shapes to different graphical operations (such as revolve), properties (such as color) and funtions (such as export).
The export function allows for direct export to a heightmap (.png) or an .STL file. The .STL-file is perfect for 3D-printing, but I am currently unsure if the heightmap can be used for Computer-Controlled Cutting.

Fusion 360:

I then started to create a paramertic model in Fusion 360. In my first attempt I used the Move-command to align sides of cube. This model responded well to parametric changes of the thickness of both material and kerf, but it couldn't handle adjustment in size of the model). I should instead have used the Joint-command!

I then decided to create just one side of the box - and make that 100% controlable by setting user parameters for size, kerf and material thickness.