Errol Burrell, HMC product specialist, Okuma America Corp. (Charlotte, NC), describes Okuma’s two types of HMCs: “The MA Series of horizontal machining centers are very stiff and rigid for heavy-duty cutting. The MB Series is designed for dynamic machining and high-speed cutting. The latest addition to the MA Series is the MA-600II, which incorporates powerful high-torque spindle options for high-volume material removal rates. It’s available with an HSK-A100 20,000-rpm spindle that boasts 50/55-kW power for everything from heavy-duty cutting to fine precision work on aluminum alloys, cast irons, and difficult-to-machine materials.” The MA-600II allows for steady milling, boring, drilling, and tapping for applications from mass production of parts to long, continuous cycles for die/mold.
Burrell foresees a future in which automation between machines of different types will be readily integrated into cells using a universal pallet system, mixing horizontals with verticals or five-axis machining centers. “Interest in automation on all of the horizontal machines is coming from across the board, from the smallest to the largest shops,” he said. “Automation isn’t out of reach for even the smallest shops.”
Okuma HMCs feature rotary pallets, pallet pool systems, Fastems systems, and robots for machining large mold and die work as well as high-volume production. Flexible manufacturing can be achieved via 6–12 multipallet APC units and multiple matrix magazines that hold up to 400 tools.
“We’re not a one-size-fits-all machine tool builder. It’s important to ask the customer what kind of work is coming through the shop and matching the right spindle and machine to that workload,” said Burrell. “We offer a 6000-rpm, high-torque spindle for machining Inconels, titaniums, and high-temp alloys, for example. For aluminum and a wider breadth of materials we offer a 15,000-rpm spindle for high-speed machining.”
HMCs Designed to Adapt Easily to Automation
“What I see for Makino’s horizontal machining centers is the need to maintain the ability to adapt stock machines to fit into a changing marketplace,” said John Einberger, horizontal machining center product line manager, Makino Inc. (Mason, OH). “For example, we often see a need to adapt standalone machines to operate in an automated environment. It’s the loudest call for change from our customers. To accomplish this, we pay a lot of attention in HMC design to make them easy to retrofit automation support options such as auto doors, fixture hydraulics, and coolant wash systems both quickly and cost effectively. As another example, we make it easy to integrate machines initially installed as standalone units into our MMC2 pallet handling system or the MMCR robot loading cell. We also offer a retrofittable robot interface that allows our machines to be integrated into an automated system managed by a master cell controller,” said Einberger.
“Our design choices are intended to maintain and increase performance levels while becoming more reliable from a total cost of ownership point of view. Our customers expect it, and we’ve been able to achieve good results with something as simple as designing our HMCs to use single-piece way covers wherever possible to significantly increase the reliability of this often problematic machine element in a high-volume environment,” said Einberger. “Moving forward, there is an increased focus on collecting data about machine performance for maintenance predictability, again with focus on reducing the total cost of ownership for our customers.”
Greater Efficiency, Stability Sought in HMC Technology
According to Bernie Otto, KIWA products manager, Methods Machine Tools Inc. (Sudbury, MA), today’s manufacturers are striving to achieve the highest levels of efficiency while increasing their productivity. There are many ways to approach these goals, including choosing reliable machines with greater capabilities, increasing automation and even adding technologically advanced accessories.
To achieve a reliable machine, builders consider machine stability in their design. One example would be the KH4500-PC6 HMC, equipped with coolant-through ballscrews. Chilled ballscrews allow a machine to be more thermally stable over longer periods of time and thus more accurate.
With reliable machines in place, large and small job shops are always looking for additional ways to be more efficient, thereby utilizing fewer people and resources. Automation is one way to increase efficiency and can come in many forms. “The efficient use of compact pallet pools allows the staging of additional pallets outside the work area. This allows the machine to run untended for longer periods of time and reduces the changeover time between jobs,” said Otto. “Also, adding more tools, either up front or in the field, allows the machine to run more jobs unattended, even with multiple programs staged to run on a mix of pallets.” He went on to say, “adding an additional rotary table to an HMC provides for 4+1 programming capabilities, coupled with the benefits of cutting efficiently on a horizontal.”
Harnessing technology can also allow manufacturers to do more with less. Implementing wireless technology accessories, like a KME CNC wireless tombstone with multiple indexing heads, can greatly decrease changeover time while increasing machine capability. With no wires or cables to bring into the work area, getting the tombstone—equipped with its additional axis—in and out is quick and efficient.
Hybrid Technology Leads to High MRR
Mitsui Seiki USA Inc. (Franklin Lakes, NJ) has adopted hybrid machining for its HMC platform in the form of GE’s Blue Arc electro-erosion metal removal technology. “The beauty of Blue Arc is that manufacturers will be able to realize higher metal-removal rates compared with conventional milling of difficult-to-machine materials,” said Robb Hudson, CEO of Mitsui Seiki USA. “Machining goes back and forth between Blue Arc and conventional milling with the heavy-duty roughing being done by the Blue Arc process. The result is that there are significantly lower perishable tooling costs when machining more difficult-to-machine materials like nickel alloys, tool steels, stainless steels, titanium, and other hard metals.” Applications that could benefit from the Blue Arc hybrid technology for roughing very large workpieces include aerospace (airframes and engines), industrial gas turbines, oil and gas, and die/mold.
Also, automation systems and software for HMCs have become more sophisticated. “Automation systems from Fastems and Liebherr, for example, link multiple HMCs into FMS lines so customers have maximum flexibility. They can run large families of parts, increasing spindle utilization from 80% to more than 90%,” said Hudson. “For scheduling, the larger automation companies have created their own sophisticated software. For example, a Fastems system can load weekly and monthly production across a family of parts and automatically optimize spindle utilization.” If production requirements change for a week or a month and a shop needs to accommodate a component with higher demand, the software will recalculate and maximize spindle utilization to the new production requirement.
Shops Beginning to See Impact of HMC ROI
The days of contract manufacturers packing their floors with vertical machining centers because of a lower initial cost and their ready availability are coming to an end, according to Don Langley, Midwest regional manager, Doosan Machine Tools America (Pine Brook, NJ). “A lot of owners are beginning to see the value of the horizontal machining center in terms of ROI and the ability to fit into crowded floor space,” he said. Doosan recently introduced its NHP4000 and NHP5000 40-taper HMCs with 400 and 500-mm pallet configurations and targeted for high-precision automotive applications with automation.
“Demands from our customers, whether in medical, aerospace, or automotive, are essentially the same. They want quicker ROI, increased production capacity, more spindle time with fourth and fifth-axis machines, and automation with pallet changers,” said Langley.
Like other machine builders, Doosan sees the trend of manufacturing coming back to the US. Automation is a critical part of the process. “Horizontals today are being set up to accommodate modular linear pallet systems, matrix-style tool changers with multiple tool magazines, as well as robotic interfaces for loading and unloading machines,” said Langley. “More and more multiple HMC platforms can accommodate fourth and fifth axes on the table or in the actual head. Our goal is to meet customer needs for best performance, lowest cost of ownership, and increased reliability through the use of industry standard FANUC drives, servos, and thermal compensation.”
