This week, Morgan and I created 3D-printed brains. We created two copies of a human brain model we found on Thingiverse, one made out of PLA with FDM printing and the other out of clear resin using SLA printing.

First, we loaded the STL file into the Preform slicer. We used the auto-orient and auto-generate supports features to prepare our file for printing (Figure 1).

After ~20 hours per brain hemisphere, the printing was complete (Figure 2). We then removed the print from the build platform (Figure 3) and put each hemisphere in the IPA wash for 20 minutes to remove excess resin from the print (Figure 4). Lastly, we cured each hemisphere in the post-curing box for ~2 hours at 60 degrees Celcius (Figure 5). While this is longer than recommended, there were still some regions of the print that were shiny and tacky until the 2-hour mark of UV light exposure. Upon second thought, an additional IPA bath may have helped clear the excess resin from the nooks and crannies faster, but there was no harm done in overcuring our print.

After this process was completed for both hemispheres, we then began the PLA replica. At first, we aimed to print the brains on the Bambu and Formlabs printers at the same time to expedite the project timeline. However, when we loaded the brain into the Preform slicer it stated that the STL file was too big to print on the tray and had to be sized down. We couldn’t figure out how to get the dimensions of the resized print from the slicer, so we decided to let the brain halves print and then measure the dimensions using calipers to decide the factor to scale down the print on the Bambu slicer.

With this in mind, once we loaded the STL file into the Bambu slicer we scaled it down such that the Y-dimension was 6 inches (the length of the SLA print) (Figure 6). The other dimensions were scaled uniformly since “uniform scale” was toggled on. After auto-orienting and auto-support generation, the slicer deemed the print time to be ~10 hours per hemisphere (about half the time of the SLA print time) (Figure 7).

After the successful completion of the FDM print, we removed the supports from both prints and began further post-processing (Figure 8).

The first step we took was to sand the two hemispheres. The PLA brain had visible layer lines that needed to be smoothed, the resin print had small remnants of supports that needed to be filed down, and both types of prints needed to be sanded on the inside face to allow each half to be more flush with the other. We used a Dremel sanding bit, a sanding block, and sandpaper to sand our prints (Figure 9).

We were finally able to assemble our prints by supergluing the hemispheres to each other. We next sprayed the assembled brain with paint primer to prepare our prints for spray painting (Figure 10).

After priming, we spray-painted our brain models pink. We wanted to paint on veins on the brain to make it look more realistic, but we encountered some difficulties in the process. The only paintbrushes we could find were foam paintbrushes, so it was incredibly difficult to get the precision necessary to paint the thin grooves. Even cutting the foam tips to a point did not solve the issue, as the sponge tip would get paint in unintended areas when pressure was applied. Neither of us was satisfied with how the painting came out (Figure 11), so we decided to pivot our approach. We decided to spray paint one more thin layer of pink on top of the red acrylic paint as a quasi-underpainting approach. With this approach, the majority of the deep grooves showed the red paint but the rest of the brain was pink as intended (Figure 12). With that, our project was finally done!

3D Print Cost Analysis