Reinventing the Box

Boxes are cool! I recently designed this latching box that can act as a framework for various other boxes that I need around the home and the workshop. It’s fully parametric, which means I can change any of its dimensions by updating a couple of parameter values in Autodesk Fusion, and then I can design all sorts of unique inserts for it for the things I want to store. Like these ones, that I designed to store my hotends and a set of heat-set insert tips for my soldering iron¹:

I put a lot of thought into solving some of the annoyances I’ve bumped into with other designs. For example, when fully opened, I want the lid to lay flat on the table, because I hate it when the weight of the lid destabilizes the entire box. To achieve this, I positioned the hinges vertically at the middle height of the closed box. And since it’s parametric, it moves up or down when the height of either half of the box is changed:

The same approach didn’t work on the latch, because I didn’t want it to extend too far up from the edge of the lid when opened. So I’ve limited how much it can extend vertically, and made the other side come up to meet it. Notice how, as the height of the lid decreases in relation to the bottom half, the latch comes up with it rather than staying in the middle like the hinges do:

Designing things that look good in CAD doesn’t automatically guarantee the manufactured pieces will fit together. This is especially true when designing for 3D printing, since the idiosyncrasies of the additive process come into play. There are clearances that must be observed–and I’ve included these into every dimension and made their magnitude configurable–but sometimes it also involves special design features. For example, instead of plain circles, I’ve shaped all the holes into teardrops, with the sharp angle pointing up. When printing the pieces lying flat (which is the fastest way and doesn’t require supports) this helps to avoid an otherwise delicate overhang that could cause a flat spot at the top of each hole.

Another example is the small space I left between the hinge and latch mechanisms and the box, without which the parts would rub together when opened:

The default diameter of the hinge and latch pins is 2 mm, but this is also of course configurable in the model. I make mine this size because I happen to own a lot of old steel bicycle spokes, and those are usually 2 mm in diameter, and just perfect for this use case. I could have designed this to print fully in-place² and forgone the spokes, but I prefer the durability of steel, and printing the box and lid as two separate parts gives me the opportunity to print boxes that are twice the size of what my print bed would otherwise allow in a single go.