What does a medium- to high-volume manufacturer of machined components that fit within an 8-in. chuck and are approximately 8-in. high do when there is a need for new capacity, particular when there are likely to be part detail changes—or entire part changes—during the foreseeable future? According to Klaus Voos, technical director, Index Corp. http://www.index-werke.de.htm (Shelton, CT), a machine tool builder widely known for its vertical turning equipment, the present options include special machines and single spindle machines.
And he points out that they both have limitations that are problematic. "With special machines," Voos says, "there is too much risk. What happens when there is a change?" Well, for one thing there is an expensive change to the tooling and to the equipment—expensive in terms of investment and downtime. "The other alternative is a lot of single-spindle machines. This is a cumbersome manufacturing method and it uses lots of floor space, manpower and maintenance." Enter Index with a radically different approach, a machine that combines productivity with flexibility, two characteristics that are often sought but which are almost just as often missed.
The machine is called the "MV200 Production Center." The "MV" signifies "Multispindle Vertical," its configuration. The "200" stands for the nominal chuck size (8-in.); smaller chucks can be used if required. "Production Center" because it provides production at a rate that brings to mind a piece of dedicated production equipment, but which provides the sort of changeover possibilities that bring turning centers and machining centers to mind.
Fundamentally, the MV200 is a CNC vertical chucker with eight stations and six spindles. The spindles feature a unique Index design. The 28-hp spindle drive motor is integrated right into the spindle. Not only is this cost-effective thanks to the elimination of components, but it also results in a compact, powerful unit.
Of the eight stations, one is for loading and another for unloading. The remaining six are for machining. Which this might mean that the number of operating stations defines the number of operations that can be performed, Index engineers have designed the stations so that each can be partitioned. This means that six becomes 12. One possibility is to have two-sided machining of a part (e.g., station 1a does one side of a part; station 1b does the other) during a single cycle. The indexing mechanism is a gear- and pulley-free, accurate positioning device.
In addition to the turning tools that are expected on a machine of this type, the machine can be equipped with live tools. Milling spindles. Grinding spindles. Even in-process gaging equipment can be installed in the machine. The tooling used on the MV200 is quick-change (e.g., Sandvik Capto). Voos notes that people might look at the machine and figure that it is the type of equipment that is setup for a particular job and just keeps running that part, day after day, week after week. But that is not the sort of thing that Index engineers had in mind for the MV200. While the machine has high-volume capability, it also lends itself to comparatively quick modifications. It may not be as quick as a standard turning center or machining center, as it generally takes a few hours not a few minutes to make a change to a different part, but it is a whole lot quicker than a dedicated machine.
Although it is configured so that there can be manual loading and unloading, the parts volume that would be typical of this machine—50,000 to 100,000 or more—to say nothing of the cycle time, which could be as short as four seconds, means that the parts loading device, called a "Linapod," would undoubtedly be the way to go. This unit, which has rods and universal joints evocative of a hexapod-style machine, does the functions of a six-axis unit. It can handle a wide assortment of workpieces.
According to Voos, a basic machine, including a Linapod but without tooling, costs approximately $1.4-million.
Compared with stand-alone machines, Voos estimates that it would take on the order of 6 to 8 to meet the output of a single MV200. Voos calculates that the piece-part production cost can be 1/5 that of conventional approaches.