Cleaning corrupt CAD models: 5-Axis Machining

Job shops commonly receive corrupted or “dirty” CAD files from their customers. These files must be cleaned or repaired before toolpaths for machining the workpiece can be created. Software solutions like SpaceClaim, developed by ANSYS Inc., can fix dirty models, with the end goal of creating “watertight” solids ready for machining.

“Anytime someone has to machine a part, typically they’re starting with a 3D file,” said John Graham, senior product marketing manager at ANSYS, Canonsburg, Pa. “As 5-axis machining has become more prevalent, the curvature of these surfaces can be very complex—hence the need for CAM software to develop toolpaths.”

The problem is that CAD and CAM don’t always speak the same language. When vendors or job shops open a file from a customer in their CAM program, the translation may not come through, introducing corruption in the model.

CAD model showing corrupted faces that must be cleaned before a toolpath can be created. Image courtesy of ANSYS.

“You may have two faces coming together with a sliver opening between them because the definition of the edge of one of those faces is off,” Graham said. He added that a face could be missing or corrupt. In those cases, the mathematics behind the scenes would be totally off target. “You don’t want your toolpath going off and cutting air.”

Many things can go wrong along the way. It’s important to identify and fix those problems. Once the collection of surfaces are clean and watertight, Graham said, the user can send that collection—also known as a solid—into a CAM
system and build a toolpath off it.

Using the automated repair tools on SpaceClaim, the first step is often to stitch faces together. “Two faces may look like they share a common edge because they are perfectly aligned,” Graham explained. “But because of the way they are defined, the system doesn’t know they actually share that edge and are connected.”