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!

Boxes 3/12

    Yesterday we continued working on our boxes. Our professor recommended that we use France’s method of joining our sides using screws and cutting slots for the screws in the sides of our pieces.
    Then he showed us how to use the laser cutter on our own. Important things to remember when using the the laser cutter are:

• Save your image as an eps
• Make sure that your lines are RGB red (red 255, blue 0, green 0) and less than .003” wide
• Print your drawing from Core and set the page size to about the same size as your image
• Use the positioning tool to position your material vertically
• Refer to the numbers on the board by the laser cutter to decide what power and speed to use for  your material
• Don’t touch the laser head or crash the material into the laser

    The hardest part of using the laser cutter is that it often takes two or three passes to cut all of the way through. You have to be careful when check to see if it has cut all through not to move the material, otherwise you will loose precision. It is possible to slow down the velocity of the laser so that you can cut through the material in one pass. But you have to be careful not to slow it down too much because you risk melting the material or starting a fire.
    I had drawn my pieces in Illustrator, and I was planning on cutting some out and testing how they fit together, but then I decided to add screws to my box, so I just started over. I like new drawing better, though, because so far all four of the sides are the same. However, I am positive that this will change when I add the movable joints.
    The moveable joints are what I am most unsure about right now. He gave us a few solutions when we started building our boxes, but I didn’t really like them. One solution was to join the two sides with fingering joints, but to make the parts that stick out curved on top so that they can rotate. Then you drill a hole through the pieces and put a rod through the whole for the piece to pivot around. The problem with this is that I don’t know how to make the curved parts, and I do not want to use the drill press. He also suggested making springs by cutting very thin pieces with the laser cutter, but I think this might be difficult to achieve. Another idea was to just use contact paper for hinges, but I think there must be a better way.

(image from http://blog.makezine.com/2011/10/25/plywood-living-hinge-technique-for-laser-cutters/)   
    I googled laser cut hinges and found that one of the most popular ways to make moveable joints with a laser cutter is to use living hinges. Living hinges are places where the material can bend because lines have been cut part way through the material to make it more flexible. People have used both wood and plastic, but wood seems to be more popular for living hinges. I want to try this, but I think I will have to do a few tests to get it to work. I do not know how deep you want the cuts to be, and I do not know of a precise way to determine how deep your cut will be. I think it will be a process of trial and error. Another thing that is important to consider is where the hinge starts and where it ends. If it starts too low on the box there will be a weird gap. The boxes are so small that I do not know if there is enough space to make the hinge wide enough that the material will flex, but thin enough that the box doesn’t have a weird gap. I think that to make a living hinge you would have to cut out the piece first and then put it back in the laser cutter to cut part way through it for the hinge. I wonder if there is a more precise way to position the laser than the arrow buttons? I am not sure how sturdy these hinges will be, but I think that they will be at least as sturdy as contact paper, and more aesthetically pleasing.
    So far all of my decisions about my box have been based on research on the internet, careful thought and observations of others. Part of the reason for this is that I don’t want to waste materials.  But I know that on Thursday I really need to actually make something and test it out.
  

Boxes 3/8

Our professor asked for each of us to submit ideas for a we project we would like to work on during the week and a half before spring break, but he didn’t give us any restrictions, so we were all stumped. So, on Thursday he told us to start designing boxes. He gave us a few restrictions; our boxes had have 2” sides, and have two fixed sides and two moveable sides. Our boxes will be judged on their performance, manufacturing and aesthetic appeal. Also, it very important that we document our process as we make our boxes.
    We talked a lot about ways that we could join the sides of our boxes. We could join them with glue or screws, or a friction hold, like finger joints. We could also use a combination of some of the methods. I was thinking about ways we could join the sides, and I wondered if you can change the angle of the laser in the laser cutter to make mitered edges? I do not think I would use mitered edges, because I don’t think that they would be sturdy enough. But I do think that they would look nice.
    When I was at a summer program we built motors, and we had to build acrylic boxes to put them in. We followed a similar design process to make our motors, but we only had one shot at making everything. We couldn’t really try things, test them and go back and adjust them. My box for my motor was a disaster. It was really wonky and misshapen. We had to use a table saw to cut the sides and we put them together with screws. We drilled holes in the acrylic with the drill press, so of course my holes were terribly misaligned. Also, it took forever for me to drill the holes because I was afraid of melting the material after they had lectured us not to. So, after that experience I am ecstatic that we have the laser cutter to do the cutting for us, and that I can completely avoid using the drill press.
    When he turned us loose to start working, I was unsure of where to begin. I began googling to see how other people had made boxes using laser cutters. It turns out that there are loads of programs online where you can enter the dimensions of you box, the width of your material and the the kerf of your laser and the program will give you a vector drawing for pieces to be cut  out by your laser. There are also tutorials for methods determining the kerf of your laser cutter.
    I also found this awesome laser-cut ukulele. All of the pieces were cut out with a laser cutter, and it looks like it is mostly held together by finger joints and glue. The neck folds in the make the ukulele more portable, but I can’t tell how he accomplished that.

(Image from http://www.designboom.com/weblog/cat/8/view/17771/laser-cut-folding-ukulele-by-brian-chan.html)
    I also saw some boxes with cool designs cut into the sides. I think it would neat if you cut designs into the sides and then put an LED on the inside. But, for now I am just going to worry about building a plain box. I would like to just use fingering joints and maybe glue if needed, but I will have to play with it to get the right fit, and I will probably have to experiment with a least one other approach. I really need to think about how I will do the moveable joints.