Technology Cuts Cycle Time
New tools are designed to keep spindles cutting metal
By Jim Lorincz
Manufacturers of cutting tools are rewriting the cost-benefit equation for their customers with advanced technology products that increase tool life, and improve cutting speeds and feeds, while addressing the critical need to reduce wasteful noncutting time.
Examples drawn from manufacturing headlines reflect the success manufacturers are having in their search for a competitive edge in a globally challenging marketplace.
- Brighton NC Machine, a family-owned contract manufacturer (Brighton, MI), adopted Widia Heinlein M750 HexaCut milling cutters to rough and finish-machine a three-piece exhaust manifold from heat-resisting ductile iron castings on four new high-speed Mitsubishi HMCs. The Widia Heinlein cutters (Kennametal Inc., Latrobe, PA) have an adjustable-wedge clamping system for holding indexable hexagonal double-sided roughing and finishing inserts with a total of 12 cutting edges. The Kyon ceramic inserts and the cutter's negative cutting angle deliver smooth milling with low cutting force, producing an eightfold advantage as cutters jumped from 30 to 240 ipm (0.76-6.1 m/min). Capacity was freed up, tool life extended, and indexing and tool change time reduced.
- RUAG Aerospace (Emmen, Switzerland) tooled up its double-spindle machining centers with positive, sharp tools and inserts to machine the titanium roller track beam for the Airbus A320. Fine-grain carbide inserts (F15M and F40M) from Seco (parent of Seco-Carboloy, Warren, MI) are used for all milling operations at cutting speeds from 50 to 70 m/min. Seco's CrownLoc Geometry M drills with exchangeable crowns are used for drilling superalloys. To ensure that the right inserts in the right quantity are available 24/7, RUAG uses the Seco-Point automatic tool dispensing unit. Day-to-day consumption of tooling is adjusted over the internet with reordering done automatically via e-mail.
- When Excel Machine and Fabrication (Baltimore) retooled an aluminum milling job to meet an 8-rms surface-finish spec with Ingersoll Cutting Tools' (Rockford, IL) Aluminator face mills, the contract manufacturer not only achieved the desired surface finish, but also got three unexpected cost savings. Surface finishes were so good that one inspection job could be eliminated; cycle time for the critical milling operation was cut in half, and, with cutting edges lasting ten times longer, indexing time became a nonissue.
These examples are not unusual. They illustrate how manufacturers are slashing cost-per-part. As long as spindles are cutting metal, the full benefit of increases in cutting data—even with more expensive tooling—can be gained.
According to Sandvik Coromant (Fair Lawn, NJ), a 20% increase in cutting data (speeds and feeds) can reduce cost-per-part by 15% compared to a 1% savings that either a 30% discount in tooling cost or even a 50% increase in tool life can return. The secret is better utilization of available machine time and squeezing better return on investment from fixed costs associated with labor and bricks and mortar. An added benefit, says Sandvik Coromant, is that capacity is increased by 15%.
Traditional approaches to developing cutting solutions include new product designs, grades, coatings, geometries, substrates, and processing techniques. Whole new classes of tools may even be created. A process that begins with R&D in the laboratory is followed by real-world application testing with customers at beta sites, and, finally, fine-tuning with application engineering. The objective is maximizing the performance of machines that can range from low-power machining centers to the most advanced high-speed, five-axis, or, increasingly, multitasking machining centers.
Swiss cutting-tool manufacturer Lamina Technologies' (Wayne, NJ) emphasizes the ability of its "lean tooling" technology to increase the time a machine tool spends actually cutting metal, i.e. being "in cycle." Citing studies that show that CNC machines are actually cutting on average only 20% of the available time, Lamina designs its carbide inserts for more accurate and consistent performance and longer tool life to reduce tool changes, setup, and gaging time.
Lamina's inserts are manufactured from advanced submicron powders to close tolerances. They can often eliminate the need for test cuts and offsetting associated with indexable inserts. Lamina employs a PVD-F (physical vapor deposition fusion) coating technique, increasing coating strength and adhesion and performance for a broader range of applications, including high-strength and corrosion-resistant alloys for aerospace and medical components.
The Z-Carb solid-carbide end mill from SGS Tool Co. (Munroe Falls, OH) reduces chatter in high-speed and high-production applications with its patented dual-helix technology. The unequal dual helix combined with SGS-patented features helps break up vibration and harmonics through varying the forces, alternating the point of cutter tooth engagement, and varying the shear angles—tooth-to-tooth and along each tooth.
In tests, the Z-Carb end mills milled 275% deeper (axial) than a standard carbide end mill without creating chatter, and while cutting at a radial width of cut equal to 50% of the cutter diam, as well as increasing feed rate 100%. A material-focused geometry, Z-Carb HTA with AlTiN coating (SGS' Ti-NAMITE) has been added for aggressive machining of superalloys, such as Inconel, Waspaloy, and Hastelloy.
Sandvik Coromant Company (Fair Lawn, NJ) is releasing its GC4225 general steel turning grade, which is aimed at the broadest range of steel machining applications. The rake face of the insert is blasted after coating, exposing the Al2O3 layer and producing an ultrasmooth surface that resists built-up edge, coating flaking, and gives better wear resistance. Gold TiN flash on the flank of the insert allows operators to easily identify edges that have been used. Testing has demonstrated increases in productivity and tool life with higher speeds and feeds.
The GC4225 turning grade expands the machining reach currently achieved by Sandvik Coromant's GC4025 grade. Typical applications include automotive parts, pumps, forgings, and castings, and parts that require toughness in machining interrupted cuts, scale, or thicker skin. The GC4225 grade is optimized for steel, but will perform well in machining stainless steel.
Sandvik Coromant's 7015 CBN grade for hard turning involves a new technique for putting the tip into the insert. The CBN is cut off like a dovetail and brazed in far enough away from the cutting zone so that the heat in-cut does not affect the braze integrity. Applications include automotive parts, ring gears, pinions, bearing cups, and drive train parts, with surface hardness from RC 58-63. The grade is designed to be used with a wiper and high feed rates.
BIG Kaiser Precision Tooling Inc. (Elk Grove Village, IL) has introduced its Fullcut Mill indexable insert end mill to the North American market. The Fullcut Mill features sharp cutting edges with both high radial and axial rake angles with up-sharp edges for milling tough materials like mold and die steel. The mill delivers quiet milling of steel or stainless steel as a result of the sharp cutting edge, with increased edge toughness due to an eccentric relief angle ground on the peripheral cutting edge. This geometry is matched for each cutter diam.
Providing an eccentric relief angle is a new approach to indexable tools, but solid end mills have been ground with an eccentric relief angle for many years to increase edge security. The Fullcut Mill is capable of larger cuts with smaller low-power machines—for milling molds and high-production parts on smaller machines with low power and rigidity. Typical applications include medical, aerospace, tool and die, and automotive. Even 30-taper machines can benefit from using the Fullcut Mill due to the lower power requirements and smooth cutting action.
Getting more edges per insert is always a way to maximize tool design. Sumitomo Electric (Mount Prospect, IL) introduced its SumiTurn T-Rex 55° triangle inserts with six cutting edges to replace the standard four edges of a DNMG insert. The T-Rex is available in the LU and GU chipbreakers with grades AC700G, AC2000, and AC3000. The AC700G grade is suited for finishing applications for steels and stainless steels and roughing for cast iron. The AC2000 grade fits applications including general-purpose machining of steels, stainless steel, and cast iron. The AC3000 is ideal for heavy roughing and interrupted machining of steels and stainless steels. Sumitomo's T-Rex has a maximum cutting depth of 0.100" (2.5 mm) The proprietary toolholding system provides rigid clamping for accurate insert indexing.
For machining hard materials, Greenleaf Corp. (Saegertown, PA) introduced its Excelerator indexable carbide end mills that use Greenleaf's WG-300 indexable whisker-reinforced ceramic inserts. The Excelerator tools are small-diam end mills to 3/8" (9.5 mm) that can rough-mill in the hardened state, reducing processing time by eliminating setup times. For instance, shops use these mills to rough-out molds and dies after heat treat when the steel is hard. This avoids the need to rough-mill while the material is in the soft state, wait for heat treat, and milling a second time for finishing.
The Excelerator is being credited with reducing cycle times for aerospace, tool and mold, stamping, and automotive industries when compared with using carbide end mills, indexable or otherwise. Savings result from eliminating operations, such as EDM and grinding, and the need for extra machine time.
Komet of America Inc. ( Schaumburg, IL) has introduced the KomTronic P70 Electronic Head, a technology that provides U-axis contouring capabilities for machining centers with the additional capacity of rapid front-end tool changes for multiple contouring operations. A single KomTronic P70 head can be used for operations such as turning, grooving, undercutting, chamfering, and contouring. The utilization of U-axis machining processes opens up the operational capability of machining centers, reducing the need for multiple machines and setups on complex components. Through its modular design, the P70 head can be adapted to CAT, HSK, or BT spindle tapers. Improvements to the design of the P 70 have made it smaller and lighter for small machining centers. Typical users include manufacturers with machining centers in high-production as well as low-production volumes with high-precision or SPC requirements.
Kennametal Inc. (Latrobe, PA) continues to advance the technology of both its solid-carbide and modular replaceable-tip drills. The latest version of its solid-carbide drill line is the SE-HP high-positive solid-carbide drill that is capable of high speed to 650 fpm (198 m/min) in cutting steel. Secret of the drill's high metal removal rate is its ability to center itself quickly, providing a soft entry into the workpiece. Point geometry combined with the latest TiAlN-coating and coating treatments provides high metal removal rates for steel and ductile iron, especially for high-production automotive applications.
Kennametal's KenTIP modular replaceable-tip drills are able to run at competitive speeds with feed rates comparable to those of solid-carbide drills, but with the advantage of consistent performance versus reground solid-carbide drills. The hallmark of the replaceable-tip drills is consistency, as the throwaway tips are virtually the same compared with reground solid drills.
Iscar Metals Inc. (Arlington, TX) continues to expand its lines of tangentially mounted inserts, pointing to the combination of the strong and compact inserts with helical cutting edges. Mounting inserts tangentially increases the web thickness of the cutter body for improved strength. The 90° Minitang family of cutters, especially for cutters less than 1" (25 mm) and smaller, have improved cutter strength and stability. The Minitang is available in either fine or coarse pitch and also with coolant-through design, and has four cutting edges per insert in diam from 5/8 to 1.5" diam (15.8-38.1 mm).
The Minitang end mill enables the operator to perform full slotting operations at aggressive DOC. One explanation is Iscar's helical geometry, which features a positive edge that allows cutting feeds of 0.004-0.010" per tooth (0.1-0.25 mm per tooth). Machining results have shown that the Minitang can increase insert life from 35 to 40% per edge with several times the cutter-body life.
Get Serious About Tapping
The days of babying your taps—and cutting ever so slowly—are long gone. In modern processes, taps not only run fast but also last a long time.
"For many years, taps were run too slow," says Alan Shepherd, product manager, Emuge Corp. (Northborough, MA). "Running them fast is actually a lot more efficient because they shear the material, instead of plowing through it."
Of course, the difficulty with doing that had been the danger of breaking the tap. "Breakage used to be a really big deal," says Shepherd. "But it's on the bottom of the list now." So manufacturers are free to exploit the freer cutting action.
And that translates into huge gains in productivity. Consider the threads that Emuge helped a European automaker make in the crankshafts that it machines from 40NiCrMo5. The Mandelli 8 horizontal machine cut the M10 x 1.25—6H threads in a twice diameter blind hole at 10 m/min. By switching to one of Emuge's Rek 1D-Z-IKZ taps, tool life jumped to 890 threads, which is dramatically more than the 100 to 160 threads produced by the old tool.
Why can modern taps offer such huge increases in productivity? There are a number of reasons. The first is that tap manufacturers are exploiting computer technology and flexible manufacturing to engineer and produce their taps for the work material. "Computerization lets you play a lot more with design concepts and try what-if scenarios," says Shepherd. "Before, you'd have to make one each time." Then when it comes time to go to production, programming software allow downloading tested toolpaths into flexible machines that make small-lot production inexpensive.
Consequently, at the recent EMO show in Hanover, Germany, Emuge was able to unveil a line of roll-forming taps designed for specific materials. The number of lobes, their shapes, relief angles, and substrates and coatings are optimized to produce good forming characteristics for specific work materials. "We've also expanded our high-speed geometries, and have taps that are now specifically for synchronous tapping," says Shepherd. The ones for synchronous tapping have much more relief to make them freer cutting and, so, must be used in a rigid holder in a synchronous spindle.
Better machining is the second reason for the huge increases in productivity in tapping over the years. Spindles hold microns today, rather than thousandths. "Machines have better positioning accuracy and don't have the backlash they used to have," adds Shepherd. "Holder technology today has improved too. Years ago, radial floating holders were supposed to help you align the tap with the hole. They caused more problems than they solved." Now that the entire process is much tighter and more accurate, Emuge and its competitors are focusing their new designs on the latest equipment so users can reap the greatest rewards.
This article was first published in the January 2006 edition of Manufacturing Engineering magazine.