PROCESS:

For our final project, we (Cal and Andreas) decided to make pawns in the shape of a bust of Shrek. We started by finding a file on Thingiverse. Upon searching the website, we narrowed down our selections to the following files:

We decided to go for the file in the first picture, as we deemed that the second one had a strange shape that would unnecessarily increase the complexity of molding. We were able to come to this conclusion, because we initially printed both shapes on the FDM printers, and were able to make a judgement call from that. Next, we downloaded the file and cut it appropriately on Meshmixer.

We decided to cut the piece in half, separating the front and back ends of the file. We chose to do it this way, as cutting the file down the center of the Shrek face would result in an alignment mark that would be difficult to post-process, considering that we would not want to do damage the details of the face. Also, we wanted to ensure that the ears of the object would mesh as intended, and we believed that cutting them down the middle would result in less overhangs when attempting to mold. The dimensions of the file (using the rectangular base) would be 65 x 80 x 58 mm

We then followed the instructions for preparing the file for 3D Printing, and we decided to print the front face, as we wanted to leave the simpler side of the piece (the back) for when we were CNCing

 

We decided to send the print to the SLA printer because all of the FDM printers at the time were in use. After 7 hours, the front face was ready:

We then made a contraption with hot glue and cardboard that would allow us to pour our silicon mold onto the 3D print, and have it stay in place long enough to cure:

We then got to preparing the file of the back half for CNC machining. Following the instructions of the google doc, we created a g-code file and sent it over to the Carvey. However, when we attempted to CNC mill onto our selected piece of wood, the g-code was consistently running ~1cm above the vertical position that it was supposed to be milling at. Despite verifying with Adulfo, who found no errors in our file prep, we were still unable to successfully CNC mill the back half.

During the final meetup, Dr. Wettergreen advised our team that we could 3D print the other half of the piece as well, because the hold-ups with the Carvey may have taken too long to resolve.

We then printed the back half, both on the SLA and FDM printers, and waited for both to finish:

(SLA print that we decided on)

Comparing the results of the two printers, we decided to also make our second half of the piece with the SLA print. We then followed the same steps of making the silicon mold, and went from there:

When we tried to align our molds, we found that our peg holes were not sufficiently extruded, and therefore we would need to create something that provided the desired level of alignment:

Using the liquid plastic, and various dyes available to us, we created 8 pieces:

When these pieces came out, there was some post-processing that was necessary. For each piece, we had to use an exacto knife to cut off the pour holes. We had pour holes on each side of the face leading to the two ears, to make sure that the liquid plastic would reach the ears when we poured it. We also had a large pour hole on the base of each half, that would allow us to pour into the main body.

After cutting all of the excess plastic off, we sanded the remaining alignment marks. Also, to get rid of the bottom pour hole, we had to utilize the belt sander:

Overall, we are very satisfied with how our pieces came out, and are glad to have learned so many new skills from this project!

COSTS

Labor Cost: $300

15 hours (for each partner) = 30 hours of work. Assuming our work is worth a lab tech’s salary, $10/hr, then that comes out to a total of $300.

Material Cost:

• Silicon: $28.49, smallest amount of silicon that we could find to buy
  • https://tinyurl.com/ssxvq32
• Liquid Plastic: $12.99
  • https://tinyurl.com/tbwlzv8
• Printer Resin: $19.99
  • https://tinyurl.com/umwg4ex
• Dye: $1.88 for a large assortment
  • https://tinyurl.com/ufdn9tv

Machine Cost: $50

• 3D printer (FDM and SLA): $50 (for one month subscription to a local Maker Space)
  • https://apps.txrxlabs.org/join-us/

TOTAL: $413.33

This is a very large amount of money, mostly consisting of labor costs. We were really surprised by this large number nonetheless!