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High Speed, 5-Axis Machining Puts Brek A Cut Above Other Aerospace Job Shops
Brek Manufacturing Company, Gardena, California, began operations in 1968 as a small machine shop with some big ideas about what the aerospace industry needed from a machining vendor.
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"They understood the benefits of 5-axis capability, not only in terms of what it could do for customers, but also the advantages it had for the shop as well," said Brek Owner-President Gene Price. When Price purchased the company in 1986, sales were about $1 1/2 million annually with 10 employees. Today, Brek employs 76 people, has $25 million in annual sales and has expanded from 15,000 square feet to 70,000 square feet. He credits the company's early commitment to 5-axis machining with not only building the foundation for Brek's sustained growth, but also positioning the company as a leader in high-speed 5-axis machining for aerospace applications.
Flying High with Structural Components
Brek Manufacturing Company specializes in the production of small to large aluminum and titanium structural components for a variety of military and commercial aircraft programs, including the C-17 military cargo aircraft, the 737, 777 and 717 commercial aircraft and the F15 and F18 fighters.
For Price, concentration on 5-axis machining has given him the capability and the confidence to bid on such major jobs as the production of large, monolithic floor sections for the C-17 cargo aircraft. These floor sections start out as 11,000 lb. of aluminum measuring 3 1/2" thick, 37" wide and 68 feet long. After machining, the sections weigh about 780 lb. each. Brek's contract calls for six sections per month.
The sections are machined on two Cincinnati Machine 100 hp, 10,000 rpm, 3-spindle, 5-axis gantries. These high-performance machines are equipped with heavy-duty milling cutters.
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Recently, Brek expanded its production capability with the addition of two Cincinnati Machine V5-2000 5-axis vertical machining centers.
"Cincinnati Machine has fitted a proven 3-axis vertical machining center frame with a twin axis tilt head to give it 5-axis capability," Price said. "The result is a machine that is relatively inexpensive for high-speed, 5-axis machining when compared with other 5-axis vertical machining centers."
The ballscrew drive of the 2-axis head gives the V5-2000 the fastest rotational speed and greatest tilt range (±40° in both A and B axes) in its class, while reducing moving mass for smooth feed and axis changes. The combination allows the V5 to speed through complex part routines with high precision. Brek uses the standard 35 hp, 15,000 rpm spindle with HSK-63A taper for optimizing metal removal rates. The Cincinnati V5 achieves a metal removal rate of over 105 cubic inches of aluminum per minute.
Improved Productivity Equals Improved Performance
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Brek uses the machines to produce small to medium aluminum airframe components--parts such as bulkheads, ribs, longerons, and other structural components. The parts range from 1" to 4" thick and up to 15" to 20" wide and 67" long. The machines run anywhere from 8, 000-12,000 rpm, and sometimes up to 14,000 rpm. Feed rates vary from 150" to 500", with the average being 300" to 400" per minute, depending upon the application.
"The driving factor in this business today is cost," Price said. "High speed machining is a plus because it helps us give our customer a lower price, high quality product while helping us reach our profit objectives."
The V5-2000 machines are being assigned some aluminum work that previously ran on the gantry machines. "We're able to process the jobs faster, yet at lower machine rates."
For example, three parts that were run together on Brek's Cincinnati 5-axis high-speed gantry were switched to the V5s. Now the company is running the parts faster on the V5s, one at a time, than on the gantry as a group.
"We rewrote the part program so that we could run at a higher rpm on the V5s, and take lighter cuts," Price said. "Loading and unloading helped as well. With the gantry, we were loading three parts at the same time rather than one at a time with the V5. One-at-a-time loading, combined with the faster processing time, significantly reduced our overall production time for that part."
Reduction in part handling time and improved throughput results in an overall reduction in the cost-per-part. There are added savings resulting from a reduction of scrap and rework as well. The improvement in part quality and the more uniform machining accuracy possible using 5-axis technology helps reduce inspection and quality control costs, further contributing to a lower cost-per-part and reduced total processing costs.
Handling Larger Parts
Aerospace structural components are becoming larger and much more complex. This is particularly true for a growing industry trend toward monolithic airframe parts in place of fabricated multi-component assemblies. One-piece parts can enormously reduce part counts and the handfitting and shimming of components in final assemblies, saving the airframe manufacturer significant time and money.The V5-2000 worktable measures 90" X 30.1" and rests on four Y-axis linear ways to support more than three tons of parts and fixtures, making it well suited for large, monolithic parts. These parts require multi-axis machining to create the complex geometries. Computer-controlled spindle manipulation allows processing of multiple surfaces, interior and exterior, without refixturing to avoid "stacking" errors that can compromise fit.
Five-axis machining regains machine idle time and helps improve utilization by reducing time spent in part handling and refixturing. Machines can run unattended for longer periods of time. Operators are then free to perform other value-added work during the longer machine cycle. The two V5s vertical machining centers are installed facing each other so that one operator can run both machines. "In some cases, we've even had the operator running a third machine," Price said.
Price credits the machines' 21-tool automatic tool changer with many of the productivity improvements he has seen in his operation. "The technology of automatic tool changers for 5-axis machines has come a long way in a short time," Price said. "By not having the operator take time to make manual tool changes, throughput and productivity increase significantly."
To Price, reducing the cost of manufacturing, meeting tight delivery schedules, and improving shop performance boil down to putting high-speed machining concepts to work. "A vertical machining center with a 4000 rpm spindle is going to cut parts three to five times more slowly. It's as simple as that," he said.