More Boxes! 3/15

On Thursday we continued working on our boxes. I focused on working on my movable joints, and trying out the living hinge.

I was completely wrong about at least one thing when it came to living hinges. I really over thought in my last post.  The material is cut all the way through instead of just part of the way. Also, the cuts are much simpler than I they look. I showed my professor the link, and he explained it to me. The cuts actually look like this:

When you bend the material they stretch and look much fancier, like this (sorry about the blurry picture):

I tried it out on a 1” square piece of plastic, and the same sized piece of wood. I spaced the cuts out 1/32” apart. The wood immediately snapped when I bent it, but the plastic actually worked out really well!

So I decided to test it out in my design. I want both of my movable joints to be at the top of my box, since it doesn’t really make sense to have a box with two whole sides that do not stay shut. A living hinge is a spring joint, so a I needed a way to hold the lid shut. Originally I planned on just having one side have a tab sticking out of it to go under the other side. But, while this made sense in my brain, my professor pointed out that there would be nothing to hold down the other side. He suggested that I put a tab on both sides to make interlocking sides. He also suggested that I put a living hinge on the tabs so that they can bend. I tested this out by making the side connected to the living hinge to the top. I left the lines 1/32‘ apart, but since my piece was 2” wide I ended up melting the plastic. So I spaced out the lines more (1/24” apart), and the piece still melted a little. Once it cooled it was fine, but it was a little warped. Next time I will space my lines 1/16” apart.

Who knew you could put so much time and thought into making a box? Do engineers make everything this complicated? When we come back from spring break we are only going to spend about another hour completing our boxes. So let me clearly and explicitly state the process I used to make this box. It feels artificial. As I wrote this it became clearer how much the steps overlap. Its a kind of hard to decide which step of the process each decision I made I made falls under.

Concept
I think that the concept was pretty much already determined for us. We simply had to build a box with 2” sides, two fixed joints, and two movable joints. All we had to do was determine specifics. I decided to make my box a cube because it seemed like the simplest, most obvious choice. Then I considered my options for the fixed sides. Because we were using a laser cutter to make our boxes, finger joints seemed like the most natural choice for the fixed sides. The only feasible options for the movable joints were contact paper and living hinges.


Decision Matrix

In my decision matrix I rated individual parts of the design rather than the design as a whole. That’s probably not the right way to do it, since engineers need to consider how their design works together as a whole, but it made the most sense in this situation because it is how I made my choices. It also seems strange that the decision matrix is before the experimentation step. I know that you should go back after your experiments and edit your matrix, but i don't know how you chose the values without any experimentation at all. It felt like the values I chose were rather arbitrary. I chose a combination of finger joints and glue as my fixed joints because I did not spend enough time testing the other options to get them right. I think that a combination of glue and finger joints is the best option for the amount of time that I have left. 

Experimentation/ Feasibility

This is the step that I probably should have spent more time on. I never really tested out anything for the fixed joints. I did observe Frances's tests with the screws and the fingering joints, and I saw that it worked really well, but I do not think it would be feasible for me to complete my box with screws because I have not spent enough time working on it. I also do not think that I have enough time to make my fingering joints fit well enough on their own. The only part that I really did experiment with was the living hinge. I know that in the future I should spend more time on this step of the design process.

I don’t think I have made it to the testing step yet, because I haven’t completed a prototype, so that’s all for now!