Focusing on Fabrication – Part Nesting

We often find ourselves exploring aspects of projects that involve casting an object.  This has lead to discussions about the amount of effort and waste material that typically goes into making formwork from a solid block of foam.  There are great examples of work exploring alternative means of creating formwork such as the work of Andrew Kudless or CAST at the University of Manitoba where consideration of the fabrication process inform the design process.  Both examples use fabric formwork which can be a materially efficient way of creating complex forms, but requires a deeper exploration and understanding of that fabrication process.  We’re also looking at ways of integrating fabrication into our design approach, and find that this focus leads to developments that we might not have considered otherwise.  Take for example trying to cast the object shown below.

formwork

The typical approach is to take a solid block of material, for example foam, and then subtract material away until the desired form remains.  The challenge here is that formwork material waste increases as the form becomes more voluminous.  There are other ways that this formwork can be constructed.  It could be broken down into two plates that are cut flat and then assembled into final formwork, or the formwork can be constructed from a series of contoured layers.

There are obvious tradeoffs with each of these approaches such as the increased number of parts in the Two Plates or Contoured variations compared to the Solid, and the different aesthetic of the Contoured.  Other factors related to durability, assembly, and repeatability would need to be taken into account when judging any of these variations, but focusing on the how the formwork will be made opens up new areas of study.  We found the Contoured variation intriguing and decided to take it forward to see how the pieces might be laid out for cutting.

Rather than placing the contour layers onto a sheet as-is, we looked at how they could be nested to keep the material that was needed to create the form while removing the excess that occurred on the back edge of each form.  This switch takes the material usage from being equivalent to the Solid variation (773 in3) to almost half the amount of material for creating the formwork (412 in3).  We were able to fine tune the amount of offset and overlap by parametrically studying the layout process, allowing us to find the variation which would use the least amount of material.  Below is an animation showing the contouring and layout process.

After going through the layout optimization we moved into actually fabricating this piece.  The end goal was to make one about 16″ tall but we started with a half scale version that was cut on the laser cutter.  Four sets of the the stacked wedge formwork pieces were cut and then inserted into a plywood box.  Steel rods were inserted into each of the arms and then hydrostone with a bit of fiber was poured into the formwork.  We’re in the process of fabricating the formwork for the large scale version which has four times as many slices.  Below is a video of that cutting process.
It can often prove challenging to move beyond how one used to make things and instead think about how a given tool allows for new possibilities or requires additional consideration during design.  An example of this would be the vast amount of scrap material that is generated when someone is first learning to use a laser cutter or CNC router.  There is a formal freedom that comes with the ability to cut nearly any two dimensional shape from a sheet material, but these parts rarely layout efficiently, usually leading to a majority of the material becoming waste.

We believe it is beneficial for designers to have access to fabrication tools so that their designs are informed by the process of making.  Digital fabrication tools have allowed for an expansion of what we consider build-able.  This is one in a series of posts where we’ll be looking at how an early focus on the fabrication process can influence the design of a object or system and the potentials that might arise from this approach to design.

7 Comments

  1. Dale says:

    I am starting a 48×96 CNCRP build…going to be working with plywood shapes…

  2. scrawford says:

    Hi Dale,

    It’s a great kit and we’ve been really happy with it. One day we hope to upgrade our machine to the NEMA34s but for now the 23s are doing just fine. Best of luck with your kit.

    Scott

  3. Igor says:

    Specifically on nesting, do you write your own scripts in Rhino / Grasshopper / Processing, or do you use certain plugins to nest your parts?

    Btw, you guys are doing amazing work, inspiring me to push forward into my thesis year!

  4. scrawford says:

    We’ve used RhinoNest in the past and had good success with it. However, laying out these parts with RhinoNest would have still used more material because the design was slightly modified to make the part nesting even more efficient.

    What are you exploring for your thesis work?

  5. SM says:

    Great post!
    I’m currently exploring different techniques in developing formworks for concrete.
    Have you consider cnc-ing metal to create the formwork?
    I’m curious what post work is involved to develop the smooth surfaces.

  6. scrawford says:

    Are you thinking about CNC-ing a block of metal? We’ve been exploring the use of Aluminum Composite Panel as a formwork material and have great success in getting smooth surfaces. The limitation is that we’re starting with a flat sheet of material that is then being folded into the formwork shape which limits the variety of forms that can be created. Check out this post for more info:
    http://lmnts.lmnarchitects.com/fabrication/casting-experiment/

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