4.140/MAS.863

Where Emilee Johnson Tries to Make Almost Anything

Build Something Big

For this week we were tasked to build something big. The idea was to use some OSB wood or pink foamcore (or something we purchased ourselves) to construct a larger object. The machine we were supposed to be using was the Shopbot, which is a CNC machine that I've seen in the Hobby Shop but have never personally used before.

Project 04a
So this week I to design a chair. The software I used to do so is relatively new open source software that was called Sketchchair. I used it because it was free, and because it was supposed to be build to specifically design what I was trying to make. Here's a side profile of it, with a dummy computer model seated in it. This software had some cool features such as sitting a person in it and modeling the physics of the chair when a force is applied. Like 123Dmake, it also slices things to essentially take a 2D sketch into a 3D chair, and the drawing options were a bit similar to Inkscape, which I've used many times in the past.
Project 04b
Random shot of the computer screen running the job. I was just excited that it had gone through at this point. I had some problems that I'll talk about shortly between generating the design and actually getting it turned out onto the material.
Project 04c
Here's the Shopbot doing what it does and cutting my chair. I used the OSB wood. If I went back and did it again, I would design the chair to be doubled up on wood or at least to use a different material in general. This is just what was available on my time frame and budget. Not the most glamorous or sturdy, but it was a proof of concept.
Project 04d
Here are the finished pieces once they were out of the machine, but prior to assembly. It's kind of like a press fit kit only it's a chair.
Project 04e
Here is a decent shot of the chair fully assembled. Everything cut pretty well and it looks as it's supposed to, but it's not stable enough yet for human sitting. I like the profile and thickness of the chair, so I think maybe just a slightly thicker material and better wood size would produce what I need.

Lessons Learned

I definitely learned more this week about trouble shooting than I think I learned any other week...even the laser cutter and website development week. Here's my laundry list of problems and how I solved them: The very first problem that I had was generally struggling to learn how to use Sketchchair. Ultimately it was fine, but the lesson learned was that if I don't feel as though I have the time, it may be good to become particularly proficient on one high end program that can do everything I need to do (Solidworks for example). The problem with using Sketchchair was that I think it's a relatively new bit of software, and so it doesn't have a lot of tutorials or support developed for it yet. You're definitely on your own to learn it. The next problem I had was transferring the job and developing the tool paths. For whatever reason, my design uploaded with some open vectors (random missing small chunks of lines) that were tedious to find and made it so that the function wouldn't trace the tool path. Fortunately for me, I was able to actually edit it on the spot using a vector drawing tool, and trimming tool to cut out excess I no longer needed. With that you can link vectors to make it one single path. My next problem came from entering the wrong x-y dimensions. The job shut down halfway through because I was essentially telling it to move 8 feet horizontally on a bed that is no where near that big. So I had to go back into the tool path screen and flip the dimensions. Then I had to move some pieces around so they'd fit again and retrace all the tool paths. I didn't have to take the wood out of the bed fortunately, because I was able to keep the first part I cut the same. My final issue came from a poor assumption I made. I thought that the machine had saved the xy zero location. Apparently when you reset, this is not the case. So when I just went to run my project, it immediately started cutting off the bed with it's preset zeros. I actually may have done the zeroing location, but then forgotten to actually hit the zero button. Regardless, the mistake cost me a piece of material and I had to abort the job, reset it and run it again. After this though, smooth sailing and I got a decent looking chair out of it. Doesn't support me, but my cat sat in it the other day and apparently it can support her weight at least. In typical cat fashion though, she jumped out when I went to take a picture and I haven't been able to catch her in it since.