My team and I embarked on an exciting challenge for our midterm project: creating two sets of replicate vascular cervical models for the LUCIA training apparatus. Our goal? To bring these models to life, we will use a combination of 3D printing and silicone molding, two powerful techniques that blend engineering with medical innovation. When comparing the two methods, 3D printing provides more predictable results but takes longer to produce the final product. In contrast, molding and casting depend on the mold’s creation but require less time overall.
Bringing the Models to Life with 3D Printing
The first step in our project was to replicate the models using 3D printing. We downloaded the STL files that contained the vascular cervical models that were available on Canvas. We uploaded the files into the Bambu Slicer, and we printed them using PLA and the 3D printers at OEDK. However, our first attempt didn’t go as planned—some details were lost due to incorrect filament sizing. The initial height of the models was 0.2 mm. With adjustments to filament width and print height (0.09 mm), we successfully produced high-resolution models that closely resembled the real anatomical structures. The prints were printed in 9 hours and 28 minutes. Now that we had the 3D cervical models (1I, 1J, 2I, 2J) we proceeded to make our positive 3D mold.
Mold-Making
We moved on to mold-making. Using Tinker CAD, we designed a mold box around the 3D models. The four separate cervixes were successfully produced. However, the positive mold presented a few issues. First, we designed slanted walls to facilitate demolding, but a gap formed between a slant and a wall. Second, the initial box dimensions (85mm x 85mm x 35mm) were too small, causing the cervixes to be positioned closely together, which made demolding challenging. To address these issues, we printed version 2 of the positive mold with dimensions of 90mm x 90mm x 35mm. However, we accidentally enlarged the cervixes. After correcting this mistake, we printed version 3, but it resulted in artificial lines on the cervixes. To enhance quality and improve success rates, we reduced the printing speed and adjusted the layer height to 0.08mm. Version 4 was successful. Although one slant is shorter than the wall, it does not impact the silicone mold. Achieving the perfect spacing for four cervical models took a few iterations, but after fine-tuning the design, we successfully printed a positive 3D mold with added structural support.
Silicone Casting for Realistic Models
Now that we had a mold that we were happy with, we decided to proceed and make the silicone. To measure the amount of silicone needed, we calculated the volume of our positive mold, and we took the volume of each of the cervixes. Once we had both measurements we deducted the volume of the cervixes from one of the positive molds and we had the volume we needed for the silicone. The silicone consisted of part A and part B, we mixed both parts in equal ratios of 110mL (part A) and 110mL (part B). We poured the silicone into the 3D-positive mold and let it dry for 7.5 hours. After the silicone dried we faced a challenging process of removing the mold from the box. We successfully removed the mold on the first try by using flatheads to let in air which made the process easier.
Fabricating the polyurethane models
The next step was to recreate one more set of vascular cervical models using polyurethane. To calculate the amount of polyurethane, we measured the volume of each of the cervixes with water which came to be 80ml. We took two equal parts of the polyurethane, measured 40ml part A and 40ml part B, and mixed it all together in a cup. We rapidly poor as the Smooth cast 300 solidified quickly, we saw a change in color and solidification in around 10 minutes. With that, we got our polyurethane cervixes. We repeated this process twice as we had trouble with the appearing bubbles, on the second try we used one of the machines at the OEDK that promotes vibrations, and that lead to the removal of the bubbles.
Post-Processing
Now that we successfully had two sets of cervical models, we started post-processing and using acrylic colors to paint the models. First and foremost we sanded down the polyurethane vascular models to match the height of our 3D models made from PLA. From this point we used paint to finish the models, the colors we used were red, pink, yellow, black and white. To finish the details on the top of the models we used both a red pen and a thin brush. Finally, for a shiny look, we coated the models with clear gloss spray paint.
Takeaways and comparison of the two methods:
- Iterative Design: multiple adjustments improved print quality and mold accuracy.
- PLA, silicone, and polyurethane require fine-tuning and proper design for best results.
- Precise measurements are key to minimizing material waste.
- Techniques like air introduction eased mold removal.
Cost Analysis:
3D printing method:
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | PLA filament | $19.99 / kg | Bambu Lab | 0.04 kg | $ 0.80 |
| Paint | $14.99 / set | Amazon.com | 0.5 set | $ 7.495 | |
| Clear Spray Paint | $0.5 / Oz | Homedepot | 0.2 Oz | $ 0.1 | |
| Labor | Prototyping Engineer (Intern) | $17 / hour | ZipRecruiter.com | 1 hr (set up + monitor 3D printing) + 16 hr (post-processing)
= 17 hrs |
$ 17
$ 281 |
| Overhead | Brush | $3.99 / set | Amazon.com | 1 set | $ 3.99 |
| Electricity | $ 0.36/day | 0.167 day | $ 0.06 | ||
| Paper Towel | $0.051 / Sheet | Amazon.com | 10 sheets | $ 0.51 | |
| Quality control | 27.5/ hour | LinkedIn.com | 0.25 h | $ 6.875 | |
| Design | Engineering and Development | $17 / hour | ZipRecruiter.com | 0.5 h | $ 8.5 |
| Misc. | Waste and Scrap | $0.17 / L | Houstontx.gov | 0.05 L | $ 0.0085 |
Sum: $ 326.34
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | PLA filament | $19.99 / kg | Bambu Lab | 0.12 kg | $1.4112 |
| Silicon | $0.48 / Oz | Amazon.com | 220 ml | $3.571 | |
| Polyurethane | $68.92 / Gallon | Amazon.com | 90 ml | $1.654 | |
| Paint | $14.99 / set | Amazon.com | 0.5 set | $7.495 | |
| Waterproof Pen | $2.49 / count | Unibrands.co | 1 count | $2.49 | |
| Clear Spray Paint | $0.5 / Oz | Homedepot | 0.2 Oz | $ 0.1 | |
| Labor | Prototyping Engineer (Intern) | $17 / hour | ZipRecruiter.com | 1 hr (set up + monitor 3D printing) + 0.25 hr (pouring silicon) = $1.25
0.25 hr (demolding) + 0.5 hr (casting) + 2 hr (sanding) + 16 hr (painting) = $14.75 |
$ 21.25
$ 318.75 |
| Overhead | Flathead screwdriver and spatula | $3.25 for one
$4.99 for one |
Amazon.com | 1 count
1 count |
$ 3.25
$4.99 |
| Brush | $3.99/ set | Amazon.com | 1 set | $3.99 | |
| Electricity | $ 0.36/day | 0.33 day | $ 0.12 | ||
| Paper towel | $0.051 / Sheet | Amazon.com | 10 sheets | $0.51 | |
| Plastic cup with mixing sticks | $0.18 / count | Amazon.com | 3 counts | $0.54 | |
| Sandpaper | $0.20 / piece | Amazon.com | 1 piece | $0.20 | |
| Quality control | $27.5/ hour | LinkedIn.com | 0.25 h | $6.875 | |
| Design | Engineering and Development | $17 / hour | ZipRecruiter.com | 0.5 h | $ 8.5 |
| Iterations | $17 / hour | ZipRecruiter.com | 1 h | $ 17 | |
| Misc. | Waste and Scrap | $0.17 / L | Houstontx.gov | 0.05 L | $ 0.0085 |
Sum: $ 402.70
https://docs.google.com/document/d/1juHQtrOy5pJ0NdOLt4RZRbXiDglUhbWbmcgeHmzc7TU/edit?tab=t.0
https://docs.google.com/presentation/d/1i208CREgHS1dKYLHT_sEyiMF0V3kG7By/edit#slide=id.p3
That is all folks, and to finish this blog like any other here is our CLEAN STATION!
