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GKN Aerospace (formerly Stellex-Monitor)

The Virtues of Virtual Manufacturing

Manufacturing a series of brand new parts with exacting tolerances under a tight deadline can be challenging under any circumstance. Now let’s assume that you don’t have the necessary machine tool equipment. And, to make matters more difficult, after you do manufacture those parts, the CNC programs are going to be used for production machining in a brand new start-up facility on the other side of the globe. Now things get a little trickier! This was precisely the task that recently faced Stellex Monitor Aerospace, Inc.

Stellex Monitor Aerospace, Inc. is a major supplier of airframe structural components and sub-assemblies for commercial, military, and space applications. The company specializes in complex CNC profile milling of large aerostructures using three and 5-axis Gantry and Bridge Mills and high speed machining techniques. Stellex Monitor Aerospace’s client list includes: The Boeing Company, Lockheed Martin / Wyman Gordon, B.F. Goodrich (formerly Rohr), Northrop Grumman, Pratt & Whitney, the U.S. Government, Bombardier, Hawker De Havilland, International Aero Engines, and Kawasaki Heavy Industries.

Stellex Monitor Aerospace was founded as Monitor Aerospace in 1948. The company has long prided itself as a leader in the industry, utilizing the latest manufacturing technology. In 1960 it was one of the first companies to operate a multi-spindle NC machine. In 1970 it was of the first operators of 5-axis, 3 spindle Gantry mills. Between 1960 and the early 80’s Monitor opened manufacturing facilities in New York, Deerfield Beach, Florida, and Puerto Rico. In 1982 they consolidated the operations into a single, newly designed 238,000 square foot facility in Amityville, NY. In 1998 Monitor Aerospace was acquired by Stellex Technologies, completing the transition from a private family business to a corporate structured organization. Stellex Monitor Aerospace is ISO 9002 and AS 9000 registered.

Today, the company employs 400 people, and continues to take advantage of the latest manufacturing technology in order to stay competitive in the tightening aerospace marketplace. CAD/CAM software plays a large role in streamlining the manufacturing process. Stellex Monitor’s 15 NC programmers use a number of software systems including CimLinc, Solid Edge CATIA, Unigraphics, NCL, and VERICUT.

Recently Stellex Monitor was awarded a contract through Cincinnati Machine for turnkey technology transfer of machining programs, tools and the NC media necessary to produce wing stringers for the Boeing 717-200 (formerly MD-95). Hyundai Space and Aircraft Systems, Co., Ltd. of Seoul, South Korea won the contract to produce the wings for the Boeing 717-200 jet liner. This program was the initial foray for Hyundai entering in to the aerospace manufacturing marketplace. This was an aggressive program and required Hyundai to invest in a large new manufacturing facility, located in Seosan, a rural location approximately 100 miles southwest of Seoul.

Cincinnati Machine was contracted to supply a host of new equipment needed to build the wings. The machining cell envisioned by Hyundai included a mammoth bed reaching 300 feet in length and housing two 7-axis Spar Mills on each end. A Sidewinder 5-axis machining center was situated in the middle of the bed length. The goal of this enormous machining cell concept was to produce the 94 different types of wing stringers in a cellular environment with minimal set-up and tooling change times.

Stellex Monitor’s job was to

  1. Develop universal vacuum and hydraulic tooling capable of handling the 94 different types of wing stringers (4-axis aluminum machined components with lengths ranging from three feet to 44 feet, and wall thickness as small as .06).
  2. Yield a modular tooling design enabling Hyundai maximum flexibility in future production opportunities. (Standard machine design and fixture parameters created serious travel restrictions and potential interferences and collisions.)
  3. Ensure that the required cutting tools and holders were standard designs to minimize the up-front expenditures.
  4. Produce the NC programs to manufacture the 94 different parts in accordance with Boeing’s specifications and quality requirements.
  5. At the end of the contract, the NC programs designed by Stellex Monitor would be used to verify the specified cycle time for manufacturing the total shipset of parts on the new Hyundai manufacturing cell.

This type of contract, with such complexities, was nothing new to Stellex Monitor. However, despite the fact the company had an extensive manufacturing facility with 54 CNC machines, it did not have the type of equipment required for this turnkey project. Additionally, because of a compressed timetable of the project, there would be insufficient time to do product verification testing on a prototype Sidewinder machine at Cincinnati. Stellex Monitor was therefore faced with the difficult task of producing tooling designs, program tapes, and cutting tool selections on a project consisting of 94 different parts – without the benefit of the actual equipment for engineering prove-out or production.

Stellex Monitor needed a way to not only model all the fixtures and tools to be used on the Sidewinder and Spar Mill machines, but to test and validate them ahead of time, before any machining actually took place. This would enable them to confidently oversee the production machining in South Korea when the manufacturing process was to begin.

The company had been using VERICUT® software to verify their NC tool paths for approximately six years. Developed by CGTech in Irvine, California, VERICUT is a program that simulates the material removal process of an NC tool path to reveal any mistakes or potential collisions. It’s also used to build and simulate entire machining centers. VERICUT was selected to improve Monitor’s testing process. The goal was to do more in-office testing and reduce the number of hours needed for on NC machine testing. “This allows the machines to stay focused on good production hours (making money). At the same time, it improves our throughput and quality on jobs being released from engineering, as our engineers can view potential problems prior to cutting the first piece of material,” said Gary Kahrau, V.P. Technology. “With the use of VERICUT we’ve been able to reduce the time-to-production on new engineering jobs. This helps bring new work to the manufacturing environment quickly with fewer up-front engineering charges. The program saves us time and money by shortening the iterative testing process, and virtually eliminating all interference issues during the cutting process.”

With VERICUT, engineers at Stellex Monitor modeled the Sidewinder and Spar Mill machines. “We were able to detect crashes with the tooling and eliminate all major problem areas prior to start-up of the machines themselves. By using VERICUT, we were able to machine run the different types of stringers, observe the cutting parameters and make corrections as well as any optimization actions – way before any metal was cut,” said Kahrau.

Using VERICUT to simulate the universal fixture and tools also enabled them to visualize the commonality and more importantly, to pinpoint the areas of non-commonality and minimize those to the greatest extent possible.

Mid-way through the program effort, Stellex Monitor acquired the second prototype Sidewinder machine from Cincinnati Machine. This enabled them to group the 94 different stringer types into families. They verified a representative part from each family by running the NC program VERICUT, then machined a first production part of each. By “virtually machining” the part beforehand, Stellex Monitor was able yield an extremely high percentage of first piece production parts that met all the pre-determined quality requirements. “The success we achieved gave us significant confidence that our team would be successful once they reached Seosan and began utilizing the machining cell for production,” said Kahrau.

After verifying the theoretical cutting development issues to yield a good part, the next step was to address the part loading, actual cutting, and actual machining issues. To minimize downtime in Seosan, and to ensure that Hyundai Space & Aircraft was producing wing stringers as quickly as possible, the team at Stellex Monitor turned to VERICUT again.

When a problem was identified in Korea, it was electronically transferred to Stellex Monitor’s design team in New York. VERICUT was used to simulate the problem and ‘see’ what was happening in Korea. Once the solution was determined, VERICUT was used to verify its accuracy. Then the corrected file, or fix, was electronically sent back to our team in Korea for implementation. “Using VERICUT enabled us to take a project that was extremely difficult from a logistical standpoint, and tackle it successfully by using utilizing the strength of the software to compliment our efforts,” said Kahrau.