Multitasking machines not only enhance productivity, but they also improve quality
The appeal of multitasking machining isn’t difficult to understand. Multitasking machines overcome some limitations of conventional machines and work their own special brand of magic in subtractively processing parts. From the earliest mill-turn machines to today’s most advanced multifunction machines featuring simultaneous processing, manufacturers have recognized that productivity-enhancing multitasking machining and quality go hand in hand. The ability to drop parts complete in one clamping from one machine removes accuracy-robbing reclamping on a second machine and provides flexibility to quickly change over to meet short-run production demand. Innovative machine configurations and flexible workholding are expanding the limits of future multitasking machines.
Testing the Limits and Pushing the Boundaries of Multitasking
“One of the primary goals of multitasking machine development is to minimize any tradeoffs,” said David Fischer, lathe product specialist, Okuma America Corp. (Charlotte, NC). “Customers don’t want to give up any milling capabilities on their multitasking lathes and they don’t want to give up any turning capabilities on the multitasking machining centers.” Okuma’s Multus series of multitasking lathes are equipped with milling spindles capable of performance equal to its large machining centers. Spindles range from 6000 to 12,000 rpm and even 20,000 rpm and achieve metal removal rates that are on par with typical machining centers. In addition, technologies such as Okuma’s Turn-cut Function that were only available on machining centers in the past are now migrating to the Multus.
“There are several key features that make multitasking machines attractive to manufacturers,” Fischer said. “Producing a part conventionally requires an operator or robot to move the part from one machine to another. In each case, a misload is possible resulting in scrap or rework. With a multitasking machine the raw material must be loaded and a finished part unloaded. Everything else is handled by the machine, eliminating the intermediate steps where mistakes can happen. The ability to change from one job to another in a matter of minutes makes it relatively painless to respond to rapidly changing production demands. For example, interruptions for that hot job no longer result in multiple machine setups to make it. Just change out the jaws, select the program and run the part.”
Flexible workholding systems that enable this quick changeover are critical, according to Fischer: “Customers need to be able to change over quickly, moving between parts that differ significantly in size and shape. In the past, these systems were cumbersome with large overhangs that resulted in restricted working ranges and loss of rigidity. The latest systems are a big improvement over the older systems being much more compact and extremely rigid. For example, we have a cell in our showroom that uses a Multus B300 multitasking machine that is tended by a FANUC robot that loads and unloads parts but also loads and unloads different pallets onto the face of the chuck. This allows the cell to change over completely automatically in about a minute. With this type of system a customer can move from one part to another without any operator intervention. Vision systems on robots are another technology that simplifies the automation of multitasking machines. With vision systems, the robot can find the part without specialized and expensive in-feed conveyors. Low-cost flat conveyors can be used and the operator can place the parts on the conveyor at random and the robot will locate and if required orientate to the part,” said Fischer.
Productivity Centers Feature Integrated Pallet Transfer, ATCs
“The idea of the ICON flexible series of mill-turn machines is to offer a cost-competitive precision machining solution with easier changeovers on the lower volume type products compared with traditional special-purpose rotary dial machines,” said Rodger Boswell, vice president-sales, ICON Technologies Division, Hydromat Inc. (St. Louis). Available in three versions, the ICON 6-150 and 8-150 for workpieces with 6″ (150-mm or smaller) cube and the ICON 6-250 for workpieces 10″ (250-mm or smaller) cube, ICON turn-mill machines feature machining stations equipped with four-axis machining modules with cartridge-style motor spindles from 10,000 to 60,000 rpm. Each machining module is equipped with its own 12-position toolchanger for a possible total of 96 tools available on a fully equipped 6-250/8 station model.
Target workpieces for the ICON 6-150 and 8-150 mill-turn are parts that are typically produced on single-spindle Swiss machines, VMCs and HMCs. The ICON 6-250 is designed for larger workpieces like those for automotive manifolds and ABS parts. One significant difference between the smaller and larger mill-turns is that a total of four three-axis modules can be mounted from the top of the ICON 6-250 machine so that there can be two spindles cutting simultaneously on the workpieces at four positions in unison.
Each 6-150 or 6-250 machine has four CNC rotary tables installed on stations 2, 3, 5, and 6 with position accuracy of ±4 sec. Each table is equipped with an EROWA zero-point clamping system to securely and accurately clamp the base pallet to the table with pallet positional repeatability of less than 0.002 mm. Workpieces are secured to the pallets using standard or custom workholding that bolts to the modular pallet systems. “Once the workpieces are secured to the pallets either externally to the machine or internally on station #1, the loading station, they are transferred to five other stations for cutting or auxiliary operations. With processes spread over four cutting stations, cycle times are greatly reduced yielding higher productivity in a smaller footprint over multiple stand-alone machining cells,” said Boswell.
New Multitasking Series Features Built-in Automation
The Nakamura-Tome NTRX-300 multitasking turning center from Methods Machine Tools Inc. (Sudbury, MA) features complete parts machining in one operation with a built-in load/unload automation system and advanced operator recognition management software. “The NTRX-300 offers state-of-the-art multitasking, automation, and software all in a compact heavy-duty machine,” said James Kucharski, national sales manager. “The NTRX-300 has the versatility and flexibility required for machining aerospace, automotive, medical, and other complex low-volume parts. Smart X Operation software makes it ideal for processing families of precision parts,” said Kucharski.
The NTRX-300 features true opposing twin spindles, either 8″ (203 mm) and 25 hp (18.65 kW) or 10″ (250 mm) and 30 hp (22.38 kW). The machine also features a 25 hp (18.65-kW) tool spindle with 12,000 rpm and full five-axis capabilities. The NTRX-300 can machine a 10″ square on the face of a part with no C-axis rotation required due to X-axis capability of 5″ (125 mm) below center travel and a Y-axis capability of 10″. The NTRX-300 is compact, taking up only 104 ft2 (9.66 m2) and rigid, weighing in at 37,480 lb (17,000 kg).
The compact NTRX-300 is available in two models: 8″ chucks with 2.5″ (63.5-mm) bar capacity or 10″ chucks with 3.15″ (80-mm) bar capacity. The NTRX-300 is designed with a long 53.15″ (1350-mm) distance between spindles to eliminate any interference of tooling during multitasking. The machine has a standard 40 tool ATC and is available with options for 80- and 120-tool ATCs.
“We’re pretty much on the cutting edge of multitasking technology with our new Nakamura-Tome (NT) Smart X Operation software,” said Kucharski. “Using Windows v. 8.1, it offers an operation-level management function to view operator clearance level. Productivity monitor function shows the status, productivity graph and capacity utilization of the machine, and a loading monitor function that offers detailed load information.” NT setting screen commands and buttons are all integrated into one screen, ensuring easy operation. The NT Smart X Screen enables an operator to view the NC program, while watching 3D interface check, or look at CNC coordinates while watching the machining area through a video camera.
CNC Replaces Multifunction Cam Bar Machining
The MS16 Plus multispindle lathes from Index Corp. (Noblesville, IN) feature six CNC spindles for turning, drilling, milling, tapping, deep-hole drilling, or slotting in each of its six spindle positions, machining bar up to 22-mm diameter. A high rate of production of precision-turned workpieces is achieved as workpieces are automatically indexed through the six positions, receiving two or more operations at each position. Design of the compact Index MS16 Plus is intended to provide the speed of a cam-controlled machine with the flexibility of CNC technology in no more floor space than a cam-controlled multispindle machine. In addition, the MS16 Plus offers exceptionally easy setup and more versatile machining options compared to cam-controlled machines.
The MS16 Plus features a total of 27 NC axes, including five NC grooving or boring slides, five NC cross-slides, one NC cutoff and/or back-boring slide, six work spindles, one NC synchronous spindle, drum indexing plus an additional five free NC axes of possible CNC-controlled auxiliary equipment. They are all controlled by an Index C200-4D CNC control. Each of the six spindle positions can include a highly stable grooving or boring slide with one NC axis and a cross slide with two NC axes (X and Z axes) that are arranged around each work spindle in a V-shape, allowing use of several tools simultaneously on each work spindle.
The speed of each of the six spindles can be controlled separately. Spindle speeds can be varied during cutting for each spindle position and each cutting edge of the tool. Speed changes and positioning of the spindles are possible even during spindle drum indexing, avoiding secondary processing times. For rear end machining, the MS16 Plus is equipped with a synchronous spindle driven by a hollow shaft motor allowing speeds up to 10,000 rpm. It can move 140 mm in Z at 30 m/min to engage more quickly several rear end machining tools on the NC cutoff slide with the X and Z axes in succession. To achieve the shortest cycle times possible, the synchronous spindle accelerates to a maximum of 10,000 rpm in less than 0.7 sec.
Multiaxis CNC Lathes Machine Complicated Parts
Chevalier Machinery Inc. (Santa Fe Springs, CA) manufactures, assembles, and tests its lathe spindles in-house in the same division as its industry-proven grinding spindles. CNC horizontal lathes and vertical turning centers are designed to meet a variety of industry applications. They include 8–32″ (203–813-mm) chuck slant bed CNC horizontal lathes with box or linear ways, 18–40″ (457–1016-mm) swing teach-in type CNC flatbed models, vertical turning lathes with 8–78″ (203–1981-mm) chucks, and multiaxis lathes with subspindle and Y-axis milling. Also for the energy industry, Chevalier’s FBL-500 series big bore lathes with 40″ swings and up to 157″ (3988 mm) distance between centers. The maximum spindle bore is up to 15″ (381 mm).
At IMTS, Chevalier will introduce two CNC lathes for machining complex workpieces with competitive pricing. “Machining highly complex parts requires more than simple two-axis machining,” said Herbert Hou, Chevalier’s national sales manager. “We are able to do more machining with the Y axis and live tooling capabilities, thus eliminating handling between machines, for more accurate and consistent production.” One of the Chevalier machines to be introduced at IMTS is the newly designed FNL-220LSY slant bed lathe with live tooling feature, an 8″ chuck, 24.4″ (620-mm) maximum swing diameter with up to 12.6″ (320-mm)maximum turning diameter and a maximum turning length up to 20.1″ (511 mm).
“Another important automation trend is using robots to load parts,” Hou said. “This is especially important for large CNC lathes like the FBL 360B slant bed, which we’ll be introducing at IMTS.” An integrated FANUC robot handles the heavy, large workpieces that its 15″ chuck can accommodate. “These are typically large oil industry parts that require turning the ID and OD and drilling holes in the flanges.” This machine is recognized in the market as FBL-360B, a 45° slant bed lathe with rigid boxways structure and programmable tailstock. It’s designed for mixed volume, short-run or dedicated high-volume applications and machining bars up to 4.5″ (114.3-mm) diameter at speeds up to 2500 rpm with a 35-hp (26-kW) motor with an optional 50-hp (37-kW) spindle motor, producing up to 1901 ft-lb (2577 N•m) torque.
Subspindle Lathes Get Jobs Done Efficiently
Multitasking subspindle CNC lathes from Ganesh Machinery Inc. (Chatsworth, CA) are designed to get the job done efficiently in only one operation. Axial and radial milling features are accurately timed and deburred without building fixtures for follow-on operations and tying up multiple machines and operators. Ganesh multitasking CNC lathe models start with the eight-axis Cyclone 70-3TMY with 70-mm bar capacity and three 16-station tool turrets for a total of 48 live tool positions. Complex work can be completed in just one operation with 7.5-hp (5.6-kW) BMT-65 tools on every tool station. The machine is also available in the smaller 52-mm bar capacity for “done-in-one” capability on Ø 2″ (51-mm) bar work on the Cyclone 52-3TMY. Both machines are also available with just two-tool turrets with 32 live tool positions.
The Cyclone 78-MSY can do “done-in-one” work with one live tool turret machining up to Ø 3″ (76-mm) bar stock or using 10″ three-jaw chucks. This 16-station BMT-65 servo turret can handle over 30 tools. Radial and axial-driven tools have full access to the fully synchronized main and subspindle. The 30-hp (22.3-kW) 4000-rpm main spindle and 7.5-hp (5.6-kW) milling spindles are optimized for efficient metal removal. The above heavy-duty machines are equipped with roller-bearing linear ways that provide twice the rigidity as ball-bearing ways, for more aggressive cutting with improved surface finish and superb tool life.
The seven-axis Cyclone CS-32 can machine up to Ø 1 3/8″ (34.9-mm) bar work using 27 tools, including 11 driven tools and nine backworking tools, in this very popular Swiss-style CNC lathe for efficient complete “done-in-one” machining. Work that has no, or very limited, live tool requirements can be efficiently processed on the six-axis Cyclone GTS-42 gang-tooled CNC lathe with a full-sized subspindle for work up to Ø 1 5/8″ (41.2-mm).
This article was first published in the May 2016 edition of Manufacturing Engineering magazine.