For this assignment we had to create a unique plasma cut diamond. From the start, I had my eyes on a very thick 3/8″ piece of aluminum that I wanted to create my diamond out of. I therefore chose a design that would compliment this. Namely, a spiral with thin members that would be too flimsy if made out of a thinner stock. For this assignment I chose to break from the recommended work flow and do my design work in Autodesk Inventor, then export a vector PDF to import into Illustrator to fix the paths. My reasoning for this is that the sketch tools such as geometric constrains and dimensions make Inventor much more powerful for designing parts with specific dimensions and geometries. I would recon that this process would likely have taken me 2 to 3 times as long had I done this entirely in Illustrator, though this would likely not be the case if I had chosen to go with a less geometric design featuring organic curves, a task that Illustrator excels at.
The next step was to plasma cut the part. This task proved to be somewhat difficult on account of the thick stock. Joe even commented while I was setting up that I probably wouldn’t have much luck with such thick plate on our plasma cutter. After a few failed attempts I did manage to dial into a speed of 40 in/min which worked about half the time. With the 4 diamonds I used about 10 diamonds worth of material. Straight off the cutter, the diamonds were pretty rough.
I decided that I would proceed with two different methods of removing the dross. For two of the diamonds I used a belt sander (bottom), and for the other two I used a chisel(top). While the chisel was faster, the belt sander gave much better results.
Hoping that I would not need to file the insides of the diamonds, I took them to the sand blaster. From this I learned two things. the first was that the chisel was not a good tool to use if you don’t have a lot of practice with it, which I don’t, because it leaves a lot of nicks in the metal. the second thing is that the insides looked terrible and would need filing. Seeing a lot of work ahead, I decided to move forward only with the pieces I had belt sanded.
utilizing a flat and triangular metal file, I was able to smooth and square the inside surfaces. This process took several hours and made me wish that this was a water jet project instead. I then sanded the top and bottom paces with the orbital sander to remove vice marks. The pieces came out looking good, in a state I likely could have left them if I wanted to meet the minimum requirements for the project.
Nevertheless, I then sandblasted the parts because I really like the surface finish it produces.
The last step was to laser etch the pieces. My primary concern was with the alignment of the piece in the machine, so to address this I started by cutting out the shape in a piece of wood so that i could repeatably slot my diamond into the same place in the laser cutter. I then did a few test runs to check the alignment on low power, before sandblasting off the light etching, putting the diamond back into the machine, then doing the final etch at full power. Due to the diamonds deviating slightly from flat, It took multiple passes at different focus depths to sufficiently etch all the lettering. The setting that ended up working the best was the fiber laser with 100% power, 20% speed.
This project took me about 1 hour to design, 1 hour to plasma cut, 30 minutes to belt sand, 5 hours to file, 1 hour to sand blast, and 1 hour to laser cut. That brings the total time spent to 9.5 hours, or a labor cost of $190. The computer time costs about 27¢ based on rental rates. The plasma cutter costs about $75 for the hour I used based on one source I found. The belt sander costs about 23¢ for the time I used based on rental rates. The laser cutter costs about $7.5 as the rate of $1/square inch. 3/8″ aluminum costs $98.10 for the approximately 2 square feet I used. altogether this brings the cost of the two diamonds to $371.10
https://www.pololu.com/docs/0J24/2
https://www.onlinemetals.com/merchant.cfm?pid=1249&step=4&showunits=inches&id=76&top_cat=60
