Current Progress
So as it stands much of my work has been in prototyping. I was advised by the teacher and one of the other students to consider using TPU as a material for constructing my claw since I wanted to rely on a flexible form instead of hinges. For those unaware TPU is a more flexible rubber based printing filament that should allow my print to deform under tension when the claw is contracted. To be completely transparent it’s been frustrating to work with. I hadn’t toyed around with Cura settings much before this so I just sort of hoped I could put in the new material, change the temperature, and everything would work out. This was not the case and I ended up dealing with a lot of jams and inconsistency in printing with some prints going perfectly and others completely failing despite identical parameters. Eventually I had to do some searching on line for other changes such as slowing feed rate, disabling retraction, and other setting tweaks that helped the flexible material print easier.
Having now reached a comfortable point with printing TPU, I have discovered interesting possibilities I hadn’t previously considered. One of which is that the rougher TPU has a lot more friction which is great for the multi-part socket design I’m using. My current prototype structure is held together entirely by the friction between the various segments. It holds shape even when I apply pressure and contort the shape so I might be able to leverage that when assembling my final design.
Speaking of the final design, as it stands it stand somewhere in the middle between the two papers I used as chief inspiration. The overall shape is basically that of a arcade style grabber claw with three prongs that collapse in inward to grasp at a single point. The motion of the claw is going to be powered by tension, string made of TPU is going to be threaded through various hollow points of the structure and when tension is applied the claw will fold inwards and close. When tension is released the structure will open up back to its resting state.
For the construction I’ve decided to use a mixed material approach with PLA serving as the structures in between the joints and TPU for the connective sockets. The flexibility and friction TPU is great for holding everything together and distorting under pressure but is bad for keeping shape and moving parts. PLA on the otherhand doesn’t have sticking issues and glides against itself very easily which is ideal for the collapsing segments which need to slide in and out smoothly when pressure is applied and released. Also using the more rigid PLA for the bones of the structure adds additional tension when the form distorts helping it return to it’s resting shape easier. I also plan to make the tension string out of TPU since it’s definitely flexible enough and that way I can customize the structure so to anchor it to the claw.
Documentation
I wanted to annotate the images so I’m sectioning them off here
Image 1: Structural segments for the claw, left most is the stable version, other two comprise the collapsing variant.
Image 2: Base socket design, sockets are removed as needed for various placements in the structure.
Image 3: Loose design sketches. Top one is of the final claw design, X’s mark collapsing points in the structure. (forgive my perspective game, I’m bad at 3D drawings), bottom was concept design for how to do collapsible segments.
Image 4: Left is early proof of concept for the triangular structure, right is actual prototype which is pretty close to the final form the segments will take.
Deliverables and Timeline
My Deliverables have remained the same, having looked into the creation of this particular design, there are a lot more moving parts than I first suspected. It’s almost constructed like a Lego with various segments responsible for different functionality. So I think reasonably I’ll probably only create one flexible claw. However that one design I expect to be pretty large, maybe a foot long, and I would like it to be able to hold some amount of weight (like at least a cup or similar).
My Timeline however has changed, mostly in that it was pushed back a week due to the tiling project. Which works out pretty well since I didn’t know we had the week of December 1st to work.
Week of November 10th: For that week I want to explore types of flexible structures, whether it would be best to use a single solid form or multi part structure and see what would be most practical and functional for a final product.
- This was accomplished, for scalability and ease of construction I’ve decided to focus on the multipart tension controlled structure similar to the example I gave in my initial pitch.
Week of November 17th: I hope to finalize the structure I plan to use for my final form and begin prototyping how the final build is going to move.
- Successfully accomplished. Mostly spent experimenting with TPU and getting the various parts I’m going to use to build the final structure working.
Week of November 24th: I hope to be well along in prototyping, and begin constructing my final build.
- I have only one other system to prototype and that’s just threading string through the structure to provide tension, so I expect this to go as planned.
Week of December 1st: Constructing the final build should be well under way along with general time to refine any problems I come across and general polish before presenting.