For this project, I worked alone to produce 5 3D-printed Harpetida scotoharpes trilobites with FDM and SLA processes. This counted as an impossible object due to their articulation joints. This was the first time I 3D-printed alone, and as such it served as a interesting experience for me to work with preparing a part, learn about the processes, and apply this knowledge with the program and machinery.
PHASE 1: Choosing a part
To begin the project, I looked around Thingiverse to see if I could find an impossible object to print. After some searching, I managed to find a trilobite file with an articulated body. As someone with who had a paleontology phase, I thought a trilobite would be a pretty neat object to 3D-print, and thankfully it was approved as an impossible object due to its segmented body.
PHASE 2: FDM with original Prusa i3 mk3
To start the physical project, I looked to first FDM the trilobites in PLA. To do so, I had to slice the part in PrusaSlicer and print on one of the Prusa machines in the OEDK. To begin, I sized the model to around 1.5 inches in the y-direction as my measurements of the capsule for the gum-ball machine was estimated at ~2 inches in height. I placed around 4 trilobites on the bed to make sure I had ample prints in case of any issues with their structure. A 20% infill and supports on the bed only were used. With that, I sliced the part and the send it off to one of the Prusa machines.
Preparing the models to print in PrusaSlicer. Estimated run time of 1 hour 36-38 minutes
After the print, I noticed that it was pretty difficult to take the parts of the bed with the flexing of the bed technique, so I had to use the scraper to remove them. It was at this moment where the parts broke. The segmented body was too small to be structurally sound, nor could it articulate.
Broken trilobite prints. Got attacked by a eurypterid maybe…
To fix the problem, I made the models bigger, now with a y-dimension size of 2-inches. This was calculated by the fact that the trilobite would not be perfectly straight at 2-inches, so it would still fit within the capsule. A 20% infill and supports on the bed only were used again. As such, the trilobites were printed again.
New, larger dimensions
The resizing in PrusaSlicer. Estimated run time of 2 hours 42-44 minutes
After the print, Cris helped remove the parts gracefully with their finger nail, which worked much better than a larger scraper, heh. With that, it was noticed that a larger model was much more structurally capable, and none of the prints broke upon removal. Furthermore, the parts articulated super well once all supports were removed! This was a successful batch of prints.
Re-printing the models at a larger size
Removing the small support pieces
Trilobites in FDM! Such fellows
PHASE 3: SLA with Formlabs form 3+
For the next part of the project, the model would be SLA printed in resin. To prepare the models, they had to be sliced in the PreForm software from FormLabs. Here, the models were sized to the same dimensions used in PrusaSlicer, now in millimeters, and then supports were added to the models as recommended.
Dimensions used in PreForm for the SLA print in mm
Model placement in PreForm with the supports. Estimated print time of 3 hours and 15 minutes
As following the SLA workflow, the models were printed, washed for 15 minutes, and then cured for 60 minutes at 60 degrees Celsius. Then, wire cutters and an Exacto knife was used to trim away at the supports on the parts. This time, the resin material did not allow for proper articulation of the part, and one trilobite lost their tail again when being removed from their supports. However, most were intact and printed well.
Cured parts
Preparing to trim supports away
Finished resin prints from SLA. One trilobite attacked again…
PHASE 4: Project Completion
To complete the project, labels were printed to be placed in each capsule. It was confirmed that the trilobites fit well into their capsules. With that, the project was complete! Hope people enjoy these prehistoric critters if they get one out of the machine.
Submitted were 3 FDM printed trilobites out of PLA, and 2 SLA printed trilobites out of resin.
Printed labels for the capsules
Complete trilobite capsules. Safe from any eurypterid!
PHASE 5: REFLECTION AND COST ESTIMATE
Entering this project, I was expecting a much more difficult experience due to the extent of the training needed for the 3D-printing machinery at the OEDK. However, while all important information to consider when 3D-printing, not all of it was information applied to the project. This made the project itself relatively light apart from waiting a long time for prints, and having to iterated the sizing of the part if anything went wrong. However, I am happy to say that things went well for my project, and it was a great first time experience working with the process on my own.
If I were to repeat this project, I would be more careful with the sizing of parts. It would help to be more sure of the size as to not print too small for a part that may need to be larger to function well. It would save time and material.
The following is an estimated cost of the trilobites:
- Material: 1kg PLA Pristine White spool (by Prusa): $29.99
- Material: SLA Resin (by FormLabs): $149.00/L x 0.03132 L = $4.67
- Overhead cost of Prusa machinery (Prusa Blog): $0.21/hr x 5 hours = $1.05
- Overhead cost of FormLabs machinery (FormLabs Community Forum): $10/hr x 3 hours = $30
- Labor: $21/hr (national average for a 3D-Printing Technician by GLASSDOOR) x 8 hours = $168
The estimated cost for all the trilobite prints is $233.71. To reduce the cost of the prints, it would again be determined on better preparing and sizing the parts for prints. This would have reduced overall labor and overhead costs for the Prusa FDM prints.
