As anyone in the gearing world knows, Oerlikon Fairfield Manufacturing is a leading provider of engineered gear and transmission systems for off-highway and original equipment manufacturers throughout the world. The company originally specialized in parts up to 48 inches in diameter, which covered virtually all mobile equipment gearing needs. But market demands for larger gear assemblies, primarily for stationary applications, required Fairfield to make even larger gears and complex gear housings to support markets outside mobile equipment. This change necessitated moving to a new generation of multifunction machines that in turn made the company’s previous four-axis CNC programming system obsolete. The solution? (Figure 1)
“We switched to ESPRIT CAM software because it provides so much flexibility to customize the postprocessor,” according to Tom Lawler, manufacturing engineer for Oerlikon Fairfield. “ESPRIT works directly with files from the CAD system we use to design our products and simplifies the task of programming multifunction mill-turn machines and five-axis machining centers. ESPRIT captures the geometry of the machine, tooling, and part so that we can visualize the complete machining operation and detect any potential crashes to ensure trouble-free operation on the machine tool.”
Oerlikon Fairfield — which offers a broad range of gear and drive solutions including gearing, custom designed gear assemblies, and Torque Hub® planetary drives—also teams up with its sister company, Oerlikon Graziano, to offer complete drive trains for a wide range of off-highway mobile equipment. Oerlikon Fairfield has recently won large contracts to provide ring gears, pinion shafts, and large bull gears used in wind turbine drive assemblies. The company’s participation in the clean energy market area exploits one of its main core competencies of producing high-precision, large-diameter gears and shafts, including both gear cutting and the complete heat treatment hardening process. As part of its strategic business focus the company continues to capture new programs in the energy market, as well as further diversifying their business. (Figure 2)
Fairfield was founded in 1919 to manufacture differential gears for the early automobile industry, and in the 1920s the company began to specialize in producing custom gears primarily for off-highway mobile machinery applications. Through the 1990s the company specialized in parts ranging from 10-60 inches in diameter on vertical turret lathes and three- and four-axis machining centers. To increase sales volume through new market penetration, the company made the decision to focus investments supporting larger and more-complex gear products. Starting in 2006 it purchased a full line of mill-turn machines capable of performing all of the machining operations required to produce gears in two setups instead of the four that are normally required. The largest of these machines handles parts up to 92.5 inches in diameter and has a 49.2 by 49.2-inch pallet. This last machine is so large that Oerlikon Fairfield had to excavate a large hole in order to get it inside their building.
The decision to move to the latest generation of mill-turn machines instantly made Oerlikon Fairfield’s previous CAM software obsolete. “We used our previous software for several decades and were completely comfortable with it, but it was obvious that it could not cope with the newer machines and it was no longer being developed,” Lawler says. “Only a few companies had software that could handle the mill-turn machines. They each gave us evaluation licenses, and we tried them out. We selected ESPRIT primarily because of the flexibility of its postprocessor. ESPRIT lets us customize the postprocessor so the program performs exactly the way we want. For example, we have configured the postprocessor to insert restart statements at various intervals in the program. Then, if the operator has to stop the machine to change an insert, he can easily restart at the nearest point rather than having to go back to the beginning of the program.” (Figure 3)
Oerlikon Fairfield also modified the postprocessor to provide a tapered offset that is used to prevent unintentional machining of a taper on long and springy parts. The problem in turning these parts is that the further the cutting tool is from the workholder, the further the workpiece deflects. The result is a taper with the diameter of the part becoming larger as you move away from the workholder. The change made by Oerlikon Fairfield allows the programmer to make the program behave as though the size of the tool were being continually reduced, so the program automatically moves the tool toward the workpiece to compensate for springiness. The result is that the diameter of the part is maintained at a constant level. (Figure 4)
Lawler says that Oerlikon Fairfield takes advantage of the close integration between ESPRIT and the SolidWorks computer aided design (CAD) software. “ESPRIT’s developer, DP Technology, and SolidWorks® have a very strong partnership,” he says. “The result is that their software works very well together. We can visualize large, complex parts much more easily. These parts would look like spaghetti when viewed as wireframe geometry with our previous software.” (Figure 5)
He goes on to add that ESPRIT also makes it possible to import the geometry of the machine tool and tooling into the part program. This makes it possible to simulate the exact geometry of the part that will be produced by the program, and also to check for the possibility of crashes. “We can tell whether or not the tool is capable of generating the feature that we needed to make,” Lawler says.
ESPRIT integrates the solid model to automatically identify the part features. In the majority of cases, ESPRIT perfectly recognizes every feature in the part. “We still have requirements for manual editing in features,” according to Shane Van Hook, team leader for Oerlikon Fairfield. “For example, the profile of a turned part is normally recognized as a single continuous feature. We break it up into smaller segments so that we can assign machining conditions separately to different diameters and shoulders.” (Figure 6)
The software also attempts to organize the features into a logical order for machining. Changing the order of a feature is as easy as dragging and dropping it to a different position in the sequence. The next step is to assign metal-cutting operations to the features that have been defined. Oerlikon Fairfield programmers normally manually assign metal-cutting operations by picking a machining operation, cutting tool, cutting speed, feed rate, etc. Oerlikon Fairfield has developed cutting conditions over the years for many of the parts it makes. Programmers enter these conditions into ESPRIT and copy them from one part to the next. ESPRIT enables users to create a knowledge base of pre-optimized machining operations that include a particular tool, cutting speed, feed rate, depth of cut, etc. (Figure 7)
“The next step is simulating the machining operation,” Lawler explains. “We can see everything, including the workpiece, tool, machine tool, and fixtures, and the software calls out any interferences.” ESPRIT enables the programmer to view each individual cut in the entire machining process as dynamic 3D solids. The programmer can also view a presentation of the part that will be produced by the program and compare the as-machined workpiece to the original design. By zooming in on the simulated mold, the programmer can determine whether or not it matches the customer’s design. The simulation process provides the ideal opportunity to take a close look at the program that has been created up to that point. Programmers often identify areas where cycle times can be reduced by improving the program.
“Many of the parts that we are making now are so complex that it would not have been practical to program them with our previous software,” he says. “These are true five-axis mill-turn style parts with angles going in all different directions. Programming time now ranges from a few hours for a simple part to two to three days for much more complex parts. We now have the ability to understand exactly what the finished part will look like before we turn on the machine. The result is that the accuracy of our parts is higher and scrap rates have been greatly reduced. These improved capabilities have helped us compete successfully in the wind turbine business, where parts must typically be held to a 0.0035 positional error over a 70 inch diameter and a turning tolerance of 0.0015. We are very excited about the benefits that the ESPRIT software package brings to Fairfield.
“This investment allows us to continue our role as a gear and drives technology leader, as well as maintain our competitive position in the clean energy market areas,” Lawler says. “We look forward to further utilizing this software to help us continually reduce costs and reach our zero defect goals.”