James Hayes, a partner at IF Then Architecture Inc was the presenter at the "From the Real World to the Digital...ad Back: digitization to fabrication workflows" session at the Royal Architectural Institute of Canada's Festival of Architecture, held May 25 in downtown Ottawa.
Hayes began by asking how architects and others translate design intent into built forms. Digitally-assisted fabrication, Hayes said, are the exact opposite of most forms of automation, where a robot or program performs menial tasks.
Hayes argued it is possible to use digital technology to extend the reach of the architect and other craftsmen rather than focus on smaller, easier tasks.
Craftsmanship is adjusting, responding and correcting errors while working, Hayes said. "From my point of view, whether something is made through craftsmanship is neither good or bad, but the outcome is entirely dependent on the process, as is the design."
Some advocates of craftsmanship suggest architects should look to the aerospace industry for new workflows, but Hayes maintained the huge costs of development in aerospace make it a cautionary tale.
The four fundamental digitizing technologies are digital photogrammetry, hand held scanners, digitizing arms, and terrestrial laser scanners.
Photogrammetry is the technique of using photographs to ascertain measurements of objects.
Photography takes 3D and turns it into 2D, and photogrammetry does the opposite. But in the past decade photogrammetry has been automated, meaning objects can be scanned from photographs very quickly.
There are three simultaneous calculations, internal orientation calibration), external orientation (pose) and point matching, which is looking for similarities between pictures. Digital photogrammetry is best suited for objects with patterns and textures, non-planar geometry, matte surface finishes and light colors.
The best practices for photographs are that consistency lighting, focal length and movement is key.
The benefits of photogrammetry are that its very portable and scalable from small details to entire buildings. However it requires specialized knowledge and you can't see the results in real time. Accuracy and resolution is dependent on the user and the camera.
Hand held scanners can be used at close range and tends to produce "clean" data with little noise. Most models are portable, and they give real-time results.
Some hand held scanners can also act as photogrammetric devices by scanning with a laser and taking high speed video at the same time.
Digitizing arms don't rely on targets or photogrammetry. They sit on a steady base and use a probe and a scanner, and physically touch the object in order to digitize it. They are also very expensive.
Terrestrial laser scanners aren't as accurate as the other scanners, but they are useful for scanning buildings and other large spaces.
In terms of fabrication, there is subtractive fabrication and additive fabrication. CNC routers and machining centers on three, four or five axis take a volume and reduce it until they achieve the desired object. Robotic mills are another subtractive fabrication technology, and can work on six, seven or eight axes. CNC Waterjets can also be used for subtractive fabrication.
Additive fabrication, such as 3D printing, takes time but over that time creates a very accurate model. This can be done through stereo lithography, Z-Printing, and SLS, where a laser builds a fine layer of nylon or metal. Z-Printing takes gypsum powder and spread sit out then forms an object through a biding agent.
Meshes are the digital result of a scan, and they are analogous to pixels. Polygon meshes are made of vertices and edges, and are triangles or quads. Prior to fabrication the mesh should be "watertight," with no holes or non-manifold faces.
Hayes demonstrated a case study of digital fabrication, where the entire surface was scanned with a terrestrial laser scanner, and then a large HVAC volume was created using a CNC waterjet system to create precise cuts in the design.
Hayes also pointed to a project for the West Block rehabilitation on Parliament Hill where digital fabrication was used to show masons how digitization technologies work. The top of a column was scanned then 3D printed. Another component was scanned using photogrammetry, which produced a rougher product which was well received by masons.
A sandstone sculpture on the East Block was also digitized, and then a mesh model was created. A robotic mill was used on a 5,000 pound block of sandstone and once the sculpture was completed, they embarked on a new project where a headless gargoyle was created by both traditional means and through digital fabrication to compare results.
Digitally assisted fabrication was also used at the Government Conference Centre (GCC) Senate chamber. Leaves from a coat of arms were hand sculpted by sculptor Phil Whyte, and then 3D scanned. The leaves were then integrated into the surface of a door.