For our final project for BIOE 555, we created a more efficient LUCIA model for usage in low-resource environments. A key objective here was to use easily replicable manufacturing techniques for a device that could be set up and taken apart quickly, to facilitate training for cervical examinations.
Based on our measurements of the existing model we were shown in class, we identified measurements for the pieces of wood we needed to cut via band saw or laser cutter.
We used Adobe Illustrator to produce .ai files for the pelvic frame, which we then sent to the laser cutter. Each .ai file was designed to the desired dimensional specifications based on the LUCIA model we measured.
Example Illustrator file for LUCIA model.
The total cutting time for all the shapes was about 15 minutes, given that most of the designs included just one shape to cut out, with some having two or three. We used a speed of 60 and a power of 80%.
Cutting the wood pieces for the pelvic frame using the laser cutter.
We then used wood glue to adhere the components that required multiple wood pieces. We allowed roughly 30 minutes for them to set.
Clamping the wood pieces together to allow for wood glue to set.
For some of the pieces that initially did not cut properly or were a bit too rough, we ran the laser cutter again and used 400 and 800 grit sandpaper to sand them down.
Sanding the rough edges of the laser-cut wood. We used 400 and 800 grit sandpaper.
For the base of the pelvic frame, we used a band saw to cut a thick piece of wood from the wood shop, then used the orbital sander to smoothen the wood edges. We glued the edges together at the desired angle of 20 degrees.
Cutting thick wood for the base of the model with a band saw.
Using an orbital sander to smoothen the base of the model.
One of the components of the original model that we thought we could improve was the securing of the cervical models to the pelvic frame itself. The existing model used an elastic fastener, and we believed we could 3D print a fastener that may eliminate the need for elastic or manual tightening. We found a model on Thingiverse that was called a Bowden clip – this resembled the design we needed.
Thingiverse Bowden clip design. We modified this to the desired dimensions to match the cervical model.
We then scaled this up slightly (it was designed for small pipes) to match the 1.2 inch diameter required for the cervical models, and then printed it with TPU filament on the Prusa FDM printer.
The initial clip was a bit flexible, so we re-printed it with slightly modified dimensions and a thicker clasp. We also used PLA to 3D print L-brackets for the assembly of the wood pieces and improve stability. It was a bit difficult finding a balance between the PLA, which was quite rigid, and the TPU, which was a big large and flexible, but we ended up going with the PLA brackets.
The L-brackets for the model assembly, as shown in Bambu slicer.
The clip fit the cervical model well.
Final PLA brackets and clip.
Finally, we used screws and wing nuts to secure all the pieces using a drill and Phillips head screwdriver. Specifically, the screws were 18-8 Stainless Steel, Phillips Head, 6-32 Thread, 3/4″ Length, and the wing nuts were 1/4 inch stainless steel wing nuts. We super-glued the TPU clip to the wood piece to secure it firmly. The final model and cost analysis are depicted below.
Final assembled model.
Final image of clean workspace.
Cost Analysis
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials
|
Wood (0.4 cm x 50 cm x 44 cm) | $15.99 | Rockler | 1 | $15.99 |
| Green TPU (1 kg) | $0.80 / ounce | Amazon | 0.85 | $0.68 | |
| PLA filament | $19.99 / kg | Bambu Lab | 0.01 kg | $0.21 | |
| Post-processing tool (Sandpaper) | $12.68/20 pcs of 9×11 320 grit paper | Amazon | ⅛ sheet | $0.08 | |
| Super glue | $7.48 / 15 g | Home Depot | < 0.5 g | $0.25 | |
| Wood glue | $4.37 / 8 oz bottle | Amazon | < 0.05 oz | $0.22 | |
| Wing nut | $1.52 / nut | Home Depot | 16 | $24.32 | |
| 3/4″ passivated screw | $0.13 / screw | Bob’s CB | 16 | $2.08 | |
| Phillips head screwdriver | 7.97 | Home Depot | 1 | $7.97 | |
| Labor | Laser cutter operator | 19 / hr | ZipRecruiter | 1 hr | $19.00 |
| Prototyping engineer | 25.91/hr | Indeed | 7 hr | $181.37 | |
| Overhead | Laser cutter usage cost | 0.14/hr | Accurl | 1 hr | $0.14 |
| 3D printer usage cost | 0.21/hr | Prusa | 2 hr | $0.42 | |
| Band saw operating cost/blade usage | ~$90 / day | Peterson Sawmills | 1 day | $90 | |
| Hand drill operating cost | $0.072 / hr | Slashplan | 10 minutes | $0.01 | |
| Total | $342.74 |
