3D Benchy Tensegrity Sculpture

Automaton Printables Report

Summary Section: 

• Created a Tensegrity sculpture with geometric and Wave"s" and a benchy on top
• The function of our project is to experiment and achieve tensegrity.
• By equally tensioning the fishing line, the forces are balanced because they are designed in a way that the two parts hang off of each other.
• This is an extremely fun project to complete and explore the intricacies of physics and tension forces
• I worked on this project with a partner, please take a look! Here is her page: https://www.printables.com/model/377922-tensegrity-table

Lesson Plan and Activity:

•  With a partner, design and create a single custom Tensegrity Structure with complexity and unique design that incorporates multiple parts and uses an assembly.

Parts List: 

• Peg (1)
• Boat (1)
• Wave “S” (1)
• Geometric “S” (1)

Assembly/Construction Instructions Section: 

Recommended tools: 

Small Phillips or Flathead Screwdriver, Small Nose Needle Pliers, Wire Cutters, Sandpaper, Super Glue or Epoxy (Epoxy would be the strongest option), 9x Small Eyelet Screws (There are slightly different steps, later on, depending on size), Fishing line (Braided may be easier to tie)

 

Step 1 Print the parts necessary: 
Print Leric_1_3dBenchy,Leric_1_BoatPeg, Leric_1_Geometric, and Leric_1_Wave. 
We used PETG for some parts; however, PLA will be more than strong enough. An infill of 15%+ is recommended. Increasing the wall count may also create a stronger surface for the hooks. 

Step 3 Marking Holes: First, mark with a pencil where each hole should be created. The holes should align so, once they are put them in, the hooks are vertically aligned with each other.

Step 3 Creating the Holes: This step depends heavily on the size of your eyelet screws.
 There are two methods I would recommend for creating the holes:

 Method 1: Heat up a needle or soldering iron that has a dimension that is slightly smaller than the diameter of your eyelet screw. Press the heated needle or soldering iron where you created your markings. Press only as deep as the "shaft" of your screw. The heated needle will melt the plastic and facilitate "screwing" the eylet into the print. 

The middle eyelets' hole positions are extremely hard to reach. We created a hole that went through the part entirely to the other side; however, you may also be able to bend a needle 90 degrees to reach inside the gap.  We used method 2 due to the small size of our eyelet. 

Method 2: You can follow the same procedure as method one using a small drill bit with a diameter slightly smaller than your eyelet screw. This depends heavily on the size of your eyelet, so I recommend buying larger eyelets for this method. Note: This method works very well, however, due to the size of the drill bits it is very easy to snap them. 

Step 4 Inserting The Eyelets: Half of the eyelets are screwed into the holes by hand or using pliers. The other half of the eyelets are individually knotted with fishing line and then inserted into the holes opposite to the ones with already inserted eyelets. Then, the unknotted side of the fishing line is tied to the eyelets yet to be connected.

Step 5 Tying the String: 

15cm and 12cm long (2cm in between)
 

To tie the string, you will need two sections of 15cm in length, two sections of 12cm in length, and one section of 2cm in length. To facilitate later knot tying add 6cm+ to the total length of the string. 

Tie one end of the string to the hook (this can be done before the eyelets are inserted to make tying easier).  We used the Double Uni Fishing knot (As shown in this video: Link). This knot looks great and is very strong; however, you can also use a square knot for this step. 

I would recommend using a square knot for the other side which will be attached to the eyelet because it is easy to tie and extremely strong. (Video on tying a square knot: Link) 

Refer to pictures as needed. Note: We opted to use a chain in the center of the sculpture, however, pre-tying a string to a 2cm length between the hooks may be easier. 

Step 6 Tensioning:

Adjust strings as necessary to maintain equal tension across the sculpture. This can be done by loosening the square knots and re-tightening them. This is the step where you check if everything is level, the tension is even, and the wire is the appropriate length. 

Step 7 TENSEGRITY ACHIEVED: You’re done. Relax. Turn on the radio. Eat a sandwich. Listen to some jazz. Learn to ride a scooter. Find a hobby. Why not? 
 

Design Choices: 

We started by drawing several potential designs for tensegrity sculptures. After evaluating the best design for 3D printing, design complexity, and coolness, we picked design 1. We liked this design because it seemed extremely stable, and would offer us opportunities to experiment with new techniques on Solidworks. 

• Our size constraints for this project were: each piece should fit inside of a 15cm x 15cm square, and the final structure should fit in a 20cm x 20cm x 20cm cube. 
• We then proceeded to a more detailed drawing with dimensions for the sculpture. (It was also at this stage that we added the benchy and came up with the idea for the wave)

 Moving to Solidworks, we used a series of steps to model the parts:

1. Wave "S"
2. Start in a sketch on the front plane
3. Center construction outline (same for both S’s) (10 cm high x 15 cm long x 15 cm wide)
4. Add construction arcs with dimensions as per the drawing (Radius of 2.5 and 3 cm, respectively)
5. Offset in both directions, and cap ends (0.75 cm, 0.375 cm in each direction)
6. Use the spline tool on the outside to create waves 
7. Extrude to length (15cm)
8. Make a peg hole with 1x1cm dimensions (this should be done after the peg is created)
9. Add holes for hooks with a sketch and extruded cut (6 Holes)
10. Add fillets where necessary
11. Geometric "S" 
    1. Center construction outline (same for both)
    2. Add equal-length geometric lines instead of S curves (big curve - 2.5 cm each) (smaller curve - 2 cm each)
    3. Offset in both directions, and cap ends (0.75 cm, 0.375 cm in each direction)
    4. Extrude to length (15cm)
    5. Add holes for hooks with a sketch and extruded cut (6 Holes) 
    6. Add fillets where necessary
12. 
    Boat
    1. Download Boat (https://www.3dbenchy.com/)
    2. Resize as needed
    3.  (Create a peg hole with an extruded cut by editing mesh (1x1x2cm)
    4. Create a negative draft for peg (this changed in the final version)
13. Peg 
    1. Make the sketch of the base(1x2cm)
    2. Extrude upward (1.5 cm)
    3. Create a draft to slope edges of pegs (This changed in final version)

• We mostly followed these steps throughout the modeling process, however, we did change some aspects of our plan: we decided to change the width of the model from 15 cm across to 9 cm across for asthetic purposes (this also made hook installation much easier) , and we opted to create a square peg instead of a drafted peg since our printer was capable of printing the overhang which we were initially unsure of. 

First Test Print and CAD: 

• We also added a pattern across the surface of the geometric "S" using patterned hexagons (this was a purely aesthetic choice). In our final revisions to the design, we also added hook holes into the models (Although the printing tolerances caused many of them to be filled), and the resulting divots leftover made hook installation easier. 
• Overall our steps stayed mostly the same, and we did not encounter any major design challenges.