by Kip Hanson
Think you need five axis work to justify a five axis machining centre? Think again.
Impellers and turbine blades, knee joints and hip implants—these and other parts with complex swept surfaces are the bread and butter of five axis machining centres. But there’s far more to the five axis story than challenging part geometries and multi-axis simultaneous motion. When used for 3+2 machining, five axis machining centres offer flexibility and part accuracy unachievable on traditional three axis VMCs. Work in process is reduced. Fewer part fixtures and setups are needed. Unattended machining is easier to achieve. Add it all up and this often makes a five axis machining centre the preferred equipment for relatively simple, orthogonal milling operations, even at production volumes.
Simpler to use, less expensive
Many shops recognize this, and have achieved similar results by mounting tilt-rotary tables on their VMCs. If you’re one of these, or are thinking about taking this approach, it might be time to make the leap to a true five axis machine.
Errol Burrell, a machining centre product specialist at Okuma America Corp., says if you can afford the slightly higher price tag, a machine with integrated five axis capabilities is the way to go. “For those who are just starting out and don’t have much money, a tilt-rotary is a practical solution for some five axis work,” he says. “But considering the high level of technology that comes with five axis machining centres these days–the fixture tracking and tool centre point control and other options that make setup and operation much easier than it once was–it’s well worth the additional investment.”
Machine tool builders are responding to this need by placing five axis machining centres within the reach of even the most cash-strapped shops. Okuma, for example, introduced its Genos M460V-5AX last November, a five axis machine that uses the company’s proven bridge-style design but is only offered in a single 15,000 rpm, 32 tool configuration, thus keeping machine costs down.
Burrell is quick to point out that this standardized build approach in no way limits the machine’s five axis capabilities. Aside from the control functions already mentioned, the Genos is also equipped with 5-Axis Auto Tuning, an option that eliminates the need for a skilled service technician during machine calibration.
“There’s this myth in the industry that the only way to justify a machine with an integrated table is by machining impellers and blades,” Burrell says. “That’s simply not the case anymore. With the progress that’s been made on CAM systems, along with the various control features that are available, setup and operation of a five axis machine is far easier compared to ten years ago. There’s simply no reason to avoid the technology, no matter what kind of parts you’re making.”
Going horizontal
Okuma’s not the only builder offering new five axis machining centre designs. Visitors to the 2017 EMO Hannover manufacturing expo saw the premier of Mazak Corp.’s HCR-5000S, a horizontal five axis that, according to vice president of sales and marketing Chuck Birkle, is going to be popular with anyone removing large amounts of material from a workpiece.
“The HCR-5000S has temperature-controlled ballscrews and an integral spindle motor rated for very long duty cycles,” he says. “That, together with a super rigid bed, plenty of flood coolant, and robust chip evacuation, is ideal for the large, monolithic structures common in the aerospace and semiconductor industries, or indeed for any customer that wants to rough and finish on the same machine.”
Birkle agrees that the price point for five axis machining centres is sinking while their capabilities are on the rise. Of course, demand and higher sales volumes are partly responsible for this happy trend, but technology plays a role as well. “Machine tool controls and servo technology is getting more powerful all the time,” he says. “And because direct drive motors are becoming so efficient, we’re able to do things like add actual turning capabilities to five axis machines by stuffing a pancake-thin motor under the rotary table, without worrying about it bleeding heat and energy like older designs would. It’s become a real enabler for us.”
Mazak, Okuma, and other five axis machining centre builders have also recognized the need for higher production levels. Most machines now are available with (or can be retrofitted for) pallet changers, greatly increasing the appeal of these machine to those shops hoping to run lights out.
“The pressures that our customers are under today here in North America are getting greater all the time,” says Birkle. “The only way we can help them meet that demand is by offering products that provide greater spindle utilization, and therefore greater uptime. There’s 8,760 hours in a year—it’s important to go after as many of them as you can.” SMT
