Part makers get a better angle for multiple-axis work

Swiss-style machine tool builders give part manufacturers a better angle for multiple-axis work.

Say your machine shop just received an order for 316 stainless fuel-injector nozzles requiring angled holes to be drilled on the workpiece face. Or perhaps your best medical customer needs miniature blood-pump impellers with complex 3-D blade geometries like those on a jet-engine turbine. How are you going to make them?

Conventional wisdom says do as much as possible on a Swiss-style machine, then chuck them up one at a time on a tilt-rotary table and tie up a $100,000 machining center just to whittle away a thimbleful of material. And then the deburring remains, which is not only time-consuming but, if done improperly, degrades part quality. There has to be a better way.

Big Step Forward

You might perform some of this work with fixed-angle drilling attachments, but these are limited. Brian Such, Elk Grove Village, Ill.-based customer support group manager for Marubeni Citizen-Cincom Inc., Allendale, N.J., explained that drilling any hole requires two angle attachments—one for the center drill and another for the drill itself—each costing upwards of $10,000. If you have two different angled holes to drill, you’ll spend $40,000 and burn up four stations. And contouring work? Forget it, because only a programmable B-axis will do.

Courtesy of Eurotech

The SwissTurn Blitz from Po Ly Gim has an independent slide with six B-axis tools that can work on either the main or sub spindle.

A B-axis? Why would a Swiss-style machine—already crammed with dozens of tools and enough axis letters to score big in Scrabble—need even more complexity? The answer is simple. On any machine tool, eliminating secondary operations saves time and improves part quality—Swiss-style machines are no exception.

A programmable B-axis means you aren’t hindered by fixed-angle tool attachments. Instead of losing an entire station to a single operation—drilling an angled hole or milling a 45° angle—Swiss machine shops can drill or mill at any angle until the cows come home, often while using the same cutting tool to machine multiple features, which is impossible with a fixed-angle attachment. The ability to do multiple-angle interpolation similar to a 5-axis machining center is also a major advantage.

It’s for these reasons that Swiss-style machine tool builders offer B-axis machines. For example, Citizen’s M432 VIII is a gang/turret machine, meaning it carries both gang-style tool posts as well as a live-tool-capable lower turret. Citizen has also equipped the machine with a B-axis tool post in the upper part of the work area, on which are mounted three rotary tools capable of multiaxis contouring through 105°.

Only three tools? “Some builders put the B-axis on the turret and add a toolchanger,” Such said. “Sure, you can get more tools that way, but it’s also more expensive to build and slower.”

According to Such, Citizen performed market surveys and found that three is the magic number when it comes to B-axis rotary tools for most Swiss operations. “We elected to do three tools on the slide based on what our customers were asking for.”

Courtesy of Marubeni Citizen-Cincom

A Citizen M432 VIII B-axis with three rotary tools on the gang-style tool post.

Courtesy of Eurotech

A Po Ly Gim CSL 42-2Y Swiss-style machine with a B-axis on the turret.

Such noted that most customers use the B-axis option more for multiple-angle drilling than for complex surfacing. One example is a hydraulic component. What previously took 85 seconds to produce on the customer’s old Swiss-style machine takes 57 seconds on the M432 VIII, with no change to feeds and speeds. “By having the B-axis on the gang slide, it allows the turret to do additional work while the slide is busy drilling the holes,” he said.

One of the biggest benefits to a B-axis Swiss-style machine, according to Such, is reduced setup time. “Not only are you setting up fewer tools, you also avoid mounting one or more fixed-angle attachments and touching off tools sitting at various angles,” he said. “And with the Cincom controller, all you have to do is set the tool in the Z-axis, program the correct angle and go.”

The controller is a key part of the B-axis puzzle. According to Such, most B-axis controls can be difficult to operate and program, so Citizen simplified its control. It partnered with Mitsubishi to develop proprietary, easy-to-use software based on the 700 series Mitsubishi control. “We didn’t just bolt another axis motor on the machine. The B-axis is completely integrated into the machine.”

As proof, Such offers a hypothetical situation: the middle of a B-axis drilling operation where the tool is buried in the workpiece at 30°. “You could shut the machine off in the middle of the cut, power it back up, go to jog mode for that tool and crank it out with the handwheel. The machine will move the tool at the correct angle. Try that with any other machine and you can kiss that tool goodbye.”

The Citizen B-axis option typically costs $15,000 to $20,000 on a Swiss-style machine that costs $460,000.

Get off the Slide

German machine tool builder INDEX TRAUB Drehmaschinen GmbH & Co. KG has come up with a different way to build the B-axis. Tyler Economan, proposal engineering manager at INDEX Corp., Noblesville, Ind., described the design of the company’s Model TNL 18-7B automatic Swiss-style production lathe as one equipped with a pivoting upper turret capable of performing main or sub spindle machining, eight tool positions carrying up to 24 tools, and programmable B-axis rotation up to 100°.

Courtesy of PartMaker

The B-axis on the Tsugami SS-207 is used to machine the blades shown here using 5-axis simultaneous machining strategies.

“This machine was introduced at EMO and is new to the U.S. market, and we’re finding it’s an ideal fit for users who have complex parts made from difficult-to-machine materials,” Economan said. “To achieve these geometries before, you had to use form cutters or angled heads. Now you can simply adjust the B-axis to whatever angle is required and machine with the same rigidity and benefits as you would on a vertical machining center.”

TRAUB may take a different design approach than Citizen and other Swiss-style machine builders, but that doesn’t make its machine easier on the pocketbook. Economan justified the “more than a Cadillac” expense of its equipment by emphasizing the machine’s ability to reduce cycle times and increase flexibility. “You can improve your return on machine investment,” he said. “In some instances, we have demonstrated that even a 20 percent increase in productivity easily justifies a 40 percent increase in machine price.”

New Kids on the Block

The B-axis option is also not new for Japanese machine tool builder Tsugami Corp. It introduced the TMU1 more than 9 years ago, and it is geared toward turning complex, multiaxis medical and aerospace parts using a 16-tool turret and a B-axis live-tool spindle serviced by a 60-tool automatic toolchanger.

Courtesy of INDEX TRAUB

Typical parts machined on the Traub TNL18.

Ron Gainer, Swiss product manager for Rem Sales LLC, Windsor, Conn., exclusive U.S. distributor for Tsugami, explained that its new SS207 B-axis Swiss-style machine was introduced last year. He said: “The SS207 is a 20mm machine with three rotary tools mounted on the programmable tool post for use on the main spindle, and three for the subspindle. With full B-axis capability on a lower- cost, gang-style Swiss machine, you can often avoid having to purchase a more complex machine with a toolchanger. It’s basically for any shop that makes a lot of angular holes or does multiaxis contouring work.”

Gainer added that, before the SS207, attachments were required to make angular holes on Tsugami gang-style Swiss machines. “Now it’s just program the code and go,” he said. “Shops are making small, complex medical parts that require B-axis operations, including contouring, rigid tapping and even thread milling and whirling. And shops are always looking for ways to reduce setup time.”