What is common between RPM and FreeD is:
- A three-dimensional CAD model is prepared beforehand that details the surface of the desired part.
- The cutting tool motion is controlled by hand.
- The position of the cutting tool with respect to the material to be cut is monitored by a computer.
- When the operator attempts to move the cutting tool cutting tool inside the surface of the designed part, the system stops the cutting process.
What is different between them is:
- The RPM monitored the position of the tool versus workpiece in 2D. The FreeD monitored six dimensions, 3D of position and 3D of angular orientation.
- On the RPM, the workpiece moved in 2D on a table top stage. Its position was monitored by X and Y linear encoders.
- The position and orientation of the FreeD is apparently detected by sensors on the hand piece monitoring an electromagnetic field sourced below the workpiece.
- The RPM prevents cutting by retracting the cutter upward, vertically. The FreeD prevents cutting by retracting the cutter backward through the hand piece, whichever way the hand piece is oriented.
- Cutting into the side with the RPM required remounting and reregistering the workpiece. Cutting into the side with the FreeD required no extra operations.