Vertical Versatility Goes Mainstream
A combination of evolutionary development and new concepts makes vertical turning the technology of choice in many applications
By Michael Anderson
Not long ago, vertical turning was reserved almost exclusively for parts too large to be held horizontally, or for applications such as valve housings, which had to be offset for facing. Today, thanks to factors including automation-friendly designs, live tooling, multiple and inverted spindle configurations, and compact footprint, vertical turning is growing in popularity in applications ranging from large complex parts to high-volume, small to mid-size units produced by both OEMs and, increasingly, contract manufacturers. The economic upsurge in industries such as aviation, defense, and energy—established users of vertical turning—has likewise spurred demand.
The evolution of vertical applications is less surprising when seen in a historic context. Vertical turning originally derived from boring equipment (in some cases fixed and in others built on-site) used to true the cylinders of early stationary steam engines. Later, the vertical turret lathe provided manufacturers with improved production and flexibility, and led to development of peripheral designs such as the Bullard Mult-Au-Matic, one of the first multistation, multiple-operation—today we would call it multitasking—machines that streamlined the production of engine blocks and helped make the assembly line possible.
Currently, vertical turning falls into several distinct, but frequently overlapping, fields. These include: conventional vertical turning for large parts and chucking applications; high production, multispindle designs for small to medium-size parts; inverted spindle machines; and specialized applications such as vertical grinding.
Manufacturers report that recent interest in conventional VTLs has been exceptionally strong. Several reasons are cited. According to Glenn Pedersen of Daewoo Machine Tool (West Caldwell, NJ), “We’re seeing more applications requiring large heavy-duty machines, even in the most basic two-axis design. Also, compared to other machines, vertical prices are more reasonable today. Job shops that previously would never have considered a large vertical are now finding that the machines are more affordable, and the work to keep them busy is out there.”
A major factor driving the use of large vertical units is the increased capability derived from options such as live tooling and multiple axes. Mark Davis of Okuma & Howa (Buffalo Grove, IL) comments, “Milling functions on the tool turret used to be rare, but the demand has increased to the point where our customers are now asking for four live spindles per turret. Performing multiple operations including milling, drilling, and even light grinding in the same setup not only saves time but, by avoiding refixturing and taking advantage of gravity, the customer can keep the part rounder and flatter.” With regard to multiple axis capabilities, Davis is positive but cautious: “Four-axis operations are fairly commonplace today. Customers are cutting channels in parts with offsets, and demanding the ability to do secondary operations. Five-axis is certainly achievable, but on a VTL it compromises some degree of strength and rigidity. You really have to think twice in terms of the part and the material whether this is the right way to go.”
Giddings & Lewis (Fond du Lac, WI) boasts a long history in both vertical turning and boring, and G&L’s Ken Campsure recognizes a synergy between the two: “C-axis and live tooling have substantially extended the uses of the VTC. In fact, in one of our applications, I like to refer to the VTC as a ‘poor man’s planer mill.’ The job involves a turbine case used in power generation. The case is machined in two halves and was previously done on a planer mill. With live tooling, the operation is done on the VTC in a single setup. It saves time and ensures a better final result.”
Among the workhorses of vertical turning are the so-called “wheel” machines used for the production of truck and heavy vehicle wheels and similar applications. Despite their high population among both OEMs and contract manufacturers, the pedestrian nature of the “Army type” truck wheel and similar parts have kept them out of the limelight. With the coming of the “gangsta” wheel sets, featuring mirror finishes, spinners, and a wide variety of complex configurations, this is no longer the case. The showy nature of these parts make them a favorite at trade shows to the extent that the visitor might imagine that enough gangsta wheels are being made to outfit the entire production of passenger cars.
Twin and multispindle vertical turning presents the largest vertical growth area, as well as the most innovative in developing new technology. According to Davis of Okuma & Howa: “The first twin-spindle units were almost exclusively used in the automotive industry by OEMs. A combination of high production capability and better operator utilization made for a strong economic appeal. As chuck sizes increased and self-contained parts-handling equipment became available, other industries began to take notice.”
Steve Ortner at Absolute Machine Tools (Lorain, OH), distributor for You Ji (Taiwan), agrees, “A twin spindle VTC is really a ‘built-in cell’ in one package.” While the markets for vertical turning have expanded, Ortner observes that they continue to be more popular with OEMs. “Most of what we sell has a defined purpose, and a large number are for multiple units. We’re seeing parts like castings, brake disks, forgings, and electric motor end caps. I think manufacturers like the fact that they have multiple choices when it comes to automation. Automated part handling can be contained on the machine or sourced separately. Multiple machines are easily linked with independent parts-handling equipment.”
For many markets, a multispindle design is desirable if it successfully addresses time, space, and cost factors, according to Tak Yamamoto, vice president of SB Machine Tools (Schaumburg, IL), exclusive North American representative of the Kitako line of VTCs. On their four-spindle lathes, says Yamamoto: “Four spindles, generally partnered as pairs, are mounted in a vertical, square pattern in a large carrier drum. When the carrier is indexed 180°, two spindles move in for machining as the other two spindles move out for unloading and loading. It operates much like a pallet changer on a machining center,” cycling the work from the loading zone to the machining zone and back again. The spindles, slides, and turrets in the machining zone work independently for flexibility in part processing methods, allowing AA/AA, AB/AB, or AA/BB operations, depending on the job at hand. Unrestricted access to the spindles in the loading position makes for simple manual, robot, or gantry loading. “Automation is especially popular among the higher-quantity producers,” he reports.
A relatively recent innovation that is demanding more attention by builders and customers alike is the inverted spindle design. Originally developed as a simpler and more flexible answer to automation, inverted spindle offers advantages, including improved chip management, which is essential in high-production situations. In inverted spindle turning, the chuck is mounted on a slide that permits it to approach and clamp/unclamp the part directly. While the simplicity of the design has great appeal in a lean manufacturing environment and allows the customer to choose from a wider variety of part-handling options, it is not without limitations, the most frequently cited of which is the inability to refixture or regrip the part. Another practical limitation is weight, although, since their introduction, vertical spindle machines have grown in size and handling capability to accommodate larger parts. Live tooling is typically more extensive on inverted spindle models than conventional multispindles and, especially in the larger sizes, customers demand a greater degree of customization.
Rick Ware of Mazak (Florence, KY) says the company has focused the development of their IVS (inverted vertical spindle) line on manufacturers doing high-volume production, which to this point has predominantly meant the automotive sector. With those needs in mind, the IVS line is designed for speed—35 hp (26 kW) and up to 7000-rpm spindle output—and ease of automation on a narrow profile. “We combine the machining side with the loading side,” Ware says, “with the spindle on top and the tool turret below.” The spindle doubles as its own gantry loading robot, loading and unloading parts with a rapid traverse speed of 4330 ipm [110 m/min]. “Also, we put an opening directly through the machine column so that the loading/unloading and part-turning operations take place within the machine, and automation can carry the part directly through it.” Because of this feature and the machine’s narrow profile, many clients opt for a turnkey package of two or more machines in line with connecting automation to handle multiple processes, he says. Milling, drilling, and tapping operations are also available. “Our largest chuck size is currently 12" [305 mm]. We’re currently developing new models to handle larger part sizes,” he reports.
At Hessapp Vertical Turning Machines (Port Huron, MI), production efficiency is key to converting customers to the use of vertical turning. The company touts their inverted spindle VTM’s ability to automatically load and unload workpieces from 2 to 28" (51–711 mm) in diameter into the workholding area. Hessapp began building inverted spindle VTCs in 1992, and introduced their patented DV-Transfer machine in 1994. The latter machine features an inverted spindle and a traditional standing spindle on the same machine base, enabling operations to be performed on both sides of a part by direct spindle-to-spindle transfer.
The increased use of live tooling on vertical units of all sizes has resulted in numerous nontraditional operations becoming commonplace. While milling and drilling are easily the most popular, tapping is used and grinding is becoming increasingly frequent. Absolute Machine Tool’s Ortner states, “While you can’t compare the finish to something you could achieve on a dedicated grinder, manufacturers are equipping live spindles with wheels for deburring and, where the tolerances are acceptable, for actual grinding operations.”
Klaus Voos, vice president of quality management of Index (Noblesville, IN), sees innovation driving all aspects of vertical turning. “Our company has built vertical machines for 14 years. We observed on other machines that turret placement often restricts or eliminates the possibility of grinding. Providing more work area has led us into some interesting applications, including in-process assembly.”
The leap from what might be termed “utility” grinding to precision vertical grinding is a reality, thanks to specialized designs. Index developed a parallel-rod kinematic system in which the spindle moves on three slides in the X, Z, and Y axis to ensure stability and high precision. Utilizing a 4" (102-mm) chuck, the system is currently in use in automotive applications and in the manufacture of high-end timepieces.
Taiyo Koki, a Mori Seiki (Irving, TX) company, is dedicated exclusively to vertical grinding. The inherent stability of vertical chucking eliminates the problem of deflection and run-out that can occur in horizontal mode when a desired surface finish approaches the single-digit-micron range.
The Taiyo Koki family of models extends from medium to large size parts, and units can be equipped with ATCs to allow internal, external, and face grinding. Applications in a variety of materials include headstocks, curvic couplings, gears, bearing races, and ceramics.
In addition to grinding, customer demands have resulted in machines configured for operations ranging from the unusual to the exceptional. Gary Hulihan of Emag (Farmington Hills, MI), has assisted customers in pushing the envelope since the company introduced inverted spindle designs in 1992: “We do a lot of work for the automotive industry, and our products show the results of those demands. We offer units designed for hard turning and grinding, as well as fixed-bridge and five-axis units, although our standard is two-axis modified to three. Recently, we delivered a machine equipped for machining, pressing, and CO2 laser welding. In today’s manufacturing environment, the more operations you can perform in the same setup, the more economies you achieve.”
Proliferation of operations, technologies and sizes has in some cases resulted in an identity crisis when it comes to machine designation. Okuma & Howa’s Davis cites the example of a new model which utilizes a vertically mounted chuck but is equipped with extensive live tooling capability. Though listed under Vertical Turning on the corporate Website, the machine has been designated with the prefix Millac, which is customarily reserved by the company for machining centers. The compromise is to refer to it as a production center.
Theoreticians in every discipline speculate on the possible but unlikely development of a universal example of their craft. The question, “If we ever find a universal solvent, how will we contain it?” has provided hours of amusement for chemists and philosophers alike. In the protocols of lean manufacturing, the combination of operations that can result in the elimination of positioning and refixturing has perhaps drawn us nearer to the universal machine tool than ever before. Should we ever achieve it, it’s more than likely that it will be a vertical.
This article was first published in the April 2006 edition of Manufacturing Engineering magazine.