Technology Shapes Shop Ambitions
Sizing up innovations; can they provide value on the toughest jobs?
By Jim Lorincz
Technology advances in machining centers—horizontal, vertical, and universal—have been coming fast and furious. Controls, cutting tools, and automating equipment have extended the reach of machining centers whether for one-off contract manufacturers or for production-oriented OEMs. Transitioning from the not-so-hot industry to the hot industry (and back again, if necessary) requires technology designed to meet the challenge. And those challenges may be posed by applications as diverse as aerospace, medical, energy, or even automotive. They come in the form of larger and larger workpieces made from the toughest materials, or the smallest, thinnest, and most delicate parts. Technical innovation can mean everything when assessing a machine's ability to meet the task at hand.
In its growth path from prototype shop to precision manufacturer, Proteus Manufacturing (Woburn, MA) sought and obtained the precision aluminum machining capability required for optical and defense components like housings for cameras, lenses, and assemblies. As volume requirements and demand for the kind of precision that requires extensive testing, inspection, and control increased, the company found itself at a crossroads. John Tamulynas III, president, explains: "We discussed our situation with our machine tool supplier, Methods Machine Tools Inc. [Sudbury, MA], who recommended that we transition from multiple VMCs to an automated HMC." Proteus purchased a Kiwa KH-45 six-APC HMC. Working with the HMC quickly dispelled any concerns he might have had about the virtues of horizontal vs. vertical machining centers.
As it turns out, Proteus was very pleased with the horizontal leap, primarily because of how the Kiwa H-45 reduced cycle time, moved the company into lights-out automation, and freed up more spindle time for other, previously strained operations. General Manager Bill Burris explains: "In the first two roughing ops, on one of our main machined components made of aluminum, the Kiwa reduced the cycle time by over 30%, and the pallet system has allowed us to go from one part to four parts at a time and run lights out. By putting our four to five jobs in one machine, we have opened up other spindles on other machines, creating more overall versatility and increasing productivity throughout our operation."
The KH-45 offers in-the-field expandable tool and pallet technology, including the ability to expand from a two-pallet machine with 120 tools to a six or eight-pallet machine with 220 tools. It features a 400-mm pallet, and travel and work envelope of 29.5 diam x 39.4" (750 x 1000 mm), and can handle a table load of 1100 lb (500 kg).
Machining center strategies are traveling along two distinct machining routes: robust heavy-duty machining of tough materials, and increasing size of machines for aerospace, power generation, and energy jobs, among other applications, according to Scott Walker, president, Mitsui Seiki USA Inc. (Franklin Lakes, NJ).
"The tendency in machining center design is to have stiffer, more resilient machine frames, higher-torque spindles, and stronger drives to push tools through tougher materials. At the same time, five-axis trunnion-style machines are getting bigger and bigger, with up to 2.5-m clearance on the trunnion. What has happened is that aerospace manufacturers are putting larger pallets on the five-axis machines to accommodate longer or larger workpieces, or to be able to fixture a complete ship set. To build helicopter rotor hub assemblies, nose and window assemblies, engine assemblies, or landing gears, they would like to put all the pieces up for machining at the same time, machine them, and ship them as a completed set ready for assembly," Walker observes.
To satisfy new aircraft and power-generation production requirements, Mitsui Seiki has released several four and five-axis machining centers. The new four and five-axis HMCs are designed for aerospace and energy applications, including airframe components, propulsion systems, landing-gear assemblies, wind-turbine gear boxes, and gas-turbine power-generation systems. Five-axis HMCs can handle a work diameter capacity of 2500-mm, 3-t work/fixture weight capacity, and a variety of increased axis-stroke options, and feature larger pallets than previous models and high-torque spindles (2700 Nm continuous). Capacity improvements for four-axis HMCs include new quill-type spindles for deep-boring operations, 5 and 10-t work/fixture weight capacity, up to 3-m axis stroke, high-torque spindles (2700 Nm continuous), and—like the five-axis models—tuned structure for heavy cutting in hard metals, large-capacity FMS systems, and the Fanuc 30i CNC.
For robust five-axis machining, Heller Machine Tools (Troy, MI) has introduced its F series five-axis HMCs with HSK 63 or 40-spindle taper and three different workhead configurations. "The machines combine a high-torque spindle with five-axis machining capability, well-suited for medical, aerospace, and mold and die industries, and for machining complex, difficult-to-machine parts in a single setup," explains Heller's Tracy Ellis. The reason for the three different high-performance spindles is the need to machine smaller, lighter parts, frequently from tough materials such as titanium, or aluminum parts that benefit from high-speed machining.
Two types of F-series machines are available; the FP and the FT versions. The FP 2000 and FP 4000 models are five-axis machining centers with a pallet changer intended for complex shapes or five-sided machining in production houses. The FT 2000 and FT 4000 models feature fixed tables for high cutting capacity and the best possible surface finish. Use of a C head or tilting head provides the fifth-axis capability. The FT 2000 and FP 2000 models have X, Y, Z strokes of 630 x 630 x 830 mm; the FT 4000 and FP 4000 have X, Y, Z strokes of 800 x 800 x 1000 mm.
Spindle technology is at the core of the new F-machine series. Three different designs are available on all models: the PCU 63 high-torque universal head; the SCU 63 speedcutting universal head, and the SCT 63 speed-cutting tilt spindle for high-speed cutting. The two swivel-head units are well-suited for complete machining of contoured surfaces of any kind, such as five-axis simultaneous machining of aerospace and medical applications.
Ellis explains: "Heller engineers determined that the most flexible, robust, and efficient way to do five-face and five-axis machining is to have one of the axes in the workhead. Using a B-axis table in combination with a universal or tilting workhead allows greater table loads, larger working envelopes, greater accessibility than five-axis machines that have two axes of motion under the workpiece, such as a tilt/rotary table or C-over-B type." The new F-series machines are compatible with all Heller automation including pallet pools, pallet magazines, and robotic solutions.
Handtmann CNC Technologies Inc. (East Dundee, IL) is well known for building gantry-style machining centers for large workpieces. For smaller workpieces, Handtmann has designed and introduced the five-axis HBZ Compact-Cell HMC for machining workpieces in the 2 x 1-m size segment. For workpieces starting from 4 x 2-m size, the company had already gained the benefits of HMC design, i.e. high material removal rates and efficient removal of chips and coolant, in designing its HBZ AeroCell.
The HBZ CompactCell is intended for applications in general metal machining, the automotive, aerospace, mold and die, and solar industry, and for machining materials from plastics, to aluminum, to steel, whether in a three-axis or five-axis mode. The machine uses high-frequency spindles rated to 75 kW, and spindle speeds to 30,000 rpm, as well as high travel speeds and accelerations to achieve high metal-removal rates in a compact footprint. Loading/unloading in the horizontal position is easily done in front of the machine. The machine is accessible from all sides, and automated loading can be accomplished with crane, rail, or pallet-storage systems with a handling portal.
Highly regarded for its transfer line and flexible-machining technology, Grob Systems Inc. (Bluffton, OH) has expanded the capability of its universal G 350 five-axis stand-alone HMC to accommodate thin, cylindrical workpieces. Key design innovation in this machine is a rotary table with a part support that enables production of workpieces for tool, turbine (aircraft), and medical device manufacturers. Specific applications require boring bars with complexly arranged inserts for seats and turbine blades. The five-axis machine works for both applications with its two rotating axes both in the table of the G 350. Blade machining, however, requires a high level of dynamics due to the abrupt reversing points at the blade transition from one 3-D surface to the other.
"A large tabletop would be problematic for small, thin, and complex workpieces, which need their entire surface to be machined," explains Bob Ruelle, account manager who is responsible for Grob's standard machining centers. "Longer tools with a greater projection would be necessary, and the risk of collision would be increased. We developed the small table and noticed that it is useful for more than just machining cutting tools and turbine blades. It can be used for parts for optical electronics, medical technology, tools, and molds used to produce electrodes."
To clamp thin, cylindrical parts vertically, a lot of space is required. "We built a table option for workpieces with a diameter of only 250 mm. In contrast, the standard table measures 570 mm. The small table has a rigid backbone for the 375-mm distance between the table surface and the tip of the support for clamping both sides. To radially clamp and hold the workpiece, instead of using fixtures corresponding to the workpiece, normally a three-jaw chuck can be designed for the rotary table."
Up to four hydraulic couplings are provided on the table for hydraulic clamping and unclamping, either through manually adjustable valves, or, optionally, through proportional valves controlled by the CNC. The stroke required to clamp different parts is adjusted by a hydraulic flow meter (at 120 bar/1740 bar) for ease and safety. Loading options for the G 350 HMC include robots, linear portal, rotary part changer, and manual loading.
MAG Americas (Cincinnati) continues to spread eagle the high-end, large-part segment of the aerospace machining market with its five-axis profilers and its newly introduced modular HMCs for pump, valve, off-road, and other components. The HyperMach H4000 five-axis horizontal profilers are slated to produce aluminum airframes and bulkheads for the F-35 Joint Strike Fighter (JSF) and the CH-47 Chinook helicopter in a two-machine cell for Pacific Contours at its Spring Valley, CA, facility.
This represents the second acquisition of MAG's high-velocity platform for tight-tolerance machining on multiple surfaces. The first was a six-machine H4000 cell for Brek Manufacturing (Gardena, CA) for precision machining of complex structures for defense and commercial aircraft programs. The H4000 is a high-speed, high-power five-axis contouring machine with full portal construction, a fully enclosed cutting zone, and material handling for precision machining of large aluminum plate and forgings. The two-machine, multipallet cell will use MAG's Cincron cell controller and automation for untended 24-hr operation.
Modularity in machine construction is providing MAG HMCs with a variety of configurations. The modular Specht 500/630 HMC sports "green design" that, among others things, allows it to sleep when idle, eliminates warm-up time, requires half the coolant and one-third the air extraction needs of previous designs, enables the machine to cut dry, wet, or MQL, and be compact—just 1.8-m wide. Modular configurations include linear-motor or ballscrew drives, CAT 40 through HSK-100 tool interfaces, six spindle options, four control options, and three five-axis configurations tailored to requirements from one-off work in job shops to agile machining lines. Control options include Fanuc 32i and 31i, Siemens 840D, or Bosch Rexroth MTX, and software options include MAG's Freedom eLog web-based production management system, Freedom eView, and Omative Adaptive Control.
For high-precision machining of components for large aerospace, power-generation, pump, valve, and off-road equipment, MAG has expanded the head options for its HMC 1250/1600 by adding a new 180,000-position Aaxis tilt spindle for five-axis horizontal machining. The 6000-rpm, 46-kW tilt spindle joins the 10,000-rpm, 56-kW spindle, high-speed 24,000-rpm spindle; the high-torque 2600 Nm spindle; and two live spindles as headstock options. The high-torque 80-kW spindle is well-suited for aerospace titanium cutting. The live spindles extend W-axis reach by up to 800 mm, enabling deep-cavity milling to high precision with shorter, more rigid tools.
One of a select few machine-tool builders that still designs and manufactures its own CNC control, Milltronics CNC Machines (Waconia, MN) is readying its next generation all-digital control, the 8200, for introduction at IMTS. According to James Broz, director of new product development, the 8200 is a real-time, RT Linux-based, all-digital control with faster, quicker, and better number crunching capabilities, especially applied to multiaxis machining, including five-axis or mill-turn machining.
Milltronics' Twin Table machining centers feature a rigid bridge-type platform with the capability of being configured as two 22 x 26" (559 x 660-mm) tables or one table measuring 44 x 26" (1118 x 660 mm). The TT series of machines are available with 24, 40, 60, and 80" (610, 1016, 1524, 2032-mm) Y-axis travels. "The TT machines are targeted to expand Milltronics' market position," says Broz. "Being bridge-style machines, they exhibit more rigidity than typical pallet-changing machines." The company's HM family of machining centers features four-sided machining with a rotary table or can handle large mold machining. A new small-travel VMC, the VM2016, will be introduced at IMTS, and showcased along with the 8200 control.
B.K. Tool Co. Inc. (Fairfield, OH) depends upon drilling, tapping, and milling operations provided by Feeler vertical machines for components made from materials ranging from aluminum to stainless. Destined for use in products such as printing presses, conveyors, or other assemblies, the components require consistently accurate machining. Mike Reed, machinist and part owner, credits the Feeler machines with being "stronger and heavier than other machine tools in our shop, resulting in less vibration during machining, so they make better cuts and are reliable."
In error situations, for example a blown fuse, the Feeler machines automatically shut down, preventing potentially costly repairs. "This is in contrast to some of the other machines on our shop floor that have required expensive servicing or tool changer repairs," says Reed. "Of course, dependability doesn't end at the machine. Service and support are important factors as well," Reed notes. Feeler machines are supported by engineering and service from Methods Machine Tools Inc. (Sudbury, MA).
This article was first published in the July 2010 edition of Manufacturing Engineering magazine.