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Picture this: several of these vertical spindle machines are arranged side to side and a simple roller conveyor running in front of them. Operators would manually load the machines; unloading is automatic. Then parts are manually moved along the conveyor from machine to machine. The result is transfer machine-like. Yet there is inherent flexibility: Not only is this, the CTV-30 (there is also a larger CTV-40), a CNC machine, but note the machine base—these machines can be moved to handle differing part requirements.
"We listened to our customers in the auto industry," said John D. Hendrick, president and chief operating officer, Okuma America Corp. (Charlotte, NC), at the announcement of two new machining centers that are the first of a series of machines that the machine tool builder is launching to meet the needs of reliable, high production coupled with flexibility. He described the machines as "a new generation of machine tools for flexible manufacturing," and as being "aimed at the auto industry." OEMs initially, but then...
The machines will be built in a new 112,000-ft2 plant in Charlotte; when running at capacity, the assembly line for the machines will be capable of outputting 70 per month.
The two machines—designated the CTV-30 and CTV-40—are both small-footprint, vertical spindle machining centers. These machines, although fully capable as stand-alone units, have been designed so that they can be lined up next to each other, as all service and maintenance points are located at the front or back; there are none along the sides. The sequence of machines would be, in effect, transfer machine-like in effect—thereby providing the high volume capabilities—while, at the same time, providing the flexibility, and possibly even agility, that is being sought in many production plants (to handle engineering design changes and/or demand shifts). A primary application area for the CTVs is in powertrain, even including the machining of transmission bell housings.
Although many of the machining center applications in higher-volume OEM (and supplier) plants are being handled by horizontal-spindle machines, Larry G. Schwartz, Okuma America senior vice president, said that the OEM engineers he and his colleagues talked with prior to the CTV development were fairly insistent on the vertical configuration. He explained that they felt that if they were able to get machines that would meet their cycle time requirements while providing a smaller footprint and a reduced price point (verticals are typically less expensive than horizontals), they would prefer the vertical design.
The use of vertical machining centers very much like the CTVs is comparatively common at OEM facilities in Japan. In order to help speed product development of the new machines, Okuma America's corporate parent, Nagoya-based Okuma Corp., entered into an agreement with Enshu Ltd. (Shizouka, Japan). Enshu produces machines of this type for Japanese auto makers. It is now providing Okuma America with the basic machine structure; the drives, motors, controls, sheet metal, and other components are being added by Okuma America. Hendrick said that the CTV machine designs were specifically developed to meet U.S. auto maker requirements, that the Enshu machines used in Japan may be based on the same iron but are clearly different from these new offerings. Not only has this collaboration with Enshu helped take 24 months out of the development time, but Hendrick cited another benefit to customers: the Enshu components have a proven track record in automotive installations, as do Okuma America CNC equipment (for example, there are 248 CNC Okuma turning machines at the GM Powertrain plant in Windsor, Ontario).
Both are traveling column-style machines. The CTV-30 is the smaller of the two machines. Its X, Y, Z axes travels are 19.7 in., 15.0 in., and 15.7 in. (+8.3 in.). The rapid traverse rate is 1,417 ipm. The spindle provides speeds from 120 to 10,000 rpm. There is a standard 12-tool automatic tool changer; it handles CAT 30 tools. Tool changes (tool to tool) are performed in one second. The floor space requirements for the machine: 53 × 108.7 in. For those concerned with machine height: it's 102 in.
The CTV-40—yes, it handles CAT 40 tools—has travels of 25.6 in. X, 17.7 in. Y, and 13.8 in. (+4.3 in.) Z. The rapid rate is 1,417 ipm for the X and Y axes; it's 787 ipm in Z. The spindle speed range is 80 to 8,000 rpm. The automatic tool changer handles 20 tools. The floor space requirements: 63 × 127.7 in.; it is 110 in. high.
Both machines are equipped with the Charlotte-manufactured Okuma OSP 700 M controls and drives. There is a recognition that many auto plants have control requirements that specify things other than Okuma; consequently, other vendors (e.g., Fanuc, Allen-Bradley) are being quoted.
The concept is to have a series of CTV machines aligned one next to the other. Instead of having one machining center perform a multitude of operations on a part, it would be likely, Schwartz suggested, that each machine would perform one or just a few operations, similar to the way parts are processed through a transfer line. Manning requirements are minimal. One person can handle from six to 10 machines, said Bruce Bowman, Okuma America's manager, Focused Industry. It is thought that part transfer from machine to machine could be manual, via a simple roller conveyor. Part load would also be manually performed, with part unload being an automatic function, located right in the machine tool. Because of the manual load and transfer, machine leveling on the floor, while still important, is not as critical as it can be with other types of machine tools. Okuma America engineers recognized that OEM factories tend to have existing personnel on site who are going to remain on the payroll, so this approach to simple and manual operation was devised, taking ergonomic requirements into consideration. This can help in production leveling.
The machine is designed and built so that little or no maintenance is required. In the event of a major problem, it would be possible to (1) have the operations previously performed by the faulty machine picked up by another unit on the line (remember: these machines have CNC control and automatic tool changers) and (2) have the machine removed from the line for repair (the machines do not require special foundations). Disconnection and replacement, according to Schwartz, can be effected in a few hours. Downtime costs are thereby minimized. AD&P