Keeping Spindles Turning
Innovative tooling technologies lead to improved productivity
By James Lorincz
“Is your company wasting money by trying to increase tool life? This may seem like a misguided question,” says Marc Kinnemann, product specialist-turning tools & grades, Mitsubishi Materials USA Corp. (Fountain Valley, CA), but the answer suggests otherwise. “In most manufacturing businesses you’ll find a couple of factions working hard but often at crossed purposes. Manufacturing engineers and those who manage cutting tool inventories are working hard to make tools last as long as possible. Purchasing personnel are working hard to spend less money. Someone, most likely a manager, is trying to reduce manufacturing costs and increase profitability. Often, those buying the cheapest tool and those trying to extend tool life are doing so at the expense of profits.”
Kinnemann’s solution is to go beyond the generally used conservative surface speeds, feed rates, and depths-of-cut that manufacturing engineers choose “under the gun to get a new job running.” Small changes in initial parameters to “better” and “best” conditions may decrease tool life while cutting machine time costs. Kinnemann believes stopped spindles and lost expensive machine time are far more damaging to productivity and profitability when compared to the relative cost of cutting tools. For example, he cites Mitsubishi grades, UE6105 and UE6110, for continuous cutting of steels at the elevated surface speeds necessary for best possible performance, and the new MP3025 PVD-coated cermet for extending tool life and producing excellent surface finish in turning steel applications.
“It’s really a worst-case scenario, a smaller tool extending further out from the spindle and running tighter accuracies.”
When talking tool life, it’s impossible to avoid talking about runout. BIG Kaiser Precision Tooling Inc. (Hoffman Estates, IL) considers runout to be the single most important factor affecting tool life. It should be the first thing that the user considers in evaluating toolholders and cutting conditions. “Two important variables in determining what runout should be are tool size and composition. With larger tools, 3/4" [19 mm] or more, runout values of 0.0005" [0.013 mm] may not impair performance and tool life; with smaller tools, we may need to do much better than five tenths,” Jack Burley, vice president sales and engineering, explains.
Reduce Runout to Lengthen Tool Life
“For example, our new Baby Collets are each inspected twice to meet the 1-µm runout guarantee. Switching to a premium toolholder and collet such as ours, can reduce runout dramatically, and increase tool life just as dramatically,” Burley says. “The higher upfront cost of a premium holder and collet is paid back rather quickly when you factor in the cost of some of today’s cutting tools. Often the payback is only a few days. The accompanying chart came from some tests we’ve performed with holders and drills with various runout values. Since acceptable runout is a relative term from shop to shop, this chart gives an idea of what will happen to tool life by decreasing runout by as little as 0.0001" [0.003 mm].”
The trend toward requiring higher accuracy is true in virtually every industry. “In general, our customers are demanding tighter and tighter tolerancing accuracy of tools with longer and longer overhangs, and smaller and smaller diameters,” observes Thomas Benjamin, Walter USA LLC (Waukesha, WI). “It’s really a worst-case scenario, a smaller tool extending further out from the spindle and running tighter accuracies.” In addition, more work is being machined in the hardened state. “We have a lineup of small diameter contouring mills for machining hardened steel from Rc 50 to 70 for the die/mold, medical device, and energy industries, among others. The Proto-max Ultra ballnose-style end mills introduced at IMTS are available from 0.004" (0.10 mm) to 12-mm diameter and feature new substrate and coatings to resist heat buildup.”
For aerospace applications, Walter’s Prototyp Proto-max Inox solid-carbide end mills feature an optimized geometry that provides enhanced stability for the cutting edges and a special surface treatment on the shank for a firm grip. A new line of whisker-reinforced round ceramic inserts is being launched for machining superalloys. With continuing growth of high-pressure coolant applications of 1000 psi (69 bar) and more, Walter offers its ValCool VPLFC heavy-duty, semisynthetic low-foaming cutting fluid for effective machining.
New Tool Designs Offer Cutting Gains
The new H400 profiling solution from Iscar Metals Inc. (Arlington, TX) is an insert with four radius arcs, which allow it to function like a button insert. “The smaller size of the H400 enables a cutter to be designed with more inserts,” says Hassan Narasimhan, national product manager-milling. “Rather than the screw clamping used for button cutters, the H400 design features wedge-type clamping, enabling cutting forces to be transmitted into the body rather than the screw taking all the impact forces. An additional relief helps reduce the wear on the inserts and increases tool life, compared with the same radius being in contact during ramping with traditional button inserts. Flat contact surface prevents the insert from twisting in the pocket, coolant holes are directed to every insert providing long tool life especially when machining stainless steels and exotic materials.” The H400 inserts are offered in three sizes and all three sizes are also offered in three geometries for machining alloy steels, stainless steels, and high-temperature alloys.
At IMTS, CGC Tools introduced the Phenom solid-carbide end mill, which features five-flute geometry for profiling with heavy depths of cut. “It’s not built for full slotting, rather for profiling at heavy radial and axial depths of cut,” explains Mark Greenwood of CGC Tools Inc. (Waukesah, WI). “The Phenom is the next generation of Gorilla Mill. It features the GMX2 multilayer nano composite coating for machining materials like Hastelloy, Inconel, 17-4 stainless, 15-5 stainless, 13-8 stainless, 718 Inconel, and 625 high-yield Inconel,” says Greenwood.
“What we’ve done is take our patented five-flute geometry and changed some of the clearance angles on the flute face and added a new multilayer nano composite coating with the result that performance is increased 13–20% based on these difficult-to-machine applications.” In any machining application, variables like workholding, toolholding, and coolants are critical considerations. For roughing applications, Greenwood recommends end mill holders with setscrew side lock for Gorilla Mills. For semi-finishing and finishing applications, shrink fit effectively controls all the variables, but hydraulic chucks, milling chucks, and some types of colleting system are also good choices. CGC Tools offers Gorilla Mills and Knuckledraggers with Weldon Flats in four and five-flute end mills and roughers.
Control Vibration to Gain Tool Life
Vibration is widely and correctly seen as the enemy of tool life. The right tool clamping system can increase cutting tool life, provide a significant cost advantage, and allow for the highest capabilities in runout even at high speeds and high centrifugal force. The popular powRgrip tool clamping system is said to deliver concentricity with deviations of less than 3 µm up to 4×D and length pre-adjustment with a repeat accuracy of less than 10 µm. High vibration dampening results from contact between interferring surfaces; between the toolholder to collet; and the collet to the tool shank. Since no clamping mechanisms are required in the toolholder, powRgrip has a high degree of rigidity compared to other mechanical toolholders. The full wall thickness is available to absorb the radial forces.
The newest addition to powRgrip is the slim PG 6 for micromachining applications in medical, optics, and watch making applications where tool life, finish, accuracy are very critical, explains David McHenry, senior product engineer. “The PG 6 reduces the outside diameter down to 10 mm into a smaller package and envelope size. Primarily you’re going to see the PG 6 used on the smaller HSK machines 25, 32, 40 machines for precision micromachining. We are able to maintain 0.0001" [0.003-mm] TIR that will make the small drills and end mills that are being used last longer.”
For materials that are used extensively in aerospace and other demanding industries, Emuge Corp. (West Boylston, MA) has introduced TiNox-Cut, a new series of end mills specifically developed to provide exceptional material removal rate and long tool life when machining today’s toughest materials. The Emuge-Franken TiNox-Cut end mills offer high performance cutting solution for nickel alloys such as Inconel 718, Nimonic and Waspaloy, titanium 6Al4V, and 316 stainless.
“The need for parts and components machined from these materials is on the rise, but they are very difficult to machine and wear out tools fast,” says Peter Matysiak, Emuge president. “TiNox has a unique variable flute spacing and a serrated chipbreaker profile along the cutting edge that provides unmatched material removal rate and impressive RA values for both roughing and semifinishing, while producing minimal tool wear.”
TiNox’s dynamic flute and proprietary cutting edge design combined with a high heat-resistant multilayer TiN/TiAlN coating provides long tool life by minimizing friction/vibration and efficiently evacuating shorter chips, which is especially important in tough, long-chipping materials. In addition, tools are made from a special ultrafine carbide grade to further maximize wear resistance.
Technologies Tackle Tough Machining
TiNox-Cut end mills are well-suited for both roughing and finishing operations. They are available with standard flat ends and feature internal coolant/lubricant capability for more efficient feed rates and chip evacuation and optionally with a selection of corner radii. The new end mills feature a tight h11 shank tolerance and a notch in the shank for mechanical clamping. The end mills range from 1/4 to 1" (6–25-mm) diameter.
For drilling large holes typical of construction and agriculture applications, Sumitomo Electric Carbide Inc. (Mount Prospect, IL) has expanded its WDX indexable drill line to include diameters from 0.5625 to 2.625" (14.3–66.7 mm) in 2×D, 3×D, and 4×D drill body lengths. “WDX drills uses two four-cornered indexble inserts per drill, one outer cutting insert and one inner cutting insert,” explains Paul Ratzki. “A job shop can drill a hole on a lathe and then cut back using it as a boring bar and a toolholder using only one tool for multiple operations. We’ve also added a diamond-like coating for nonferrous applications.”
For 90° shoulder milling, the Sumitomo’s WFX series features a redesigned cutter containing a 90° lead angle for part squareness. The inserts’ convex cutting edge provides an optimized toughness with an integrated wiper for an excellent surface finish. The series includes coarse, fine, and super fine pitch cutter bodies. The coarse and fine pitch are offered in the 2 to 8" (51-203-mm) diameter range; while the super fine pitch is available in the 2–5" (51–127-mm) diameters.
High-speed machining with rotating tools creates air turbulences that frequently influence the coolant and prevent it from optimally reaching the cutting tool as desired. Instead of reaching the cutting tool and cooling it, coolant fans out before reaching the tool. Haimer USA (Villa Park, IL) has developed its Cool Flash-System, a shrink chuck which wraps the coolant around the tool like a jacket and protects it against such disturbances.
With the Cool Flash-System, the bores are introduced in the clamping chuck, where the coolant is transported to the face area of the toolholder. The Cool Flash has a disk positioned at the face side of the Cool Flash chuck, which releases a narrow circumferential gap in the direction of the tool. The coolant accumulates at this point on the Cool Flash, builds up a high pressure in this chamber and is distributed over the entire scope of the tool shaft. From this small reservoir, it flows over the tool shaft directly as a closed jacket and is therefore unaffected by air turbulence. At the end of the shaft area, the coolant is pressed into the flutes, flushes them out and then reaches, even at high speeds, the cutting edges of the tool directly without atomizing, where it cooling effect develops.
With Cool Flash, no additional sleeves or separate mounts are required for the optimum cooling, which normally promotes the shrinking process. Haimer shrink chucks can also be shrunk in and out normally using the Cool Flash Option, and the stability, stiffness, and interference contour of the original Haimer chuck remains unchanged. ME
This article originally appeared in the October 2012 issue of Manufacturing Engineering magazine. Click here for a PDF of the article.