We created hooks from our fingers using modeling and casting materials for this homework. This project required attention, time management, and precision.

Step I: Molding

To create a mold for the fingers, we prepared a mixture of alginate (33 g) and water (115 g) in a little silicone cup. I moved the mixture around for ~2 minutes until there were no lumps in the cup.

As soon as the mixture was ready, I submerged my index and middle finger into it and waited until the mold hardened. Once the mixture was solid enough, I carefully wiggled my fingers to remove them from the mold, ensuring the cast was intact.

Step II: Pouring the Plaster

After the mold was finished, I used the plaster provided and mixed it with water (two parts plaster to one part water); I used the markings on the silicone cups as a reference for this process.

To ensure a smooth consistency, I poured the plaster powder into the water while I was mixing it. This helped me ensure that there were no chunks of plaster in the mixture.

Later, I carefully poured the plaster mixture into the alginate mold, paying close attention to not overpouring the mix and accounting for the volume of the screws. After I was done pouring, I put the screws on top.

Step III: Extracting

After letting the plaster dry overnight, I carefully removed the fingers, holding them by the screws and wiggling them carefully until they were completely removed from the alginate mold.

Step IV: Repeating the Steps

Once the mold was free of the fingers, I repeated steps II and III. Unfortunately, I waited too long to take the second set of fingers out, and they broke as I was trying to do so. The alginate developed mold (mold molded).

Step V: Post-Processing

I decided not to sand the fingers because I liked the amount of detail, so I proceeded just to spray-paint a single coat of red paint; then I let them dry for 20 minutes (as instructed on the can), then I attached a tag with my name, cleaned the last surface I worked on, then placed the dried fingers on the ENGI 210/BIOE 55 table for grading.

Cost Analysis

Cost Type	Cost	Price	Source	Quantity	Total
Materials	Alginate	$18.99 /1.5 lb.	Amazon.com	0.073 lb	$0.92
	Plaster of Paris	$22.55/8 lb.	Walmart.com	0.2 lb	$0.56
	Screws	$9.47/153ct.	HomeDepot.com	2 screws	$0.13
	Red Spray Paint	$5.98/can	HomeDepot.com	0.1 can	$0.60
	Matte Clear Coat	$5.98/can	HomeDepot.com	0.1 can	$0.60
Labor	Injection Molding Operator	$18.00/hr	Ziprecruiter.com	1 hr	$18.00
	Prototyping Engineer (You!)	$13.00/hr	Self	1 hr	$13.00
Overhead	Facility Cost (Machine Time)	–	–	–	–
	Quality Control	$34.07/hr	Zippia.com	5 min	$2.83
Design	Engineering and Development	$37.08/hr	Zippia.com	5 min	$ 3.09

Total Cost: $40.03

Once the alginate mold has been made, costs associated with molding and casting will decrease. Alginate for subsequent iterations won’t need full preparation, reducing material waste. Labor costs for molding and pouring plaster will also decrease because these steps require less time after mastering the process. Facility overhead, while not itemized here, would similarly decrease with optimized workflows. However, costs for quality control and post-processing (e.g., spray painting) will remain consistent per unit. Over time, the average cost per finger hook should drop as more units are produced using the same mold.