Case Study: Going to Great Lengths
When plans for North America’s largest five-axis gantry machine were set in motion, the challenge of establishing a massive machine with an X-axis the length of three quarters of a football field was daunting. This was the task undertaken recently by Ingersoll Machine Tools (Rockford, IL) to the benefit of W Industries (Detroit), a leader of metal products manufacturing.
The job of developing a huge gantry machine that is 20 feet wide by 204 feet long (with 8 feet under its gantry) is challenging, to say the least. To find accurate, reliable linear scales at those long lengths was originally thought impossible. “We approached Heidenhain Corp. (Schaumburg, IL), one of our longtime partners, with this exceptionally long linear scale challenge and they met it,” explains Martin Honer, a controls project engineer at Ingersoll. “It is an impressive sight on what we call our Cybermill.” Now at W Industries, this Cybermill is running around the clock, guided by two 72 meter Heidenhain linear scales-the world’s longest-running down the length of the guideway.
Large Parts in Good MeasureRooted in work for the automotive industry, W Industries has recently expanded its capabilities, highlighted by this extraordinary mill. Since spring of 2010, W Industries has successfully been using the Cybermill to machine huge high precision parts for aerospace and defense applications, with quotes now out on many alternative energy jobs.
“With this large mill as part of our mix, we are growing at a rate that no one really anticipated,” explains Jason Sobiek, director of aerospace manufacturing at W Industries where it is said that 100 employees are on tap to be added annually. “We even get calls at the front desk asking for us to quote jobs.” As an industry leader, W Industries has three Michigan locations and houses 24 mills. “With this giant Cybermill, we are now working on a program for the AirBus A350 airplane for Spirit, borne of a government bond that we believe is the largest to be issued in the state of Michigan,” says Sobiek. This high definition, high tolerance project consists of two long tools for the fuselage, both 16 feet by 70 feet, which utilizes about ⅓ of the travel of the Cybermill.
All three of the axes on the mill include linear measurements provided by Heidenhain‘s 382C sealed linear scales-X axis is 200 feet, Y axis is 26 feet and Z axis is 8 feet. To put the Cybermill’s size into perspective, staff at W Industries estimate that one could stack 78 Hummer H2 sport utility vehicles (without tires) two-high, three-wide, end-to-end within its table. Within that amount of space, many types of large structures can be machined, including large molds, jigs, fixtures and composite tooling.
Currently taking off into the aerospace industry, this Cybermill is routinely doing what others cannot, such as wing and fuselage bond tools and molds. “We plan to also be involved with flight hardware and special aerospace projects in the near future,” says Sobiek. “The aerospace industry is in an early upward build trend of new fleets. The next 10 years should be very good for this industry and W Industries is very excited to be a part of that growth.”
The alternative energy industry sector also is in growth mode and W Industries is on board here with this Cybermill as well. “We can machine any part of a windmill,” says Dave Hislop, W Industries NC programming specialist, “from a blade, hub assembly to a nose cone. We believe we are unique in this ability because a turbine blade can be 100 feet long or a mold 200 feet. We believe this is one of the only pieces of equipment in the world that can build these single pieces. We are quoting many windmill parts jobs right now.”
World Class Linear MeasurementLong-length machining jobs are fast becoming a forté of W Industries. “We are happy to see W doing so well in this area,” says Ingersoll’s Honer. “The positional accuracy on these long Heidenhain linear scales is ±5 microns and the repeatability is exceptional. We chose these scales because Heidenhain makes the best feedback equipment in the business, and we were pleased that their LB scales carry distance-coded reference marks.”
The distance-coded reference marks (semi-absolute) on the LB scales are extremely important on large machines as they allow it to “home” or ascertain its position at startup very quickly. At every startup, subsequent electronics find the absolute reference (home position) after traversing a very small distance. Conventional machine referencing involves physically travelling the machine axes to a fixed home position that could potentially be many meters away. Distance-coded reference marks speed and simplify such reference runs.
“On W’s Cybermill, for example, the X-axis homing cycle with distance-coded reference marks are of great advantage as they could save over three minutes over a typical system-with a home limit switch at one end of the travel if the gantry was at the other end of its travel,” explains Honer. “In general, this system also saves machine wear and tear, and is more convenient for the operator, particularly if large work pieces are involved where axes may have to be moved in order to avoid collisions.”
Because more than 450 feet (150 meters) combined of these two groundbreaking LB distance-coded linear scales had to be installed at W, technicians from Heidenhain offered to assist in their installation. W staff mounted the housings and each 72-meter scale tape, bearing surface and protective sealing lips were installed by Heidenhain over a five-day period. “It was an exciting opportunity for us,” explains Paul Hood, Heidenhain service technician. “All, including the intermediate gaskets and scanning units, had to be just right. The housings are dial-indicated and needed to be within 0.004 flatness and parallel. Then the scanning head and bracket has to be mounted correctly providing for a 0.06 air gap over the entire 72 meters. The installation went well.”
“Soon after, we had third parties out with laser trackers to check the machine, and the results were outstanding,” adds Sobiek. “It is a very accurate machine.”
Exceptional Accuracy on Spindle TooHoner adds, “Overall, accuracy and repeatability are critical on a machine of this size. It is important to note that the tools on the spindle of the gantry are moving on some pretty big arcs and they too need to be very accurate.”
The Cybermill’s spindle head operates at 16,000 rpm with 50 kw of power. “This amounts to cutting very accurately at approximately 1,000 inches per minute,” explains Hislop. “This is a very high speed, a phenomenal rate, especially unique for its size.”
To handle the measurement of the angles within the spindle, two absolute Heidenhain RCN angle encoders are used: one on the C axis (the joint between the RAM and the red spindle head) and on the B axis (the joint at the tool that allows the tool to angle). The B axis must move ±100 degrees. “The angular positional accuracy on the spindle head is 20 arc seconds with repeatability of 10 arc seconds,” says Honer. “Both Heidenhain linear and angle encoders continue to provide the accuracy we need on the Ingersoll machine tools. I have to add that since we send machines all over the world, it is also important to us that Heidenhain is an international company and we know we can always get support.”
The JourneyThe evolution of this giant machine at Ingersoll began in 2006 where it first served as a shorter prototype at their facilities in Rockford. There it was tested and used to successfully machine the invar tooling for the Boeing 787 wing skins. At that point, two gantries were installed on a single X-axis bed, offering high productivity and flexibility, at the same time allowing very long parts to be loaded.
As part of its diversification plans, W ordered this machine in 2008 as a single-gantry machine with a much longer X axis. Heidenhain’s record-breaking linear scales led the guideway in this long length endeavor. The addition of more gantries is always an option here as the extremely long length makes it truly unique.
BenefitsThe X-axis homing cycle with distance-coded reference can save more than 3 minutes over a typical system.
With the large mill as part of the mix, W Industries is growing at a rapid rate-more than 100 employees are on tap to be added annually.
The Cybermill is routinely doing what others cannot, such as wing and fuselage bond tools and molds.