Condition of vibration involving the machine, workpiece and cutting tool. Once this condition arises, it is often self-sustaining until the problem is corrected. Chatter can be identified when lines or grooves appear at regular intervals in the workpiece. These lines or grooves are caused by the teeth of the cutter as they vibrate in and out of the workpiece and their spacing depends on the frequency of vibration.

Substances having metallic properties and being composed of two or more chemical elements of which at least one is a metal.

Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.

The majority of the cutting tools used by Imagine for machining cobalt chrome are coated, 2-flute, ballnose endmills, ranging in diameter from 0.5mm to 3mm, with neck lengths from 4mm to 14mm. Spindle speeds range from 15,000 to 35,000 rpm, depending on tool diameter.

Tendency of all metals to become harder when they are machined or subjected to other stresses and strains. This trait is particularly pronounced in soft, low-carbon steel or alloys containing nickel and manganese—nonmagnetic stainless steel, high-manganese steel and the superalloys Inconel and Monel.

To control chips, Dahms recommends the radial chip thinning technique, especially when applying Oak View Tool’s CC series endmills, which have at least six shallow-depth flutes.

The Ceratizit Group’s Schleinkofer seconded this, citing studies from Europe that compared the number of components from a traditional powertrain engine to a fully electric one in order to determine the volume and amount of machine materials. “The results showed that, for electric powertrain vehicles, there was 70 percent less machining compared to traditional automobiles,” he said. “This will significantly affect the metal cutting industry.”

When the shift does go into full effect, however, the decrease could be dramatic. Drape and others explained that, where a typical gas engine might contain 120 to 140 components and require 30 to 40 unique carbide tools to machine, an EV reduces both of these by perhaps 80 percent or more. And while that’s a large figure, “the biggest impact on carbide usage will come from transmissions,” he said. “These contain far more parts that will likely be unnecessary as automakers transition to EVs. Engines are small potatoes by comparison.”

When considering an ultrasonic machine, Sutor emphasized looking at the advantages of the equipment, such as extended tool life, high surface quality and accuracy. “If these points are interesting for you, the ultrasonic technology is a step forward for your company.”

Oberg Medical produces an array of cobalt-chrome medical parts. From top to bottom: tibial augments used in knee replacements, a full tibial augment primarily used in total knee-revision surgery, and a trapezium implant used in the hand to replace the joint that controls thumb movement.

Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.

Kennametal’s Davis is in full agreement and thanked advances in computer software and machine tool technology for the past decade or two of continuous improvement. With that in mind, he also thinks the carbide tooling industry will see some fundamental changes in the near future. “All of us continue to develop better cutter geometries and coatings, but the key will be to bring those down to the micro level rather than the macro,” he said.

Times have changed, as has carbide, more properly known as tungsten carbide or sometimes cemented carbide. We won’t explore its long history here except to say that this most important of all cutting tool materials’ 100th birthday is approaching, and as with all centenarians, it behooves us to evaluate whether it’s time to turn this machine shop veteran out to pasture.

“Solid ceramics can be used in place of solid carbide in some applications, especially for roughing,” said Danny Davis, senior staff engineer at Pittsburgh-based Kennametal Inc. “However, carbide is typically still needed in conjunction with ceramics to complete many parts. In addition, ceramics require very high surface speeds to plasticize the material properly and make the tools work as they should. Not every machining center has the necessary spindle rpm, nor the rigidity. That equation will change as we and other suppliers introduce ceramic end mills in larger diameters and develop ceramics able to cope with less stringent operating parameters. Even so, it’s not always the perfect solution.”

Oberg machines cobalt-chrome bar stock and castings and one challenge the company faces is securely holding the castings during machining. The near-net shapes have complex contours and typically there is no flat surface to grasp, Hoffman explained. As a result, the company spends a good deal of time designing and building fixtures to enable rigid workholding.

Structure of a metal as revealed by microscopic examination of the etched surface of a polished specimen.

As for PCD tooling, Todd White, sales director for Scientific Cutting Tools (SCT) Inc., Simi Valley, Calif., echoed what others here said: With automakers and especially the aerospace industry shifting more materials to composites, cutting tool makers should expect increased demand for PCD products as well as solid-carbide tools with special diamond-like coatings (DLC) to help cut them.

Linear distance traveled by the cutter during the engagement of one tooth. Although the milling cutter is a multi-edge tool, it is the capacity of each individual cutting edge that sets the limit of the tool, defined as: ipt = ipm/number of effective teeth 5 rpm or ipt = ipr/number of effective teeth. Sometimes referred to as the chip load.

To minimize workhardening and the damage it can cause to even a properly designed cutting tool, the tool must be kept loaded and continue to shear the workpiece rather than rub it, according to Hoffman. “You have to bite into the material, but you cannot sit there and dwell,” he said. “You have to stay in the cut.”

Materials composed of different elements, with one element normally embedded in another, held together by a compatible binder.

Chung emphasized the importance of keeping tool wear to a minimum when milling dental implants, which have tolerances as tight as 20µm.

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Raun of Iscar has a similarly long history in the cutting tool business. “Compared to the carbide rod that was available when I entered the industry, the hardness and density have risen to a very high level,” he said. “Because of this, it can withstand wear and cutting forces far better than it once did. Couple that with today’s advanced coatings and, as others have mentioned, the geometries and edge preps that are now available, and you’re left with far more capable cutting tools than were previously available. I feel those advancements will only continue as the technology behind them improves.”

Compared to titanium, cobalt chrome infuses more effectively with other materials, such as a ceramic or composites, which covers the understructure and makes the restoration look more aesthetically pleasing. “You mimic the natural tooth color,” Chung said. “Titanium doesn’t have very good bonding with porcelain, so some people stay away from using it.”

Sandvik Coromant’s response was much the same as Ingersoll’s. “Like other cutting tool manufacturers, we’re very much in the development stage, although we do expect 3D printing to contribute to our offering in some unique and very productive ways,” said Lind. “That could be from a prototyping standpoint, as one might expect, but there’s also the potential for complex, advanced engineering solutions. As I said, it’s still early in the game—but stay tuned.”

Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.

Hoffman added that Oberg creates the datum structure in the parts so the features that are held are held consistently throughout every step of the operation, including when a part moves from one machine to another. Therefore, variability is not introduced into the process.

Hoffman noted cobalt chrome’s abrasiveness dulls cutting edges, but doesn’t typically cause them to chip or break. A degraded surface finish is the telltale sign of a worn tool, he explained, adding that most implants require a 20 µin. Ra finish off the machine to allow polishing to a 2 µin. Ra finish if required by the customer. Oberg regrinds worn tools, but to ensure quality, the company doesn’t use them to machine other implants.

White, Lind and Davis noted that much of this demand for PCD and other material-specific cutting tools will come from the automotive market, where electric vehicle (EV) production will continue to increase as the world moves away from internal combustion engines (ICE). Duane Drape, national sales manager for Horn USA, Inc., Franklin, Tenn., sees much the same trend, although he tempered his remarks by stating that gas-electric hybrids will likely serve as the bridge to all-out EVs.

Cutting tool materials based on aluminum oxide and silicon nitride. Ceramic tools can withstand higher cutting speeds than cemented carbide tools when machining hardened steels, cast irons and high-temperature alloys.

Au contraire, said a host of cutting tool manufacturers; each of the suppliers interviewed for this article is in full agreement that carbide has a long and productive life ahead of it.

The challenge of cutting cobalt chrome is compounded when the workpiece has hard, abrasive intermetallic compounds in its microstructure. “The hard spots are about 58 HRC,” said Matt Dahms, founder and president of Oak View Tool Co. LLC. “That’s the problem.”

Material-removal operation in which an abrasive slurry flows between a tool, vibrating at a high frequency, and a workpiece.

Ceratizit disagreed, at least from a production perspective. “Keep in mind, we and others are pressing inserts in two seconds, so I don’t see how this would work with 3D printing,” Schleinkofer said. “The process is far too expensive. Also, consider that dense cemented carbide cannot be produced by laser sintering. You can only print green parts, so a trip to the furnace for sintering after the 3D printing process is always necessary. However, 3D printing does provide us with more flexibility in terms of implementing customer requirements and opens new design possibilities, which we can use to offer our customers highly optimized, individual solutions in minimum time. It is an ideal solution for small volumes and high component complexity.”

Hardness is a measure of the resistance of a material to surface indentation or abrasion. There is no absolute scale for hardness. In order to express hardness quantitatively, each type of test has its own scale, which defines hardness. Indentation hardness obtained through static methods is measured by Brinell, Rockwell, Vickers and Knoop tests. Hardness without indentation is measured by a dynamic method, known as the Scleroscope test.

Substrate and coating technology continues to advance, enabling ever more capable tooling that will significantly improve efficiency and profitability for the machining industry. That is according to Sarang Garud, product manager at Walter USA LLC, Waukesha, Wis. “That being said, we expect to see more aluminum used in the automotive and other industries, so polycrystalline diamond (PCD) will also grow quite a bit, although carbide will remain number one.”

Radial chip thinning is the effect of taking a radial WOC less than 25 percent of the milling tool’s diameter. The chip thickness based on the calculated feed per tooth will diminish as the radial width decreases, resulting in a lighter actual feed per tooth. This causes the tool to rub the workpiece rather than cut it, so the feed needs to be increased as the radial depth decreases. The result is a lower temperature at the tool/workpiece interface, a decrease in cycle times and longer tool life.

In detailing the accuracy of ultrasonic machining, McKimson noted each ultrasonic tool is obtained from a 25-position toolchanger and a Renishaw probe monitors its position. Technicians often load three sets of the tools needed for the 66-piece runs, ensuring virtually 24/7 unattended operation. According to McKimson, accuracies are from 2µm to 4µm, and process reliability has significantly reduced scrap.

Ability of the tool to withstand stresses that cause it to wear during cutting; an attribute linked to alloy composition, base material, thermal conditions, type of tooling and operation and other variables.

Abrasive process that improves surface finish and blends contours. Abrasive particles attached to a flexible backing abrade the workpiece.

“Bar stock is like butter compared to castings,” Dahms said. “The castings seem to vary, and when it’s that tough of a material, just a little difference makes a big difference.” He added that the tools used for a cast application have stronger edge prep.

To enhance efficiency when cutting medical-grade cobalt chrome, the Columbia City, Ind.-based toolmaker developed the Ortho-Cut “CC” series of endmills. Oak View Tool also makes CC specials, such as keyway, form and dovetail cutters. “The series is designed for cobalt chrome and those types of tough materials that workharden and tear up a typical tool,” Dahms said.

When milling understructures for dental restorations, titanium is often the workpiece of choice, but cobalt chrome is another option that offers advantages, according to Felix S. Chung, president/owner of Imagine Milling Technologies LLC, a Reston, Va.-based dental milling center.

According to Sutor, most of DMG’s ultrasonic machines are automated with either a robot or a linear magazine. “For the dental industry, complete 24/7 automation is available,” he said.

The next step is translation of the digital impression to a RenShape mold, using conventional machine tools. Usually, the required structures are simultaneously designed, and then the mold with coping is sent to the DMG Sauer ultrasonic dental machine for preparation of the final structures. This is where Core3dcentres processes advanced and expensive substrates, such as cobalt chrome, ceramics, lithium disilicate and zirconia.

Going a step further to ensure repeatability when machining cobalt-chrome and other parts, Moser said Judson A. Smith uses workholding receivers, including ones from Hirschmann, Erowa and System 3R. The receivers can be transferred from machine to machine, such as from a milling machine to a wire EDM, without removing the part from the fixture. “You also have the ease of knowing where your datums are and not having to try to find a datum,” he said.

Moser noted the company tends to apply uncoated carbide ballnose and other endmills to cut cobalt chrome, with some tools having a titanium-nitride coating for enhanced wear resistance. When the metal’s hardness makes it too much of a pain to mill or turn, or part features are too small or delicate for those machines, the shop will wire or sinker EDM it. “That way you don’t have to worry about a very small cutting tool that just wants to ping right off once it touches the part,” he said.

Nonetheless, tool selection is only one piece of the machining system puzzle. “What is most important to be successful is to have a robust process that incorporates effective workholding, a solid machining approach and the latest in cutting tool technology,” Hoffman emphasized. CTE

Yet Walter Tools suggested that an EV’s greater percentage of aluminum components also puts the squeeze on cast iron, the automotive industry’s longtime darling. Ironically, this trend will cut into this sector’s consumption of ceramic and especially CBN tooling, the latter of which can withstand far higher cutting speeds in cast iron and hardened steels, and has therefore gained market share over recent years. Here again, carbide is expected to emerge victorious.

Mendell Machine’s Storlie also understands the value of the right high-quality tool for the job. “Getting the proper tool is so critical because, if you don’t have it, you might only last 20 parts,” he said. “With the proper tool, you might get a few hundred parts.”

Staying tuned is good advice for any technology, and carbide cutting tools are no exception. SCT’s White assures us that carbide substrates and tool coatings will continue to evolve to keep pace with material advancements.

The endmills also have unequal index geometry to minimize vibration and corresponding chatter. They have a carbide substrate with at least 10 percent cobalt to enhance tool toughness. The tools can be coated with aluminum titanium nitride or ordered uncoated if the orthopedic company has not yet validated the toolmaker’s coating, Dahms noted. He added that the coating, however, can extend tool life at least 30 percent. “The substrate, coating, geometry and edge prep are key,” he said. “If you’ve got those four things figured out, you can make the tools work really well.”

“Electric vehicles are indeed beginning to have an effect on the overall amount of carbide that automakers are using,” he said. “However, EVs are still a very small portion of the market, and I think we’re probably two decades away from their taking a meaningful share. Until then, the need to produce ICE, hybrids and EVs concurrently will likely increase the demand for cutting tools of all kinds.”

It’s Drape at Horn who perhaps best sums up the situation, stating that “3D printing will eventually take some business away from machine shops and cutting tool manufacturers, but until it’s able to provide greater accuracy and surface quality, you’re still going to need solid-carbide tools for the finishing work.”

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In addition, Dahms promotes using the full-flute length when machining cobalt chrome, and noted Oak View Tool designed the CC series tools to handle that type of cutting. “A lot of people do surfacing where they’ll use Z-level depths to remove material,” he said. “We want to get in and out quickly, because every time you use a Z-level depth, you’re putting more heat into the part and getting workhardening.”

“Carbide has a unique combination of hardness and toughness that is hard to match in other cutting tool materials,” Garud said. “When combined with the advanced coatings that we currently have and will continue to develop, it offers a very large application range that can’t be matched.”

Regardless of the machining methods, cobalt chrome’s high cost makes scrap unacceptable, and up-front process design is critical to producing good parts, according to Oberg’s Hoffman. What shouldn’t be considered an unnecessary expense is the cost premium for high-performance cutting tools to effectively cut the metal.

Oberg Medical uses high-speed machines from GF AgieCharmilles to produce some of its cobalt-chrome medical parts.

Substance used for grinding, honing, lapping, superfinishing and polishing. Examples include garnet, emery, corundum, silicon carbide, cubic boron nitride and diamond in various grit sizes.

Grooves and spaces in the body of a tool that permit chip removal from, and cutting-fluid application to, the point of cut.

Combined variations of all dimensions of a workpiece, measured with an indicator, determined by rotating the part 360°.

The types of tool wear typically seen include abrasive, crater and notch, according to Judson A. Smith’s Moser. Abrasive wear is primarily the result of hard particles in the workpiece rubbing or grinding the cutting edge. Crater wear occurs when hard-particle grinding removes tool material from the chip face, and can be remedied by selecting a positive geometry and reducing the speed to lower the temperature in the cut. Notch wear is concentrated at a tool’s DOC and generates burrs.

Ceratizit USA Inc., Warren, Mich., is another cutting tool manufacturer active in the ceramic milling arena. And while Dr. Uwe Schleinkofer, head of research and development at the Ceratizit Group, agreed that ceramics development is ongoing, he doesn’t see it challenging solid-carbide cutting tools anytime soon. “Ceramic does have a place and is often the best solution in dry conditions and accelerated spindle speeds, but its use in the future will continue to be in these niche applications.”

When holding the cutting tool itself, Dahms recommends toolholders that minimize total indicator runout when machining cobalt chrome. “Shrink fit is the perfect world,” he said, adding that high-quality milling chucks are suitable. “Those chucks are much better than the standard Weldon-flat, slip-fit holders. That’s out and old school.” With the correct tool geometry, tool pullout is not an issue, according to Dahms.

That’s just a sampling of the overall enthusiasm for solid-carbide cutting tools and the productivity gains they bring to the table. Competition notwithstanding, experts at Kennametal, Ingersoll Cutting Tools, Horn USA, Ceratizit, and Scientific Cutting Tools all concurred that carbide use will continue to prosper over the next decade and beyond.

The DMG Sauer 20 ultrasonic machine with a robot loader at Core3dcentres has a Siemens Sinumerik 840D sl CNC. The CNC recognizes the workpiece pallet, which is coded by patient name to reportedly eliminate error.

Cobalt-chrome alloys are a good fit for medical and dental parts, but machining them can be a headache.

Machining operation in which material is removed from the workpiece by a powered abrasive wheel, stone, belt, paste, sheet, compound, slurry, etc. Takes various forms: surface grinding (creates flat and/or squared surfaces); cylindrical grinding (for external cylindrical and tapered shapes, fillets, undercuts, etc.); centerless grinding; chamfering; thread and form grinding; tool and cutter grinding; offhand grinding; lapping and polishing (grinding with extremely fine grits to create ultrasmooth surfaces); honing; and disc grinding.

But as Walter’s Garud alluded to, what about advanced cutting tools made of PCD and cubic boron nitride (CBN)? And whatever happened with all the hoopla over solid-ceramic end mills, with glossy magazine photographs showing flames spouting from Inconel workpieces seeming to spell certain doom for carbide, at least when it came to the milling of superalloys? Surely carbide can’t compete against these ultra-hard and abrasion-resistant cutting tool materials?

“You can try to cut tool costs but you’ll lose money in scrap and just induce more risk in terms of more tool changes and tool adjustments, tool breakage, poor surface finishes and rework. We’ve seen all of that happen if not using the right cutting tool,” Hoffman said. “I tell my guys all the time: Don’t step over a dollar to pick up a dime.”

Hoffman agreed that shrink-fit holders work well when cutting cobalt chrome. “Everything we machine from the medical side is HSK 63, all Haimer shrink fit,” he said. “This allows us to maintain a 0.0001 " TIR on our cutting tools, which is vital for achieving fine surface finishes and improved tool life when cutting cobalt chrome.”

And Drape of Horn said carbide and carbide cutting tools are always getting better, “but unless there’s some new mineral that’s found in abundant supply and is relatively easy to get, it will be in baby steps rather than leaps and bounds.” He suggested that these improvements will primarily come in the form of more advanced edge preps and coatings more so than the carbide, although all three are necessary pillars of high-performance cutting tools.

“Cobalt chrome is extremely challenging to machine,” concurred Russ Moser, machining manager for medical parts manufacturer Judson A. Smith Co., Boyertown, Pa. Although the material has a tendency to workharden, he said cobalt chrome’s high hardness causes the shop more problems. “It becomes even more difficult once the hardness gets up in the 50-HRC range.”

“At the end of the day, everybody has access to the machines, everybody has access to the cutting tools, but what makes or breaks your approach is the process itself and the workholding,” he said.

Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

Las Vegas-based Core3dcentres USA is located near the Las Vegas Institute for Advanced Dental Studies, where restorative and cosmetic dental techniques are taught to practicing dentists and laboratory technicians.

After a cobalt-chrome chip is produced, it’s critical to evacuate it from the tool so the heat in the chip doesn’t penetrate the tool, Moser pointed out. He added that he judges if the process is creating proper chips by their color and looks for a tan to bluish-black shade.

That’s true for parts made of both metal and polymer, yet Iscar’s Raun said it’s the former that will present the greatest challenge for cutting tool manufacturers. “Additive technologies such as metal powder bed and binder jet raise the potential for entirely new alloys, ones that are both stronger and more wear-resistant than existing metals. I’ve heard of tungsten blended with aluminum, for instance, which I imagine would be quite difficult to machine. As more and more of these hybrid materials come online, it’s going to tax cutting tool companies to come up with solutions able to productively machine those materials.”

Woksa of Ingersoll painted a similar picture. He noted that, while the technology to 3D print solid-carbide and indexable tooling is under development, it is virtually impossible to compete with current carbide production technology. However, carbide insert product development will be impacted, since specials and small batch carbide tools and inserts can be produced faster and more economically if a die set is not required. “Also, there’s the potential to develop unique capabilities such as coolant-through holes with pinpoint accuracy that would otherwise be impossible,” he said.

“If it can be done, 3D printed carbide will open up new possibilities for tool design and give us the ability to quickly customize them for specific applications,” he said. “It certainly has the potential to change the playing field for the industry overall, providing advantages to those that can effectively use it.”

Combined variations of all dimensions of a workpiece, measured with an indicator, determined by rotating the part 360°.

Process similar to ram electrical-discharge machining except a small-diameter copper or brass wire is used as a traveling electrode. Usually used in conjunction with a CNC and only works when a part is to be cut completely through. A common analogy is wire electrical-discharge machining is like an ultraprecise, electrical, contour-sawing operation.

According to Chung, cobalt chrome is also not as challenging to machine as titanium because titanium chips don’t effectively absorb and transport heat away from the tool/workpiece interface. This means coolant is typically required. Cobalt chrome, on the other hand, can be machined dry, he pointed out, adding that the company applies a silicone-based cooling agent when producing titanium restorations on its Datron dental milling machine. “There’s not a lot of water mixture with it,” Chung said, “and that [cooling agent] can get very messy.”

And Steve Lind, vice president of solid round tools for the Americas at Sandvik Coromant, Mebane, N.C., said his company expects to see continued growth in the solid-carbide market for the foreseeable future. “I attribute much of this to cutting tool manufacturers’ increased design capabilities, along with more advanced grinding equipment. The result is a wide selection of products that allow the industry to take full advantage of today’s sophisticated machining technology.”

Because cobalt chrome can workharden, CC tools have an edge prep combined with an effective shear angle, Dahms explained. “It’s so tough of a material, you have to hit it with the best of both worlds.”

Process that vaporizes conductive materials by controlled application of pulsed electrical current that flows between a workpiece and electrode (tool) in a dielectric fluid. Permits machining shapes to tight accuracies without the internal stresses conventional machining often generates. Useful in diemaking.

“Solid carbide use is growing, and growing tremendously,” said Thomas Raun, chief technical officer at Iscar USA, Arlington, Texas. “Granted, indexable and interchangeable systems enjoy a big piece of the pie, but there’s still a huge number of applications where you can’t replace a solid-carbide end mill or drill.”

“It ranks at the top in terms of difficulty,” said Steve Storlie, vice president of business development for Mendell Machine and Manufacturing Inc. The Lake-ville, Minn., medical parts manufacturer specializes in implants, surgical instruments and diagnostic equipment, as well as serving the defense and aerospace industries. It is no stranger to tough jobs. “We do all kinds of titanium,” he added. “We do titanium every day.”

Cutting tool manufacturers are using finite element analysis (FEA) to understand how much heat and force will be generated during the cut, and determine optimal helix angles and chip formation long before the tool is made. Machine tools are improving as well, with many suppliers using CNC grinders able to hold 1 μm or better accuracy. Both enable the production of cutting tools that, not so long ago, were impossible to manufacture. Said Davis, “Since I started with Kennametal nearly four decades ago, the technology has advanced by leaps and bounds.”

“The process is more or less a grinding process,” said Dr. Uli Sutor, senior account manager for DMG Vertriebs und Service GmbH Deckel Maho Gildemeister, Pfronten, Germany. He added that the ultrasonic tools move 2µm to 4µm about 50,000 times a second and only remove material that’s sintered or harder than 62 HRC. “It is not possible in material like titanium.”

Jim Hoffman, director of manufacturing for Oberg Medical, Freeport, Pa., emphasized the importance of a tool’s corner radius. “You’re not going to go in there with a sharp-corner tool,” he said. “It just breaks down too quickly.”

Added to titanium-carbide tooling to permit machining of hard metals at high speeds. Also used as a tool coating. See coated tools.

The tooling experts at Sandvik Coromant think so as well. “Where ceramics and other advanced materials are designed to work well, they typically do,” said Lind. “Oftentimes, they’re then used in conjunction with solid-carbide tooling for roughing. In both cases, it points to the industry’s growing use of more material- and application-specific cutting tools. This is particularly true for the heat-resistant superalloys (HRSA) material groups, but also in composites and for high-volume applications where consistent tool life and cost per part are critical.”

Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.

“High-performance tooling means fewer tool changes, longer tool life, faster cycle times and more predictable processes,” said Davis. “When you add it all up, the slightly higher cost for one of these tools is very easy to justify. And contrary to what many might think, cutting tools represent such a small fraction of a part’s overall manufacturing cost that it would be a shame not to maximize a CNC machine tool’s performance as much as possible by using the proper tooling.”

Most of the experts here mentioned a similar corollary in the additive manufacturing space. Here, 3D printed parts emerge from the resin tank or build chamber not quite complete. Critical surfaces must be machined, holes reamed or bored, and even relatively open tolerance features brought into specification. Due to the relatively high value of these parts—some of which take hours or days to print—it’s likely that carbide cutting tools will be the preferred solution for finishing them.

At its facility, Core3dcentres prepares CAD files developed from data typically gathered with an iTero oral scanning wand or CAD files from scans of conventional dental impressions from a patient’s mouth, which are then digitally captured in a dental scanner. Software is used to image the impression, beginning the process of creating a crown, bridge, abutment, coping, implant or full denture restoration.

“We do light step-overs with full-flute depths to try to buzz the material off quickly,” Dahms said. “It gets the surface footage back up to where the heat is right for the coating. Also, we get a high enough feed rate to make parts fast enough, so everybody is excited.”

Retired machinists reading this might reminisce over the hand-sharpened bits of Carboloy 883 carbide lying dusty and begrunged in the backs of their toolboxes. Compared to the high-speed steel tool bits these one-time Cincinnati Milacron and Davenport operators cut their teeth on, tungsten carbide’s widespread adoption back in the day meant faster feeds and speeds, longer tool life, higher part quality and a bigger pile of parts on the bench at the end of each shift.

Cobalt-chrome alloys are available as bar stock and can be cast into complex near-net shapes. The cast blank requires less material removal, but has a tough skin to get through or an inconsistent composition throughout the casting or both, noted Oak View Tool’s Dahms.

Blanks of material are loaded into the ultrasonic machine’s 66-position feeder station and delivered to the work zone by a Motoman robotic arm with Schunk pressure grippers.

Alan holds a bachelor’s degree in journalism from Southern Illinois University Carbondale. Including his 20 years at CTE, Alan has more than 30 years of trade journalism experience.

“Carbon fiber and aluminum workpieces continue to become more prevalent,” said Ed Woksa, director of product management and marketing at Ingersoll Cutting Tools Inc., Rockford, Illinois. “Because of this, PCD and DLC tools will continue to replace solid-carbide end mills and drills in some nonferrous and composite applications, particularly in high-volume production. As anyone who’s used it knows, PCD allows significantly higher cutting speeds compared to solid carbide, leading to increased productivity. This is especially important on modern CNC equipment, where faster spindles and look-ahead software technology enables greater throughput. When properly applied, PCD tooling also provides much longer tool life in these materials, providing many opportunities for lights-out manufacturing.”

Like his peers, Davis of Kennametal thinks material-specific cutting tools make good sense. Yes, general-purpose or so-called “GP” tools have their place, particularly for job shops and others that machine diverse materials and workpiece geometries. Yet it’s tools tailored to a specific application that often provide the greatest return on investment.

After machining a few parts for a job, Oberg has captured enough data to understand the process, making it a predictable job, Hoffman pointed out. Operators can then access the tool-life management data and change tools as needed based on the number of parts or minutes a previous tool lasted.

In addition to machining titanium and cobalt chrome, Imagine also makes zirconia understructures, which require minimal material to be added because zirconia is similar to ceramic. Regardless of the workpiece material, each understructure has its own unique, organic shape to match the patient.

About the Author: Alan Richter is editor of CTE. He joined the publication in 2000. Contact him at (847) 714-0175 or alanr@jwr.com.

“Also, any 3D printed part that needs a thread will likely require a trip to the machining center or lathe,” said SCT’s White. “From my side, the most cost-effective way to achieve this—especially given the lower production quantities associated with 3D printing—is with a solid-carbide thread mill.”

Milling cutter held by its shank that cuts on its periphery and, if so configured, on its free end. Takes a variety of shapes (single- and double-end, roughing, ballnose and cup-end) and sizes (stub, medium, long and extra-long). Also comes with differing numbers of flutes.

Changing automotive technology aside, other factors are also at play. Ingersoll Cutting Tools’ Design Engineering Manager Dennis Roepsch pointed to improvements in plastic injection molding, additive manufacturing and investment casting technology, noting that “some workpiece components no longer require machining or have minimal machining requirements. For example, aluminum intake manifolds are often being replaced by molded composite plastics. Also, near-net shape workpieces reduce the amount of material that needs to be roughed, further reducing carbide use.”

In addition to cobalt and chromium, the metals used in the medical industry contain various alloying elements with desirable wear- and corrosion-resistance properties for implants, such as shoulder, knee and hip replacements. For example, CoCr28Mo6 ASTM F75 contains 58.9 to 69.5 percent cobalt, 27.0 to 30.0 percent chromium, 5.0 to 7.0 percent molybdenum, up to 1.0 percent manganese, silicon and nickel, up to 0.75 percent iron and up to 0.35 percent carbon. Cobalt chrome is stronger than stainless steel, but weighs twice as much as stainless and is brittle under impact loading. Hardness ranges from 40 to 50 HRC or higher.

Carriage or drum attached to a machining center that holds tools until needed; when a tool is needed, the toolchanger inserts the tool into the machine spindle. See automatic toolchanger.

Manufacturers of medical and dental parts face an array of challenging workpiece materials, but cobalt-chrome alloys might take the cake.

According to Garud at Walter Tools, the two will probably need each other in other ways as well. As with all new technologies, he suggested that it can be difficult to see the universe of possibilities and effects 3D printing will have on solid carbide tooling over the long term. And yet, additive has already gained the ability to print titanium and Inconel components for aerospace and other industries—and done so far quicker than most would have expected. Printed cutting tools seem a possibility.

Tim McKimson, the company’s worldwide director of engineering, explained that the decision to cut ultrasonically rather than use other techniques was relatively easy, given the inherent wear conditions and high cost of conventional cutting tools. In the ultrasonic process, a combination of electrolysis and fluid lubrication act in concert to create an ionic attraction of particles, removing material in a predictable and accurate way, without the mechanical stress implicit in conventional machining.

Compared to other difficult-to-cut materials, such as 17-4 precipitation-hardened stainless steel, Hoffman said Oberg might cut surgical implant-grade cobalt chrome 40 to 50 percent slower because it’s more challenging. Generally, the surface speed is about 200 sfm and the feed rate from 0.0004 to 0.005 ipt, depending on the DOC, when applying a 3- or 4-flute endmill.

The takeaway is clear: Even though 3D printing might eventually accomplish what many in the industry have feared since its inception more than three decades ago—namely, less demand for traditional manufacturing—it’s more likely that additive and subtractive will complement one another.

Oak View Tool designed its Ortho-Cut “CC” series endmills for machining medical-grade cobalt chrome. They are available with corner radii for added rigidity or for matching the size of the part feature.