New CNC Technology Boosts Efficiency and Productivity of Aerospace Machining

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This complex hydraulic manifold, machined by BAR Engineering & Manufacturing,
operates critical actuators in a military aircraft.
Photo courtesy of BAR Engineering and Manufacturing.

Two manufacturers--one using 5-Axis milling and the other employing creep feed grinding--save time and money by using machines with advanced digital controls.

One of the specialties of Siemens Energy & Automation, Inc. is advanced CNC technology that's designed to save time and money while increasing productivity in basic or high-speed machining. Faster machining speeds, reduced setup and downtime, and advanced communication protocols are among the reported benefits of the company's control technologies, used in applications ranging from 5-axis milling to creep feed grinding.

Siemens's machine tool control systems include the Sinumerik 840D, which Siemens calls a "digital NC system for highly sophisticated tasks." It's a universal and flexible CNC system that's tailor-made for complex, multi-axis high-speed machining. The company also offers the Sinumerik 802D, a digital control well-suited for basic turning, milling, and grinding. It's an operator panel-based control system that combines the numerical control (NC), programmable logic controller (PLC), and human machine interface (HMI) in a single unit.

Following are two machining case studies that illustrate the efficiency and productivity advantages of the Siemens Sinumerik 840D and 802 CNC systems.
 

Aerospace Shop Reduces Machining Time for Complex Parts with 5-Axis CNC Milling

Asher Sharoni is the president of BAR Engineering & Manufacturing, Inc. (www.barcnc.com), a 30,000 square-foot aerospace machine shop in Cerritos, Calif., that he bought with his wife, Tova, in 2005. The previous owners started the operation in 1985. "We liked the name, so we kept it," says Sharoni. Since that time, this fast-growing shop has won a Boeing Certified Preferred Supplier Award, received excellent ratings on the Boeing Commercial Airline Group's ISBA, and become AS9100 and ISO9001:2000 certified. The company is also certified to produce nuclear-grade products, and is working to initiate a Six Sigma program with Boeing. The shop sells to numerous tier suppliers of Boeing and other aircraft builders, as well as the military sector, in the highly competitive Southern California market area.

Among BAR's products are numerous hydraulic manifolds, profiles, structures, and turned parts to 120 inches in length. They are made from various alloys of steel (including 300M and 9000S), as well as aluminum, titanium, platinum and magnesium, Inconel, and more.

Despite all of its successes, Sharoni says that "we knew we had our limitations and we needed to differentiate ourselves from the pack."  The result of his investigation, along with that of his 27 design, manufacturing, and operations personnel, was to step into the five-axis machine tool world. "In these economic times, we knew we were taking a risk to make that investment, but we carefully researched the available options, and decided this was the best move for our shop," he says.

The process involved seeking out the suppliers of five-axis milling machines--most of which, Sharoni found, were highly priced and used for large structures. Not surprisingly, their footprints were large and their heights exceeded his shop's physical limits. He then discovered the DMU50 from DMG America, and its local technical center in Los Angeles.

"Most of our milled parts are smaller and shorter runs, in the range of 10-15 inches high and 24 inches long," Sharoni says. "We were doing everything on three- and four-axis machines, mostly Haas and Fadal. They were good and we did quite well with them, but we knew we were missing out on many jobs."

In the DMU50, the shop found a smaller footprint, affordable price, less power consumption, and more user-friendly control than expected, according to Sharoni. "All our operators were accustomed to the basic control, and they thought the CNC on this machine--a Siemens SINUMERIK 840D power-line--would be too complicated," he said. "But they found the exact opposite was true. The control is powerful yet very user-friendly. We were able to train our operators for both our day and night shifts in a short time, which really surprised us, since our operators had never run a Siemens control before."

One of the company's jobs was to produce a hydraulic manifold that had previously been made on a four-axis machine. Initially, the question was whether to make the part as a casting or a forging, but the quantities were too low and made both of those routes cost-prohibitive. The block of aluminum needed to be machined in a very complex set of convolutions, each requiring a separate set-up, owing to the number of internal holes on compound angles. Twenty-three set-ups were needed to make the part, resulting in a slow cycle and considerable scrap. Because each hole required a special set-up, there were 11 set-ups just for the internal holes. Also, foundation plates and custom blocks were needed to run this part, further slowing the cycle. It was a very precarious, tedious, and time-consuming job, Sharoni recalls.

On the DMU50, the job could be hogged out on the outside, and all port-holes, hydraulics, and even the inner holes machined without the need of separate set-ups. In the end, the part was made in four set-ups, reducing the machining time by two-thirds and the scrap significantly. "We went from walking to running overnight," Sharoni said. In comparison to the time that was necessary to complete machining of this part using a 4-axis machine, the DMU50 was said to have dramatically reduced the machining time by more than 60%.

On another job, an order of 30 pieces had been run, only 18 were delivered, and the others were being scrapped. When Sharoni informed the customer of the acquisition of the DMU50 and its inherent capabilities, the customer increased the order by an additional 20 pieces because of its rigid tolerances. The run time dropped from 20 hours to 4 hours, in that instance. "We went from a typewriter to a PC on this job," says Sharoni. He said the DMU50 produces his parts 95 percent finished, in most cases, requiring only a small lathe and milling operations on the clamped side and inaccessible areas due to limitations of the rotating carrier of the table. In another case, a customer had a sand casting part that was very difficult to machine because of the variations in the castings. BAR Engineering & Manufacturing has proposed to completely machine the part as an alternative to continue with the troublesome casting, or reinvest in a new casting process. The difficult part was machined in two days to the amazement of the customer, which now seriously considers a complete hog-out.

By adding a rotary table to the DMU50, a six-axis cutting theater could be achieved, resulting in even greater flexibility, more jobs, and increased profit, according to Asher Sharoni. With a 16-position tool changer, many of the jobs can be accommodated, though Sharoni says he will be looking for a larger tool changer on his next five-axis machine, already under consideration for purchase. The shop is also looking into adding a simultaneous five-axis machine, which would enable it to move into the arena of blades and impellers.

Virtually any drawing or e-file format can be accommodated, and the ShopMill program onboard the Siemens CNC can simulate the actual cutting path in a track-able sequence to determine the cycle time and prevent tool collisions. It also allows faster, more accurate quoting, while reducing scrap and time-to-first-part, Sharoni says. "The machine control actually modifies the part program, when needed, and that is a real asset to us, as we learn more about five-axis work on each shift."

In addition to the machine tool and CNC technology, Asher Sharoni cited the superior service and support he received from Udo Herbes and his team at the local DMG tech center, as well as from Daniel Martinez, the Siemens CNC end user support manager for the West Coast, as key influencers in his decision to buy from these companies. BAR Engineering & Manufacturing is considering purchasing more DMU50/70 machines as it positions itself as experts in machining more difficult parts utilizing 5- and 6-axis machines as standard operations.
 

Turbine Engine Parts Manufacturer Saves Money, Improves Production with Creep Feed Grinder Retrofit

The Honeywell Engine and Systems facility in Greer, S.C., produces turbine engine components, working primarily in high nickel-based aircraft materials. Recently, three of the facility's creep feed grinders that were controlled by PLCs with positioning capability had become prone to failures and crashes, and two of the machines were no longer in use. The Honeywell unit decided to retrofit all of the machines with CNCs and turned to Brooklyn Technical Services, of Brooklyn, Conn., for assistance. Brooklyn Technical Services specializes in the retrofit and rebuild of creep feed grinders and roll grinders, working on brands such as Blohm, aba z&b, Maegerle, and Waldrich Coburg. The firm's owner, Cliff Divine, had previously retrofit six machine tools at the customer's facility with CNC packages.

"My objective here was to devise a cost-effective retrofit solution that would be easy for the machine operators to utilize," Divine explains. "I selected the Siemens SINUMERIK 802D for this grinding application, because it provides a lot of value for the customer in a compact package. In addition, Brooklyn Technical Services was one of the first retrofitters to use the 802D in a grinding application and we had excellent results for our customers."

In this case, the existing onboard components of the creep feed grinders also lobbied for the CNC that was chosen, according to Divine. "Because the machine had Siemens analog servo drives and motor packages, we were able to save a significant amount of money," he said. "By using a Siemens ADI4 interface board, we were able to use all the existing servo drive and motors."

For this application, Brooklyn Technical Services initially developed a series of custom dressing and grinding cycles, which utilize a series of permanently definable user variables. In this case, the retrofitter was able to assign a series of plain text commands into the user data table. The value that the operator enters is stored until the operator changes that value. Divine noted that other controls required the entering of this information at each use of the cycle. By using plain text, the operators are more readily able to recognize the use of each variable.

"Who knows what the programmer has user variable R20 designated for?" says Divine. "Or what letter 'B' signifies, when in one cycle it might mean grinding feed rate and in another cycle it means dress amount?  Simple language like grinding feed rate, wheel surface speed, and dress amount are much easier and faster for the operator to understand. And, there are fewer chances for error." He also explained that Brooklyn Technical Services is able to place checks within the part programs to verify that the values entered by the operators fall within a specific range, thus preventing crashes and scrapped parts.

The Siemens SINUMERIK 802D combines all CNC, PLC, HMI, and communication tasks in the panel control unit (PCU). This maintenance-free PCU integrates PC-based hardware and the PROFIBUS interface for the drives and the I/O modules. The CNC can control up to four digital feed axes. The spindle is also fully controlled by the PCU. In addition to the digital interface via PROFIBUS, it also offers an analog interface for the spindle.

In this application, the CNC controls the axis and spindle movements of the creep feed grinder. The programs are stored in the machine's memory, and the CNC is linked to the host DNC at the customer location. "Because the user data are all plain text and the values stored remain after each cycle, the operators find the set-up to be very easy and fast," Divine adds. "We provided set-up programs that allowed the operators to jog the grinding wheel to the part and automatically calculate and load the fixture offsets. Our initial dress program sets the wheel diameter and pre-dresses the form into the wheel without operator intervention."

Since the retrofit, the machines have been running for nearly a year, and, to date, no crashes or machine failures have been reported. As Honeywell manufacturing engineer Dan Hicks comments on the retrofit, "It's the best grinder I ever saw for $35,000 (the cost of the retrofit)."

Brooklyn Technical Services has served the aerospace, hydraulic pump and motor, paper industry, and job shop market sectors since its inception in 1993. The company has developed a reputation for CNC retrofitting and currently installs all levels of controls on the machines that they rebuild.

Commenting on the support that Brooklyn Technical Services receives from its CNC supplier, Divine said that the people in the Siemens controls applications department are "some of the best" he's ever encountered. "I chose to work exclusively with Siemens some years ago, because of their application engineers," he says. "The sales engineers have worked with me to specify the right control for each application. Often times, they've been able to satisfy my requirements, when other CNC suppliers said they could not. When I purchased my first CNC from Siemens, they sent an applications engineer to my facility to train me. I was amazed that they did this at no cost. Other CNC suppliers wanted to charge me by the hour for their training."

Divine further notes that the Siemens CNC packages are adaptable to his machine needs. "Through the use of their machine data tables, an integrator can easily enter the pertinent data on the machine. It seems every eventuality has been incorporated into these controls. Siemens has already integrated most of the components. Through the use of function blocks in the PLC, there is little needed to set up the machine control panel or the set-up panel; even the display is predefined. This approach has saved me hundreds of hours of integration time."