THE PROCESS
The first step of this project was to find an impossible object that could only be manufactured using 3d printing techniques. I landed on the excavator since I liked how the arm was articulating and the body had spinning wheels.
Once I picked out my object, I worked in the 3DPrinterOS software to scale and slice my print. From there I was able to easily queue my print on one of the printers, and then from the main operating computer, start my print.
There wasn’t much to do for post-processing when using the Prusa FDM printers, since all I had to do was remove the print from the bed, and then carefully remove the supports and be done.
Once I had completed 3 prints using the FDM printing technique, I moved on to using the Prusa printers and the SLA printing technique. As detailed in the reflection, I had problems with the first couple of prints, but I eventually decided to scale down my print and printed 2 of those.
(two FDM prints)
The post-processing for SLA prints wasn’t too bad but definitely was more complicated than that for FDM printing. After the print was completed, it needed to be washed off for 15 minutes to dispel any remaining resin not attached to the print. After that, the print needed to be cured for an additional 15 minutes to fully harden the resin. Finally, the supports could be removed, and the prints placed in the containers.
(image a classmate took of SLA printer, washer, and resin refill bottle)
REFLECTION
In the beginning, this project seemed like a pretty simple task, using the FDM Prusa i3 printers since all of my FDM prints printed quickly and successfully. However, when I moved over to using the SLA Formlab printers, the first couple of times I tried printing my part to scale, they 1: took 10 hours each, and 2: failed both times. I spoke with Fernando, and he determined that the reason for the first failure, which had resulted in only part of the part printing, was that there was a scratch on the bottom of the bed which was preventing the UV laser from printing along the cut. This required that the printing bed be replaced, so my print was incomplete. The second time, I wasn’t there to take the print of the bed, so I’m not sure what went wrong with it.
However, when the first print failed, although incomplete, the very end of the arm printed, so I was able to test how the hinge acted between the scooper and the top beam of the arm. This allowed me to figure out that SLA prints with tight tolerances most of the time are impossible to print given the nature of the printing technique. I had to reevaluate the direction of my project at this point, deciding whether or not to continue to print at scale even though the print wouldn’t fit in compartments fully extended, or scale the print down. I decided to scale the excavators down in the end, but I don’t think that I’d want to include them in the gumball machine, as they don’t articulate and I wouldn’t want someone to be stuck with a non-functional print.
I think for the future, SLA prints are great since they don’t have the obvious 3d-printed texture that you get with FDM printers, but the lack of ability to print hinges is a pretty big downfall in my opinion, at least in the scope of this project.
COST ESTIMATE
Raw Materials
- PLA (3 FDM Prints) = $0.81 (estimate from 3DPrinter OS)
- Resin (2 SLA prints) = ~$1.00 (estimate from SLA OS)
Labor
- 2 hours = $30 ($15/hour)
Overhead
- Unknown
- SLA printer fixed cost = ~$4000
- FDM printer fixed cost = ~$800
Total Cost = ~$32
This would work out to be ~$6.20 per print. This is a pretty steep cost for these 5 prints, but at scale, these prints wouldn’t require any labor, so the cost per print would be around $0.30, which is much more reasonable.
