It was “a lot of work” and a big investment. But, St. Pierre says, “No one’s looking at this project saying it was a bad investment. Everyone says they wish we had done this earlier.”
Conversely, St. Pierre cautioned, many of these tools are complex, with unequal indexing and variable helices, and many outside vendors don’t want to regrind these tools unless they made them originally. So if you can’t regrind them yourself, you’re locked into a limited supply, which is a costly and potentially risky place to be.
CNC tool grinders and the required ancillary equipment represent a significant investment. So GKN’s management asked St. Pierre to study its tool consumption and project the potential savings it could achieve by taking tool grinding in-house. One key factor, explained St. Pierre, was the fact that many of the tools could be reground multiple times. For example, he pointed to tapered ball-nose end mills, which can be sharpened to the desired “true form, every time.”
Both systems use Schunk hydraulic chucks that clamp different diameters with the insertion of an intermediate sleeve. In GKN’s case, a robot changes out the sleeve. As St. Pierre says, “The roboSet (or the MX7 loader) has all the sleeves already inside and knows where they are. Let’s say Batch No. 1 is a 1/2 in. tool. The robot will grab the 1/2 in. sleeve and load it into the chuck. Then it will run all those 1/2 in. tools and do the required reporting. Once that’s done, it’ll swap sleeves, grab the next size tool, and then start running that program. You just have to write the program and select your schedule.” GKN customized its pallets to hold five different sizes, and St. Pierre said that they can run 20 different tool designs through the ZOLLER in one unmanned shift.
“That way we can help each other out,” says St. Pierre. “We can send programs to each other, we’re grinding the same way…. If they need us to make some tools, they can send us a program, we can run the tools, ship them back, and the tools are exactly as if they’d made them there.”
Metrology
Taking Tool Grinding In-House
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You might think that an in-house grinding shop wouldn’t make better cutting tools than the specialized manufacturers. But owing to its focus on GKN, and St. Pierre’s willingness to experiment, the team has in fact “beaten out a fair amount of tooling from other very well-known tool manufacturers,” says St. Pierre. “Not that that’s our intention. It’s just that we’re able to really focus on our operations and our products, and customize a tool for that production environment. We have the ability to tweak tooling just for us.”
The ZOLLER »titan« also has a robot loader, which ZOLLER calls the »roboSet2«. What’s more, all four grinders plus the measuring machine can automatically change tool diameter during lights-out operation. That’s important, says St. Pierre, because they make “400 different part numbers for GKN. We’re not making batches of 1,000; we’re making batches of 15–20.” And with very few exceptions, they have to inspect between 10 and 100% of all their tools. So flexible workholding is essential to prevent a bottleneck.
St. Pierre’s tool room significantly improves GKN’s overall efficiency simply by delivering the tools the production floor needs quickly. And it’s not just regrinds. “We’re currently using the ANCA machines to grind everything from 1/8 in.-diameter tools up to 1 x 8 in., with a 5.50 in. length of cut,” explained St. Pierre. “We do a lot of one-off custom tooling and whatever emergency repairs are needed…. Any tool that can be made outside, we now make. We make composite tooling, special material tooling, tooling for plastic, wood… whatever we need to do.” Lead times for custom tools are as little as one day, he added, and a maximum of two weeks. “And if you want just one, we make you one.”
Tweaking designs to improve machining
GKN uses ANCA tooling software to produce highly detailed prints of its tools, “instead of just the dummy solids that the industry is used to,” says St. Pierre. “So we’re able to include all the parameters of the actual physical tool and how it’s designed.” These prints then dictate the inspection routine. “On a standard tool, we go through 22 to 30 different parameters…. But we make a lot of variable index, variable helix tools, so we have to check every flute, especially on a setup.” St. Pierre added that a full, detailed inspection “might take 10 minutes, but you can customize those programs and get it under a minute to check” a subset of specific features.
More on the ANCA-ZOLLER partnership
If you’re ready to take the plunge into tool grinding, the next most important consideration is which tool grinder you should invest in. Naturally, ease of use and support are key factors, and it’s wise to think beyond the machine builder. Ask your current suppliers what machines they use and whether they are willing to share programs or offer other assistance. For GKN, ANCA was a clear choice because it’s a market leader and the Swedish operation had ANCA machines.
Jeremy St. Pierre led the creation of an in-house tool grinding operation at GKN Aerospace Engine that paid for itself in only two years. Image provided by ZOLLER.
Faster turnaround
Having said that, St. Pierre recognizes that GKN is a large company that spent a fortune on tools, so starting smaller makes more sense for many companies. He also suggested taking a close look at the “easy wins,” the tools that are both important and doable, “before you say, ‘We can bring in everything.’” Then you can confidently specify the grinder and associated gear, and see if the numbers work.
One surprising discovery St. Pierre reported was being able to eliminate the need for coating on many of their tools by instead honing the cutting edge in an OTEC drag finishing machine. “Our tools are lasting longer edge-prepped than they were coated,” St. Pierre says. “We do coat many of our tools if they’re being used for high-temp machining. But we make a lot of tapered balls for »titan«ium, and we’ve done a lot of testing. We just edge-prep a tool, and it lasts. Sometimes we’ve had four times the life of previous tools.”
GKN also has a stand-alone wheel dresser to condition the wheels offline. But as mentioned earlier, if it’s an unmanned shift, the MX machines can be both grinding and measuring the tools in process, plus measuring and dressing the wheels. Meanwhile, the ZOLLER would be performing finished tool inspection on previously ground tools.
Other ancillary equipment
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St. Pierre summarizes his approach as “push things until they break and then dial it back to make that best tool.” They’ll try tools at the attached GKN plant if there are idle machines, or send them to GKN’s Swedish location, where they have a dedicated testing machine and can provide immediate feedback. They’ll also give sample tools to companies they’ve worked with over the years and ask for their input.
It should be emphasized that although St. Pierre had years of manufacturing and problem-solving experience when he started the project at GKN, he’d never ground a tool. That also holds true for everyone who joined the team thereafter. “I hired people that I knew were mechanically inclined and understood the real world and how you shouldn’t overcomplicate things,” says St. Pierre. “They were all nervous at first, but the first thing we did was fly out to Michigan for two weeks of training with ANCA. And then we started running.” They’ve been learning ever since, and made some mistakes, he says. But only once have they sent out a tool that failed.
To meet QC requirements, GKN requires a stand-alone measuring machine of the »titan«’s caliber. But the ANCA’s measuring capabilities overlap with those of the ZOLLER. How would you divide the tasks they can both perform? Can the machines cooperate? For St. Pierre, besides achieving the required tool quality, the goal is maximizing productivity. So, for example, if an operator is available, he’d prefer to use the »titan« machine to scan a tool profile and send any needed compensation data to the grinder, rather than use the ANCA’s internal laser. This keeps the MX grinding tools.
Arguably the second-most important investment decision for a tool room, especially one serving an aerospace company, is the inspection equipment. ZOLLER, based in Ann Arbor, Michigan, was another natural fit. First, GKN already had ZOLLER presetters, and St. Pierre appreciated the smooth working relationship already established. Second, ZOLLER has a close partnership with ANCA, resulting in solutions that make both machines more capable. So GKN opted for a top-line ZOLLER »titan«, which can automatically measure every tool attribute optically, including the flute form and the edge prep.
Automation with high accuracy
GKN is also beginning to use the ZOLLER to measure the grinding wheels, which again maximizes the MX’s productivity. “We’re getting the equipment in to set up the ZOLLER to do all the wheel measurements, so we can set up a whole batch and then just streamline data into the grinders,” says St. Pierre.
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