Contact us today:
Zimmermann portal milling machine features twin gantries, twin rotary 6-axis milling heads, twin CNCs with completely independent operability to machine parts up to 960 inches in length
Triumph Structures – Wichita, a Triumph Group company, brought a unique challenge to the engineers at Zimmermann (Novi, Michigan) and the solution has yielded various benefits to this major supplier of aerospace components. As Harry Thurmond – President at Triumph Structures – Wichita explains, “We had requirements for spars and stringers that often reached 22’ in length, but we also do a variety of production jobs on smaller sections such as bulkheads. This creates the need for fast, reliable and adaptable machine tools.” In this current mode of manufacturing, Triumph Structures – Wichita considered a variety of options to expand on the capabilities of their existing milling machines, some of which had been in operation for decades.
Triumph Structures – Wichita specializes in complex, high speed, monolithic precision machining and sub assembly of Aluminum and Titanium structural airframe components often with wall thicknesses down to 0.020 inches. Currently, 21 individual 5-axis machining centers are resident in this facility, with a maximum length of 960 inches. Over 20 other 3-axis and 4-axis machines complete the machining capability for aluminum structures. Triumph Structures – Wichita runs a gamut from build-to-print precision machining of aluminum and hard metal, small-to-large parts, especially aircraft wing spars, Skins, bulkheads, and landing gear components.
While the machine capabilities at Triumph Structures – Wichita were clearly substantial, it was determined that a need existed for a particular machine that could be used to serve multiple purposes. First, the machining of very long parts with volumetric compensation to manage material expansion and the tool tip position over a very long cutting cycle, often multiple days, was required. Triumph Structures – Wichita has extensive experience in this area, given its market focus. However, it was posited that a single machine might also be capable of running multiple smaller parts or operate in twin fashion, occasionally using the entire machine bed with both heads working the same part in tandem. Clearly, the latter scenario would demand extremely close attention to collision avoidance between the gantries, as well as the consistency of surface machining at the points where the twin machining heads intersected.
For the requirements presented by Triumph Structures – Wichita, the optimal machine necessitated that Zimmermann, a longtime partner and portal machine supplier to Triumph, modify its popular FZ100 machine with twin gantries, each equipped with a three rotary axis head and independent Siemens Sinumerik 840D sl CNC.
As Zimmermann Inc. President Matthias Tockook notes, “We had a variety of machine styles available, but the best solution was a head with three rotary axes, A-B-C integrated in a forked milling head. This provided simultaneous 6-axis cutting in a very compact design, with no pole position, less overall axis rotation, a constant feedrate capability and improved surface quality.”
The individual head machining time scenario was further detailed. If the maximum time was achieved using an A- and C-head with infinite C-axis, the alternative A-B-C integrated rotary axis head could accomplish the same work in 25 percent of that time.
In designing the final work envelope and machine structure, Zimmermann engineers determined the best solution was a removable break wall built into the midpoint of the machine bed, which would allow completely independent operation of the entire machine, literally running as two machine tools in one. When removed, the machine bed could accept parts up to 960 inches in length and process them using the twin heads working in tandem and monitored for total collision avoidance by the two CNCs onboard. Owing to the unique volumetric compensation feature of the Siemens CNC, where the execution of the machining is based upon the actual tool tip position, the point of intersection for the twin heads was found to be an easily addressed and resolved issue. Surface integrity on the workpiece would be preserved, while machine and operator safety would remain paramount.
This machine was built over a period of eighteen months. Parts were sent to Zimmerman to be fully tested prior to being erected onsite at Triumph Structures – Wichita.
In operation, according to Harry Thurmond, the Zimmermann head design provides significant advantages in speed on the typical peaks and pockets found in aerospace structure machining, working in tandem with the look-ahead feature on the CNC. “It slows down and speeds up in anticipation of the next required surface contour. Over long run times, this can translate into an improvement of 35 percent or better, because there is no deburring or polishing required. We routinely get better than a 125 RMS finish on inside pocket surfaces and up to a 32 RMS on the outside of the Series 7000 aluminums we run. Combined with the flexibility of the machine to work a single structure or individual workpieces simultaneously, we have been quite satisfied with the results to date.” On longer runs, Thurmond adds, the chilled coolant used on the Zimmermann is helpful in minimizing thermal expansion of the material, a critical factor in long run machining work here. An added advantage, the machine is used to produce workholding and fixturing devices. Lastly, Harry noted that the Zimmermann machine is equipped with test probes, so it can be used as a CMM to measure workpieces in process.
The 3-axis head avoids the pole position of the traditional 2-axis A-C head at A = 0º. In this Zimmermann head design, the B-axis moves +/- 15º inside a rigid curved guideway for handling the inner sloping and especially the pockets typically found on aero structures, so simultaneous 6-axis machining is achieved with high surface finish integrity.
The new machine at Triumph Structures – Wichita is further equipped with a stationary clamping table, fixed mounted side walls, DemTec composite fill on the base and side walls for enhanced stability and vibration damping. Backlash-free drives on both sides with rack-and-pinion mechanisms are sealed from contamination and guided on both sides. All axes have feed rates to 60m/min and accelerations to 4m/sec2. Each head can access a 60-position toolchanger on the machine.
For communication of data from the machine, Triumph Structures – Wichita integrates the CNCs into their Ethernet network via DNC and hard-wiring. Through a remote monitoring feature on the Sinumerik 840D SL CNC, Zimmermann is also able to maintain awareness of all conditions on the machine in real-time.
At Triumph Structures – Wichita, design to CENIT CAM post-processor operations are done through Vericut simulation at the CAD station.
Harry Thurmond notes, “We had grown steadily over the last decades, since our incorporation of 5-axis work in the 1990s, and were ready to jump to a new level of competence for our customers, who represent the top players in both commercial and military aircraft, making Triumph Structures – Wichita a more value-adding supplier. Our part length capability had been 22’ here in Wichita and we were committed to expanding it, to compete in the 40’-80’ part ranges. As with all aerospace structure machining, material removal rates are extremely high. We can start with a 5600 lb. workpiece that ends up at 100 lb., for example.” Harry further noted this means the machines at Triumph Structures – Wichita must be very robust with high-precision control of the cutting cycles, which often run for multiple days.
Commenting on the CNC selection, Matthias Tockook of Zimmermann observed, “With all the challenges we had on this machine, including the axes of motion, the integration of the twin gantry movements, the substantial safety factors involved and the need for independent and also co-dependent gantry operations, we quickly determined that only twin Sinumerik 840D sl CNCs could handle this job.” The machine built for Triumph Structures – Wichita also includes Siemens servo motors and drives plus spindles running at 73kW/95HP and 27,000 rpm in operation.
Triumph Structures – Wichita specializes in complex, high speed, monolithic precision machining and sub assembly of Aluminum and Titanium structural airframe components.
For more information on this story, please contact:
Siemens Industry, Inc.
Drive Technologies — Motion Control (Machine Tool)
390 Kent Avenue
Elk Grove Village, IL 60007
Attention: John Meyer, Manager, Marketing Communications
Others involved in this story may also be contacted:
Zimmermann Inc. — Portal Milling Machines
24371 Catherine Industrial Drive
Novi, MI 48375
Attention: Matthias Tockook, President