Note: this guide refers to the Spiderclaw V1 and V2, which were intended for the V2 OpenBCI prototype board. The Spiderclaw V3—to be used with the latest OpenBCI Board (V3)—is currently under development.
Here, you’ll find everything you need to get started printing and assembling our current 3D-printable headset prototype that is intended to work with the OpenBCI Board. In addition, this guide includes instructions on how to begin modeling a new headset or modifying the existing headset design. The designs introduced here are a starting spot, but are far from finished. We hope that you, our fellow brain-hackers and makers, will jump in and help improve the 3D-printable EEG headset for OpenBCI. We still have a long way to go!
It’s important for the future of BCI innovation that there are systems capable of sampling data from every region of the head. Some applications may benefit from looking at the entire brain with evenly spaced electrodes, while other applications may require densely populated electrodes, targeting a more specific region of the brain. Also, everyone has a different head size and shape. For these reasons, our primary design constraint in the creation of our early headset prototype was customizability. Our long-term vision is to establish a collection headset designs that are 3D-printable and easy to adapt to different head sizes and numerous applications of BCI.
The current headset design implements the 10-20 system – the internationally recognized method for placing electrodes on the human scalp in the context of EEG. To maximize the customizability of the system we went with a hierarchical, snap-together design. We have established terminology to more easily distinguish its parts. The naming system is analogous to the hierarchy of the human body. The electrodes you will use with the OpenBCI Board are mounted into a finger of the headset. The electrode’s wire is then routed from finger, to hand, to arm, to body (where the OpenBCI Board is mounted). An arm consists of arm segments, which can be printed at different lengths to account for different head shapes and sizes. The below designs detail the pieces of the most recent design of the Spiderclaw. Designs from Spiderclaw 1.o are not included but can be accessed by downloading the 3D files of Spiderclaw v1 from the 3D Files section.
Critical Dimensions (NOT V3 HARDWARE)
Modeling From Scratch & Modifying Existing Designs
Note: if modeling from scratch, jump to step 3.
1) Download 3D files from the “3D Files” section below (file types .obj and .stl work w/ most modeling platforms).
2) Open the files in the 3D modeling software of your choice and go crazy.
3) If you don’t have prior experience modeling for 3D printing, we recommend you check out the following resources:
– Shapeways: Things to Keep in Mind When Designing for 3D Printing
– Make: Ultimate Guide to 3D-Printing 2014
– Getting Started with 3D Design – MakerBot
– Modeling for 3D Printing with Shapeways
– (if you have other good resources, please share them with us)
4) When working, be sure to pay attention to the critical dimensions specified in the Critical Dimensions section. You must be sure that your design works with the OpenBCI board and electrodes that come in the electrode starter kit. Other than that, your head is your limit!
5) When you are finished with your design, export your models in the filetype .stl and then upload them to your 3D printer’s slicing software. Examples of slicing software include MakerWare (for MakerBot) or the open-source software Slicer (for Lulzbot and a number of other printers). There are many slicing applications out there; check out this Make Magazine issue that covers all sorts of awesome 3D-printing info.
Printing The Headset
1) From the 3D Files section below, download the .stl files for the headset.
2) Once you’ve downloaded the appropriate .stl file(s) upload them to the 3D-printer slicing software that works with your printer. Note: depending on the print volume of your printer, you may need to download the pieces individually and rearrange them in your slicing application. You may also need to print in multiple sessions to get all of the pieces you need.
3) Export the G-Code, upload it to your printer, and print your headset!
To assemble your headset and attach the OpenBCI Board, there are additional things you’ll need to buy and do:
Clipping, Filing, & Sanding
You’re going to need to clean up your 3D-printed pieces. Use snippers, plastic files, and sand paper to remove excess plastic and make sure that all of your parts fit together nicely. The following kit has filing tools that work very well with the current headset design’s dimensions. Note: The headset is designed to nest together with some resistance between all of the connections. If you remove too much plastic while cleaning up the pieces, there may not be enough resistance for your headset to stay firmly assembled.
Rubber Bands & Screws
The current headset design uses a tensile mechanism to create downward pressure on the scalp. You need to use rubber bands to provide the tension between the printed pieces. The headset was designed to work well with orthodontic rubber bands (used on braces). Currently, the best rubber bands we’ve tried are 3/8″ Light and 3/8″ Medium. The OpenBCI Board mounts to the body using three screws. They are 4-20 Thread, 1/4″ Length screws.
Adjusting the Size & Fit
Adjust the strength and placement of the rubber bands to optimize the tension of the various parts of the system. You will need to add and remove tension from sections to prevent buckling, allowing for the electrodes to stay in place. Also, adjust the length of the arm segments of your 5 arms so that the nodes of the arm segments (where the hand connects to the arm segment) are above the black dots seen in the left-most graphic of the 10-20 System diagram seen in the Design Overview section.
Inserting The Electrodes
NOTE: in order to download the files below, you need to right-click the link of the file you are trying to download and then select “Save Link As…” The file types .obj and .stl are industry standards for 3D modeling and 3D printing. They will work with the majority of 3D modeling software and 3D printing slicing applications. The .mb file type is specific to AutoDesk Maya, the software we used to model the up-t0-date version of the OpenBCI headset. There are many other 3D modeling software that might be easier to learn and better suited for 3D modeling with the intention of 3D printing (see the Modeling From Scratch & Modifying Existing Designs section).
For the most recent iteration of the Spiderclaw, we designed for full modularity by having every component of the system be snap-and-go. It also implements the new octagon shape of the OpenBCI Board into the design of the body. The biggest drawback that we’ve found in this design is the localized areas of tension along the arms (at the connections between arm segments). They tend to cause buckling of the arms, making it difficult for the electrodes to stay in place. The highlight of iteration system are definitely the hand/fingers, the electrodes that we’ve been testing with nest nicely into the negative spaces of the fingers as you can see in the image above. I imagine that the next iteration will be an overlap of designs 1 and 2, with a better system for applying evenly distributed normal pressure to the scalp at all contact points along the arms. We are considering a tensile system similar to the ligaments of a human hand. This would entail a single thread/wire that pulls tension down the entire length of the arm, as opposed to localized tensile connections at the joints.
NOTE: for a full Spiderclaw 2.0 headset, you’ll need:
x1 – body
x11 – arm segment (3 for the top arm segment, and 2 for all of the others … sizes depend on your own head size)
x5 – arm end
x5 (or more) – hand
x10 (or more) – finger
.STL Files (recommended for printing)
body (one size fits all)
arm segment (short, medium, long)
arm end (one size fits all)
hand (one size fits all)
finger (one size fits all)
test electrode (the electrode size may change, meaning the finger will need to be re-designed)
.OBJ Files (recommended for modeling)
.MB File (if you want to work directly from the up-to-date Maya project directory)
This is the first design of the Spiderclaw. It was designed during the Kickstarter campaign when we thought the OpenBCI Board was going to be a hexagonal shape. Because we shifted to an octagonal design of the PCB, the “body” of this design is no longer valid, but we do believe that there are some merits to the simplicity of it’s design over the newer version. This design allows you to print each arm in a single piece, making assembly easier, but making the entire system a bit less customizable than Spiderclaw 2.0. The hands of this design do not have detachable fingers (or electrode holders). Instead, there are 3 different types of hands (1-electrode, 3-electrode, and 5-electrode). Additionally, we have had problems with the mechanical connection between the hands and arms with this design. The fasteners of the hands quickly break after overuse. This influenced our decision to use a mechanical connection that didn’t require the plastic to flex in Spiderclaw 2.0.
Share Your Suggestions & Designs!
Email us at [email protected] w/ the subject line “My Headset Design” with your files and some screenshots and pictures of your design and prints. Once we confirm that it works with the OpenBCI Board, we’ll publish your design to our site and Github! We’ll 100% credit you for the design and link to your site.