For the midterm, my group and I were tasked with making LUCIA models for Rice360. We had the option to choose between various different diseased cervix models and decided on recreating the cyst models.

The first thing we did was 3D print our 3D-printed positive mold as well as our four individual 3D-printed cervix models. To do this, we downloaded the SLDPRT files for each of the aforementioned pieces. We then assembled the chamfered box with the four cervixes and set that to print and then in a separate printer started printing our four individual, stand-alone cervixes. For our first print we had set the layer height for the print at 0.1mm. When the prints came out, we were not satisfied with the quality of the detail at the top of the cervixes and decided to reprint everything with a smaller layer height of 0.08 mm. Even this small change did result in a visible improvement in the smoothness of the finish at the top of the cervixes. The four stand-alone cervixes that were printed together took an hour and 50 minutes to finish, while the positive mold took a little over 4 hours to complete.

The next part was for us to use the positive 3D printed mold and create a negative silicone mold. To do so we started by understanding that the ratio between the Part A and Part B of the silicone molding set was to be 1:1 by weight. In order to understand how much we would need to fill the mold, we filed it with water and measured the volume. Next, we divided this volume by two for Part A and Part B. In doing these calculations, we came to measuring out about 124 mL of Part A and then weighed this volume using a scale. We then weighed out as precisely as we could 124 mL of Part B, and then mixed the two solutions. We then sprayed some mold release along the inside surface of the mold to allow for easier removal of the silicone after it had been cured. Lastly we poured into our positive mold from a corner until it was filled and tried our best to get rid of bubbles by hitting the sides and knocking the mold against the table.

After over 24 hours, we returned to the OEDK and as a class made our polyurethane casts. To do so we started by struggling to remove the silicone mold. We eventually needed to use two screwdrivers to pry out the silicone. Prior to using the Smooth-Cast 300, we had to again measure the volume of the individual cervixes to determine how much we would need without being wasteful. We once again filled each of the negative cervixes with water and measured the volume in this manner. This came out to around 60 mL, but were instructed to create about 80 mL of polyurethane. We then did so by pouring out equal parts by volume of Parts A and B of the Smooth-Cast 300. This specific product had a pot-life of 3 minutes so after mixing the two solutions for about a minute and 20 seconds, we started filling in our molds. This process was rather satisfying as we could see pretty quickly the polyurethane casts set. The mixture also emitted a lot of heat and was a little alarming at how hot it got.

After our first round, we were not satisfied with how the lettering turned out and decided to run the process again since it only took about 20 minutes to do so. However, even when we used different techniques like doing only one cervix model at a time and trying to hold open and fill the lettering first, we had marginal improvements and after remaking the 1C and 1D models, we decided to stop as it was not worth finishing the 2C and 2D models.

Now that we were done with creating our two sets of cervixes, the last step was to post process and paint them. For post-processing, we simply took some sandpaper and smoothed out the tops and sides of all the models. We then went outside and using a combination of red and pink spray paint that was sprayed into a cup, used a paintbrush to apply the paint to the models. We did have some mishaps like different colors every time we had to respray more of the red and pink paint into the cup but after a couple times of going over them, we were pleased with the outcomes. Finally, we painted to the tops, highlighting the cysts, matching the reference models, and went over all the models with a clear gloss finish.

If we were to do this process again, I think the main thing I would change would be the way we painted the models. After observing the way some of my classmates approached the painting process, I would experiment with airbrushing to paint the LUCIA models. Xavier and Carter did so and the consistency of the color throughout the model as well the finish it leaves was amazing and something I would love to do.

Below is a link to the cost analysis of 3D printing vs. molding and casting our models:

Midterm BIOE 555 Cost Analysis

Lastly, here is a picture of our clean workspace!