Goal: create five 3D printing pieces using 2 types of printer

Time:  10/28, 11/4, 11/6

Creation process

• Design

I wanted to create something fun and usable. Since I like sharks, I found some shark clips on Thingiverse. I and I think it is an impossible object because it is a small movable piece done in one print with parts passing through another to achieve the movement. I also think it is too small to be manufactured without the use of 3D printing.

• Printer 1: FDM

My first print was using the FDM, which was way too small for post-processing.  I also used a skirt instead of a raft (want to see what it looks like), but the result had lots of extra materials on the back. Through this first try I learned that this clip design is functional, but will require raft support and more post-processing. 

Thus, I made my clip bigger and learned from the first try to add raft support and it worked. Thus I printed 6 more sharks using the FDM. As a result, 4/6 were functional and ready for post-processing.

        

I accidentally used the glue filling for one of them so the result felt sticky and soggy. Another one’s jaw was not thoroughly cut through, so I tried to use an ultrasonic knife but it was too much for the clip and destroyed the piece 🙁

• Printer 2: SLA

I printed 4 sharks in total using SLA. I created support for my first one, but sadly, the sharky broke when I took it out. So I used this as a practice for the washing and the curing process, then used superglue to put it together. Through the first try, I was able to familiarize myself with the SLA design & printing process, and I learned that SLA does not favor moving parts. Thus I decided to try my luck on another SLA machine.

        

On the second try, I printed one shark using full support. Luckily it didn’t break, but it didn’t cut through 😂 I checked with the lab assistant for my design execution and found no issue. Thus I think this happened because 1. it is a small moveable piece 2. too much support was added, so there wasn’t enough spacing leading to parts merging (not during curing, already merged after print)

        

Thus I tried 2 other support options: mini support (left), and no support (right). And I hypothesized that the no support will probably create the best outcome.

However, none of the results worked. The mini support cut more but still not fully through, same with no support. The no-support condition not only didn’t thoroughly cut through, but it also created more extra materials on the back because there was no support, which require more post-processing. Here is a comparison of all four SLA pieces:

  

p.s. out of curiosity, I tried “opening” the SLA shark jaw using the ultrasonic knife to see where the merge occurs. But this broke the entire piece, and I found that the movable parts have completely merged with the head, thus when I slice the jaw line, it also cut the movable part as well.

• Post-processing

Besides washing, and curing the SLA pieces, I also used small clippers & pliers to cut off extra supporting materials. Since the piece is tiny, the moving path was very narrow with uneven material surface, causing big friction between parts. This made the movement really rough and I even have to manually close the jaw after I press it open. So I used an ultrasonic knife to slightly melt down the touching area to smoothen the uneven materials and expanded the moving space carefully while creating bigger separations between parts. Lastly, I cut off extra materials to ensure aesthetics. I also used a metal brush to “sand” off the rough surface, which was quite interesting.

Final result

    

 

Cost Analysis

0.02 (1st) + 0.08*6 + 0.25 ( resin: $25/kg * 0.01 kg) ~ $0.75

Overhead: 10$

Variable cost: 20$*7hrs =140$

Total ~151$