Focusing on Fabrication – Material Efficiency

In Galileo’s Dialogues Concerning Two New Sciences there is a passage where he describes the relationship between cross sectional area and bending stiffness.

Galilei, Galileo. Dialogues Concerning Two New Sciences (1914), pg 151

It’s a fairly straightforward principle, and highlights the concept behind my favorite type of structural system; the space frame.  The strength of a space frame comes from creating rigid cells that spread material over a greater cross section than if that same amount of material was used in a solid block.

Initially, space frames were only used for flat or arc based geometries because the components could be standardized, but parametric modeling and digital fabrication have reduced the need to limit the number of unique parts.  This has made it possible to explore more complex forms that have the potential to be tuned for specific purposes.  Space frames tend to require a lot of pieces so their use is limited to situations where their structural efficiency outweighs the complexity of constructing them.  We’re interested in finding opportunities to use them for more typical floors, walls, and roofs or other loading bearing systems at scales smaller than the long span roof structures of convention centers and airports.

In graduate school, I became fascinated with trying to find ways to develop a space frame joint that had a large degree of formal flexibility.  One approach was to have a joint that was physically flexible with a range of adjustability through the use of ball and socket joints.  The other approach was to have a joint that was digitally flexible by using a family of unique parts customized for the angles at each joint.  More recently this research has continued with the idea of a digitally flexible system where the adjustability is handled within the parametric model, but now instead of the struts and connectors being separate pieces that are fastened together, the entire system is bent from one sheet of material.  The starting point of the design was reducing the overall number of pieces.  This evolved into a process of using as much of a sheet of material as possible without decreasing its spanning area.  There is very little material that is not used within the structure, unlike the previous folded version with cut sheets which used less than half the starting sheet.Folding patterns into material has been used to increase the stiffness of material and give it a defined form, but the footprint of the material tends to shrink because of the folding.  In this approach, the material footprint stays the same, but the depth is increased by creating a series of cuts, producing sets of arms which are then folded together to create rigid tetrahedrons.

singleCellPrototypetwoCellPrototype
largePrototypelargePrototypeInside

We previously shared this research, but at the time we weren’t able to easily test the system with full-scale fabricated pieces.  Recently, we returned to this research and were able to cut out the prototypes shown above with our CNC router.  We’re using aluminum composite material for the prototypes.  This material has two aluminum skins, separated by a core which is typically polyethylene.  The advantage to this material is that it can be scored through the first aluminum skin and almost all the way through the core and then the parts can be easily and cleanly folded by hand.  A challenge has been how the arms are attached to each other.  The first attempt used three screws to hold them arms together at each overlap, but we’re now exploring a single piece of hardware that clamps a set of arms against the opposing sheet.  Again a driver with these connections is to reduce the number of pieces as much as possible.

The next step is to begin prototyping instances of this system that has varying depths within a sheet and also trying to deform a sheet of cells into taking on more complex forms similar to what is shown below.

cellTypes

8 Comments

  1. Hey Guys,
    Great stuff here! Assume you’ve seen the TexFab project Spin Valence – somewhat similar line of research:
    http://tex-fab.net/2012/09/spin-valence-second-round-progress/
    http://www.archdaily.com/247650/applied-research-through-fabrication-competition-finalists-announced/finalist_1/
    I like the potential though of being able to vary the depth and/or adapt the system to a more complex form/surface.

  2. scrawford says:

    Yeah that project is great. Here’s another similar one by marble fairbanks
    http://marblefairbanks.com/?p=36
    We weren’t aware of these when we started this research a few years back but they’ve been a source of inspiration since then. Both of them have nice fastening methods something that we need to work on more with our system.

  3. You might also look in to some methods other than mechanical fastening – i.e. spot welds or plug welds with laser-cut steel or stainless. I know you’re using the aluminum composite because you can mill it, but if the research progresses, other materials might become more appropriate!

  4. scrawford says:

    The first version I made was actually cut of out steel with a dremel tool by hand.
    http://lmnts.lmnarchitects.com/wp-content/uploads/2013/02/firstVersion.jpg
    The aluminum composite is nice because the folding is so nice and we can cut it but eventually I think it’ll move back to steel. I was considering a similar idea of using spot welds and beyond that trying to imagine how the cutting and forming might be done industrially. Might it be possible to stamp these pieces into shape?

  5. Michela Tonelli says:

    I’m a student of faculty of architecture of Florence. In the design my skills it’s Rhino+Gh and you are an inexhaustible source of inspiration. Interesting work as always, thanks for sharing.
    Michela

  6. Hey Scott – Not sure if you could ‘stamp’ these, especially if each cell ends up being a different depth, although you’d need to speak with someone who works with that sort of process. There might be tooling which could accommodate varying depths? A more readily available option would be brake-forming. You’d need to think about the order in which the ‘folds’ would be made and limitations on the reach of the tools/dies in the press brake. This could be an interesting variable and really legitimize the testing with a fairly available process. You could, for testing purposes, ‘perforate’ seams to be folded and bend by hand (keeping in mind this greatly reduces the structural capacity of the ‘fold’). This could be done via water-jet or even better by laser. Once you have more final designs, fold lines could be etched directly on the part (or very small ‘relief’ cuts made at the ends of fold lines – SolidWorks can actually put those in for you!) Marking the folds makes it easier for press-brake alignment/operation.

  7. Gil Rosenthal says:

    SCRAWFORD – You are an absolute Genius!
    Solving the non-uniform space-frame question has conceptually
    bugged me on and off over the years – and your approach of digital
    form finding and pushing the frame out of a 2D plane is brilliant!!!
    and that also includes solving the joint-specific connection as componentized
    2D elements – as shown in the 1st clip .

  8. scrawford says:

    Gil,
    Glad to hear you appreciate this research. Space-frames have fascinated me for a long time and I’m constantly looking for new ways to design/fabricate them and apply their structural concept in ways that aren’t dependent only on linear elements and nodes. There are a couple more systems that I’m playing around with at the moment and will be posting on sometime in the near future.

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