Rockville, MD-Automated Precision Inc. (API) announced that Northrop Grumman Corporation has successfully deployed API’s Volumetric Error Compensation (VEC) to achieve higher accuracies on their large-volume machine tools. Northrop Grumman sought greater machine tool accuracy for the F-35 Joint Strike Fighter production and has selected API’s VEC to achieve the high tolerance machined parts.

“API’s Volumetric Error Compensation is a true game-changing technology for anyone with large and complex machine tools,” says Dave Maxham, global marketing director at API. “Older technology considers each machine axis separately, stacking errors from three or more individual coordinate systems. This limits the mapping of errors to three linear axes and 21 error parameters which has proven very challenging for large five- and six-axis machine tools. We recommend the innovative process to the entire F-35 supply chain.”

VEC uses a unique, global, free-form error model to allow error mapping of every point with its six degrees of freedom in the machine’s entire working volume, regardless of the number of axes or machine complexity. This holistic approach results in machine tool compensation done in real time, improving the tool center point accuracy between four- and tenfold on most quality built machine tools.

An exhaustive battery of on-machine testing and evaluation at Northrop Grumman’s Palmdale facility has shown that VEC achieved the desired tolerances for F-35 production and completed the task in less than one day. “The biggest advantage of VEC,” Maxham states, “is achieving these impressive accuracies in a fraction of the time it would take using a 21 error parameter model. Some of the larger and more complex five- and six-axes machines used to take weeks to compensate, but now most can be done in less than a day, virtually eliminating thermal drift in the measurements.”

Wayne Bromiley, a Northrop Grumman facilities engineer, summarized his experience this way. “API’s VEC improved our machine tool performance considerably. It reduced the calibration times for these machines from one week of 12 and 14-hour days down to one eight-hour shift. This improvement saved us a major amount of down time and made the machines more available for production use.”

VEC is the heart of the VALMT project funded by NCMS which was recognized with the Defense Manufacturing Excellence Award given out annually by the National Center for Advanced Technologies (NCAT) in December 2009. “The innovative VALMT project will save the DoD millions while ensuring weapon systems are mission ready and available for our war fighters when they need them,” says NCMS Vice President Chuck Ryan. “This technology will also pave the way for reducing the manufacturing costs of commercial ships and aircraft, benefitting both government and industry.”