Electronic system and method for compensating the dimensional accuracy of a 4-axis CNC machining system using global and local offsets

An electronic method for compensating the dimensional accuracy of a CNC machining system comprising:

• receiving setup information through an interface, the setup information including feature descriptive information and part information, the feature descriptive information including a local coordinate system, and the part information including a global coordinate system;
• receiving measurement data from a coordinate measuring machine and through an interface, the measurement data relating to one or more measured dimensions of a machined part;
• calculating a plurality of CNC offsets from the received setup information and measurement data, wherein calculating the plurality of CNC offsets includes:
• calculating a global offset, wherein the global offset is an adjustment of a position or orientation of the global coordinate system;
• and
• calculating a local offset after calculating the global offset, wherein the local offset is an adjustment of a position or orientation of the local coordinate system within the global coordinate system after adjusting the position or orientation of the global coordinate system in accordance with the global offset;
• and
• outputting the plurality of CNC offsets.

An electronic system for compensating the dimensional accuracy of a CNC machining system comprising:

• a four axis CNC mill configured to machine a feature into a part, the four axis CNC mill having a global coordinate system;
• a coordinate measuring machine configured to measure a plurality of dimensions of the part, and to provide an output corresponding to the measured dimensions;
• and
• a compensation processor in communication with the four axis CNC mill and coordinate measuring machine, the compensation processor being configured to:
• receive setup information that includes a plurality of nominal dimensions, each nominal dimension corresponding to a measured dimension of the part, wherein the setup information further includes feature descriptive data including a nominal position of a feature of the part;
• receive the output from the coordinate measuring machine;
• calculate a plurality of CNC offsets;
• and
• provide the plurality of CNC offsets to the four axis CNC mill;
• and
• wherein calculating the plurality of CNC offsets comprises:
• computing a plurality of deviations between the measured dimensions and the corresponding nominal dimensions;
• relating the plurality of deviations to a plurality of global CNC offset variables within the global coordinate system of the four axis CNC mill;
• optimizing the global CNC offset variables to minimize the deviations;
• analytically computing at least one remaining deviation of the plurality of deviations after optimizing the global CNC offset variables, wherein the at least one remaining deviation is the deviation that remains after optimizing the global CNC offset variables;
• and
• computing a local offset to minimize the at least one remaining deviation after optimizing the global CNC offset variables, wherein the local offset is an adjustment of the nominal position of the feature within the global coordinate system.