The long journey know as the ENGI 210 midterm started with a trip through good ole’ 507 Mechanic Movements. After flipping through the various movements, I ended up deciding to go with Mechanical Movement #144. It seemed appropriate for me to construct my device around a scissor design because my ENGI 120 project was centered around a scissor lift. 

Once I decided on my movement, I moved to Adobe Illustrator. I traced the above image to make my own versions of the segments. After going through that process, I realized that my Illustrator reproduction just wasn’t accurate enough to work smoothly in a device. As a result, I switched to developing my pieces in SolidWorks. SolidWorks allowed my to make sure every one of my pieces had uniform geometry and properly dimensioned lengths. Once I developed my pieces in SolidWorks, I would add them to an assembly that I used to test the interactions between the various pieces. If my new piece interfaced correctly, I exported a drawing of the piece from SolidWorks to Adobe Illustrator. For some reason, the drawings were often scaled versions of the properly dimensioned piece, so I had to scale them back to normal in Illustrator. Once I had the proper versions of my main arm pieces properly imported into Illustrator. I cut a small scissor mechanism to make sure my idea worked using some very crude pins.

Thankfully, my first idea worked!!! After seeing that my idea worked, I set to creating a system of pins for my scissor. For my pins, I used 1/4” dowels (by my personal measurement of a number of the dowels, they were actually had a 0.245” diameter. To make the pins, I cut segments of dowel that had a length of four times the laser cutting wood’s depth (20.4 mm in length).

My first idea for securing the pins was to use laser cut pin caps. These caps would be disks with an inner hole of an ever so slightly smaller diameter than the diameter of the pins. I cut out of couple of them and tested them on some sample pins. Thankfully, this idea worked! (I got pretty lucky with initial ideas working. This saved my a lot of time.) I used this type of pin cap for the rest of the project. At this point, I thought I was not super far from the finish even with post-processing. Apparently, I am atrocious at estimating post-processing time.

Once I got the pin caps worked out, I made drawings for both of my spacial end arms of the scissor. One of the special arm designs was a short arm with two circles rather than three. The other was nearly as long as the normal arm but with the end circle removed. Once these drawing were complete, I laser cut my full scissor component. In addition to laser cutting the scissor component, I also made the pins and pin caps for the scissor component. After cutting the pieces, I sanded the living hell out of all the arms. By the time I was done sanding (2 or so hours later), my pieces were all incredibly smooth, looked great, and worked great. I then put together my scissor component using temporary pins in the middle holes.

After sanding my pieces came finishing them. I really liked the look of the natural variations in the coloration of the wood, so I decided to use a type of finish that would preserve that look. This is when I discovered my truest love, butcher block oil.

I finished my scissor pieces with the butcher block oil and grew more and more in love with it as I went. By the time I was finished, my pieces looked awesome if I do say so myself. At this point, I decided that I was going to finish the rest of the wood in my device with butcher block oil.

Next, I laser cut my handle. I sanded and oiled the handle in the same way that I had processed my other pieces. Once I attached the handle, the scissor component looked like this:

After the scissor mechanism was completed, I had to move to my plasma cut component, the pincers (or fangs, whatever you feel). This set of plasma cuts went much more smoothly than my cuts during the plasma cutting lab. The one oddity was that, for some reason, the Torchmate software decided that it needed to have the plasma cutter cut the path twice for each piece. I cut three pieces just in case I messed up the post processing for one of my pieces later on.

Once the pieces were cut, I angle ground and filed them. When angle grinding, I ground the pieces until all the dross was gone and the piece was nice and shiny. I tried to grind in such away that the patterns from grinding were consistently in one direction, giving the piece a better look. I would like to point out that angle grinding to remove dross is incredibly satisfying. Stuff like that is what gets me out of bed in the morning. When filing, I did actually file down what is theoretically my super sharp tip. I cut my finger on it accidentally, making me realize that I probably should actually file it down a bit.

After angle grinding and filing, I decided to put some kind of protective layer on the pieces so that they don’t rust over time. Just like I like the look of post-sanding wood, I also really like the shiny look of post-angle grinding metal. As such, I wanted to apply a clear finish to the pieces. I ended up deciding on an anti-rust, clear, glossy spray. My first attempt failed (it didn’t dry as fast as I thought it would, and I messed up the coating), so I had to angle grind that coating off and try again. My second attempt worked like a charm, giving the metal an extra bit of glossiness.

Once I finished all the post-processing of my metal pieces was finished, I attached them to the proper places on my scissor mechanism with some good ole’ JB Weld. This was actually pretty tricky considering the fact the my scissor was all assembled. The fact that it was assembled made it really awkward to find a good spot to place my clamps. Tori came in really clutch here both as an extra pair of hands and as a source of clamping ideas.

The next step after setting up my JB Weld to dry was laser cutting my large mounting box and two pieces to fill the gap between the handle pieces. During this cutting process, I made two pretty embarrassing mistakes. The first was that I was stupid and didn’t do a final check of my cut before starting the job. I accidentally pasted three copies of my handle-filler rather than two and forgot about the third copy. This led to a large hole in my box wall, causing me to have to re-cut that wall. Unfortunately, my walls were giant so re-cutting wasted a lot of wood.

The second mistake I made was that during my next cut, I accidentally hit the power switch on the Epilog because the manufacturers of the Epilog thought it was a good idea to have the power switch where it can easily be hit by a knee. This stopped my cut half-way through, causing another large waste of wood because nothing had been fully cut but a lot of area had been partially cut or engraved. Eventually though, I got all my pieces cut.

The first thing I did after laser cutting was sand and oil my handle-fillers. Once that was done, I wood-glued the handle-fillers in between the handle pieces. This time clamping was easier due to my prior experience with the JB Weld. Next, I sanded the hell out of the sides of the box until they were really nice. Then, I applied butcher block oil (my favorite) to both faces of the all the sides of the box. Once again, the wood came out looking really good if I do say so myself. Once the oil settled for a short bit, I assembled the box.

Now that the box was assembled, I could finally make my long dowel pins. Four of these long pins slid along slots in the side of the box. The other long pin was anchored into one spot on the box. These pins were oiled with butcher block oil.

Once the long pins were finished, I dared to take the clamps off my JB Weld and wood glue spots (The JB Weld had been in place for around six and a half hours and the wood glue had been in place for around 2 hours). Blessedly, the JB Weld and wood glue held very well. All that was left at this point was to integrate the scissor component with the base. After a little bit of less than success, I (with some clutch assists from Josh and the other Nick) got the contraption all put together. The very final step (other than playing with it) was to apply some tallow to the slots to improve the movement of the long pins. Then I was finished!!!!!!!!!!!!!!!!!!!!!!

– Nicholas Lester