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Multitasking Machining


Done-in-one setup makes parts better


By Jim Lorincz
Senior Editor 


Multifunction machine tools have been around long enough in various configurations for manufacturers to appreciate their potential for cost-saving, quality production of parts from miniature connectors to transmission housings for off-highway equipment. Development of true multitasking machines, however, has removed them from the category of special machines.

Manufacturers have made them one of the fastest growing categories of CNC machine tools because they improve competitiveness. They offer the flexibility to meet just-in-time delivery of a variety of parts in smaller lot sizes. They consolidate the processes of many machines, improve accuracy, and save time formerly required for multiple setups as work was moved from machine to machine and operation to operation. Finally, they employ resources of people and capital equipment more efficiently, a definite plus that the most astute accountants can appreciate.

The most familiar multitasking machines are NC lathes with live tools in the turret, mill-turns, and Swiss turning centers. NC lathes with a Y axis that allows turrets to move from side to side have full milling or drilling capability. They can mill, drill, and machine off the spindle centerline. A B axis allows rotation around the Y axis for drilling at an angle or contour milling.

Machines described in this article range in price from more than a hundred thousand dollars to over a million dollars. That hardly qualifies them as commodity machines; yet, increasingly, these multitasking machines form the backbone of advanced machining operations for everyone from contract manufacturers to OEMs.

Trends in the design of multitasking machines include packing more punch into a limited and crowded work area with extra slides, more horsepower, even matching subspindle horsepower to that of the main spindle, putting more driven tools in the cut at the same time, and developing sophisticated software and controls for collision-avoidance, scheduling, and production analysis.

For machine tool manufacturers with extensive experience in building CNC lathes and turning centers, developing multitasking machines is a natural next step.

Romi Machine Tools Ltd. (Erlanger, KY) developed its multitasking E series turning centers to perform turning, boring, milling, and tapping in one setup in a machine with a compact footprint. The E 320 turning center can be configured with one or two spindles, C axis, live tools, and Y axis for mid to high-volume production. The left spindle features a belt-driven cartridge-style gearless headstock with a high-torque 25 or 35-hp (18.6 or 26.1-kW) GE Fanuc AC spindle motor with a variable speed drive.

The right spindle can match the left spindle with a similar 25-hp spindle motor. The slant-bed style E 320 series has a swing of 27.55" (700 mm), a maximum cutting length of 23.62" (600 mm), distance between spindle faces of 41.26" (1048 mm) and a cutting diam of 12.6" (320 mm). The E series includes an E 280 model, which features 15-hp (11.1-kW) spindles, as well as a double-turret, double-spindle E 220 model.

Quest multitasking CNC lathes from Hardinge Inc. (Elmira, NY) offer a wide range of options, including, in addition to the Y axis, live tooling, polygon turning, high-speed main and sub-spindles, C axis on main and subspindles, high-pressure coolant, air blast, tool touch probe, and part sensor. The Hardinge-designed and built jaw chuck/collet-ready spindle design permits faster spindle speeds for faster cycle times and maximum part rigidity as parts are gripped close to the spindle bearings, resulting in increased concentricity.

When equipped with Hardinge's patented HydroGlide hydrostatic linear guideway system, the Quest CNC lathes have the rigidity and precision required for hard turning, as well as the improved crash protection that hydrostatic design offers.

The concept of "done in one" rules today, especially as complex parts can be machined from bar stock or from solid, often eliminating the leadtime and expense involved to design and produce castings and forgings. Manufacturers have been quick to recognize and study their potential for maintaining critical tolerances between features by eliminating multiple setups and the time and accuracy lost moving from operation to operation.

At its Technical Center, Caterpillar Inc. (Peoria, IL) works in alliance with its machine tool suppliers to evaluate the potential of equipment and processes that can range from prototype work to production for next-generation Caterpillar equipment, according to Jim Reeb, director of manufacturing research and development. Caterpillar is currently working with Cincinnati Lamb's H5 Geminex series machine for machining and turning powertrain components.

The H5 Geminex machine is a flexible solution for processing medium-sized and large parts requiring milling and turning in a single setup, combining four and five-axis machining and high-speed turning.

"We're doing some horizontal types of machining and turning on ductile housings," says Reeb. "We'll develop the process at the Tech Center and once it's worked out, we'll release the machine to our Decatur, IL facility for installation and production."

Early experience with the potential of multitasking machine cells led Sandvik Mining and Construction (Sandviken, Sweden) to move production of its DTH (down-the-hole) rock drilling bits from the low-cost manufacturing environment of Mexico to Sweden in 2001. The DTH rock drilling bits are made from alloy steel forging blanks in 200 different types, of which 15 types are most frequently produced in batches varying from eight to 48.

Making the move possible was the performance of a multitasking cell featuring three Nakamura STS-40 super multitasking turning centers with robotic workpiece handling. The cell is able to perform all turning, milling, drilling, and button-hole drilling, including a hardening cycle, of the alloy steel DTH drill bits in five days with 12 operators. The previous conventional method required seven machines and 50 people. Standardizing on the Sandvik Coromant Capto interface and selecting twin-edge tooling with two inserts in each toolholder enable each machine to independently perform complete machining of drill bits.

The need to be competitive in its manufacturing processes is no less important to a machine tool builder than it is to its customers. In mid-November 2005, at the unveiling of its latest investment in advanced technology at its headquarters and manufacturing facility in Florence, KY, Brian Papke, president, Mazak Corp. said: "It is naïve to be committed to manufacturing in the US without a plan to become cost and price competitive."

To support production of its Nexus family of machines, many of which have multitasking capabilities, Mazak implemented lean manufacturing practices, including building to market demand rather than forecast and developing modularly assembled systems. A Palletech automation system for "done-in-one" manufacturing was installed. Production capacity for Nexus machines at its Florence facility has risen to 140 machines per month.

Manufacturing cells at Mazak's Florence facility feature Integrex multitasking machines produced by parent company, Yamazaki Mazak (Oguchi, Japan). Mazak has installed two Integrex-500HS multitasking machines teamed with robots for part loading and material handling within the flex cells. A large Integrex e-1060 V/8 multitasking center is being integrated with an existing HMC FMS to allow more flexibility in processing medium-sized machine components.

In its product mix, Mazak numbers 11 different Integrex multitasking models and another 20 models with some degree of multitasking capability. In recognition of the unique challenges in programming and operation of multitasking machines, Mazak has established a Center for Multi-Tasking and Manufacturing Excellence for training customers in all aspects of multitasking machining at its National Technology Center, which was doubled in size.

Following introductions in Japan last summer and at EMO 2005, Mori Seiki U.S.A. Inc. (Irving, TX) introduced its new NT Series of integrated mill-turn centers to the North American market in November. The NT Series is said to be the product of a complete rethinking of the design and construction of the multitasking machine with the goal of integrating milling and turning functions completely to deliver the same performance levels achieved by each process on dedicated machines.

The NT Series employs both DCG (Driven at the Center of Gravity) technology and the box-in-box construction of its NH Series horizontal machining centers, along with a turret with a built-in milling motor.

The NT Series comprises nine models with spindle, lower turret, and no center support options bringing the total number of variations to 66. NT Series machines have a B axis (± 120º) that uses a direct drive (DD) motor, eliminating backlash and making high-speed rotation possible. Maximum spindle speed is 5000 rpm with a maximum tool spindle speed of 12,000 rpm.

The turret with built-in milling motor first introduced with Mori Seiki's NL Series of CNC lathes reportedly minimizes heat generation and vibration while eliminating transmission losses. The NL CNC lathes are available in four classes and six specification variations. Some 70% of the NL lathes ordered have been equipped with the multitasking capability of the direct-drive milling motor turret.

Mori Seiki's MAPPS III control system for fast processing and collision prevention. completely checks for interference in 3-D in real time for spindles, workpieces, soft jaws, tools, holders, and turrets. Component collisions are prevented at all stages from setup to program operation since interference is detected in all automatic and manual modes.

General engineering and aerospace contract manufacturers working in difficult-to-machine materials such as titanium, Inconel, and hardened steels are regarded as prime candidates for the M35 and M35-G multitasking models introduced by WFL Millturn Technologies Inc. (Novi, MI) at EMO 2005.

The M35 series is the newest and smallest of WFL's product lineup of mill turn centers. The M35 series features a maximum turning diam of 420 mm, workpiece lengths up to 2090 mm, and a total of 92 tools, including the lower turret. WFL's largest mill turns can process workpieces to 6.5-m long, providing multifunctional turning-boring-milling units for complete machining of complex chuck and bar workpieces in one setup.

The M35-G delivers high torque and feed forces to get the full potential of tools weighing up to 15 kg and measuring 450-mm long. The 20-kW milling spindle has a maximum torque of 165 N•m above 1100 rpm. Tool change takes place in a fixed and clearly defined position above the left-hand main spindle. The changing device ensures swift replacement and transfer of tools no longer required to the magazine. Tool systems can be HSK-A63, Capto C6, or KM63.

To avoid collisions in automatic and manual operation, WFL offers a patented software option called CrashGuard, a real-time software extension of the CNC. Based on an internal 3-D model of the machine, CrashGuard provides realistic modeling of all special functions of the control, such as five-axis interpolation, rotation of coordinates, spline interpolation, and synchronizations, as well as correct and automatic representation of all machine cycles and macros, whether created by the machine manufacturer or the end user.

Weingärtner Maschinenbau GmbH (Kirchham, Austria) has expanded its Rotomill pick-up whirling/milling machines with the introduction of the Rotomill MPMC (multiproduct machining center). The Rotomill MPMC is equipped with a pick-up, high-power machining head and a five-axis interpolating controller for production of balanced/unbalanced chucking parts and heavy shafts, as well as for box-shaped housing-like components with dimensions up to 1.5-m diam workpiece envelope to 11-m long.

Processes such as turning, milling, boring, deep hole drilling, and tapping can be performed on the Rotomill MPMC in a single setup. Virtually any mechanical cutting method can be realized, including turning, milling (both with B and also U axis), as well as drilling, tapping, or hobbing.

Applications include production in one setup of extrusion cylinder and feed extruder screws, precision and special tubes for the oilfield industry, large crankshafts, cam shafts, motor housings, aircraft landing gears, and heavy drive shafts for the energy, ship building, and defense industries. Other industries that use the systems include the paper industry, mining, electrical (including turbines), electrical shafts, compressor, and plastics industries.

With quality requirements in the mechanical engineering industry and especially the automotive sector becoming increasingly stringent, EMAG LLC (Farmington Hills, MI) has combined hard turning and finish grinding for fast removal of metal and finish machining of parts. The demand for tighter tolerances and expanded machining capabilities requires the complete machining of components in a single setup.

EMAG, which offers workpiece-specific solutions for batch production in the automotive, hydraulics, and pneumatics industries, points to the need for multifunctional machines and dry machining, particularly of hardened workpieces. Reasons include ecology, environmental compatibility, and the rapid rise in waste-disposal costs for cutting oils.

EMAG's VSC DS turning and grinding centers are being used to machine workpieces, such as transmission parts, gearwheels, sliding sleeves, link pins, components for CVT gearboxes, roller races, rocker arms, bearings, and bearing rings. The combination of grinding and hard turning generates the smallest possible amount of heat on the workpiece surface. Rough hard turning is immediately followed by finish grinding without changing setups.

The pick-up concept allows the EMAG VSC DS turning and grinding center to load itself just like all the other VSC machines. The machine benefits from thermal stability, as work spindle, grinding spindles, turret, and machine base are all fluid-cooled.


This article was first published in the February 2006 edition of Manufacturing Engineering magazine. 

Published Date : 2/1/2006

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