In 1999, Protomold (now a service of Proto Labs), Maple Plain, MN, changed the face of plastic injection molding with a computerized process that could turn a 3D CAD model into real injection molded parts in five days. The process was faster than traditional molding and, for quantities from a handful to several thousand, it cost less. This let designers quickly get prototypes with all the properties of production parts for early functional testing.

"In the early days, we focused on simpler parts," says Proto Labs CEO Brad Cleveland. "Just automating the analysis of 3D models and converting the models to toolpaths for our CNC milling machines took over a million lines of software code. Over time, the models we could support grew in complexity. For instance, we used to use simple straight-pull molds. Undercuts — later indentations in a part that could entrap it in a mold — could interfere with mold opening and part ejection. So we wrote more code to detect undercuts and produce toolpaths for the 'side action' mold components that would form lateral features," he says. These cam-operated mechanisms are mechanically withdrawn from the part before the mold opens, allowing the A and B-side mold halves to open without interference.

Fast forward in time and the company says when it comes to its process, fast no longer means simple. Complex features molds now support include:

• Bumpoffs, or parts with slight undercuts that can be "bumped" out of the mold without using side actions. This capability relies on elastic deformation of the cooled resin.
• Steel pins attached to the aluminum mold to create tall, thin holes.
• Molds with sharp corners, thanks to EDM.
• Pickouts, or detachable mold parts for features that cannot be produced using side actions.