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Personal fabrication is currently a one-way process: Once an object has been fabricated with a 3D printer, it cannot be changed anymore; any change requires printing a new version from scratch. The problem is that this approach ignores the nature of design iteration, i.e. that in subsequent iterations large parts of an object stay the same and only small parts change. This makes fabricating from scratch feel unnecessary and wasteful. In this paper, we propose a different approach: instead of re-printing the entire object from scratch, we suggest patching the existing object to reflect the next design iteration. We built a system on top of a 3D printer that accomplishes this: Users mount the existing object into the 3D printer, then load both the original and the modified 3D model into our software, which in turn calculates how to patch the object. After identifying which parts to remove and what to add, our system locates the existing object in the printer using the system's built-in 3D scanner. After calibrating the orientation, a mill first removes the outdated geometry, then a print head prints the new geometry in place. Since only a fraction of the entire object is refabricated, our approach reduces material consumption and plastic waste (for our example objects by 82% and 93% respectively).

Low-fidelity fabrication systems speed up rapid prototyping by printing intermediate versions of a prototype as fast, low-fidelity previews. Only the final version is fabricated as a full high-fidelity 3D print. This allows designers to iterate more quickly-achieving a better design in less time. Depending on what is currently being tested, low-fidelity fabrication is implemented in different ways: (1) faBrickator allows for a modular approach by substituting sub-volumes of the 3D model with building blocks. (2) WirePrint allows for quickly testing the shape of an object, such as the ergonomic fit, by printing wireframe structures. (3) Platener preserves the technical function by substituting 3D print with laser-cut plates of the same size and thickness. At our CHI'15 interactivity booth, we give a combined live demo of all three low-fidelity fabrication systems- putting special focus on our new low-fidelity fabrication system Platener (paper at CHI'15).

Even though considered a rapid prototyping tool, 3D printing is so slow that a reasonably sized object requires printing overnight. This slows designers down to a single iteration per day. In this paper, we propose to instead print low-fidelity wireframe previews in the early stages of the design process. Wireframe previews are 3D prints in which surfaces have been replaced with a wireframe mesh. Since wireframe previews are to scale and represent the overall shape of the 3D object, they allow users to quickly verify key aspects of their 3D design, such as the ergonomic fit. To maximize the speed-up, we instruct 3D printers to extrude filament not layer-by-layer, but directly in 3D-space, allowing them to create the edges of the wireframe model directly one stroke at a time. This allows us to achieve speed-ups of up to a factor of 10 compared to traditional layer-based printing. We demonstrate how to achieve wireframe previews on standard FDM 3D printers, such as the PrintrBot or the Kossel mini. Users only need to install the WirePrint software, making our approach applicable to many 3D printers already in use today. Finally, wireframe previews use only a fraction of material required for a regular print, making it even more affordable to iterate.