In this assignment we learned to use the waterjet cutter and post process metal. The diamond shapes to cut were downloaded from the Canvas folder of the class.

To personalize them a bit I chose two images from thenounproject.com, one diamond would have the cat face and the other would have a happy face. I was warned about small shapes being difficult for the water jet cutter, so I removed the pupils from the cat face. Also, the dark spaces of the cat face would be cut out by the waterjet cutter, which means it would cut out the nose and eyes completely as they were surrounded by dark space. Therefore, I added a few lines between the nose and the eyes to the edge of the face so they would have something to keep it intact. This resulted in my cat wearing goggles. I did not need to make any adjustments to the happy face. I also made sure to use shape builder in Adobe Illustrator so the waterjet program would know what shapes are being cut out.

Once I have the vector file, I simply follow the instructions of the waterjet cutter and load in the file to the program. One thing to note, the wet lab did not have any metal sheets left that had enough clean space. So, a lab tech helped get a piece of scrap aluminum for me from the machine shop. There was a long piece sticking out from the sheet that was preventing the metal sheet from fitting in the waterjet cutter, so I had to cut it off with a hacksaw. We then measured the thickness of the metal, input it into the program, and set the waterjet bit and water level accordingly.

  

It honestly took a few tries with the auto-pathing tool of the waterjet cutter to get a path that cut the inside shapes before the outer diamonds and didn’t cut into the parts of the diamond that we were keeping. However, we eventually got a cutting path that we liked. Another issue we had was the drain of the waterjet cutter kept getting clogged by broken pieces of the plastic platform in the cutting bed. So we had to keep cleaning off the drain head to make sure it was draining properly and the correct water level was maintained.

   

Once the diamonds and their shapes were cut out, we cleaned them off and let them dry. Then we used a file to smooth all the cut edges. I found that when filing the outer edges, I could be very efficient and smooth by scraping the full length of the diamond edge along the file and controlling the angle at which I’m filing (see picture in the center). Once the edges felt relatively smooth (or at least didn’t scratch me), I moved on to the wire brush to smooth it even further. I especially used the wire brush to try to remove the burs on the smaller corners and curves of the shapes, where the file could not fit. Once I was satisfied that the metal was even smoother and definitely didn’t scratch me (image on the right), I moved on to sandblasting the pieces. This was to prepare the pieces for powder coating and to hopefully further remove any imperfections in the metal. After sandblasting, the pieces did not feel any smoother (it actually made it uniformly rougher) but it did remove whatever outer coating was originally on the metal.

   

We liked the smooth, glossy finish of powder coating and the kind of pastel-looking colors, and we wanted to train with using a powder coater (which we’ve never used before). So we decided to do powder coating instead of spray painting. We got the equipment from the wet lab and set it up outside the OEDK. Using the powder coater turned out to be much more difficult than expected. The powder would not stick to the metal evenly and would even refuse to stick at some areas. We tried doing our best to clean the metal stand, the grounding clip, the paper clips we were hanging the pieces from, in an attempt to make sure there was good conductivity. We also tried shifting around the contact point of our pieces to the paper clips to try to get the uncovered areas closer to the contact point. It would have also been nice if we had a compressor that auto-maintained pressure at a set level, instead of having to manually turn it off and on every few seconds to maintain the pressure between 5-10 psi.

Once we felt that we had a good coating of powder on our pieces, we moved it to the oven in the wet lab. We were careful not to touch the coated metal to anything, though we may have not been completely successful in doing so. There ended up being a couple of small spots that looks like the powder got knocked off at some point. The oven was set to 400 degrees Fahrenheit for 20 minutes.

After the oven cools down, we have our finished pieces. Unfortunately, the powder coating was not as even as I’d hoped but it did have that nice smooth and glossy finish.

 

Cost Type	Cost	Price	Source	Quantity	Total
Materials	Aluminum sheet metal	$0.12 /in2	Lowes.com	12 in2	$1.44
	Powder Coating Powder (Eastwood Hotcoat Powder Coat Candy Orange)	$15.99 /8oz	Eastwood.com	0.5 oz	$1.00
Labor	Waterjet Operator	$15 /hr	Ziprecruiter.com	1 hr	$15.00
	Powder Coater	$18 /hr	Ziprecruiter.com	0.5 hr	$9.00
	Prototyping Engineer (You!)	$39 /hr	Salary.com	1 hr	$39.00
Overhead	Facility Cost (Machine Time)
	Waterjet Cutter	$30 /hr	Techniwaterjet.com	1 hr	$30.00
	Powder Coater	$8 /ft2	Fixr.com	0.08 ft2	$0.67
	Quality Control	$20.72 /hr	Indeed.com	0.5 hr	$10.36
Design	Engineering and Development		Covered in Prototyping Engineer		$0
	Iterations		No additional iterations made	1	$0
Misc.	Waste and Scrap	$0.12 /in2 (aluminum) $2 /oz (powder)		15 in2 0.5 oz	$1.80 $1.00

Total Cost: $109.27