Trending toward productivity: Medical Manufacturing

Courtesy of Haas Automation

Five-sided machining in a single setup on a Haas UMC-750 vertical machining center.

The U.S. economy appears to be on the mend. In January, the Manufacturers Alliance for Productivity and Innovation gave a tentative thumbs up to sustained business expansion through the first half of 2013. And the Institute for Supply Management’s manufacturing index rose again in January, painting an optimistic picture. Maybe it’s time to buy that machining center you’ve been thinking about.

Before you whip out your checkbook, though, some homework is in order. There’s a lot more to machining centers than spindle speeds and rapid traverse rates. Sure, you’ve had good results over the years buying machines based on that, but that might be the wrong criteria in this brave new manufacturing world. You’re facing growing competition from overseas and down the street, so you owe it to yourself to take a look at what’s changed in the years since you bought your tried and true 20 “×40 ” vertical machining center.

3+2>5

Most everyone’s seen them at trade shows—5-axis wonder machines whittling away at intricate shapes such as motorcycle helmets, jet turbine blades and titanium knee implants. Recently, 5-axis machining centers have redefined many shops’ definition of complexity. But maybe you don’t do complex aerospace work, or you simply can’t afford to spend $500,000 on a machine tool. And 5-axis programming is way too complicated, right?

Think again. “In our market at least, 90 to 95 percent of these machines are used for ‘3+2’ rather than simultaneous 5-axis work,” said Bryan O’Fallon, product technical specialist at Haas Automation Inc., Oxnard, Calif. “Sure, you still have the guys doing impellers and turbine work, but that’s more the exception than the rule. The typical 5-axis user is the shop looking for setup reduction.”

Why use the most challenging machine in the milling department for setup reduction? Because a 5-axis machine doing 3+2 machining can produce a complete workpiece in a single clamping (3+2 machining is where 3-axis milling is executed with the part locked in a tilted position using the 5-axis machine’s two rotational axes).

“Let’s say you have a cube-shaped part,” O’Fallon said. “A lot of shops might tumble a part across multiple vises on a VMC to hit each side of the workpiece or maybe use two machines. But with 3+2 you can rotate the part to every face and get it all done in one clamping, assuming it’s been properly fixtured.”

This one-and-done method requires far less handling than similar setups on a 3-axis machine, reduces fixturing costs and provides higher workpiece geometric accuracy, he added. “Once you’ve rotated the part into position, it’s just like programming a 3-axis VMC,” O’Fallon said. “It’s much simpler than simultaneous 5-axis machining.”

And the 3+2 process is appropriate for more than this kind of one-off work. Production shops with relatively simple parts also can take advantage of it, according to O’Fallon. “You might have a pallet with multiple sides, maybe a tombstone fixture, and use it like a horizontal machine. For large volume work, you can load lots of parts in a single setup.”

To support these shops, Haas developed the UMC-750 VMC, a $150,000 machine that is an alternative to more costly 5-axis machining centers. “You can still do 5-axis simultaneous machining on the UMC-750, but to address the considerations just mentioned, we’ve really pushed 3+2 for this machine,” O’Fallon said.

Why should shops consider a 5-axis machine when they’ve been getting inexpensive 3+2 capability for years by bolting 2-axis trunnion-rotary tables to 3-axis VMCs? The problem with this option, he said, is the Z-axis travel.”There’s a lot smaller work envelope with a trunnion-rotary table. When a trunnion rotary is mounted to the table of a VMC, it eats up a considerable amount of the Z-axis travel, even before fixturing the part. The UMC-750 provides a much larger work envelope—a full 20 ” of Z-axis travel—with better access to the part, for about the same price as a trunnion-equipped VMC. It’s attractive for job shops in particular that might be doing low-volume 5-axis work one day and 3-axis production the next.”

Hiring R2-D2

Did your operator call in sick again, the day after the Super Bowl? Looks like the only way you’ll get those parts done on time is to run them yourself.

For many small shops, the challenge isn’t the machine, it’s the people. Sure, if you had sufficient production volumes, you could buy a robot and tell that operator to stay home forever, but everyone knows robotic parts handling is only for automotive suppliers, right?

Not so, said Darryl Smith, automation manager for Doosan Infracore Machine Tools, Pine Brook, N.J. Over the past 18 months, Smith has seen increased interest in automating machining centers.

“For production work, you just can’t afford to have somebody stand in front of a VMC anymore,” Smith said. “The cost of automation is dropping, it’s increasingly difficult to find qualified people and you’re not going to be successful against foreign competition without it. Companies have to do more with less.”

Courtesy of Doosan Infracore Machine Tools

Automation can work for short-run production, even in lot sizes once considered too small for robotics.

Good reasons, perhaps, but robots are still considered expensive and difficult to set up. Smith countered that the cost of robotics for machining centers has dropped more than 25 percent over the past 5 years. “When you look at automation, everything works toward lower cost—cheaper computers, better software and higher robotics usage throughout the industry.”

As an example, Smith cited Doosan’s Doocell automation system, with a 6-axis FANUC M-10iA articulating robot for part loading/unloading. The complete $130,000 system includes the robot, automatic doors and grippers.

Changeover is simple and quick. “To change grippers, there are no more than 12 screws to take out,” Smith said. “I was at a shop that was doing complete changeovers in less than 30 minutes.”

The reason automation works for low-volume production is simple. “If I have 10 jobs that I know repeat on a regular basis, I’m going to get really spanking good at turning those jobs over,” he said. “Over the course of a year, I’ll get faster and better at it. The trend is toward using some level of automation for this type of repeat work, which keeps shops in business.”

Smith admitted that the use of robots in job shops is still relatively rare. “This is far from mainstream,” he said. “But it’s a painful fact for everyone that there are fewer people going into manufacturing, and it doesn’t appear to be getting any better. Look at Bobcat in North Dakota, or John Deere in Iowa. Labor costs are relatively low in these areas, but these companies have tons of automation. So it’s not just about the people; part quality, process predictability—everything factors into it.”

Real Estate Considerations

Doing more with less extends to conserving shop floor space as well. “We’re seeing smaller footprints in the equipment itself,” said Michael Minton, national application engineering manager for Methods Machine Tools Inc., Sudbury, Mass. “Especially in medical and other high-tech industries, floor space is at a premium where parts are small and volumes are high. Job shops as well are looking for smaller footprints without losing the work area in their machines. People want to fit as many spindles as possible into a given floor space.”

To address this issue, Methods offers the FANUC RoboDrill D21-series VMC, the smallest of which is sometimes referred to as the “phone booth” at just 40 ” wide. The machines also offer reduced processing time and lower costs, according to Minton. As a rule, a 30-taper spindle ramps up faster and is tooled more economically than a 40-taper spindle—search any popular tooling catalog and you’ll see 30-taper toolholders costing 20 to 30 percent less than their larger cousins.

“In situations where you don’t have automation, small machines make it much easier for an operator to feed multiple machines since he doesn’t have to walk as far.” Minton also pointed out that small machines fit well in an automated cell configuration, optimizing floor space and allowing the robot to efficiently service the machines.

Courtesy of Doosan Infracore Machine Tools

Remove a handful of screws, pop in a new gripper, and this robot is ready for the next job.