Celeritive is changing the way companies reduce energy consumption while increasing profitability.
Cycle time and tool life are examples of the kinds of machining process variables that manufacturers often aim to improve. By comparison, energy use typically does not get the same level of attention. In fact, the energy use of a given machining process is not even likely to be measured or tracked. While power is expensive, it's not nearly as costly as the machine itself or the tooling consumed in the cut. Plus, choices related to tool path, cutting parameters and so on all directly affect cycle time and tool life. The energy used to remove a given volume of material is much more of an untouchable matter of physics.
Or so it would seem...
Researchers with GKN Aerospace recently demonstrated something about energy consumption in CNC machining that is very different from this view. Working under the National Center for Defense Manufacturing and Machining as part of the U.S. Air Force's Sustainable Manufacturing Initiative, GKN found considerable margin for saving energy in the machining process. The company's aircraft component production plant in Hazelwood, Missouri applied one of its flexible machining cells to this project, which aimed to discover just how much energy could be saved in aircraft part machining. The research focused on a titanium 6Al-4V sample part designed with deep pockets that are typical of defense aircraft components, and it used equipment that is just as typical—namely, horizontal machining centers that had been in service for more than a decade. Using a power meter, researchers measured the effects of various attempts to save energy in this machining application. What they found is that strategic choices related to tools, coolant, programming and parameters can all combine to reduce the level of energy use by 73 percent of what this plant's established processes would normally consume.
Such savings provide for "sustainability" in multiple ways. While the term usually implies lowering energy use, keeping a job commercially sustainable involves holding costs low enough that the part remains in production. These aims are not contradictory. The programming-related findings of the sustainability testing are particularly promising, not only for the energy reduction, but also for the cost reduction and increased capacity resulting from cycle time improvements.
GKN researchers used VoluMill software from Celeritive Technologies to obtain more efficient tool paths for pocket milling. Rather than following the shape of the pocket, VoluMill tool paths aim to keep the stress on the tool consistent by avoiding sharp changes in feed direction. Toolpath moves therefore continually curve, bearing no resemblance to the shape of the final feature for most of the machining. The consistency that these tool paths provide potentially makes it safe to raise speed and feed rates much higher than the programmer would risk in a tool path that includes areas of significant stress fluctuation. Because of the way this faster cutting contributes to energy reduction, the test process that consumed 1.18 kilowatt-hours per cubic inch of material removal using GKN's baseline machining methods consumed just 0.60 kW-hr/in3 once VoluMill was used for programming. Supplementing this gain with higher-flute-count tools, through-tool coolant and coolant recycling brought the energy use down to 0.43 kW-hr/in3.
McMillan Machine Company saves up to 65% on energy costs.
Duncan Davis, General Manager, McMillan Machine Company, estimates that in the first four months of using VoluMill, he saved $5,000 in programming time and 200 hours or $16,000 in cycle time. The increased tool life that VoluMill toolpaths provide has saved $3,000 in cutting-tool costs. Furthermore, Davis said McMillan likely saves 65 percent on energy costs when running a VoluMill toolpath since the machine is running more efficiently and for less time to complete a job. McMillan's coolant bill also has decreased, by 20 to 25 percent. "We're keeping things a lot cooler with the consistent tool load and by taking the shallower radial depths of cut, and the solvent isn't breaking down as fast and is lasting a lot longer," he said.