Archive for October, 2008

Model: pre-assembly

It is pretty clear we need centering to put this together!


3D printing scale model

The scale model is being printed on the ZCORP 3D printer in one of the MIT Architecture’s Design Fab Labs. This machine allows to build a 3D object from a CAD model. After slicing the solid model into horizontal slices, it places very thin layers of a white powder (basically a fast setting plaster, similar to plaster of Paris) and uses a regular inkjet printer head to deposit the bounding liquid where the plaster should harden. This process is repeated until the model is fully printed.

After the powder-base printer is done, we needed to excavate the model from the build tray. I felt like a true archeologist looking for a lost city, but there were also a few flash backs to happy times in the sandbox as a child.

After excavation, the brittle pieces need to cure in the oven and then want to be coated with a wax. Anyone fancies solving this 70 piece 3D puzzle?

Thanks to Chris, Patrick and Junno for helping with the 3D printing.

70 piece vault

The vault is finally entirely cut up! 

We now want to 3D print a scale model of this block assembly. Because we could only get one overnight printing session on the machine, we needed to fit the entire cut-up vault into one 3D printer batch (8in x 10in x 8in). This results in a scale model of approximately one foot squared. Things had to move fast to be ready to print, so no time left for nice packing… Enjoy my packing chaos!

Ready to print! The estimated printing time for our model was about 7 hours.

Cutting it up (2)

The chosen cutting pattern is mapped onto the previously generated interior surface (a). These cut lines are extruded outwards perpendicular to the inner surface and intersected with the outer surface to generate the cutlines of the outer surface (b).

Because of the complex curvature of the inner surface (= the result from the form-finding process), this method does not necessarily create clean cut lines on the entire outer surface. In the convex parts of the vaults, this method renders clean voussoirs (= masonry units/blocks), but it becomes messy in the transitions to concave parts. The intersections therefore need to be cleaned up and interpreted in these areas to get satisfactory cut lines. Connecting the interior and exterior cut lines gives the vousoirs (c).

Cutting it up (1)

The cutting pattern is being informed by the force lines (black) and topo-lines (orange) of the target thrust surface (a). This results in a solution that reflects -and emphasizes- the structural logic of the vault, but also helps recognizing the different transitions in vault typologies of this design, going from a groin vault part, to a more domical cap or the flaring edges of an Isler-type ‘free-form’ vault.   

On the three-dimensional thrust surface, we are laying out possible approximate stone layouts (b). The average stone size is about 3 by 6 feet, with an average thickness of 1ft resulting in pretty heavy pieces of stone (about one ton each!). Cuts will be made perpendicular to this surface to avoid sliding and guarantee proper arch action.

Shaping the volume


Load-bearing stone, Unreinforced masonry vaulting, Stone form-finding, Structural masonry vault, Free-form masonry, Equilibrium shapes, Funicular design