Undergraduate degree from the Dept. of Production Systems Engineering, Toyohashi Institute of Science and Technology. Graduate degree from same university. Joined Okuma in 1986. Involved in the development of the GI-N internal grinder, MA-H horizontal machining center, and MULTUS intelligent multitasking machine, among others. Since 2008 has guided development of VTR-A.
Nishimoto: There is rising demand in various parts of the world today for large parts to be used in railroad cars, airplanes, construction machinery, and power generation plants. These parts require a lot of heavy-duty cutting, including difficult-to-machine and thin or cylindrical materials. Machine tools are needed that can provide high accuracy, high-quality cutting, but also that can be used in many environments. The VTR-A series was developed to respond to such customer needs as turning centers with a double-column construction that can easily cut or mill workpieces of various sizes, from thin material to boring of long, cylindrical workpieces.
Nishimoto: Many customers associate double-column structure with Okuma, and we thought we could take our know-how in high accuracy, high efficiency machining of large pieces, which we built up through our experience with double-column machining centers, and apply it to vertical turning centers. In fact, many customers told us when we were still at the stage of doing marketing surveys that if we made a double-column turning center they'd like to try it out. Making a highly reliable double-column machine obviously requires a good structural design, but it also demands advanced manufacturing technology that can't be acquired overnight, from parts machining of the bed and crossrail to precise assembly of these parts. Okuma is a pioneer in this field, and with delivery of more than 7,000 double-column machining centers to the market we have gained the trust of our customers. Okuma’s strengths in analysis, design, and manufacturing technology, which were built up over many years, are all brought together in our double-column machines.
Nishimoto: In the VTR-A series we sought the optimum rigidity for a large turning center, with improvements based on computer structural analysis (FEM) and evaluation experiments, on a double-column machining center base. For example, to accommodate the load on tools we increased the clamping power of the turning holder with curvic coupling that maintains strength with a clamping cylinder and engagement cogs. We also included an accurate drive for ram elevation with a two-ball-screw drive system and a built-in motor drive for the milling axis. This has less vibration that a gear and timing belt system and provides higher quality machining. We incorporated much of the technology we had developed with machining centers not only for basic machine rigidity but for milling functions as well.
Nishimoto: The VTR-A series has a 250 square ram, which is among the largest for machines of this class, so that it can easily handle even heavy cutting of 10 mm2 with 600 mm tool projection. The ram also provides stable machining of recesses with projection of 1,250 mm*. This easy cutting contributes to improved productivity. We've released a video of the VTR-160A in action, which I hope people will take a few minutes to watch. (*option on VTR-160A)
Nishimoto: The thing we worked hardest to get right was chip discharge. Many customers have told us that working on a vertical lathe was essentially a battle with chip discharge, and that even a machine which could cut through material easily was no good if it had poor chip disposal. We therefore made good chip discharge a priority, and gave the machines wide chip drops on both sides and direct injection of coolant from an eyeball nozzle built into the ram, so that coolant injection is less likely to be affected by chips. We also have options such as rotating scrapers around the table to rake out chips and a holder that breaks up chips with high pressure coolant. Some operators have also told us that they like to check the tool tip or chip discharge during operation, and so we have included four interior lamps as standard equipment for a bright work environment. Other options include an ATC lineup and 2-pallet APC with a focus on high-mix, low volume production and difficult-to-machine materials.
Nishimoto: Each customer has unique machining methods and know-how, and there is much we still don’t know about customer applications in the field of large machining centers. So feel a need for more information collection and analysis. At the same time, we also feel certain that we can further apply the technology and know-how we have gained from our experience in other fields to the world of machining centers. Therefore, we plan to put our full efforts into providing the best machines and methods while listening closely to customers, and develop the VTR-S series products that will be of the greatest benefit to customers.
