Making Cutters Clever
- October 3, 2017
It takes more than sharp edges to maximize cutting tool performance
Since the publication of the original Machinery’s Handbook in 1914, the first thing machinists have done upon opening it is to dog-ear the speeds and feeds section. Thirty editions later, their descendants might be using Post-It notes instead of a folded corner, but machinists still refer back to “The Bible” or equivalent tooling catalog for their cutting tool advice.
After more than a century, that might be changing. Thanks to several new technologies, the days of plugging in “best guess” feeds, speeds, and depths of cut might be coming to an end. No more chatter, no more premature tool wear or unexpectedly broken cutters—just tell the machine tool, computer, or mobile device what you’re trying to accomplish and the software will take care of the rest.
Searching for stability
One of these technologies is BlueSwarf, which according to company co-founder Dave Barton, determines the optimum machining conditions for any combination of cutting tool, toolholder, and CNC machine before the first chip is ever made, eliminating the tedious testing common in most shops today. “Typically what happens is, the machinist puts the tool in the machine, gets the tooling catalog out and plugs in whatever surface speed and feed rate is recommended. He or she then starts the program, the tool starts to chatter, and they back off or go find another tool. It’s just trial and error, playing around with different variables until they find something that works.”
Barton says BlueSwarf allows the programmer to pull up a dashboard and know immediately how the tool is going to behave under specific machining conditions. This is made possible by predetermining the “stability lobes” for any given combination of cutter, toolholder, machine, and material, an activity performed using one of BlueSwarf’s Machining Dynamics (DC) kits—load the desired tool assembly in the machine, “tap-test” it at various RPMs, and send the resulting data to BlueSwarf for analysis and dashboard preparation. “The dashboards are interactive,” he says. “You can try unlimited cutting scenarios offline and see the results immediately. When the program hits the shop floor, it’s going to work right the first time.”
Partners in Optimization
Because BlueSwarf looks at all aspects of the machining system from the cutting tool to the casting, the company has partnered with other industry leaders to map out specific tooling and machine combinations. One of these is cutting tool manufacturer Fullerton Tool, which together with Briney Tooling Systems, machine builder Okuma, and BlueSwarf, has developed a series of dashboards for their products, eliminating the need for customers to tap test on their own machines.
“We’ve designed several end mills that work quite well in this application,” says Fullerton president Patrick Curry. “This includes the AlumaMill G3 and our four flute Fury advanced performance series tools, both of which have special geometries, coatings, and substrates for high performance machining. These are offered with a proprietary anti-pullout connection, developed jointly with Briney, that is then balanced and delivered to the customer as a complete unit.”
A number of those cutting tool and toolholder combinations have been analyzed on Okuma equipment using BlueSwarf technology, thus determining the optimal metal removal rate parameters for each. Customers can then test drive these products on a website designed specifically for this purpose, without having to actually purchase them.
Much more than harmonics
“Our smart tool concept not only improves metal removal rates, but also reduces downtime due to setup and in-process tool changes,” Curry says. “Each tool assembly comes with predetermined offset values–there’s no need to send it to the tool crib for balancing or presetting, you can just put it in the spindle and go. When the cutter’s dull, stick the entire assembly back in the box and send it to us for reconditioning. And since there are dashboards available for each tool combination, programmers know exactly what’s going to work and what won’t in advance. No more guesswork.”
What works is a 100 per cent increase in tool life. Fullerton and BlueSwarf say customers report substantial improvements, not only with tools lasting longer, but at elevated feeds and speeds as well. And when tools do wear, they do so evenly and predictably, increasing the number of times they can be re-sharpened. “We also find that, because you have a better understanding of what the tools are capable of, you can have more confidence when bidding on new jobs,” says BlueSwarf’s Barton. “Everything simply runs more smoothly.”
Use the force
Another approach to cutting tool optimization starts with the toolpaths themselves. Pete Haas, Vericut product specialist at toolpath simulation software provider CGTech, says the company’s physics-based Force product performs cut-by-cut analyses of chip formation and cutting tool forces to deliver significant savings in machining time.
“In the old days, we used catalogs to look up ‘what’s the cutting speed or chip thickness supposed to be?’ and then plug those values into the machine program or use it in our calculations,” says Haas. “But the cutting tool manufacturers have all of this data electronically, plus a lot of other geometry information like helix and rake angles besides. We pull that down from the cloud directly into the software and use it to understand the physics behind the cutting process.”
Instead of the “beer can” approach, where a cutting tool is displayed as a simple can-like cylinder, CGTech uses an anatomically accurate representation. This allows for complex, real-time calculations of what’s going on as the cutter is being pushed through the part, adjusting the feedrates and breaking up toolpaths to optimize the metal removal process.
“I’ve been a programmer for 30 years, and can honestly say this technology is revolutionary,” says Haas. “In the past, we always aimed for average chip thickness, crossing our fingers that there wouldn’t be some crazy geometry somewhere along the toolpath that would break the cutting tool, or needing to back off so much that you lost cycle time. Force keeps the cutting forces constant, and therefore allows you to maximize feedrates without worrying what will happen. The time savings are tremendous.”
Keeping an eye on things
Increasing the intelligence of toolpaths can also happen once the machine is actually making parts. The Industrial Internet of Things (IIoT) and Industry 4.0 promise additional revolutions in the way machining cycles are optimized. For example, the ability to perform in-process gap analysis on cast parts, automatically speeding up through air cuts, or sensing spindle loads and adjusting cutting parameters on the fly—these are only two instances where on-board sensing will one day drastically impact production throughput, part quality, tool life, and more.
Jeff Rizzie, director of digital machining for Sandvik Coromant, says that day has come. The company’s Prometec Promos 3+ solution provides machine and process monitoring capabilities, accessing a variety of signals available throughout the machine tool to make humanlike decisions. “We’re talking about adaptive control technology, which will only increase in power over the coming years,” he explains.
“The Promos can be instructed to look at a sensor on the spindle to check for heat or vibration, or detect whether a tool is getting dull. It can then tell the machine to ease up on the feedrate, change tools, or call an operator if it’s a serious problem. On the other hand, it might sense that there’s plenty of power available and tell the machine to speed up within certain predefined parameters.”
Rizzie anticipates a day (and soon) where toolholders and even cutting tools have onboard sensing capability, able to send data to the machine, the cloud, or a shop floor control system. “Here’s an everyday example: one of the biggest reasons we break drills is because the coolant hole gets clogged,” Rizzie notes. “It’s such a simple thing to avoid if you just put a sensor in the end of the tool to detect coolant flow.”
Sandvik Coromant is going down that road with its CoroPlus suite of IIoT solutions. The Bluetooth-capable CoroBore+ boring head, for instance, has remote adjustment via a tablet computer or other mobile devices. And Coromant’s Silent Tools+ connected adapters transmit in-cut data to a remote dashboard, providing better process traceability.
Rizzie anticipates both of these solutions will soon be integrated directly with various machine controls, and will in turn bring automated adaptive control capabilities to these important holemaking functions. “We’re working with shops that are leveraging our Promos solution to their advantage. As these technologies mature, you’re going to see even more cool stuff coming to the market. The most successful companies will be those that take full advantage of it.” SMT