E-Sharp News March 2024

Whether you use a lot of cutting tools, or sometimes find yourself desperately lacking the right tool, you’ve probably considered making your own. Or at least sharpening your worn tools. But how do you decide if taking tool grinding in-house is the smart decision? It’s a question GKN Aerospace Engine faced, and Principal Manufacturing Engineer Jeremy St. Pierre walks us through their considerations. Plus, he offers priceless advice on best practices if you make the leap.

 

Cost savings lead to 2 year payback

CNC tool grinders and the required ancillary equipment represent a significant investment. So GKN’s management asked St. Pierre to study their tool consumption and project the potential savings they could achieve by taking tool grinding in-house. One key factor, explained St. Pierre, was the fact that many of their tools can be reground multiple times. For example, he pointed to their many tapered ball nose end mills, which can be sharpened to the desired “true form, every time.”

Conversely, St. Pierre cautioned, many of these tools are complex, with unequal indexing and variable helices, so many outside vendors do not 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.

St. Pierre also found that some of their high volume tools were very expensive just because they were not standard in the industry. “Instead of having a half inch cutter, we might have a 0.485 inch cutter diameter. Because that technically is a custom, we were paying a premium and ordering 12 weeks of tooling. And we had long lead times.” By calculating their true cost of tooling, including the frequency with which they had to “send out 70 tools at once to get a good price,” St. Pierre was able to make a strong case for investing in an even more capable tool room than originally envisioned, with 4 ANCA MX7 Linear tool grinders, a ZOLLER »titan« measuring machine, and a full compliment of support equipment like a wheel dresser and a drag finisher. Yet the pay back time turned out to be just two years.

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.

Faster turn around

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 one-eighth inch diameter tools up to one by eight inch, with a five-and-a-half inch 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 2 weeks. “And if you want just one, we make you one.”

Tweaking designs to improve machining

You might think that an in-house grind shop wouldn’t make better cutting tools than the specialized manufacturers. But owing to their 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,” said 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.”

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 their 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.

St. Pierre also credits ANCA (based in Wixom, MI), with helping meet some of his tool design challenges. “I go to Michigan a few times a year, because the trip is worth it. If I’m struggling, I usually give ANCA tools that not many people are making, and we’ll sit down together and design it. Or they’ll call me and we do it over the phone. Within a day or two, we’ll have a tool together. And they don’t ask anything for it. They just want to know how it’s going. They’ve helped out a lot.”

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 observed. “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.”

In addition to the higher performance, St. Pierre added, edge prepping also eliminates the roughly one-week lead time required for coating, plus that cost and the extra shipping and handling. “A regrind might cost $5, or  $100,” he continued. “But if it’s a $5 regrind, it’s still a $10 coating. Now you’re basically at three times the tool cost. We can eliminate that with a process that takes a few seconds.” (GKN’s average honing time is about a minute, and the OTEC processes 25 tools at a time, according to St. Pierre.)

Independent profit center

St. Pierre’s tool room is attached to GKN’s Aerospace Engine plant in Newington, CT, but it’s run as a separate profit center. They service all 7 GKN Aerospace Engine sites in North America, plus they sell tools to other local aerospace companies. They’ve even been able to bring in outside work for other companies to add revenue. It’s a sidelight for GKN, but it’s also worth considering this possibility when deciding to pursue in-house tool grinding.

Choosing the right grinder…

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 if they are willing to share programs or offer other assistance. For GKN, ANCA was a clear choice, because they’re a market leader and the Swedish operation had ANCA machines.

“That way we can help each other out,” explained 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.”

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,” recounted 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 added. But only once have they sent out a tool that failed.

St. Pierre raved about ANCA’s software: “All their stuff, whether it’s recalibrating, recommissioning, reteaching a position when you’re doing automation, it really walks you through. It’s the most user-friendly machine I’ve ever used. I can take someone from the floor who’s never seen the machine and they can make a tool within half an hour. Design one on the machine and grind it without knowing what they’re doing.”

…And the right measuring machine

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, MI, was another natural fit. First, GKN already had ZOLLER presetters, and St. Pierre appreciated the smooth working relationship they’d 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 opted to add robot loaders to all their ANCA MX7 tool grinders, plus internal wheel dressing and measuring. The machines also have an integrated laser that can scan a tool profile and automatically compensate the grinding program to correct for any deviations from the nominal form. These features combine to enable the machines to produce tight tolerance tools throughout an unmanned shift. “We hold ourselves to plus nothing and minus a half thou on our tools,” said St. Pierre. “And a tighter tolerance on some tools. If it’s a ball nose for finish machining, we’ll hold a couple of tenths.”

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, explained St. Pierre, because they make “400 different part numbers for GKN. We’re not making batches of 1000, 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.

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 illustrated: “The roboSet [or the MX7 loader] has all the sleeves already inside and knows where they are. Let’s say batch number one is a half inch tool. The robot will grab the half inch sleeve and load it into the chuck. Then it will run all those half inch 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 their pallets to hold 5 different sizes and St. Pierre said that they can run 20 different tool designs through the ZOLLER in one unmanned shift.

GKN uses ANCA tooling software to produce highly detailed prints of their tools, “instead of just the dummy solids that the industry is used to,” as St. Pierre put it. “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 ten 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

In order to meet QC requirements, GKN requires a standalone measuring machine of the »titan«’s caliber. But notice how 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.

St. Pierre also referenced situations in which the operator may be unsure of how to make an adjustment. “We’ll use the ZOLLER to make the measurement and send it back to the grinding program to make corrections. It’s nice that they can speak to each other pretty easily, and it wasn’t too hard to set up…We’ve used it on more advanced tooling where there are so many parameters that one thing can affect the other. So we let the ZOLLER help us with those.”

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,” said St. Pierre.

GKN also has a standalone wheel dresser to condition the wheels off-line. 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

Any tool grind shop also needs coolant filtration and temperature control, which at GKN is handled by double vessel Transor systems. Cut off machines are also handy for sizing carbide blanks. Here, GKN took a creative approach and opted for a Makino U6 wire EDM. As St. Pierre put it, “the price difference wasn’t significant enough to justify spending that much on a machine that can only cut off. So, we bought a wire EDM to do custom cut offs in large batches. We also make our own fixturing and inspection gauges for the whole company. That machine paid for itself the first year making things that aren’t related to grinding tools.” St. Pierre added that they will also use the EDM to cut tool profiles and then grind the flute and OD in the ANCAs. “We can hold grinding tolerances on our EDM.” They’re already using it to make steadyrest bushings for the ANCAs.

Add ZOLLER’s TMS tool management software, a 3D printer for robot grippers and other tooling, a Modula VLM storage tower, and a laser marker, and you’ll see that GKN’s tool room is as self-sufficient as it is efficient.

It was “a lot of work” and a big investment. But as St. Pierre summarized it: “No one’s looking at this project saying it was a bad investment. Everyone says they wish we had done this earlier.”

 

Jeremy St. Pierre led the creation of an in-house tool grinding operation at GKN Aerospace Engine that paid for itself in only 2 years (Image provided by ZOLLER)

6 March 2024