Help with CNC router

[Frenchie461]

Hi, I'm Brian French, I'm the person responsible for operating the CNC router for 461. Our router has been having an interesting problem where it loses it's zero settings, both the machine zero at the bottom left corner and the program defined zero at the corner of the piece. It only does this intermittently, so we can make parts, but it takes more tries than it should. The zero always shifts to the left, but the direction in the Y and Z are random; it's cut 3/4 inches into the machine bed, but it's also missed the part by nearly an inch above.

Just for reference, the toolpaths are generated by using the sheet metal function of Autodesk Inventor 2011. The files are then converted to a .dwf using the shop drawing feature. From there the .dwg is moved over to the CNC control computer, where V-Carve 6.0 generates the toolpaths that get executed on the CNC via Mach 3 CNC controller.