Rotary Air Force
Rotary Air Force, of Saskatchewan, Canada, has manufactured Gyroplanes since 1970. A Gyroplane is an experimental, ultra-light aircraft with its lift and drive provided by a free-wheeling rotor system. Technically, it’s not a helicopter, as the craft requires a minimum of 50 feet for a runway. Gyroplane kits are sold in the U.S. for use in crop dusting, cattle control and pleasure.
"We build aircraft and, of course, everything we build has got to be right on the money. It’s got to be right; somebody’s life is depending on it,” said Shane Seitz, manufacturing manager of Rotary Air Force.
At the beginning of 1994, the company decided to upgrade their manual machining operations to CNC. The objective was to increase productivity and quality, while decreasing cycle times and the time it takes to complete prototypes. A dozen machining centers were evaluated over a four-month period. In July 1995, the company purchased a Haas VF-3 machining center.
The VF-3 weighs 12,500 lbs. and has travels of 40" x 20" x 25" (xyz). It has a 15-hp motor, geared head, heavy-duty water-cooled spindle, speeds up to 10,000 rpm, and a 20-pocket electronic tool changer. The high-speed, dual 32-bit Fanuc™ compatible control is also built by Haas.
“We were a manual machine shop transferring all our machining operations to CNC,” Seitz said. “The VF-3 has a nice control that’s really simple to use. You know the control is simple when the guys you’re training pick up on it fast,” he said. “The VF-3 has all the power and spindle rpm we need, and it gives us the most bang for the buck.”
Advanced OneTouch™ features on the Haas-built control save training and production time. For example, Haas OneTouch™ power-up turns the power on, homes all axes, picks up the #1 tool and loads it into the spindle, so the machine is ready to make chips. Tool-length setup stores offsets for 50 different tools (new VF-3’s store 100 offsets), and can be programmed with either radius or diameter, whichever the operator is most familiar with. Work coordinate offsets are loaded automatically with one button after touching-off the part. OneTouch ™ tool offset sets tool length offsets with one button, and another button loads the next tool automatically for offset measurement.
Prototype Production: From Months to Weeks
“I can draw an air foil with our CAM system, and send the program via DNC to the VF-3 for testing in less than a day,” Seitz said. “We can prove the program in single-block mode and edit right on the machine’s control. Once we get the first part out, we don’t have any QC problems with tolerances that don’t fit. There’s no deviation from one part to the next,” he said.
The company has found the tool-load monitor, tool-life management and single-block modes critical to proving out parts without crashing tools. The tool-load monitor keeps track of spindle load for each tool, and warns when the load exceeds an operator-defined safety margin. So when the tool load alarms are set to tight tolerances, the machine shuts down before a tool crash occurs. The tool-life management system keeps track of how long a tool is in the feed mode. When tool time exceeds operator-defined parameters an alarm comes on, virtually eliminating damage to the part from a dull tool. Single-block mode allows one line of code to be run at a time. The operator pushes a button to execute each line of code.
Formerly, prototyping required drawing a profile and sending it to a vendor. From the drawing the vendor generated a CNC program, then made the cut. If there were additional changes to the prototype part, the whole process had to be repeated until the part was correct.
“Now, 5,000 lines of code can be generated and machined in just five hours. CNC programs are sent to the Haas for proofing and editing,” Seitz said. “Short programs and basic editing are done right at the mill. It brought our prototype-to-production time down from months to weeks.”
Smooth Surface Finish
“The most critical component on the gyroplane is the hub bar that holds the main rotor blades. It was redesigned this summer,” Seitz said. “The tolerance is 0.0005-inch and the surface finish must be smooth. Many of our components require a smooth surface finish, so we use double point or single point mills at 9,500 rpm to turn out surface finishes like glass. The hub bars look like mirrors, with surface finishes of 0.3 micrometers. That’s proof the VF-3’s spindle and fixture are super rigid,” Seitz said.
The VF-3’s accuracy of ±0.0002- inch is attributed to heavy castings that reduce vibration, and ball screws mounted at both ends to reduce thermal growth. Wide-stance castings and a liquid-cooled spindle further enhance rigidity.
Made of solid 6061 T6 Aluminum, the hub bar is 211/2" long by 3" by 11/2". Its sides are flat, but at angles. Viewed from the side, it’s machined into a very flat V with 15-degree slopes on each side, and a flat center section. The hub bar determines the rotor-blade angle. This angle is partially determined by machining, then the hub bar is put into a pressure jig and bent to the exact coning angle. These angles must be within ±0.001-inch tolerance to clear the rotor head components. “The final operation is boring holes in the end of the hub bar,” Seitz said. “Since a special fixture stands the 211/2" bar on end for this operation, we needed the long z travel the Haas VF-3 provides.”
Rotary Airforce just put its first aluminum mold into production. It’s a compression mold for the 163-inch long fiberglass rotor blade. Machined in sections out of aluminum, it has a tolerance of ±0.001-inch This is the first time the company’s been able to machine molds out of solid aluminum blocks. The blocks are assembled together to form an aluminum mold that can be heated and cooled.
“Tolerances are super critical when you’re machining a mold in pieces,” said Seitz. “The tolerance on the rotor mold is 0.001-inch, because once the rotor is made it has to be hand finished.”
“Spindle speed and feed override features on the control allow us to vary the speeds and feeds at any time during machining operations,” he said.
“The VF-3 is very fast. I can feed tools up to 300 inches per minute and rapid at 710 inches per minute, with smooth tool changes. We like the VF-3,” Seitz said. “It proved to be a profitable investment.”