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Assignment 2 - OpenSCAD

Due Monday 9/18 at 11:59 pm. You must work individually.

Goal

In this assignment, you will design a parameterized object (or a set of objects). You will use OpenSCAD to create your objects. OpenSCAD is a software for creating solid 3D CAD objects. It is free software and available for GNU/Linux, MS Windows and Apple macOS.

You are not required to 3D print your creation at this time. However, please make sure to design something that can be easily 3D printed. For example, you may need to separate your object into pieces and lock/glue them back together after printing.

OpenSCAD is not an interactive modeler. Instead it is a 3D-compiler that reads in a script file that describes the object and renders the 3D model from this script file. Your task in this assignment is to write a set of OpenSCAD scripts to create the objects. These objects will be printed in the future.

You will be responsible for using OpenSCAD to create a parameterized object with a reasonable complexity. Your design should be a single OpenSCAD file with any number of modules. All the parts of your designs must be created by a single high-level module. The parameters of that module are the exposed parameters of your parametrized model. The requirements of your design are:

• Use of loops
• Use of CSG
• At least two different parameters exposed
• Everything should be modular (i.e, use auxiliary modules for subparts)
• Sufficient complexity (e.g., not few spheres stitched together)
• Present a few examples of the same design with different parameters
• Explain the parameters of your high-level module and give the approximate range

Make sure your parameters are "interesting." Here are some guidelines.

• A simple "global scale" is not an interesting parameter. Instead, think about some additional changes that occur as a result of changing the scale. For example, if designing a table/chair set, when the scale of the table increases, the number of chairs increases discretely.
• Do not make your parameters be a simple discrete switch. For example, do not use a parameter as a variable for a switch statement: switch(param) { case 'foo': ... case 'bar': ...}.
• Imagine that you are a designer creating a customizable object for casual users. Try to expose parameters that make the most sense for the casual user: e.g. a cylindrical container could have a customizable volume, not radius and height.
• Expose high-level parameters that control more than just a single low-level parameter value. For example, do not expose values of two parameters, where the value of one parameter depends on the value of another (e.g., the radius of the lid and radius of the pan).

Getting Started

Using the OpenSCAD Modeler

You will use OpenSCAD to create your 3D models. It is pretty straightforward to install OpenSCAD.

• Download OpenSCAD installer.
• Create your designs with OpenSCAD language in the script panel.
• View a list of OpenSCAD built-in functions.
• To view your design from OpenSCAD, you need to Compile your code. This can be done by selecting "Compile" from the "Design" menu, or simply by pressing F5.

Export for 3D printing

Ultimately, you will 3D print your designed model. In order to 3D print you will need to export your objects from OpenSCAD as an explicit mesh. A typical file format for 3D printing is the STL file format, which is supported by OpenSCAD for importing and exporting. To export your design, you need to:

• "Compile" and "Render" your script. This can be done by selecting "Compile and Render" from the "Design" menu, or simply by pressing F6.
• Export to STL file. Select "Export as STL..."" from the "Design" menu, then enter a filename in the ensuing dialog box. Do not forget to add the ".stl" extension.

Note that sometimes you might be able to compile and render your design but you will not be able to output the STL file. One of the typical reasons is that the object created is not a valid 2-manifold. If it happens, you may refer to the example in http://en.wikibooks.org/wiki/OpenSCAD_User_Manual/STL_Import_and_Export for further reading. It is important to test the export function incrementally as you build your model. Do not wait until the last moment to export!

Online Tutorials

There are some tutorials online:

• OpenSCAD User Manual: http://en.wikibooks.org/wiki/OpenSCAD_User_Manual
• OpenSCAD Tutorial Series on the Makerbot blog: http://www.makerbot.com/blog/2012/11/08/openscad-design-tips/
• OpenSCAD beginners tutorial: http://edutechwiki.unige.ch/en/OpenScad_beginners_tutorial

Example Designs and Implementation Notes

There are some example designs built into OpenSCAD. You can see them by selecting "Examples" from the "File" menu. Below, we show some more examples from Thingiverse etc. that may be helpful as an inspiration.

• Robotic finger with hinges: http://www.thingiverse.com/thing:221560/
• Skateboard: http://www.thingiverse.com/thing:172002/
• Lamp shade: http://www.thingiverse.com/thing:11385/

• Gardenia Wall Mount Toothbrush Holder

• Avoid copy-and-paste of code for the repeated components. For example, create a module for the wheels of the car and reuse it, rather than repeating the code for a wheel four times.

Required for 689 students

• Create designs that include parts that can be moved with respect to other parts (e.g., hinges, sliders, etc.)

Evaluation

• Working OpenSCAD script (see below)
• Writeup (see below)
• 3 minute in-class demo

What to hand in

Please provide a report with your submission (PDF). The report should include the following:

• Images of your designs, with various parameters and their explanations. Give the valid range for each parameter.
• Were there any references (books, papers, websites, etc.) that you found particularly helpful for completing your assignment? Please provide a list.
• Are there any known problems with your design? If so, please provide a list and, if possible, describe what you think the cause is and how you might fix them if you had more time or motivation. This is very important, as we are much more likely to assign partial credit if you help us understand what is going on.
• Do you have any comments about this assignment that you would like to share?

Create a zip file named NETID.zip (your email ID; e.g., sueda.zip) so that when you extract it, it creates a folder called NETID/ (e.g., sueda/) that has (ONLY) the following in it:

• Your PDF report
• Your OpenSCAD script