Papers

Digital to Physical

An idea is sketched out on a napkin over lunch. The designer fires up her laptop and breathes digital life into it in SketchUp. The concept is tweaked, rendered, and uploaded to
3-D Warehouse.

Anybody can then mash the design up even further, pushing and nudging a concept.  Now you can download that .skp file, scale it to whatever size you like, and build it out on a 3-D printer.

Yep, it’s now possible to literally watch an idea go from napkin to digital to a physical object in a matter of a few hours. There is something inherently powerful about holding a scale model in your hands. The design just seems a bit more concrete. Issues and space relationships make more sense. A physical model almost always guarantees a spark of innovation from the experience of touching and seeing.

In the good old days a physical model from a CAD application meant looking at 2-D views and busting out the Exact-O knife and Band-Aids. It usually ended with cutting foam board until the wee hours of the day fueled by adrenalin and espresso. Balsa wood forests were decimated all in the name of architectural and structural models. Emergency rooms
made fat profits on stitches. All this was before 3-D printing.

History of 3-D Printing
3-D printing originally came about during the 1980’s pushed by the design demands of product engineers. Driven by the need to prototype ideas quickly and yet achieve tight
tolerances for manufacturing, the technology was fairly rough at first. The biggest challenge was how to take what existed on the screen and translate this into a set of instructions a machine could read to assemble models. Click here to see videos on AEC and 3D printing.

Enter the .stl File
File formats can be a confusing aspect of 3-D printing. Like all computers, 3-D printers are big dumb machines that need specific instructions to take bytes and translate that into
useful information.  The .stl file provides the coordinates in space to build a physical object. The convention for doing this has been the STL file format which stretches back to the early 80’s. In the Wild West days of 3-D printing, there was no sheriff in town and unfortunately

no cross-platform standards and protocols were not developed. (By the way, STL stands for Stereolithography or Standard Triangulation Language. Our favorite STL Definition: Stupid Triangles and Lot’s of them.)  Read more what is an STL file here.
Yes, the shape to describe all that information comes back to a good old fashioned triangle and its normal vector. Think of it this way: Normal vectors are basically a big fictitious arrow that sticks straight out from the middle of a triangle. This arrow tells the 3-D printer
all about how to read the information as it relates to the surface of the object.

Mesh Surfaces of Triangles
When you line up all these little funky shaped triangles, you literally make a “mesh” over the top of an object. The more irregularly shaped the object is, the more the number of triangles is needed and the denser the mesh. It actually looks a lot like the bags of
onions or oranges you find at the grocery store.
Now, all these triangles have to line up and share a common edge. If they don’t, our big dumb 3-D printer gets confused as to how the surface is laid out and decides to not put any material down, in effect leaving a hole. The usually happens when the normal vector (the big pretend arrow sticking out from thetriangle) is facing the wrong way.
Here lies the challenge of 3-D printing: You can have tens of thousands of triangles and they all have to line up next to each other, share common edges, AND have their arrows sticking out in the right direction.

Whatʼs Ahead
As SketchUp continues to be adopted at an accelerated rate and making the cross-over to a 3-D printer gets easier, look for a new design conversation to take place. Being able to quickly to jot down an idea and render it out with ease does wonders for online communication and remote collaboration.
However, there is something weirdly satisfying with holding your idea in your hands.
File issues will continue to be the biggest hang-up in making the crossover. With .stl files being the preferred format for 3-D printers for over 20 years it looks like we’re stuck working in that box. As the demand grows to take an idea offline and into a physical format, the electronic tools will catch up.

Tips for 3D Printing with SketchUp
The idea of designing with 3-D printing as an eventual goal can make the file conversion go much easier. For example, many buildings are designed without a bottom and plunked down on a surface. Making sure that a design is as “watertight” as possible drastically cuts
down on clean up.  Also, think in terms of hollowing out models or building shells.  This will help cut down on raw material costs and CAD time to clean up the file.
Click here to see examples of architectural models.

Working With .skp Files
As always, the community of SketchUp has come up with a few tricks for .stl files. You can read more on this thread regarding exporting .stl files straight out of SketchUp using a Ruby script.
The other option is to export the .skp file into your favorite third party CAD package and from here export it again as an .stl file.