A Quick Guide to 3D Printed Case Design with ICE-V Wireless

On this project page I'll explain how I designed this enclosure so you can apply the same techniques to your own designs! I will be assuming you already have some experience with CAD modeling, since there's no way I could cover everything here.

I designed the case for the ICE-V Wireless, which is an FPGA development board which combines the ICE40UP5K FPGA with the RISC-V based ESP32 C3 Mini. Go to store.GroupGets.com to find out more and get one for yourself! You can also buy this case there if you don't want to print it yourself.

Features:

• Printable on any FFF/FDM printer
• RGB Snowflake
• Buttons with hidden compliant mechanism
• 3 piece design with separate battery compartment
• Top side GroupGets logo and text printed in the XY plane
• Side text printed in on the Z axis

DesignProcedure:

Step1: Import the 3D Board Files into Fusion 360

If you don't have access to the 3D files for the board, start by making a simplified version in your CAD program. Even if the board's dimensions and 3D files are available, it's good practice to verify with calipers. Those dimensions don't often come with tolerances or include imperfections left from de-paneling the PCBs.

STEP files are my preferred format for working with PCBs in Fusion 360 and can easily be exported from the KiCAD PCB editor. It's important to not start creating your enclosure from the STEP file itself, otherwise Fusion won't track the design history like it normally would. You'll be left with a tangled list of extrudes, fillets, and chamfers instead of a neat design timeline.

Save the board's STEP file to Fusion and create a new design file to work from. Then insert the STEP file into the new file.

Step2: Create an Outline of the PCB

It can be helpful to start by creating a sketch on the surface of the PCB. and generating an offset perimeter. An offset of 0.4mm or more should ensure the PCB fits comfortably. Consider the dimensional precision of your 3D printer and adjust accordingly.

I only recommend using this offset perimeter for reference lines. STEP files often have imperfections that will later cause problems with symmetry. Construct an outline using the construction lines for reference.

Step3: Consider your Hardware and Mounting Options

The ICE-V Wireless has mounting holes sized for M2 screws, so that's what I designed around. Heat-set threaded inserts are fantastic for 3D printing. They are easy to install and don't wear out the holes like self tapping screws for plastic. CNC Kitchen or McMaster-Carr are good places to shop for hardware.

The heat set inserts go into the battery holder base, but if the battery holder isn't needed an M2 nut can go in these hexagonal holes in the top. Then a shorter 10mm M2 screw can come in from the bottom.

Screwless designs are possible, but they can be tricky to model properly. Clips will likely be a weak point and break after a few uses. If it won't need to be taken apart, a bit of glue will get the job done.

Step4: Extrude, Sketch, Repeat

Form the case into the shape you want it, but don't add too much detail just yet. This will be a time consuming process. If you need to go back and change something, you don't want a bunch of fillets and chamfers to slow you down.

Remember you are designing for additive manufacturing, so be conscious of overhangs and bridging. Also be sure the smallest features are printable with the nozzle size you plan to use. Again, consider your particular machine's capabilities. Small features in CAD may seem larger than they really are.

If you have antennas, it's good practice to avoid having any material too close. It may effect the antenna's performance. Espressif recommends a cutout in the PCB under the antenna as well, but as long as there's clearance in the ground plane it's not a big deal.

Once it starts to take shape, print a sample and check how everything fits together. It's easier to adjust the tolerances before the model gets too complicated.

Step5: Creating Compliant Buttons

This is the most difficult part of the design and may require some trail and error to get it right. Fortunately, rapid prototyping is easy with 3D printers. There are plenty of ways to go about this, so I'll just leave you with the diagrams below to use as a reference.

One feature that would improve this design is an overhang on the opposite side to prevent the button from being pushed too far when the PCB is not there to limit travel.

Step6: Add Text, Logos, and Other Fine Details

A color change after the first layer will give good contrast to text and logos on that face. When adding text in the XY plane, the nozzle size will limit how small the text can be. Not all fonts are created equal. Choose a sans-serif style font with rounded features and wide spacing. Here I used the bold OCR A Extended font for both the top and side faces.

For this case, I wanted the RGB LED to shine through a snowflake to compliment the ice theme. SVG is a good format for importing logos. The Scalable Vector Graphic can be used to create 2D sketch features.

Step7: 3D print the final prototypes and optimize the design.

A new feature in Prusa Slicer 2.5.0+ is the Arachne perimeter generator. Now perimeters with varying extrusion width can be printed. This feature is great for text and logos, so be sure to enable it. Features as small as 65% of the nozzle size can be printed reliably.

To change the print color after the first layer, you can add a pause command to the gCode before it starts the next layer.

The text and logos will be treated as bridges in the slicer. These first layer graphics will look best with a bridging extrusion around 1.2. This won't be ideal if there is bridging at higher layers, but some slicers will allow for different slicing settings at different layers.

Summary:

1. Take some measurements and import your PCB step files if available to use for reference.

2. Create an outline. Only use the PCB STEP model only for reference to preserve your design timeline. About 0.4mm of clearance is usually safe to start with.

3. Consider your mounting hardware. Plastic self-tapping screws are cheap, heated inserts offer the best re-usability, and glue for permanent screwless designs.

4. Build out the basic structure. Consider your machine's capabilities, avoid adding too much detail, and leave extra space for antennas. It's usually a good idea to print a sample here to check your tolerances.

5. Add fancy features like buttons.

6. Add logos, text, and final touches.

7. 3D print, optimize, and iterate.

I hope this guide can be useful in designing your own 3D printable enclosures for your projects! If you have questions or need me to clarify something, I'll do my best to answer in the comments.