A user-friendly 3-D printing interface for customizing designs

Design tool lets novices do in minutes what would take experts in computer-aided design hours
September 4, 2015

A new browser-based interface for design novices allows a wide range of modifications to a basic design — such as a toy car — that are guaranteed to be both structurally stable and printable on a 3-D printer. (credit: the researchers, edited by MIT News)

Researchers at MIT and the Interdisciplinary Center Herzliya in Israel have developed a system that automatically turns CAD files into visual models that users can modify in real time, simply by moving virtual sliders on a Web page. Once the design meets their specifications, they can hit the print button to send it to a 3-D printer.

Currently, 3-D printing an object from any but the simplest designs requires expertise with computer-aided design (CAD) applications. Even for the experts, the design process is immensely time-consuming.

“We envision a world where everything you buy can potentially be customized,” says Masha Shugrina, an MIT graduate student in computer science and engineering and one of the new system’s designers.

The researchers presented their new system, dubbed “Fab Forms,” at the Association for Computing Machinery’s Siggraph conference in August.

How Fab Forms works

Fab Forms begins with a design created by a seasoned CAD user. It then sweeps through a wide range of values for the design’s parameters — the numbers that a CAD user would typically change by hand — calculating the resulting geometries and storing them in a database.

For each of those geometries, the system also runs a battery of tests, specified by the designer, and it again stores the results.

An automatically created Web App using Fab Form (credit: Maria Shugrina et al.)

Finally, the system generates a user interface, a Web page that can be opened in an ordinary browser. The interface consists of a central window, which displays a 3-D model of an object, and a group of sliders, which vary the parameters of the object’s design. The system automatically weeds out all the parameter values that lead to unprintable or unstable designs, so the sliders are restricted to valid designs.

Moving one of the sliders — changing the height of the shoe’s heel, say, or the width of the mug’s base — sweeps through visual depictions of the associated geometries, presenting in real time what would take hours to calculate with a CAD program. “The sample density is high enough that it looks continuous to the user,” Matusik says.

If, however, a particularly sharp-eyed user wanted a value for a parameter that fell between two of the samples stored in the database, the system can call up the CAD program, calculate the associated geometry, and then run tests on it. That might take several minutes, but at that point, the user will have a good idea of what the final design should look like.


Abstract of Fab Forms: Customizable Objects for Fabrication with Validity and Geometry Caching

We address the problem of allowing casual users to customize para metric models while maintaining their valid state as 3D-printable functional objects. We define Fab Form as any design representation that lends itself to interactive customization by a novice user, while remaining valid and manufacturable. We propose a method to achieve these Fab Form requirements for general parametric designs tagged with a general set of automated validity tests and a small number of parameters exposed to the casual user. Our solution separates Fab Form evaluation into a precomputation stage and a runtime stage. Parts of the geometry and design validity (such as manufacturability) are evaluated and stored in the precomputation stage by adaptively sampling the design space. At runtime the remainder of the evaluation is performed. This allows interactive navigation in the valid regions of the design space using an automatically generated Web user interface (UI). We evaluate our approach by converting several parametric models into corresponding Fab Forms.