Grinding Strategies Go from Good to Great
Smart Manufacturing Magazine June 2019
By Kip Hanson
How software, automation, and abrasive advances are sending parts and tool grinding into overdrive.
Maybe your company specializes in aerospace or medical components, and you need to produce complex geometries in metals too tough to cut via conventional machining methods. Or maybe you work in or own a tool and cutter shop, and are looking for faster, more cost-effective ways to produce drills, end mills, and form tools. Whatever the reason, and whatever the requirement, you’re in luck. As with most metalworking technologies, grinding—more properly called abrasive machining—has improved greatly in recent years.
How so? For starters, grinding wheel manufacturers have developed new bonds and superabrasives
that clearly deserve the title “super,” capable of removing more material in less time than ever before. And grinding machine manufacturers are delivering ever more capable equipment, rigid and powerful enough to take full advantage of those advanced abrasives, while adding smart features like automation, remote monitoring and intelligent software systems to their machine tools.
Simply put, grinding has entered a new era of productivity and part accuracy; if you’re not taking advantage of it, you could be missing out on significant opportunities for process improvement, increased product quality, and a boost in the bottom line.
Better Control is Critical
A key driver for this is a shortage of qualified machinists. That’s according to Shane Farrant, national product manager for grinders at JTEKT Toyoda Americas Corp., Arlington Heights, Ill., who added that making the human-machine interface (HMI) easier to understand is a necessary first step towards minimizing the effects of a less-skilled labor force.
“A simpler, more intuitive HMI is one of the many machine enhancements we’ve developed for our lineup of universal, cylindrical, camshaft, and crankshaft grinding machines,” he said. “This means a user-friendly format, with greater reliance on pictures and other graphics to aid setup and programming procedures.”
There’s also been a big push towards an Internet of Things-based (IoT) working environment. For example, the diagnostics page on Toyoda’s TOYOPUC touch control displays coolant levels, machine vibration, oil temperature—anything that might translate to poor part quality or create a production issue will send an immediate alert to whoever’s responsible for fixing it. In addition, it’s possible to collect this information from the machine control and push it to a networked database for historical analysis.
Another timesaving feature is the automatic generation of alternative programs, which an operator can call up if there’s a process-related problem. JTEKT Toyoda Proposal Engineering Manager Steve Earley said this conversational control option is available on the company’s GE6 roll grinder, a machine that has also benefited from some modifications to the casting, motors, and other components, all designed to reduce vibration and increase machine accuracy in this specialty application.
The materials used to make the lithium batteries used in electric vehicles are quite thin, he explained, and the rolls producing this material must therefore be extremely accurate, with very fine surface finishes. “When an operator is setting up the machine, the control will present a generalized program to start with, as well as two alternates—one that’s more aggressive for faster cycle times, and a more conservative program that produces better surface finishes,” Earley said. “Based on the initial results, the operator can easily decide to switch to whichever set of machining parameters provides the best part in the shortest time possible.”
Larry Marchand, vice president of the profile group at United Grinding North America Inc.,Miamisburg, Ohio, agreed with the need for easy-to-use controls, especially as grinding machines become more capable. But he said there’s also a tremendous call throughout the manufacturing community for reduced work-in-process and fewer machining operations, leading United Grinding and other companies to adopt the so-called “done-in-one” approach to reduce operator touch time and increase value per operation.
To support this, United Grinding has introduced “additional processes, operations, and features” to profile grinding machines that were once very single-purpose. “Customers want to add more value in a single part handling,” said Marchand. “We’ve seen a big demand for machines with automatic tool changers, making it possible to grind the workpiece and then bring in a drill or milling cutter to complete the part. This eliminates secondary operations, reduces part lead time and improves quality.”
Does this mean machine shops should trade in their CNC machine tools for a do-everything super grinder? Not at all. Just as multitasking machines do a darned good job of milling a slot or grinding a journal, a multitasking grinder can now perform tasks once reserved for machining centers and drill-tap machines—that said, neither style of machine tool can replace the other. As Marchand pointed out: “If you have a part that’s grinding intensive, you’re always better off with a dedicated grinder.”
There are several reasons for this, he said. Grinding requires substantially more cutting fluid than milling and turning operations, aimed precisely at the intersection of the workpiece and wheel. Driving a wheel that measures a couple feet in diameter requires plenty of horsepower, far more than is available on an average chipmaking machine. Finally, holding tenths and single-digit surface finishes all day is something most CNC grinders excel at because they are designed to optimize these operations. Machining centers? Not so much.
Tackling the Tough Stuff
These capabilities are especially relevant with metals high in nickel, chromium, and cobalt, Marchand said. “A lot of our business comes from customers producing parts from Inconel and Rene, materials that—at least in their hardened state—are nearly non-machinable. Their only option is EDMing or grinding, and thanks to the rigidity, power, and accuracy of modern grinding machines, plus the availability of superabrasives that were unavailable until recently, most opt for the latter.”
One of the leading manufacturers of superabrasives is Norton|Saint-Gobain Abrasives, Worcester, Mass. Alfredo Barragan, senior corporate application engineer for super-abrasives North America, said grinding was once considered a “finishing only” process, but, with the development of increasingly capable grinding technology, has evolved into a mainstream machining process. In order to achieve the greatest success with this process, however, equally modern abrasives must be applied.
“Traditional resin or metal-bonded diamond matrix wheels tend to be really dense,” Barragan said. “Being dense is a good thing because it gives you a robust structure and helps to provide a strong bond that holds that structure together, but it does raise one consideration: the wheel tends to load faster, which in the long run reduces productivity. Norton Winter Paradigm hybrid bond wheels solve this issue.”
The wheels are said to provide a combination of enhanced grain retention with high levels of porosity, thus reducing cutting forces. Higher porosity also reduces loading—the wheel grinds cooler, more freely, with less downtime, ultimately producing more parts per day. Depending on the abrasive used, hybrid bond wheels efficiently grind carbide, advanced ceramics, hardened tool steels, and the high-temp alloys United Grinding’s Marchand just mentioned.
There’s more to this than abrasives technology, though. Like the machine tools to which they’re attached, the wheels themselves are getting smarter, with embedded RFID tags for better asset management, streamlined procurement, usage and dressing information tracking, and safeguarding against operator error.
Nor is Norton|Saint-Gobain restricting its efforts to abrasive products. Its 4Sight process monitoring and diagnostic system provides IoT functionality similar to that discussed earlier, with brand-agnostic, real-time monitoring of grinding machine values like spindle load and machine utilization, and the ability to store data for trend analysis or send alerts as necessary. “This is one of the biggest initiatives of the year for us, and together with our smart tag systems, serves as the foundation of our Industry 4.0 solution,” said Barragan.
Coming to Your Screen: V@dison
They’re not alone. Vollmer of America Corp., Carnegie, Pa., together with its parent company, the Vollmer Group, is working on a number of tools and services designed to “digitally transform” grinding operations. Branded as V@dison, these include the V@ screen for enhanced visibility of machine parameters, V@ check for process simulation, V@ boost to optimize machine performance according to the workpiece, and V@ guide for more consistent preventive maintenance.
Vollmer is still in the early stages of this initiative, but North American Sales Manager Shannon Fox said there’s still plenty of low-hanging improvement fruit available to the grinding community. Chief among these is automation—Fox pointed to the robotic part loading and wheel changing capabilities of its VGRIND 360 tool and cutter grinder as one example, options that Vollmer and indeed most machine tool manufacturers install on a routine basis as their customers work towards lights-out manufacturing.
Simulation is another routine request. Though Vollmer’s V@ check system is still under development, Fox noted that the NUMROTOplus software offered on Vollmer and other brands of grinding equipment is a mature, well-accepted alternative. “Simulation is becoming more important as grinders grow more capable,” he said. “The quarters are tighter, tool geometries are increasingly complex, and many machines—ours included—allow the use of multiple wheel packs in a single job, raising interference concerns. Without simulation, you run the risk of crashing a very expensive machine tool.”
Seeing is Believing
Simulation is important for other reasons as well. Melbourne, Australia-based ANCA CNC Machines, for example, uses it to predict tool imbalance in variable pitch end mills. “That’s one of the trade-offs with high-performance cutters—because the flute spacing is irregular, they’re inherently out-of-balance,” said Lucas Hale, global marketing manager. “To combat this, we’ve developed simulation software that calculates imbalance and adjusts the NC program to offset it by removing additional material in strategic locations. The tool comes off the grinder perfectly balanced, delivering extended tool life and better surface finish on the machined part.”
Hale agreed on the call for automation, including robotic part and wheel handling, but offered a number of additional ways to pump up productivity. Where routine “sticking” of the wheel to remove loading was once done manually, ANCA has automated it, reducing labor costs and extending wheel life. ANCA’s software and machines are said to provide “significant ease-of-use,” reducing setup time. And laser-based measurement systems provide in-process verification of cutting tool accuracy and geometry, followed by automated offsets or wheel dressing to compensate for wear.
And ANCA has taken that process one step further. Through collaboration with companies such as Zoller Inc., a leading provider of tool presetting equipment, ANCA has developed an interface that supports automated inspection and feedback to the CNC grinder—a robot places the cutter in the presetter, which measures it and sends the results to a software system that adjusts the machine as needed. This “closes the loop,” Hale explained, and together with integrated blank management systems, allows customers to “load up hundreds of tools, press go, and come back the next day to completed cutting tools,” he said.
“Basic machine construction has also improved over the past five years or so,” Hale continued. “For instance, linear motors have become far more common in our industry. They not only contribute to the quality of the cutting tools and therefore the quality of the parts being made with them, but linear machines move much faster than ones with ballscrews, reducing cycle times. And because there’s less wear and tear on machine components, equipment life is extended. This is why linear motors have pretty much become a standard component of any high-precision, high-performance grinding machine.”
First Part, Good Part
Just as JTEKT Toyoda is addressing the shortage of skilled machinists with more intuitive control software, Rollomatic Inc., Mundelein, Ill., is working to make machine setups both easier and faster. That’s because most tool and cutter manufacturers are no different than any metal cutting job shop; they are faced with smaller batch sizes and shorter lead times, making setup time a larger percentage of any production run. One part of the solution? Better software.
“For decades, shops have burned through three, four, five workpiece blanks per setup, gradually dialing in the machine until they get a good piece,” said Eric Schwarzenbach, president of Rollomatic Inc. “But by using intelligent software, it’s very possible to reduce the number of scrap workpieces, with zero being the ultimate goal. Not only does this reduce material costs, but setup time as well.”
The software assists the operator by making a 3D representation of the machine tool, workpiece, and grinding wheel, Schwarzenbach said, eliminating the need for a dry run. The operator can speed up the animation, slow it down, back up or zoom in on problem areas, helping him avoid potential collisions between the wheel pack and workpiece. And when the animation is done and the machine is actually making parts, the software works to eliminate “empty moves” and shortens security distances to a minimum.
Smart software is great, but Schwarzenbach was quick to point out that the machine tool and its related systems are equally important. The more accurate and stable the machine tool, the easier it is to hit the target dimension on the first try. Also, improved wheel dressing technology, automated calibration procedures, faster controls that process calculations more quickly, and hybrid wheel bonds that are wear-resistant, free-cutting, and retain sharp corners longer are critical. These factors play a big role in faster setups and an improved ability to make the first part a good part, with shorter cycle times to boot.
As others have mentioned, automated wheel changing is another grinding game-changer—Schwarzenbach said Rollomatic’s high-speed changers can swap out a wheel pack in five seconds, arbor-to-arbor, and achieve grind-to-grind times of 11 seconds. The benefit goes beyond shorter cycle times, however. “If you have a pack with four wheels on it, the collision potential is higher than one with one or two wheels. This complicates the setup. So, if you can split up a large wheel pack and afford the 11 to 12 seconds of wheel changing time, then that’s the preferred way to go in this day and age.”