Exploration of Tensile Structures in Context of Ergonomics

This is a documentation my process for a final project for 24–672 Special Topics in Design, DIY, and Fabrication in Carnegie Mellon’s College of Engineering.

This project began as a continuation of the previous assignment about resin casting — for context, read about it here.

As I approached this final project, I wanted to test myself in the fabrication of a product, without sacrificing form and design.

THE CONCEPT

Emerging from a successful cast of the “seahorse,” I knew I wanted to deeper explore artifacts at this scale; thus I began thinking about ergonomics and different types of grips.

Moodboards for manufacturing inspiration in addition to ideal demographic

Additionally, I considered different types of structures I could apply to the “grip” I was developing. As I fell deeper and deeper into a research hole, I needed to accept that this project was going to be more form and concept driven rather than solving a specific problem.

Immediately I thought of Frei Otto and his work with lightweight, membrane-like structures —on such a small scale, I wondered if the “tensile-structure” approach could afford an interesting interaction.

CAD

It became clear to me that the form itself was going to take on a rather organic and complex shape — thus when it came time to CAD, I decided to try out Fusion360.

Having only been familiar with Solidworks before this, taking on Fusion was certainly a challenge.

building faces to build in three dimensions

After a horrifying amount of time spent sitting in front of Fusion, I was able to sculpt a form that resembled what I was looking for. This solid form would serve as my base model for the rest of my process. Upon finishing, I extruded a lighter shaped cut and sent it to the printer so I could move on with prototyping.

Still interested in tensile structures, I needed to face my next challenge — figuring out how to stretch string across the “valleys” to achieve an elastic interaction. After some thinking, I applied the Voronoi algorithm and how its cell based structure could act as the skeletal structure to string a net across. Thus, I pulled the part back into Fusion and played around in the sculpt environment. However, after investing more hours into the program, I realized there was no conceivable way I could achieve the cell pattern I needed with solely the sculpt environment. Upon further reading, I discovered an alternate program online called MeshLab that had the Voronoi algorithm built into the program.

Meshlab

I imported my .stl file and began experimenting with different ratios of poisson-disk sampling till I found what I liked, then I sent it to the printer as well.

FIRST GEN OF ITERATIONS

The first batch of prints on the Form2

After the first batch came out of the printer, I felt rather satisfied, but was still bothered by the fact that ergonomically, the grip wasn’t comfortable to hold yet. Considering I had guessed my way through the proportions on the 3D model, I wasn’t surprised that some of the “valleys” were much too small. Luckily, at this point, I was rather familiar with the program so I adjusted the model and prepared it to print again.

As for the testing of the tensile structures, I took a cordless drill and drilled holes along the contours of the form. While this was rather risky, I was able to drill through with minimal damage to the solid structure. I figured that the holes themselves would not take on an exorbitant amount of stress and the force due to tension on the strings would disperse along the entire form.

grip studies + first batch of printed grips in different materials (clear +flexible)

NEXT STEPS

Upon completing the first iteration, I pulled in some of the angles on the model and tested the string on other forms. From an orthographic standpoint, the grip I had originally modeled was rather jarring and frankly, uncomfortable to look at.

The grip needed to take on a more recognizable form, so I took in the angles and resolved some outstanding curves. I considered what makes people want to click on lighters — what about their shape and semantics make people want to interact with lighters?

FINAL FORM

After an excruciating iterative process, I landed on final form. It is printed out of tough resin on the Form2 printer and strung with waxed thread to create a tensile structure. The elastic interaction allows for a more comfortable grip that accommodates different hands.