D printing is growing more and more common, but the ability to create designs for it is not. Any but the simplest designs require expertise with computer-aided design (CAD) applications, and even for the experts, the design process is immensely time consuming. Researchers at MIT and the Interdisciplinary Center Herzliya in Israel aim to change that, with a new 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 the user's specifications, he or she hits the print button to send it to a 3-D printer.

"We envision a world where everything you buy can potentially be customized, and technologies such as 3-D printing promise that that might be cost-effective," says Masha Shugrina, an MIT graduate student in computer science and engineering and one of the new system's designers. "So the question we set out to answer was, 'How do you actually allow people to modify digital designs in a way that keeps them functional?'"

For a CAD user, modifying a design means changing numerical values in input fields and then waiting for as much as a minute while the program recalculates the geometry of the associated object.

Once the design is finalized, it has to be tested using simulation software. For designs intended for 3-D printers, compliance with the printers' specifications is one such test. But designers typically test their designs for structural stability and integrity as well. Those tests can take anywhere from several minutes to several hours, and they need to be rerun every time the design changes.