Hey guys, welcome to CNC machining week. I decided to CNC some candy corns, which started out very frustrating but ended up being okay-ish. Let’s get into it:

Starting from the CNC machine training, I was looking at the Noun Project for which noun I wanted to do for the assignment. Originally, I was going to do a corn husk, but those were too detailed. Hannah suggested candy corn instead, which I thought was an even better idea (especially during these fall months). I picked my candy corn, sent it to the CNC software, and went to work. To make the candy corn stripes distinguishable, I decided to make the depths different; from top to bottom, I made the depths 0.1in, 0.2in, and 0.3in, respectively. I added tabs to both sides, and the top and bottom. Last, I made sure that my cuts were in the proper order (pockets before contour), and sent my file to the machine.

 

The file said it had about 40 minutes to go. All was going smoothly until the last 5 minutes, when the contour was happening, that I saw that the CNC bit was shredding the barriers between my candy corn stripes (pictured). I realized that this was my fault, I made the barriers too thin for the bit I was using.

I changed my file to make these barriers thicker; to do this, I just downscaled the three inner parts of the candy corn by 0.75. I once again sent this to the machine, hit go, and watched for 25 minutes until my wood started to move around and consequently, incorrectly cut my piece :(. I attributed this to the tape losing its adhesion to the sacrificial wood, vacuumed out the machine, and tried again. This time, I strapped my wood down with more tape in addition to the tape that was on the bottom, but had the exact same problem in the last 5 minutes of cutting. Pablo scoured Reddit for me and found the suggestion to sand the wood before attaching the adhesive to it to ensure maximum stickiness. I did this, extensively vacuumed out the machine, taped the bottom, strapped the wood down again, and had the exact same problem. At this point, I was really frustrated because I had just gone through 4 pieces of wood in total and spent almost 3 hours just watching the CNC machine do its thing.

Since we’ve all used up a good bit of wood and the CNC machine is all booked up until the assignment is due, I just decided to call it quits and work with two of the results I got. Originally, I was going to just leave them as is, but after a good hour-long sulk in the OEDK computer lab, I got some motivation to do some post-processing. First, I went outside and spray painted the stripes of the candy corn with yellow, orange, and white spray paint using masking tape to section them off. Somehow getting orange spray paint on my face was the tip of the iceberg for this CNC disaster, but led to me thinking “I’m already here, let’s really finish this thing off.” So I went inside and used a handsaw to get the candy corn out of the wooden blocks. Since MOST of the contour was finished, this was a pretty easy process, as the wood was about 5/6 of the way cut. I then sanded the sides and the back of the pieces and called them done, and honestly I’m decently happy with the results (even if you can tell where the wood started to move around)!

If I were to do this again, I would have:

1. Allotted myself more time to do the project.
2. Sanded the sacrificial wood: this was a suggestion I found online, but I didn’t want to screw up the machine in any way. This could have been a way to keep the tape sticking to the wood.
3. Let the spray paint fully dry before hacking away at the wood and sanding. I noticed that a lot of the sanded bits ended up drying with the spray paint.

COST ANALYSIS:

Cost Type	Cost	Price	Source	Quantity	Total
Materials	4.5×3.5 wooden blocks	$2.79/10 pieces	AliExpress	2 pieces	$0.56
	Orange spray paint	$5.98/can	Walmart	~1/25 can	$0.24
	Yellow spray paint	$5.98/can	Walmart	~1/25 can	$0.24
	White spray paint	$5.98/can	Walmart	~1/25 can	$0.24
Labor	CNC Machinist	$24.49/hour	Indeed	1 hour	$24.49
	Prototyping Engineer (You!)	$38/hour	ZipRecruiter	0.5 hour	$19.00
Overhead	Facility Cost (CNC Machine)	$0.28/hour	CircleMWoodworking	1 hour	$0.28
	Quality Control	$41/hour	ZipRecruiter	0.5 hour	$20.5
Design	Engineering and Development	$48/hour	ZipRecruiter	0.25 hour	$12.00
	Iterations	Negligible	Negligible	Negligible	Negligible
Misc.	Waste and Scrap	Included in materials cost for wood	Negligible	Negligible	Negligible

 

TOTAL: $77.55