Unisig recently acquired this Okuma MCR-A5CII machining center.
A common concern in complex part manufacturing is minimizing setups. Eliminating time wasted by repositioning the workpiece partway through to accommodate the orientation of the machine tool is one of the very things that has made technology such as five-axis machining centers so popular.
But five-axis machines may not suit every application. For large workpieces, such as components for Unisig’s deep-hole drilling machines, one alternative is a bridge mill capable of five-sided machining. One such machine, Okuma’s double-column MCR-A5CII 35 × 100, enables Unisig to keep semi-finished part production in house and decrease some of the labor-intensive finishing work on its large, complex machine components.
Though similar in name, five-sided and five-axis machining are two different animals.
Five-Sided vs. Five-Axis Machining
In a 2013 article, Okuma Senior Applications Engineer Dennis Nichols explains the difference between five-sided and five-axis capability, at least in terms of Okuma’s double-column machining centers. Here’s a summary:
Five-sided: A machine with this ability uses multiple machining heads (or “attachments,” as Okuma calls them) that are loaded/unloaded automatically from a storage area to perform either vertical or horizontal work. Loaded with both a vertical and a horizontal head, the three-axis machine can then work on all five exposed sides of the workpiece.
Five-axis: A five-axis machine provides the three linear axes found in typical vertical or horizontal machines, but with the addition of B and C rotational axes. These axes can all be independently and simultaneously engaged in order to perform complex contouring with a single head.
Okuma’s MCR machine is of the former variety, using multiple attachments to switch automatically between horizontal and vertical work and therefore reach the top and sides of the component. Meanwhile, the piece sits tight in one position on the 118 × 394-inch table. This is particularly helpful when the workpiece approaches the machine’s capacity of 61 tons. With such large parts to machine, this MCR uses a 6,000-rpm, 50-taper spindle to keep production going at a reasonable clip.
Note that Okuma offers a variety of such machining attachments, including extended verticals, fixed angular heads (for 3+2 machining) and universal (B-/C-axis) attachments.
Other Ways to Get Around
Of course, Unisig is a machine-tool manufacturer, with big needs and big spaces and lots of resources to suit them. To put the MCR-A5CII’s scale into perspective, Unisig modified its facility to include a deep, specially-engineered foundation weighing 650 tons with helical piers to support the combined weight of the machine and its 50-ton, 40-foot-span crane!
Here’s a time-lapse video of Okuma installing its own:
For less…epic…situations, there are other ways to get around the workpiece.
Angle heads: Some shops, like the one covered by Derek Korn in this article, opt for angle heads that can enable horizontal machining on a three-axis VMC.
Fixturing: Some workholding options are designed to enable five-sided access to a workpiece on three-axis machines, such as the Quadrok plus clamping system from Hainbuch.
Rotary tables: Five-axis rotary tables, like those available from Lyndex-Nikken used by the shop in this case study, enable a three-axis VMC to reach all five sides of the workpiece by moving the table relative to the vertical spindle.
Those considering a machine like the MCR-A5CII should head to the Techspex database and compare it with platforms like SNK’s RB-VM, which functions on a similar concept to the MCR series but with a four-axis configuration.