For this midterm project, my team (Sradha, Abby, Ishika, and me) created two sets of LUCIA cervical models for the cyst: one set was 3D printed, and the other was polyurethane cast. Along with this we made a 3D printed mold and a silicon cast mold for the models.
We started of doing the easy task first – given we have the .stl files for the cycst models, we 3D printed them first (PLA).
After this we did two processes simultaneously: creating the 3D printing file for the mold using tinkercad and solidworks, and painting the 3D printed cysts. We had issues inserting the slope inside the mold using tinkercad, and so we moved to solidworks. After several hours at the computer and some heavy help from the internet we finally managed to make the file. The first time we 3D printed it, it came out incorrect. There we supports in the print, even though we did not apply any, and this pressed into the PLA in a manner that distorted the prints. We printed them again, and this time it was fine.
When the 3D printing was happening, we were painting our cyst 3D prints. We understood this is not an art project, but it sure felt like one as we were trying to match the aesthetics of our model to the actual LUCIA models as much as possible. In hindsight, perhaps we should have used some heavy duty primer before we painted to make it even smoother. We each took responsibility for one of the cysts, mine was 2D. After this we put a gloss coat over them.
Now we were working on the silicone mold. First we calculated the volume of the cervixes (assuming they were perfect cylinders), this value came out to be 13.5cm3 per cervix. We subtracted this amount from the volume of the container, which was 350 cm3, which came out to be around 300 cm3 in total. We took 150 ml of part and part B of silicon each, mixed them together and then poured the mold. Before we put the silicon in, we also sanded the 3D mold to make sure we made it as smooth as possible without removing any critical details.
Once the mold set, we gently unmolded it using an exacto knife.
We then calculated the volume of the cervixes again, this we poured water in the mold and poured it out into a marked glass. The volume came out be around 60 cm3, but as a class we decided to stick to 80 cm3. we mixed 40 ml of both part a and part b of the polyurethane. We set a time for 90 seconds to make sure we were getting the mixing and the pouring done within that time. The mold set in under 10 minutes and we were ready to pop it out. The polyurethane models were smoother at first look, but developed more paint lines when hand painted.
Now we painted the polyurethane models, trying our best to match both the LUCIA model, and the painting we did for the 3D models. Matching the colors would have been easier if we had painted both the 3D printed and the polyurethane cervixes at the same time, once again I was responsible for “2D” cyst. Once done we gave these models a gloss coat too.
This exercise taught me how hard it is to aesthetically match two products, even when following the exact same process. A tip I learned is to mix enough of the paint the first time, so I don’t have to struggle to match it the second time!
Cost Analysis:
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | PLA Filament | $25.99/ 1 kg | amazon.com | 0.2 kg | $5.20 |
| Silicon
|
$31.42/500 mL | amazon.com | 400 mL | $25.14 | |
| Polyurethane Part A + Part B | $25.09 /1 pint | amazon.com | 80 ml | $4.27 | |
| Acrylic Paint (24 colors) + Paint Brushes | $25.99 – ($0.54/fl oz) | amazon.com | 2 fl oz | $1.08 | |
| Gloss Spray Paint | $5.98 per 12 oz can | Home Depot | 0.25 oz | $0.12 | |
| Plastic Cups | $14.99 for 25 | amazon.com | 4 | $2.40 | |
| Popsickle sticks | $4.98 for 100 | amazon.com | 5 | $0.25 | |
| Ruler | $1.96 for 1 | amazon.com | 1 | $1.96 | |
| Labor | Prototyping engineer | $36/hour | ziprecruiter.com | 2 hours | $72 |
| 3D Printing Operator | $23/hour | ziprecruiter.com | 3 hours | $57 | |
| Total | $169.42 |
Feasibility for Mass Production
| Number of products | 3D Printing | Mold Casting ( Silicon + Polyurethane) |
| 50 | Time: Much Faster
Quality: Higher Cost: $0.70 for 4 cervixes. $0.175 for 1 cervix print $0.175*50 = $8.75 total to print 50 cervixes |
Time: Slower
Quality: Lower Cost: $7.90 per 1 cervix $7.90 * 50 = $394.875 total to print 50 cervixes |
| 100 | Time: Much Faster
Quality: Higher Cost: $0.70 for 4 cervixes. $0.70*25=$17.50 total for 100 cervixes |
Time: Slower
Quality: Lower Cost: $4.27*25=$106.75 total for 100 cervixes |
| 1000 | Time: Much Faster
Quality: Higher Cost: $0.70 for 4 cervixes. $0.175 for 1 cervix print = $175 total for 1000 cervixes |
Time: Slower
Quality: Lower Cost: $7.90 x 1000 = $7900 total for 1000 cervixes |
Assumptions made:
- 3D printer is already purchased/access to a 3D printer is available
- There is no time constraint or deadline for creating the number of products
- Cost of creating 4 cervixes with 3D printing is $0.70
- Cost of creating 4 cervixes with Polyurethane casting is $31.59 (first time only and
- includes the 3D printed box, silicone, and polyurethane)
- Cost of creating 4 cervixes with Polyurethane is $4.27 every time following the first
- Assuming that we only make the 3D printed box and silicone mold once for all products made (50-1000)
Clean workspace:
