Kokopelli Quickstart: Machining Parametric Living Hinges

Kokopelli Quickstart: Machining Parametric Living Hinges
A CNC-machined acrylic living hinge, cut on a ShopBot CNC router. Acrylic is quite brittle and will typically snap when bent, however – a pattern of small cuts in the material allows it to become quite flexible.

koKokopelli is a parametric, comparative, implicit framework for computer-aided design created by Matthew Keeter. At the moment, kokopelli is suitable for 2D and 3D modeling, and some even use it for PCB design. It can export .pngs, .svgs, and .stls, and there’s basic built-in CAM for 2-, 3-, and 5-axis subtractive machining. It’s like OpenSCAD with built in CAM. This quickstart was originally published as a supplemental sidebar to Keeter’s article Turn Codes Into Things, which provides a more detailed explanation of the software’s capabilities.

Parametric Living Hinge Examples

This tutorial will get you started with a basic, pre-configured, graphical user interface example that will enable you to create, simulate and fabricate your own custom living hinges – without touching the code (unless you want to). The application comes with built-in graphical interface examples that enable you to configure the parameters with sliders – or you can dive right into the code.

Download and Install kokopelli

To begin, you’ll need to download and install kokopelli:

The kokopelli application and source are available via Matt Keeter’s GitHub. Kokopelli is also available as a Mac application.

Install the software according to your preference. If you choose to download the Mac application, unzip it and launch the app.  Or if you’d rather build from the source, check out these instructions on the wiki.

Parametric Living Hinge 101

Keeter has included a kokopelli living hinge example has built-in sliders that make it simple to create your own bespoke flexibles from rigid materials using digital fabrication tools. The parametric living hinge code was originally created by 2014 Fab Academy student Terence J. Fagan and then improved by Matt Keeter. If you’d like to learn more about how he created the code from scratch, check out his tutorial.

Launch kokopelli

After installing, open kokopelli by click on the icon in the unzipped folder or launching it from the command line.


To Open the Example File

Use the “open” option in the  file menu to navigate to the examples folder.  You MUST use the file menu to open the file or the graphical elements will not appear.


Click on the “examples” folder.


Then open the “hinge.ko” file. 


Use the sliders to customize your hinge – or edit the code directly. 


Drag the sliders to modify the hinge attributes, then adjust the piece size and border thickness by dragging the nodes on the top right corner.


Designing For Fabrication

When creating your hinge, design for your materials, fabrication method, and desired flexibility. Densely packed small cuts create more flexibility but are only suited to laser cutting. If you are using a router/mill, your smallest possible cut width is limited to your tool dimension.

Original code by 2014 Fab Academy student Terence J. Fagan and improved by Matt Keeter. Red acrylic lamp customized using kokopelli and fabricated by Anna Kaziunas France.
Red acrylic lamp customized using kokopelli and fabricated by Anna Kaziunas France.

CAM and Fabrication Options

After configuring, export the file and fabricate it. If youʼre using fab lab machines or plain G-code, you can send the file directly from kokopelli.

I’m dying to see what you’ll create! If you’ve made something using kokopelli – post the link in the comments or contact Anna Kaziunas France at anna [at] makermedia dot com.

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Anna Kaziunas France is interested practical digital fabrication focused project documentation (anything that turns codes into things), as well as adventures in synthetic biology, biohacking, personal genomics and programmable materials.

She's currently working on the forthcoming book "Design for CNC: Practical Joinery Techniques, Projects, and Tips for CNC-routed Furniture".

She’s also the Academic Dean of the global Fab Academy program, the co-author of Getting Started with MakerBot and compiled the Make: 3D Printing book.

Formerly, she worked as an editor for Make: Books, was digital fabrication editor and skill builder section editor for Make: Magazine, and directed Make:'s 2015 and 2014 3D Printer Shootout testing events.

She likes things that are computer-controlled, parametric, and open— preferably all three.

Find her on her personal site, Twitter and Facebook.

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