A5: Subtractive Fabrication and CNC milling

Time to box all these feelings up... in a CNC milled box.

I spend all of this week in work-related travel, so with a compressed timeline, I optimized heavily for fabrication and materials.

My box would be as simple as possible -- to the point where the entire box can be made using a single part fabricated six times.

Unfortunately, I relied on butt joints, that are quite unreliable, but at least they were something that could be milled and assembled quickly.

The initial sketches focused on a part that would fit multiple times

OneNote sketches for the part that would be used for the box

To plan for the edges I measured the FR1 to ensure the joints would work well together.

Measuring FR1 with callipers - 1.5mm thick

I then created the actual part -- starting with a 5 centimeter square, that I later changed to 4cm (to optimize for material) because each FR1 board was 7cm * 10cm -- this would allow me to do 2x parts per FR1 board.

OnShape sketch for the part

After extruding the part for the 1.5mm that the FR1 measured, I had the main part for the box.

OnShape sketch for the part

Before manufacturing, I verified that the part actually worked.

OnShape assembly of multiple parts to form the box

It did!

OnShape assembly of multiple parts to form the box

I exported the DXF into KiCad to create a Gerber file.

KiCad app with exported DXF

I imported the Gerber file into Bantam Tools, which looked right.

Bantam tools screenshot with part outline

Once at the Mill, I followed the recommended instructions to prep the job -- e.g. creating the FR1 sandwich and using double-sided tape. I then entered the resulting measures in Bantam Tools.

Bantam tools settings for milling the part out of FR1

And off it went:

Othermill milling the FR1

The outcome of the milling was pretty nice.

Milled pieces

After some light assembly

Box sides put together

Added more sides:

Box sides put together

Box sides put together

The final box resting fully assembled with all the sides holding up.

Completed assembled box

The box fit really well, but needed some careful touch to stay assembled.


The floor is lava lvl:CIA vault... or me assembling my box using crappy butt joints.

Note to self: BUTT JOINTS SUCK (for this assignment).

 

Credit where credit is due: Thanks to Gabi for the insights on how to operate the Othermill and the recommendation to use tape.

 

Source files for the box: