Dave Ward, horizontal product line manager at Makino (makino.com), says that about 60% of the horizontal machining center market is represented by 400- and 500-mm pallet size machines. And Makino has long offered machines of this type, with its a51 and a61 machines, respectively.
Within the horizontal market, Ward says, the auto industry represents a large percentage. Among the workpieces that are being processed on this type of equipment, he says, are engine blocks, heads, bed plates, and transmission components.
Perhaps taking a page from the auto industry, where vehicles are developed on platforms, Makino has used the a51 and a61 machines as the basis for two new machines, the a51nx and the a61nx.
Sticking with the a51nx for the sake of simplicity here, Ward points out that compared to the a51 it has a 14% larger work envelope. That is, its X, Y, Z dimensions are 22 x 25.2 x 25.2 in. vs. 22 x 22 x 23.6 in. The significance of this, he explains, is that when you’re looking at high-volume production, the a51nx allows the ability “to put more parts in front of the spindle to amortize the non-cut time across more parts or it gives you the ability to run a larger part on a smaller platform.” That is, because the strokes on the a51nx are longer than what is conventionally found on a 400-mm machine (including Makino’s own), it is possible to handle parts that otherwise might be put on a 500-mm machine. That capability provides a savings of 13%. It also, he points out, provides savings in other areas, as well, including floor space, fixtures and tooling, and energy costs. (And while on the subject of the axes, the rapid traverse rates for each are 2,362 ipm and the cutting feeds are 1,968 ipm.)
The 14,000-rpm standard spindle for the a51nx provides 22 kW (29.5 hp) of continuous output, which is up 19% from the previous machine. It also provides 240 Nm (177 lb-ft) of torque. This means, Ward says, that the 40-taper machine can do the sort of metal removal—such as engine cubing—that might otherwise be performed on a larger machine. (He also points out that in order to deal with the power they’ve “made sure the bones of the machine are well suited to handle it,” as in improving the casting design and using a rollertype design for the linear guides.)
The standard toolchanger handles 60 tools that can be up to 16.9 in. long and 6.7 in. in diameter. And one important aspect that Ward notes is that the tools can weigh up to 26.4 lb. He says that whereas some other machine manufacturers are opting for lighter toolchange mechanisms, which means lighter tools are accommodated, they’re finding that as users are going for combination tools—as in a boring bar capable of generating four diameters—these tools tend to be heavier rather than lighter. (Perhaps the others are looking for faster toolchange time? It’s 0.9 sec. tool-to-tool for the a51nx.)
Another interesting feature of the machine is “inertia active control” for the direct-drive (rather than wormgear-driven) rotary table. Ward explains that the table, which has a maximum payload of 1,100 lb., can index 90° in one second. What the active control capability allows the user to do is to program the acceleration/deceleration of the table based on the mass on the table, rather than just having a default that is predicated on the maximum payload. This results in cycle time savings.
The a51nx features a center-trough design that allows the chips to fall down into what he describes as a “river of coolant that washes the chips out to the lift-up chip conveyor.” But aren’t there fewer chips to handle given the fact that there are more near-net shaped castings? That’s the desire, Ward admits, but adds, “The reality of it is that it doesn’t end up working very well because there can be porosity issues, so while it might be designed to minimize stock, there is 2 or 3 mm of stock being added back to get rid of the porosity. And if you don’t have enough power to get through the cut . . .”