Cranks and Pins Take a Spin
Technology focuses on least-cost production
By Jim Lorincz
CNC turning machines, by their very nature, are designed, built, and selected with specific characteristics and jobs in mind. Simplifying setup, controlling chips, and minimizing operator intervention are characteristics that can increase expectations of manufacturers for quality work at the least possible cost.
CNC lathes have progressed to the point where multifunction capabilities are almost expected, especially as parts become increasingly complex, and productivity through cycle time improvement and increasing use of automation are leading to untended operation. These machines are becoming less dependent on the operator"chasing the part" to manually intervene with offsets.
Machine-tool builders achieve these results with advances in technology that control vibration, provide thermal stability, and, as a result, roundness and accuracy. Typical approaches to achieving these results are found in today's technology.
- Large scale machining
- Simplification of setup
- Modular design
- Cellular configuration
- Simultaneous machining
Machine-tool builders incorporate these design approaches to maximize turning performance with an eye on markets as varied as precision-machining contract manufacturers to the transportation and automotive industries and OEMs who supply the beefy machines that pump oil, move earth, and power electric-generating equipment.
Oil-country machining still heads the list of hot markets for turning center manufacturers. Leadtimes have stretched out, taxing the ability of builders to meet demand and leading to developments in machine technology and cellular combinations. Okuma America Corp. (Charlotte, NC) and its Partners in Thinc have brought automation to an oil-coupling cell that combines the capabilities of the Okuma Lathe Oil Country (LOC), the LOC650 and V80R vertical turning lathes, and an overhead Fanuc gantry robot. The principal challenge: establish the machining process to run uninterrupted by operators who need to stop the machines to remove chips, from chuck jaws, robot grippers, and the like.
Scoring in oil country, however, is not the Partners in THINC collaborators only recent conquest, as it continues its participation in the motorsports industry by extending its technical partnership with Richard Childress Racing (RCR; Welcome, NC) through 2012. Developed in 2001, the Okuma Technology Center (OTC) at the RCR campus has eight Okuma CNC machines, including grinders, lathes, and machining centers. The total will more than double in the near future.
"The Okuma Technology Center will be moved to a larger building on the campus so Rick Grimes, manufacturing manager and his team can expand their product line and increase their total output beyond the already tens of thousands of pieces they manufacture each year," says Richard Childress, RCR president and CEO.
A motorsports manufacturing highlight for the newly expanded OTC is the Multus B300BB/SBW multifunction turning center that is currently machining test cuts for two aluminum pulleys for RCR's NEXTEL Cup and Busch Series racing teams at the Partners in THINC facility. "We use an ABB robot to load and unload the machine, and Marposs gaging for post-process gaging of parts," explains Jeff Estes, director of Partners in Thinc. "All of the machining data are linked into the Kennametal Toolbox and the Zoller Presetter.
"Feedback from the postprocess gage is immediate enabling us to make any adjustments that need to be made before the next part is run," says Estes. "An important benefit is that incorrect keying in of numbers on a key pad is eliminated, avoiding crashing the machine or losing the tool," he says.
The Multus cell differentiates between which of the two independent parts are being run simultaneously with a vision system on the ABB robot, which identifies the part and communicates with the control so that the correct program is called up.
Partners in THINC is an Okuma initiative that includes 27 partners: ABB-Auburn Hills, BigFix, BLUM Lmt Inc., Brown & Sharpe (a division of Hexagon Metrology Inc.), Caron Engineering, ChipBlaster Inc., Extrude Hone, Fanuc Robotics America Inc., Gosiger Inc., Infinity Rebuild, Iscar Metals' Exact Software-JobBOSS, Kennametal, Koma Precision, LNS America Inc., Marposs Corp., Midaco Corp., Okuma America Corp. Renishaw, Sandvik, Schunk Inc., Shell, Symatec, Trend Micro, Wilcox & Associates, Zeiss, and Zoller.
Sometimes winning machine tool business means being positioned with a supply of the right machines when a market is ready to take off. Romi Machine Tools Ltd. (Erlanger, KY) had the right machines ready for the continuing demand in the oil and gas industries. Romi was able to meet demand for its M33 and M43 CNC lathes with 33" (838-mm) swing and 9.9" (251-mm) through-holes, and 43" (1.1-m) swing and 14.7" (373-mm) through-holes, when they were needed.
Next up for Romi is the introduction of a CNC combination lathe that couldn't be farther in size and scope from the behemoths it produces for the oil patch. Romi is aiming its C420 combination lathes at smaller shops, short-run small parts, secondary-operation work, and tool and die shops. The C420 is positioned as an entry-level CNC that has an easy-to-use control that graphically portrays each step in the machining process, making it well-suited for the role as a teach lathe.
The lathes will be offered in two packages: one has a manual tailstock, an 8" (203-mm) chuck, and quickchange manual tool post; the other has a pneumatic tailstock and footswitch, 8" pneumatic chuck and footswitch, and eight-position electric turret. These machines will come with the Siemens Sinumerik 802D sl control.
New bigger machines continue to be developed for the oil and energy services industries and for heavy equipment manufacturers, in response to continued strong demand. When Mazak Corp. (Florence, KY) held its Mazak Energy Expo at its Houston Southwest Regional Headquarters and Energy Services Technology Center, it rolled out the largest Nexus QTN 450-II M multitasking turning center to date. It provides 120" (3 m) between centers, 7.2" (182-mm) bore, plus deep drilling, boring, and honing capability.
The Nexus QTN 450-II M features an integrated high-torque spindle and programmable tailstock. It offers 1761 lb-ft (2388 nm) of torque from its optional 50-hp (37-kW) integral spindle motor and 6.5" (165-mm) through-hole—a 7.2" (182-mm) through-hole is optional. A 12-station drum turret holds rotational tools driven by a 10-hp (7.5 kW), 4000-rpm milling spindle for milling, drilling, and tapping, in the same setup.
The QTN 450-II M at the Energy Expo was equipped with a modified NC-programmable tailstock with a special toolholder instead of a center to drill, bore, or hone large-diam bar or shaft workpieces. Once a tool is set up, the specific process is automatic, reducing throughput time while freeing the operator for other jobs.
The modified tailstock can travel 96.25" (2.4 m) when the machine is equipped with a steadyrest or 116.13" (2.9 m) without. The tailstock provides up to 2923 lb (13,000 N) of thrust, and an optional fully automated steadyrest can support workpieces ranging from 1.96 to 7.87" (50–200-mm) diam.
For hard turning and hard milling, Hardinge (Elmira, NY) has introduced its RS-Series of Super-Precision turning centers. The RS series features a quickchange, collet-ready spindle for such applications as those found in the medical device, automotive, and aerospace industries, among others. Materials harder than 80 RC can be machined.
"With the RS-Series, we have the ability to maintain tighter tolerance over time so that you have less human intervention, chasing an offset to maintain the tolerance," explains Jeff Ervay, product manager-turning. In addition, the RS-Series models feature the Eppinger Self Alignment (ESA) top-plate tooling system.
"The ESA top-plate tooling system enables us to have every station checked to be on centerline in the Y plane," says Ervay. "That capability is especially important for live tooling such as small-diam drills, reamers, and end mills that are running at 8000 rpm. They need to be exactly on centerline. Using the ESA system, we are able to adjust each individual station to run as true as it can on centerline. This capability is especially important in hard turning, where a high or low tool will produce poor results, such as bad surface finish, excessive tool wear, and poor roundness. The ESA system eliminates that concern because the tool is on centerline."
The advantage of the quick-change, collet-ready spindle is that the need for an adapter is eliminated, putting the work closer to the spindle bearing where closer tolerance and part roundness are achieved. "We grind the taper right into the spindle for precise location of our collets. You might say it's an advantage if you have it. Customers will always find a way to get the finish and accuracy they require, even if it means they have to add another process like centerless grinding. The unique collet-ready spindle helps in this regard, as it helps minimize extra part handling due to processing components on the same machine," says Ervay.
The RS-Series is designed to have automation in the form of gantry systems, robots, stacker tables, and devices of that type integrated. Also, Hardinge has a turnkey department to offer engineered solutions.
Delta Hi-Tech (Chatsworth, CA) depends on machine flexibility to produce simple to complex parts using the RatioLine of mill-turn centers from Index Corp. (Noblesville, IN). Shaft or chucked parts are processed by identical main and counter spindles that allow complete machining in a single setup with up to four live tools in the cut at once.
The complement of Index and Traub turning centers is enabling Delta Hi-Tech to handle parts for applications in the electronics, communications, machine-tool spindle, medical part, and aerospace industries in varying volumes, faster and faster. "We learned how to manufacture very high quality parts with Index and Traub, and put ourselves in a very good competitive position," says Joe Ostrowsky, Delta Hi-Tech president and owner.
Five Index Y/B-axis G200 machines with spindle-through bar capacity of 2" (50.8 mm) feature two turrets capable of holding up to 32 live tools. Two tools can be in the cut at all times, reducing cycle times, and the Y/B axis permits inclined off-center drilling and milling. The Y-axis slide is configured as a quill for rigidity, and the B axis is driven by a torque motor, providing a feed axis for fifth-axis interpolation.
The tool magazine for the G200 includes four disks, each with a 40-tool capacity. A SCARA-type gripper picks and loads the tools into the spindle within the machining cycle, and the G200 is equipped with a motor spindle as a tool carrier in conjunction with the tool changer.
The company also has two G200 compacts without Y or B axes, as well as an Index C65 automatic CNC turning machine with three turrets and as many as 42 live tools, with the possibility of having three tools in the cut at once. The company also uses two Traub TNL26 CNC Swiss fixed and sliding-headstock machines to supplement production of a brass fiber-optic lens component that is machined on three G200s.
"We are a job shop, so we take jobs that may be two or three pieces to half a million parts," explains Juan Carlos Casarrubias, CNC programmer. "This year, we are looking at 750,000 pieces of a brass fiber-optic lens component with tolerances of ±0.0003–0.0000" [0.008 mm], but the Index G200 has no problem holding it. Everything else on the part is +0.0002" [0.005 mm], with diam tolerance of +0.0004–0.0000" [0.010 mm]. We have special cutting tools for this part, but regardless of the tooling, if the machine was not highly repeatable, it would not matter. The brass fiber-optic lens components is dropped complete, needing only minimum tumbler deburring, before plating. Cycle time on the G200 is 2 min and 10 sec."
For high-volume production, Mori Seiki USA Inc. (Rolling Meadows, IL) has introduced its NZ series of multi-axis machines for high-volume production machining of bar, shafts, flanges, and precision equipment. The NZ2000T3Y3 features three turrets with built-in milling motors and a Y-axis function. Within the NZ series, users have the option of selecting from two turrets without a Y-axis function to three turrets with the Y-axis function. "The NZ version with three turrets has 16 stations on each turret, so that three turrets can be cutting simultaneously on two spindles to bring cycle time down," Jeff Snow, applications manager, explains.
The NZ series is available in the NZ1500 6" (152.4 mm) and NZ2000 8" (203.2-mm) chuck versions. "The NZ series is designed for high production complex turning, where the users would have to do two-axis turning and then take the part and put it in a machining center for milling, drilling, and the like. It offers the opportunity for one setup completion of a finished part in untended operation," says Snow.
"The NZ, which is a multiturret version of the successful series of CNC lathes, can certainly do anything that a 30-taper machining center can and most of what a 40-taper machining center can," Snow points out.
Introduced in April in Chicago by Mori Seiki, several NZ machines have been shipped and test cuts for hydraulic parts, valve spools, and Inconel fittings for fire hoses have spurred interest, particularly in the automotive industry, says Snow. A 3-D interference checking function that runs on the machine's MAPPS III controller enables operators to monitor the complex movements of the turrets in real time.
High-speed gantry loading of the Kitako HS4200i four-spindle CNC lathe from SB Machine Tools (Schaumburg, IL) is intended to accomplish smooth, untended operation with no idle time for part loading/unloading. The HS4200i boasts X-axis loading feed rates of 6700 ipm (170 m/min) along with carrier indexing time of 1.5 sec and 0.3-sec turret indexing per station.
Kitako's four-spindle technology cycles work from the loading zone to the machining zone and back again. Operating much like a pallet changer on a machining center, the system transitions parts in and out of the machining zone in as little as 8 sec each. The HS4200i's four spindles are mounted in a horizontal square pattern in a large carrier drum. The drum's positioning accuracy is ensured by a large-diam, precision-toothed, curvic coupling. Spindles are generally partnered as pairs, so that as the carrier is indexed 180°, two spindles rotate to the machining area as two spindles move out for loading and unloading. The two spindles in the machining zone, along with the respective slides and turrets, work simultaneously as well as independently.
Dual-slide flexibility offers a variety of part processing methods: two onesided parts can be machined in exactly the same time (AA/AA operation); if the two sides of a part are of near-equal cycle times, first and second operations can be done simultaneously (AB/AB); if the first and second cycles are significantly different, as in many applications, idle time can be eliminated by using an AA/BB approach.
The HS4200i's maximum spindle speed is 4500 rpm (5000 rpm optional). Each slide on the HS4200i features a high-speed, eight-station drum turret; chuck sizes are 8" (203.2 mm).
Available for the first time in the US for high mix and high-volume production, the TNW-3500R automated lathe from Fuji Machine America Corp. (Vernon Hills, IL) provides turning, drilling, and milling operations all in one machine. Twin spindles, a gantry robot, and slant bed are combined with a live-tool turret for secondary operations. Live tool motor power is 3/5 hp (2.2/3.7 kW). Automation is built in with a gantry loader with a capacity of 22 lb (9.9 kg) and dual 10-tool turrets.
The TNW3500R's A2–6 spindle is driven by a 15/20-hp (11/15-kW) spindle motor and operates at a maximum of 4200 rpm. The TNW-3500R is equipped with a work stocker with 12 stations, chip conveyor, and a set of turret holders, as well as the Fanuc 310i-A CNC control.
Cranking Out Large Oilfield Parts
The capability to tackle large parts can be a real competitive advantage, particularly for manufacturers in certain niche markets such as the oil industry. Adding large-part turning to an operation involves more than just buying larger machines, however as Norton Manufacturing Co. (Fostoria, OH) discovered. Founded in 1950, Norton is a manufacturer of crankshafts for engines, pumps, and compressors, working with forgings, castings, and billets to precision-machine machine crankshafts up to 6' (1.8-m) long.
Norton, which also produces cranks for farm equipment and aircraft engines, expanded into a new area—machining oilfield cranks. By their very nature, the cranks are much larger than those found in the automotive sector. Tolerances in critical areas can be just as tight, however, and Norton knew that to be competitive in oilfield, it not only had to add machining capacity, but it had to integrate the new operations into its existing processes.
CNC Programmer Matt Hoiles explains that Norton could transfer its existing base of knowledge to the new job. "With our automotive background, we're able to implement many of the same quality processes into the oilfield cranks. We can meet the demands for high quantities. We not only ship on-time, but we actually exceed deadlines because of our existing structure and expertise."
Jason Burt, Norton's engineering manager, explains that Norton's performance benefited from its existing quality initiatives. "We have to meet the demands of the automotive industry, so we practice lean manufacturing, and we are QS 9000 and ISO 9001-certified."
Norton integrated a large turning center with live tooling, the Johnford ST-130CS turning center from Absolute Machine Tools Inc. (Lorain, OH), into its operations. By using one large CNC lathe with live tools, the company added turning and milling capabilities without the need to purchase multiple machines. "Obviously, one machine takes up less floor space and requires fewer operators," says Hoiles, and the company is also able to handle larger cranks and more styles.
"With larger turning centers, we can take heavier cuts, which, in turn, reduces cycle times and speeds production," Hoiles says. Heavy cutting capability is particularly important, because Norton cuts oilfield cranks from 4140 steel bar into parts weighing as much as 4200 lb (1905 kg). In addition to the size of the machine, price and availability were important considerations, Burt says.
Bars are loaded into the ST-130CS turning center, which cuts down the ends to make the crank hubs. After the main diam is turned, Norton removes the crank and sends it onto other equipment for processing. In between these other operations, the crank returns to the lathe for operations including milling grooves, drilling holes, chamfering, and milling keyways. These additions operations require use of live tools and a 20-hp (14.9-kW) spindle on the turning center.
"We wouldn't be able to do half the operations we now do on the one machine without live tools. With the volumes we put through our machines, we need the capabilities to keep expanding," Burt concludes.
This article was first published in the October 2007 edition of Manufacturing Engineering magazine.