The end mills are available in four geometries: barrel-shaped, oval form, taper form and lens shape. Oval and taper form mills are suited for curved shapes such as blades or straight-walled pockets, freely engaging more of the cutting edge. Barrel design mills provide effective flank milling to the sides of spiral grooves and similar applications, according to Emuge. Lens-shaped mills excel in narrow channels or in lands on molds. Specific CAM systems software, such as Mastercam and hyperMILL, are required to support and compute the geometries.

The advantage of multi-flute end mills is that operators can take higher feed rates because of the reduction in DOC and stepover with high-temperature, heat-resistant materials. “These metals don’t like to be machined in the conventional way with large DOCs and large radial stepover and slow feed rates,” said Ball. “Multi-flute tools allow increased MRRs without work hardening because you can run faster feed rates and lighter radial stepovers with more teeth.”

Not every part is a good candidate for high-speed machining. The choice of strategy is a function of the part geometry and size. Some of the testing that’s being seen has been calling for machining Inconel, titanium, and stainless with light depths of cut, high speeds and low radial engagement and feed rates.

The ECY-S5 end mill with five flutes features a general-purpose substrate and AlTiCrSiN coating (IC608) for shoulder or full slot high-speed milling or trochoidal or peel milling. Its primary application is stainless but it can also be used to machine nickel-based, high-temperature alloys.

He pointed out that while getting material roughed out is difficult and can cause multiple problems, optimized roughing with 6-10 percent maximum radial stepovers is effective on heat-resistant superalloys (HRSA) and titanium. “And you can use these same tools to then finish a lot of these parts as well so you are using more traditional side mill finishing,” he said.

It is different with PH stainless, some duplex stainless steels, and titanium alloys where speed can be increased to get more productivity out of the tool. “Duplex stainless steels that have a lot of nickel and chrome content machine more like Inconel materials because of the high nickel content. So, it’s essential in machining high-temperature alloys to understand the alloying elements in them,” he said.

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Horn’s DSFT end mills—part of the DS line of high-DOC, low-radial-engagement tools—are designed for trochoidal machining. To be effective, DS tools require a solid machine spindle with close runout and a capable controller for programming. CAD programs are available to create simulation of machining time estimates to decide whether traditional end milling or high-speed machining is best. In addition, there are a number of software tools available to evaluate the economics of these tooling decisions.

Here’s how leading tooling manufacturers are helping customers put these tools to work in machining titanium, nickel-based alloys, superalloys, Inconel and stainless steel.

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Our range of pendular grinding wheels ensure that fettling work can be performed with reduced exertion and higher stock removal rates. In this type of machining, one of the greatest challenges is vibration during application. Through intensive and ongoing development, we can supply product into the market with significantly reduced vibration levels enabling operators to work more efficiently.

He added: “We have started to play a lot more with variable indexes and [helixes] in multi-flute cutting tools because of their potential for more cutting pressure due to increased tool contact with the workpiece. However, it’s necessary to change [helixes], rakes and indexes to vary the geometry in such a way that it breaks up chatter and harmonics and still retains the tool’s ability to cut efficiently.”

“We determine the process and program and run it within a range of speeds and feeds and estimate a cycle time,” Bruhis said. “Once the customer has a chance to run the program that we have set, we then can get feedback with real machining time results and, if the cycle time is too long and the cost is not in line with expected results, we make the required adjustments.”

“When major OEMs call me in, it’s generally to improve tool life, the process, or both,” Bruhis continued. “It could be a new project with them facing a serious issue. It might be a problem with part quality, or cycle time or delivering parts in time or total cost, but it’s almost never because of the cost of the tool since YG-1 offers a very attractive performance-to-cost package.”

Like other companies contributing to this article, Horn USA Inc., Franklin, Tenn., stresses both the importance of multi-flute tool design and customer collaboration for tooling success. “I would describe us as an engineering-driven company that approaches tooling solutions for its customers with finesse,” said Edwin Tonne, training and technical specialist. Horn, which is well known for its grooving and cut-off turning tools, offers a broad line of products, including solid-carbide end mills, drills, and indexable milling cutters, as well as its turning products. More than 40 percent of its cutting tools are specials. Horn has developed multi-flute end mills used to machine titanium, Inconel, stainless and other high-temperature-resistant metals using high-speed and high-efficiency machining strategies to achieve the highest MRR.

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According to the company, time and cost savings and increased part quality result. Tool life is increased due to shorter toolpaths. Tolerance deviations due to heat warping at the tool are minimized, and axial deviations of the machine are smoothed, offering a higher quality surface finish in a shorter time frame. Circle Segment end mills feature unique forms with large radii in cutting areas of the mills, allowing a larger axial DOC during prefinishing and finishing operations.

Understanding the composition of these materials is key to understanding the limitations with cutting speed. “Workpiece hardness and material composition have a huge bearing on machinability,” he explained. “Nickel-based, cobalt-based, and ferrous-based superalloys have certain alloying elements in them that won’t allow elevating the sfm because you can’t eliminate the heat in the cut no matter what you do with the width of cut or cutting speed. [Cutting speeds have] to stay between 80 to 110 sfm depending on the hardness of the material.”

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In recent years, the foundry industry has undergone a major transformation with improvements in casting methods and the introduction of new metals and associated alloys. These changes impacted various processes in foundries but especially fettling, as high demand is placed on the ergonomics and performance of grinding tools in order to effectively remove risers and excess materials in the most productive time possible.

Removing metal is important, and doing it fast enough to make money is more important. To capitalize on the latest machining strategies for milling difficult-to-machine materials, Iscar Metals Inc., Arlington, Texas, continues to add to its lines of multi-flute, solid-carbide end mills, according to Bryan Stusak, national product manager–milling. Iscar has designed solid-carbide end mills specifically for milling strategies, including high-speed milling, high-efficiency milling, optimized roughing and proprietary CAM strategies like Mastercam’s Dynamic Milling.

Seco Tools has developed specific geometries, coatings, carbide substrates and edge preps for these difficult-to-machine materials. The company’s latest development in coatings is its patented HXT silicon-based coating for higher thermal resistance and abrasion resistance. “What we have found is that these same tools can be used to cut easier-to-machine metals such as tool steels, stainless steels and cast iron. So we’re now able to use these high-efficiency milling strategies to increase tool life and productivity on a broader range of easier-to-machine materials,” said Ball.

“Finishing is typically done with a 45o helix end mill for hardened materials up to 65 HRC because the higher helix angle shears the material more effectively,” he said. “End mills with a 60o helix angle are used on nonferrous materials like aluminum and even high-nickel-content alloys in finishing applications. In general, a variable pitch end mill with a 35 to 38o helix angle is the most common we see in the industry because it has a good balance of edge strength and core diameter, and it’s a little bit more up sharp in the cut where it slices through the material more effectively vs a 30o helix end mill.”

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Our vitrified and resin bonded Superflex mounted points offer you solutions for the highest quality requirements. The wide range of applications also requires ceramic points that strike a perfect balance in terms of chip performance, surface finish and longevity. Ceramic points are often used in mould-making and finishing processes.

Cycle times for five-axis machining of molds, blades and other complex aerospace and medical parts can be reduced up to 90 percent with Circle Segment solid-carbide end mills, according to Emuge Corp, West Boylston, Mass. While manufacturers performing high-speed machining may be familiar with using traditional ball nose end mills to make small stepover passes, Circle Segment end mills use high stepover passes up to 10 times greater than ball nose end mills to cut out large areas of material, maximizing efficiency and minimizing cusp height.

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Stusak emphasized the benefits of these machining strategies by explaining that the basic principle of metal cutting is forming a chip properly in relationship to edge geometry so that you are shearing the material, not plowing it. Both roughing and finishing benefit from optimized machining strategies, but especially roughing, where machining time can be greatly reduced.

“In evaluating machining for large aerospace parts, for example, while I’m not a programmer, in most cases I can look at the program and tell what ought to be changed,” said Bruhis. “In the last few years between traveling and working all over the world, if I can’t review the program, I have my customer send a video of the simulation and hold an online meeting to discuss possible program modifications. Through Skype interactions, I do simulations and alter programs constantly.”

Besides the component, programming strategy and software play into this as well. If a shop is performing high-efficiency or high-speed milling, it must have the horsepower and torque required to drive the tool. If it runs the wrong software, there will be a lot of costly, wasted moves.

An angle grinder is one of the most important tools for stock removal of all types of metals. Our diverse range of grinding discs cater for almost any and every application within the foundry industry, including high chrome castings, where care should be taken as these are prone to crack if the incorrect products are used during application.

These optimized high-speed and high-efficiency machining strategies are the wave of the future. And they are here today. According to Ball, 80-90 percent of CAM software suppliers have some sort of optimized milling strategy for roughing and 80-90 percent of the major cutting tool manufacturers have some sort of multi-flute products for these strategies.

For grinding large and heavy components, the use of cup wheels is recommended, as they are exceptionally robust and durable. Composition of cup wheels make them suitable for large area grinding of welding beads as well as fast material removal. When working with cup wheels, it is particularly important to ensure that cup wheels are used only on angle grinders with diameters of 178 mm. Smaller machines tend to rotate too fast, while larger ones rotate too slowly. In addition, a special protection cover is required to ensure sufficient levels of safety during operation.

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“All four of those strategies are essentially the same,” said Stusak. “We have developed multi-flute tools, and specifically a seven-flute tool with chip splitting technology to allow very light widths of cut depending on the length of the flute on the end mill. These strategies actively manage all four of the attributes in the CAM systems—including the radial width of cut, the arc of contact, chip thickness and the feed rate—for optimized performance,” he said.

The Superflex AS30T, ZA24R PREMIUM, CA24Q CERAMIC and the AS24R INOX ULTRA grinding discs are available in various diameters and have been proven to be the preferred product for grinding applications on stainless steel, high chrome, A2 steel, and manganese due to their exceptional longevity, stock removal properties and ability to decrease downtime due to minimal disc changes.

The ECI-H4S-CFE end mill is a short, four-flute design with different helixes (35o and 37o) and variable pitch for chatter dampening. It can be used for high MRR roughing and finishing, with full slot milling up to 1×D. It is also available with the new AlTiCrSiN IC608 coating for machining at elevated temperatures.

The highest MRR possible in high-speed machining with multi-flute tools occurs when the process engages the full flute length of the tool. The more flutes, the larger the core diameter for rigidity. Typically, the first thing to look at when considering high-speed machining is the size of the part and flute length to decide the diameter of the tool, according to Horn. An inch of actual flute length might be handled by a 3/8" (9.5-mm) diameter tool, and two inches of actual flute length by a 5/8" (15.8-mm) diameter tool.

When one looks at the new range of “super alloys” being developed, it has become increasingly evident that machining of these materials will be a serious challenge. Grinding has proven to be one of the preferred methods of shaping these alloys, as abrasive tools have achieved a far greater success rate over those of machine tools. With new innovative grinding machines being developed, grinding and machining times of components have been significantly reduced from hours per part to minutes per part.

YG-1 has developed standard tools specifically for high-speed machining of titanium, but about 30 percent of its tools for this application are still custom made, with special lengths and corner radii. “One of the trends with high-speed machining is the increased number of flutes needed to take light cuts and run very fast,” he said. “The trend of the last five years is for five, six, seven and nine flutes,” he said. The advantage is longer tool life and better heat and chip control as well as machining performance.

These machining strategies require more just than the right carbide grade, insert and geometry—the way of approaching the material is also critical. The goal of high-efficiency machining is to reduce the width of cut and increase the length of cut to reduce cutting forces, which allows faster machining. Sometimes it is quicker that way, and sometimes it is quicker using traditional high-feed cutters. Many times with dynamic machining there can be much wasted movement. Applying it depends on the application and complexity of the features, such as pocketing, that are involved.

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With high-temperature-resistant, nickel-based alloys being used more commonly by its customers, Seco Tools LLC, Troy, Mich., is focused on maximizing metal removal rates using high-speed, high-efficiency optimized roughing strategies, according to Jay Ball, solid-carbide product manager.

Apart from versatile mounted points, we also stock a range of tungsten carbide burrs that are made from tried and tested, high quality cemented carbide types on the most modern CNC grinding machines. Our Superflex tungsten carbide burrs are used on a wide range of handheld, pneumatic and electric machines as well as on industrial robots. Thanks to their versatility, they can be used on a variety of materials. To provide a solution at hand for the full spectrum of applications, Grinding Techniques offers a wide selection of premium quality tungsten carbide burr shapes. The range easily meets the general demands of economic efficiency, high stock removal rates, simple handling, and excellent longevity.

If it’s a very shallow “depth of part,” the machinist will not get the economy of the end mill and high speed and will experience a lot of excess vibration. The reason is if a shop runs a shallow axial depth of cut, it reduces MRR and the operation may not be as efficient as other methods with larger radial and shallower axial stepovers.

Advanced cutting tools can maximize metal removal rates (MRR) when machining even the most difficult-to-machine materials. Powered by the latest CAM programs, these machining strategies are known variously as high-speed, high-efficiency, optimized roughing and also by proprietary brand names like Mastercam’s Dynamic Milling. Tools such as multi-flute, solid-carbide tools benefit from the latest advanced technologies in machine look-ahead, high-speed spindles, coatings and geometries.

The ECKI-H4R-CF four-flute end mill features corner radii for aerospace applications and either of two coatings, IC300 TiCN or IC900 AlTiN. It offers variable pitch and variable helix and a special edge prep for machining titanium.

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The ECP-H7-CF multi-flute (seven flutes) end mill has a hard substrate, IC902 ultra-fine carbide grade with 9 percent cobalt, and is TiAlN PVD coated. It is suitable for machining various materials, including hard steel and cast iron, at high cutting speeds, according to Iscar.

Cutter paths vary and can include profiling, slotting, and pocketing. Workpieces can vary in complexity and size as well. YG-1 has tools for specific materials like titanium, Inconel or aluminum as well as general-purpose tools for smaller shops and multiple applications.

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It’s important to have the right CAM software to avoid wasted rapid travel movement, which increases cycle time. There are times when it is better to take a more conventional cutting pass. One example is when the width of cut is short with, say, a 0.5" (12.7-mm) end mill with the intention of cutting a length of the part that’s 0.5" long and the process needs to remove 0.3" (7.62 mm) of material. In this example, Horn recommends taking all the material off in one or two passes instead of 30 passes. To be efficient, the tool must stay on the part and limit time-wasting retraction.

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Another popular tool known for its versatile application where precise results are required for difficult-to-access areas, are straight grinders or die grinders, as they are more commonly known. These power tools are hand-held and used for grinding, sanding, honing, deburring or machining of material. The name stems from one of their earliest applications: tool and die work, where they are used to create the precise contours of dies and molds. Their versatile applications make them a popular tool.

“Processing these materials with conventional machining processes tends to work harden them,” he explained. “Using high-efficiency milling and optimized roughing, there is a lot less heat generated because you are taking lighter radial stepovers and depths of cut (DOC), but not putting a lot of heat into the workpiece,” he said. “Where the typical solid-carbide end mill used for roughing and finishing typically had four and five flutes, with high-efficiency milling now taking over the industry we have added six-, seven- and nine-flute tools.”

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The goal is to maximize flute length because that’s what will provide the best MRR in combination with 5 and 10 percent stepovers. Another way to determine tool selection is to decide whether to simply switch to high-feed milling and ramp in with a conventional end mill and rip the stock out.

The following is a consensus report of an interview held with Tonne, Eric Carbone, application and sales engineer; John Kollenbroich, head of product management; and Jeff Shope, application and sales engineer.

There are other advantages. “By minimizing the width of cut you can elevate the surface footage on most alloys, with the exception of nickel-based alloys,” said Stusak. “You can’t elevate cutting speed that much because it is impossible to eliminate the heat in the cut, but for Ti6Al4V we have case studies where we have machined up to 400 sfm at 4 percent radial engagement with these tools.”

Horn’s solid-carbide tools with seven or nine flutes with large DOCs and 10-15 percent stepover—as a rule of thumb to start with—help with these strategies, but the machine tool must have the required acceleration and deceleration. An older machine with rapids of 600 ipm will not be sufficient. Similarly, the look-ahead that newer machines have is also required.

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Bruhis described how he evaluates and determines an approach to a titanium machining project. “I typically inquire first about the machine capability, whether three-, four-, or five-axis, vertical or horizontal, fixturing and tooling,” he said. He added that in the majority of cases, specific end mills are selected based on axial or radial cut, speeds and feeds, and programming for high-speed and high-efficiency machining.

The objective of both high-speed and high-efficiency machining strategies is to improve MRR, according to Yair Bruhis, global product and application manager for YG-1 Tool Co., Vernon Hills, Illinois. High-efficiency machining increases cutting by limiting air cutting time. “Because the two machining strategies are so effective, people want to switch everything towards them,” said Bruhis. “But it all depends on the part and the machining parameters. Sometimes, I can look at the part and state that it can’t be machined with high-efficiency strategies because of the shape and complexity of the part, or the machine’s capabilities, or the part features and programming, among other factors.

Chip-splitting technology reduces the radial tool pressure encountered with long lengths of cut and helps break up the chips, producing more manageable chips for the operator or the chip pan or conveyor to remove, Stusak explained. “The key to machining difficult-to-machine materials is the radial engagement,” he said. “You want to minimize the width of cut or arc of contact to beat the heat.” By minimizing the width of cut, not as much heat transfers into the tool because of the limited amount of cut time on the end mill.

“I talk to a lot of people in aerospace and the trend has changed in the last 10 or 15 years,” Bruhis continued. “It’s not the cost of the tool any more. Customers want to know the real cost of metal removal. There are a lot of cases where I meet with engineers or programmers and they clearly voice that they do not care about the price of the tool. Cycle time and tool life are the most important considerations.”

He also noted that the trend in titanium alloys and exotics machining in the last four or five years is toward high-speed machining for medium to large parts because the cost of removing titanium or Inconel is much higher than that of aluminum or steel.