Week 2: Press-fit Construction Kit

I made a laser cut press-fit cardboard box that imitates the appearance of a plastic milk crate.

Here is the plastic milk crate I took inspiration from:

And here is the cardboard replica!

Ok, so it's not exactly an identical replica. I tried to boil it down to some essential features (the rounded handles, the diamond holes, the vertical and horizontal lines that stick out) to make someone think "Oh hey, that's a milk crate!". Now I need to make cardboard milk bottles to put in the crate...

How I did it

First, I laser cut some cards with slots of different sizes to figure out what size to make the press-fit joints in my design. I figured out that 0.16 inches was just right (not too loose or too tight).

Then, I drew all my pieces in SolidWorks. Usually I go for Adobe Illustrator when I draw things to be laser cut, but this time I decided to get out of my comfort zone and try something I'm less familiar with. Also, SolidWorks has the added advantage of allowing you to assemble the pieces to make sure everything fits right before you make the pieces in real life. Here are the two box sides that fit together with quarter inch slots that go up halfway the height.

These are the top and bottom pieces. The top is designed to make a quarter inch rim around the top and fits in the tabs on the top of the side pieces. The bottom piece has tabs that fit in the slots on the bottom of the side pieces.

To make the horizontal and vertical lines that stick out, I made long skinny pieces with tabs that fit into slots on the faces of the sides:

Then, I assembled all the pieces together (and gave it a nice cardboard-like appearance just for fun). It was good that I did this extra step since I had to adjust some of the dimensions that I miscalculated. If I had designed this in Illustrator, I likely would have figured out my mistakes only after cutting...

On to the laser cutter! Here are some of the pieces I cut:

And here it is assembled!

Lessons Learned

• Building assemblies from parts in SolidWorks is a good way to test if your part dimensions are right and if they will fit together. Trial and error on a computer screen is less painful than trial and error with physical pieces.
• It's a good idea to test a variety of slot sizes on the laser cutter to get an idea of what size to make them before you design and cut all your pieces.
• The slots on the sides of the boxes were too thin and long given how flexible the cardboard was. I cheated a bit and glued them down after assembling the crate, but in the future I should probably change the design.
• Originally I designed the bottom with the slots and the bottom edges of the sides with the tabs. Luckily, before I cut them, I realized that that was a poor design since the bottom would fall out if I put anything sufficiently heavy in the box.

DXF files for the crate parts:

top
bottom
side 1 (cut 2)
side 2 (cut 2)
horizontal box lines (cut 8)
vertical box lines (cut 12)