New router enhances the precision of woodworking

Anyone who has tried to build a piece of furniture from scratch knows the frustration of painstakingly cutting pieces of wood, only to discover that they won't fit together because the cutting was not quite accurate enough.

That's exactly what happened to Alec Rivers, a PhD student in the Department of Electrical Engineering and Computer Science (EECS), when he attempted to build a simple picture frame using woodworking equipment he had inherited from his grandfather. Despite measuring and aligning his tools as best he could by hand, Rivers found that he could not produce shapes with enough precision to make them all fit together. ''I was getting incredibly frustrated, because just as with any home project I would cut things out and they would look about right, but none of the pieces would line up,'' Rivers says.

But rather than simply throwing the pieces of wood into the trash and settling for a store-bought picture frame, Rivers decided there had to be a better way. So he and colleagues Frédo Durand, an EECS associate professor and member of the Computer Science and Artificial Intelligence Laboratory (CSAIL), and Ilan Moyer, a graduate student in the Department of Mechanical Engineering, began developing a new kind of woodworking router - a drill-like cutting tool - that could automatically cut out accurate shapes from a piece of material by following a digital design. The result is a handheld device that can adjust its position to precisely follow a digital plan when the user moves the router roughly around the shape to be cut.

The team will present its device this week at the Siggraph conference in Los Angeles.

''You load the system up with a digital plan that you would like it to follow, and then you are only responsible for getting it to within a quarter-inch or so of that plan,'' Rivers says. ''The device then adjusts the position of the cutting bit within the tool to keep it to the plan.''

For the device to follow the design, it must know exactly where it is on the sheet of material at all times. So before beginning to cut, the user first moves the device over the raw material, while an on-board camera films the surface and then stitches together all the video frames it sees into a single cohesive 2-D map of the piece. To ensure that the system can locate itself even when the material has no distinctive pattern or markings, the user simply places stickers containing a black and white contrast pattern on the sheet to be cut.