“We work very intensely with the OEMs and tier 1 companies on projects, along with our application engineers who help all our customers in the industry. Also, there is always the demand created by new and improved machine tools. Manufacturers and their customers want turnkey projects which includes us providing solutions. In these situations, there is a lot of collaboration between the cutting tool supplier, the machine tool builder, the fixture manufacturer and the end user. Our specialists work with all involved to support each other.”

Possible combinations and their machining characteristics, according to Kennametal’s Composite Machining Guide, include fiber reinforcement materials like carbon fiber/graphite fiber, glass fibers, ceramic fibers, polymer fibers, and tungsten fibers. Poly matrix materials include epoxy, phenolic, polymide, and polyetheretherketone (PEEK). Machining characteristics of CFRP/CFRP and CFRP/metal materials are impacted by the abrasiveness of fibers, fiber size, fiber diameter, fiber length, volume of fiber percentage, and fiber layout, i.e. unidirectional or fabric weave. For example, fiber abrasiveness increases with strength and diameter. Short fibers tend to delaminate, as do unidirectional layered composites.

“Improvements can be made to the carbide grade, the substrate and the coatings. And there are ongoing developments with machine tools which means there is always a research partnership needed between us and the manufacturers. When a machine tool comes along with new performance capabilities, this allows the cutting tool developers to create products that match the improved performance of the machine tool.”

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OSG USA Inc. (Glendale Heights, IL) offers a full range of tools engineered to machine abrasive composite materials for aerospace, automotive, and medical applications, among others. OSG continues to develop custom roughing and finishing routers and drills for CNC applications. The company’s composite tools include drills and routers that feature OSG’s patented ultrafine diamond coating for applications ranging from trimming carbon fiber and glass cloth to machining tough laminates.

One recent innovation for composites and stack drilling is Iscar’s new head for the Multi-Master line, which provides the ability to mount a variety of changeable heads on one shank quickly and easily. “The novel new head comprises PCD cutting edges and composite-optimized geometries for performing roughing, semi-finishing, and finishing operations in sequence. This geometry enables opening of cavities and slots and performing shoulder applications. Since the shank is thinner than the cutting tip, contact and friction with walls is reduced, so the operation runs cooler,” said Cline. Another promising newcomer is the Iscar SOLIDRILL-REAM, a combination drill and reamer for producing more accurate holes in a single step. Separate brazed-in PCD inserts on the same shank handle the drilling and reaming.

Iscar has developed new ICF (interchangeable) drilling heads geometry for drilling CFRP and CFRP laminates, combining small point angles and positive rakes. “The geometry provides low axial forces for smooth penetration during the cutting process without splintering phenomenon which is critical on thin-wall workpieces. The new heads are produced in the new grade IC107 which combines IC07 hard submicron substrate and CVD diamond coating for prolonged and predictable tool life. SUMOCHAM for composites is suitable to be used on CNC or PKM (parallel kinematic machines) machines, and for robots and powered feed machines, a special connector is available,” said Cline.

Milling composites, like drilling, is equally challenging. If the tool encounters several different layers at the same time, you need to engineer the process, taking all limitations into account. “If you are progressing through the layers pass by pass, you may have to change parameters to match the layer,” said Tom Raun, national product manager- milling. “That’s the reason why Iscar has designed many of the most popular styles of milling cutters and routers available in versions optimized for CFRPs and complex laminates. The SOLIDMILL solid carbide end mills for rough and finish end- and side-milling now come with optimal diamond coatings, and TANGSLIT slitter and TANGSLOT slotters now are available with PCD tips, as are Heli2000 indexable inserts for 90° milling applications. All have proven effective in wing strut and airframe applications,” said Raun.

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Werner Penkert, Kennametal, manager aerospace solutions engineering EMEA, says: This new grade is a development from our carbide grades, KC725M and X500 which are well-known for their reliable performance and long tool life. It increases speed by around 30% but still with excellent tool life.”

According to Iscar, the current cutting tool material of choice for composites is a solid-carbide shank with thin PCD coatings, brazed-in PCD inserts or PCD veins at the cutting edge. The solid carbide shank provides the rigidity and dimensional accuracy necessary to maintain close tolerances on size and location as well as smooth surfaces. Solid carbide also makes it possible to start with an optimal cutting geometry that minimizes cutting forces, heat, uncut fibers, cups, fuzz and burrs while controlling chips. The thin PCD coating (or insert) provides the wear resistance at the cutting edge to maintain that optimal geometry over long service intervals. Thin PCD coatings deliver the wear resistance of diamond while preserving the ideal cutting geometry machined into the carbide shank. By contrast, CVD (chemical vapor deposition) inevitably creates a thicker diamond layer that may detract from optimal geometry.

RobbJack has developed cutting tool solutions like its solid PCD-tipped W-Point drills for drilling carbon fiber-reinforced polymer (CFRP) parts like wing spars to eliminate poor quality cuts and expensive scrap. “The W-point geometry supports the materials as it pierces through and its sharp outer edge shears the material without delamination, uncut fibers, or fiber pullout. The solid polycrystalline diamond tip outperforms diamond-coated carbide drills for tool life up to 25 times longer than uncoated carbide,” said MacArthur. He recounted how one manufacturer was going through 25 carbide drills to make one ship set of wing spars, scrapping many very expensive parts in a costly and unstable process. “RobbJack’s solid PCD-tipped W-point was the only tool that could meet the manufacturer’s exacting design and performance standards, cutting over 4000 clean holes in tolerance; other tools struggled to get 160 holes. Cutting tool savings totaled $548,290.08 per year,” said MacArthur.

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At AeroDef Manufacturing 2017, CGTech will showcase the steps needed to get from a CAD-designed composite part to CNC programs. Highlighted will be the implementation and use of machine-independent, off-line NC programming software for automated fiber placement (AFP) and automated tape laying (ATL) machines, such as the work being done at NASA’s Langley Research Center using a 16-tow Electroimpact automated fiber placement machine. Current customer projects to be highlighted include the use of robots, lasers, probing, and ultrasonic knives. AeroDef is the leading annual aerospace manufacturing conference and exposition, where aerospace companies can find new ways to apply, machine, finish, and automate composite processes. Technical session topics will focus on advanced manufacturing technology, including modeling/simulation, autoclave, thermoplastic composites, additive, automation, NDT, and bonding and assembly.

Iscar offers these tips for successful machining of composite materials. The harder the matrix and higher the reinforcing fiber content, the more PCD coatings/inserts will be needed at the cutting edge. When hole size allows, orbital drilling with a solid-carbide end mill or helical interpolation using the Multi-Master with PCD-coated tips is preferable to straight twist drilling.

OSG’s EXOPRO ARTO-D-RRSM diamond-coated drill/reamer is for cutting carbon and glass fiber composites. It features a tapered four-flute design and OSG’s diamond coating. The drill/reamer features a straight-flute, elongated double-angle geometry. According to OSG, benefits include limited peel-up at hole entrance, limited exit delamination, and smoother and sharper cutting edges, providing up to 50 times longer tool life.

The aerospace sector is an important market for Kennametal and its tool development as the advanced engineering involved always poses new machining challenges. An example of this is the tooling specialist’s membership of the Advanced Manufacturing Research Centre (AMRC) in Sheffield, where along with aerospace OEMs and other industry stakeholders machining and materials research is carried out for aerospace and other high-value manufacturing sectors.

In short, take everything into account in tool selection, including the relative thicknesses and location of the metal and plastic layers. It is a balancing act. A stack heavy towards the metal favors solid-carbide tools with internal coolant. If CFRP is the main part, PCD carbide tools would be preferable.

Due to production rates ramping up for new aircraft, particularly in the commercial market, developers of cutting tools are constantly under pressure to deliver faster and more efficient metal removal rates. In an industry that often uses difficult to machine materials such as titanium this throws up some demanding challenges.

Kennametal has launched a new insert grade named KCSM40, targeted to machine high temperature titanium alloys widely used for aerospace applications. Ed Hill spoke to the cutting tool specialist about its products designed for difficult-to-machine materials. Due to production rates ramping up for new aircraft, particularly in the commercial market, developers of cutting tools are constantly under pressure to deliver faster and more efficient metal removal rates. In an industry that often uses difficult to machine materials such as titanium this throws up some demanding challenges. Kennametal has developed a new carbide grade, KCSM40, said to greatly enhance cutting of titanium Ti6Al4V and other high tensile strength alloys. Werner Penkert, Kennametal, manager aerospace solutions engineering EMEA, says: This new grade is a development from our carbide grades, KC725M and X500 which are well-known for their reliable performance and long tool life. It increases speed by around 30% but still with excellent tool life.” The KCSM40 grade has an advance cobalt binder that provides very high thermal fatigue resistance. In addition to the new material substrate Kennametal’s proprietary AlTiN/TiN coating enhances wear resistance at the cutting edge. Cutting edges still performing well after 100 minutes of machining Ti6Al4V at 47m/minute with a .0067ipt chip load More speed In trials, the target cutting speed for KCSM40 in titanium Ti6Al4V was 175 SFM (53m/min) while achieving greater than 20 cubic inches per minute (327cm³/min) metal removal rate for 60 minutes. Not only has KCSM40 achieved this, but results of milling titanium at speeds up to 270 SFM (85m/min) at a lower radial depth of cut have been achieved. Scott Etling, director of global product management, for indexable milling at Kennametal, explains the radial engagement of the milling cutter to the workpiece is one key component when optimising the cutting speed. “At higher radial engagements, the insert is cutting the material for a longer time which creates more heat at the cutting zone,” He says. “The heat will not transfer into the titanium chips as is the case when milling steels so controlling the heat is critical. Lower cutter speeds at higher radial engagements is good practice. At lower radial engagements, higher cutting speeds can be achieved.” Kennametal has carried out extensive trials using a new HARVI Ultra helical milling platform to mount the new inserts. It achieved over 100 minutes of tool life running at 155 SFM (47m/min) with a 0.0067ipt (0.12mm/tooth) chip load. The radial depth of cut was 25mm and the axial depth of cut was 76mm. “The edge condition on the KCSM40 grade insert still looked great,” states Etling. “And we are getting many other fantastic results. In one face milling operation on a hardened steel wear plate the number of passes was reduced from 234 to just 22. I am very excited how KCSM40 will benefit our customers.” Demand for higher metal removal rates was the main driver for Kennametal to develop the new grade. “Cycle time is very important because all aircraft builders are under pressure to deliver higher volumes,” notes Penkert. “When companies invest in new machine tools, they want to process the parts much faster. However, customers also require secure processes with other developments such as increased automation. “These days it is rare that a machine operator will be constantly monitoring a machine. Machine tools also use high pressure coolant so it’s very difficult to see what is happening at the cutting edge. A secure manufacturing process is essential because of the value of the parts being produced and the value of the machines they are being made on.” Kennametal has carried out extensive trials using a new Harvi Ultra helical milling platform Heat and steam Titanium poses particular challenges when being cut because of the high temperatures generated at the shear zone. Coolant can vaporise even before it makes contact with the workpiece. “You need high pressure coolant because of the super-heated steam in the shear zone,” Penkert explains. “It’s very important to protect the carbide tools from heat because there can be a softening effect where the cobalt binder weakens and your cutting process is no longer secure.” Kennametal carries out many trials with it customers to help them come up with efficient cutting strategies. “We have good data about our cutters’ tool life but you always have to judge what is happening with an application in the real world,” Penkert continues. “We have to consider what material is being cut, the stability of the machine tool, the clamping, the lubricant etc. All these variations have to be taken into account including the part being made itself. Is it thick and stable or thin and instable? “Our data is a starting point but then we have to prove out strategies in a manufacturing cell. Here we can monitor the wear, so after a number of minutes of cutting we have an accurate idea of the wear rate which occurs in that application.” Along with its metalcutting products used for machining high grade alloys, Kennametal has also developed a range of cutting tools for the increasing amounts of composite materials used in aerospace. “We anticipate that composites will continue to grow in aerospace,” says Penkert. Kennametal has a number of products for composite machining. These include trimming tools, which mill the outside edge of a part or tools that drill and then mill from the inside of the part. We also have tools for contour milling of CFRP. “We are also involved in the assembly of the aircraft with hole drilling. This can involve drilling through CFRP/aluminium or CFRP/titanium stacks. This can be difficult because you have to prevent burrs on the entry and exit of holes, avoid delamination and fibre breakout and we have to provide a geometry that can deal with these different materials in one operation. Another factor is composite materials are highly abrasive. In these circumstances we find PCD is a very good cutting grade or diamond film coated drills.” More Kennametal tools used for aerospace applications such as turbines Adding advances The aerospace sector is an important market for Kennametal and its tool development as the advanced engineering involved always poses new machining challenges. An example of this is the tooling specialist’s membership of the Advanced Manufacturing Research Centre (AMRC) in Sheffield, where along with aerospace OEMs and other industry stakeholders machining and materials research is carried out for aerospace and other high-value manufacturing sectors. Werner Penkert, Kennametal, manager aerospace and defence solutions EMEA “We work very intensely with the OEMs and tier 1 companies on projects, along with our application engineers who help all our customers in the industry. Also, there is always the demand created by new and improved machine tools. Manufacturers and their customers want turnkey projects which includes us providing solutions. In these situations, there is a lot of collaboration between the cutting tool supplier, the machine tool builder, the fixture manufacturer and the end user. Our specialists work with all involved to support each other.” And Penkert believes there are still possibilities for cutting tool performance to be enhanced. “Improvements can be made to the carbide grade, the substrate and the coatings. And there are ongoing developments with machine tools which means there is always a research partnership needed between us and the manufacturers. When a machine tool comes along with new performance capabilities, this allows the cutting tool developers to create products that match the improved performance of the machine tool.” www.kennametal.com

Two recent product introductions, the EXOPRO AERO-LHX and EXOPRO AERO-D-REAM, combine special geometries and ultrafine diamond coatings to achieve extended tool life and solutions for common difficult-to-machine material combinations. Typical applications include carbon fiber, glass fiber, CFRP/Nomex honeycomb, glass-fiber reinforced plastic (GFRP)/Nomex honeycomb, CFRP/Al honeycomb, Al/Al honeycomb, and carbon/carbon combinations.

“At higher radial engagements, the insert is cutting the material for a longer time which creates more heat at the cutting zone,” He says. “The heat will not transfer into the titanium chips as is the case when milling steels so controlling the heat is critical. Lower cutter speeds at higher radial engagements is good practice. At lower radial engagements, higher cutting speeds can be achieved.”

Another tool that RobbJack has developed for composites is a solid diamond-tipped drill with multifaceted geometry. “The compound 135° and 20° tip geometry has tested to be the best drilling solution across the most diverse range of carbon fiber composites,” said MacArthur. “The new multifaceted solid-diamond tipped drill produces the cleanest holes I’ve ever seen in carbon fiber materials. There is no delamination or uncut fibers in almost every material we have tested in our machining lab. “

Along with its metalcutting products used for machining high grade alloys, Kennametal has also developed a range of cutting tools for the increasing amounts of composite materials used in aerospace.

ANT Industries, a leading manufacturer of aero engine and gas turbine components in Atherstone, Warwickshire, has announced a significant milestone in its commitment to quality and excellence.

Enhanced software is available that increases the ability of manufacturing engineers to analyze, optimize, and document the CNC programming and machining process for advanced composites. For example, the latest release of Vericut CNC from CGTech (Irvine, CA) can simulate all types of CNC machining of composites, including drilling and trimming, water jet cutting, riveting, mill/turn, and parallel kinematics. The release features several enhancements designed to increase workflow, enabling users to quickly access only the menu choices needed at the time. A new ribbon bar helps users find the functionality they need quickly and with minimal mouse clicks.

Kennametal carries out many trials with it customers to help them come up with efficient cutting strategies.

For machining composites, there are three common types of drills—solid carbide, diamond-coated carbide, and PCD (polycrystalline diamond), according to MacArthur. “Each has its place. Carbide drills are usually used only for manual operations because of their poor tool life. Both diamond coating and PCD are the drills of choice for most applications in abrasive composites like carbon fiber. Diamond coating is excellent for drilling, and in some applications you can even increase tool life over PCD drills. Diamond-coated drills, however, can’t be resharpened like PCD cutters and are disposable. PCD drills are an excellent choice for drilling in CFRP materials. PCD tools tend to outperform diamond-coated drills in materials with high plastic content because they can maintain a sharper cutting edge.”

Kennametal has launched a new insert grade named KCSM40, targeted to machine high temperature titanium alloys widely used for aerospace applications. Ed Hill spoke to the cutting tool specialist about its products designed for difficult-to-machine materials.

Iscar offers a wide selection of PCD drilling and milling cutters for a wide range of composite-specific industry applications. “There are drills suited for thicker materials with aluminum on the bottom, as well as for thinner materials with the CFRP on the bottom,” said Pat Cline, national product manager-drilling. “There are combination drill-countersinks and drill-reamers, slotting cutters and combination mill/drill cutters. The bottom line is that possibly for the first time since reinforced composites came on the scene, you can find a no-compromise tool for any conceivable composite machining task,” said Cline.

“You need high pressure coolant because of the super-heated steam in the shear zone,” Penkert explains. “It’s very important to protect the carbide tools from heat because there can be a softening effect where the cobalt binder weakens and your cutting process is no longer secure.”

In thicker composite structures, beware of heat buildup as well as chip jamming. Select drills with narrow flutes, wide gullets and tighter spirals that complete the hole before things get too hot and in addition consider coolant.

Match speeds and feed to the layers in the laminate. Be ready to change parameters for each layer as the drill progresses.

The sheer volume of composites being used in the aircraft industry seems to dwarf all other applications and is expanding rapidly due to their inherent advantages of durability, resistance to corrosion, and high strength-to-weight ratio. Difficulty of machining can vary greatly depending on the combinations of matrix material and fiber reinforcements chosen. Composites are as varied as the matrix formulation, fiber type, fiber content, fiber orientation, and build-up of the material.

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“The edge condition on the KCSM40 grade insert still looked great,” states Etling. “And we are getting many other fantastic results. In one face milling operation on a hardened steel wear plate the number of passes was reduced from 234 to just 22. I am very excited how KCSM40 will benefit our customers.”

A new generation of cutting tools from Iscar Metals Inc. (Arlington, TX) is tailored specifically for machining all types of advanced composites. The new breed of carbon fiber-reinforced plastics/laminates are lighter and stronger than ever and elevate performance levels in applications ranging from downhill skis and tennis rackets to military aircraft and automobiles. Although composites technology is helping automakers reach their lightweighting goals faster, as a workpiece material composites have raised fabrication challenges, especially machining.

Select the tool geometry based on the last material in the stack. If the last material is a plastic, use a tapered drill with a long point angle. If the last layer is aluminum or titanium, a high-shear drill with a sharp point angle will exit more cleanly and leave less burr. The tapered drill would just smear aluminum.

“Our data is a starting point but then we have to prove out strategies in a manufacturing cell. Here we can monitor the wear, so after a number of minutes of cutting we have an accurate idea of the wear rate which occurs in that application.”

“We are also involved in the assembly of the aircraft with hole drilling. This can involve drilling through CFRP/aluminium or CFRP/titanium stacks. This can be difficult because you have to prevent burrs on the entry and exit of holes, avoid delamination and fibre breakout and we have to provide a geometry that can deal with these different materials in one operation. Another factor is composite materials are highly abrasive. In these circumstances we find PCD is a very good cutting grade or diamond film coated drills.”

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In trials, the target cutting speed for KCSM40 in titanium Ti6Al4V was 175 SFM (53m/min) while achieving greater than 20 cubic inches per minute (327cm³/min) metal removal rate for 60 minutes. Not only has KCSM40 achieved this, but results of milling titanium at speeds up to 270 SFM (85m/min) at a lower radial depth of cut have been achieved.

Kennametal has carried out extensive trials using a new HARVI Ultra helical milling platform to mount the new inserts. It achieved over 100 minutes of tool life running at 155 SFM (47m/min) with a 0.0067ipt (0.12mm/tooth) chip load. The radial depth of cut was 25mm and the axial depth of cut was 76mm.

Kennametal has developed a new carbide grade, KCSM40, said to greatly enhance cutting of titanium Ti6Al4V and other high tensile strength alloys.

Titanium poses particular challenges when being cut because of the high temperatures generated at the shear zone. Coolant can vaporise even before it makes contact with the workpiece.

Be sure the process reliably breaks up the titanium chips into small, easily ejected pieces. You especially don’t want to risk a titanium chip jamming the hole in a composite. Again, the most effective remedies are slower speeds and pecking cycles.

The KCSM40 grade has an advance cobalt binder that provides very high thermal fatigue resistance. In addition to the new material substrate Kennametal’s proprietary AlTiN/TiN coating enhances wear resistance at the cutting edge.

“These days it is rare that a machine operator will be constantly monitoring a machine. Machine tools also use high pressure coolant so it’s very difficult to see what is happening at the cutting edge. A secure manufacturing process is essential because of the value of the parts being produced and the value of the machines they are being made on.”

“Cycle time is very important because all aircraft builders are under pressure to deliver higher volumes,” notes Penkert. “When companies invest in new machine tools, they want to process the parts much faster. However, customers also require secure processes with other developments such as increased automation.

With advances in material sciences and the ability to design composite parts with new virtual software technology, cutting tool manufacturers are being challenged to continually evolve and develop solutions for these versatile materials. “Common challenges in machining composites are excessive tool wear, delamination of layers, uncut fibers, fiber pullout, and scrapped parts in both milling and drilling,” said Mike MacArthur, vice president-engineering, RobbJack Corp. (Lincoln, CA). “Another challenge when machining composites is that they are made in an autoclave as unmachined parts and don’t always match the CAD file associated with the part. When that happens, multiple operations are needed to bring them into the tight tolerances required.”

“We have good data about our cutters’ tool life but you always have to judge what is happening with an application in the real world,” Penkert continues. “We have to consider what material is being cut, the stability of the machine tool, the clamping, the lubricant etc. All these variations have to be taken into account including the part being made itself. Is it thick and stable or thin and instable?

For shallower holes, use stubby, straight-shank drills. For deeper holes, design the process for absolutely reliable ejection of all types of chip. Consider “peck drilling” and even coolant flushing, if possible.

The EXOPRO ARTO-LHX is a diamond-coated, low-helix drill designed to eliminate uncut fibers and delamination when cutting tough laminates. The drill features triple angle geometry and OSG’s diamond coating, ensuring smoother and sharper cutting edges that provide up to 40 times longer tool life, according to the company. Triple-angle geometry reduces push-out exit delamination and the low-helix style geometry provides sharper cutting edges to help shear tough fibers.

“We anticipate that composites will continue to grow in aerospace,” says Penkert. Kennametal has a number of products for composite machining. These include trimming tools, which mill the outside edge of a part or tools that drill and then mill from the inside of the part. We also have tools for contour milling of CFRP.

Cutting edges still performing well after 100 minutes of machining Ti6Al4V at 47m/minute with a .0067ipt chip load

When titanium is in the stack, the preferred practice is everything that composites hate. To avert work hardening and overheating and to keep chips controllable, select tools with low reliefs and rake angles and a low spindle speed. Although coolant or mist is not generally used, it may be unavoidable for titanium because of heat and/or chip flushing.

RobbJack has been able to grow wear-resistant diamond on the cutting edges of carbide tools. “One solution we have developed is a combination tool that trims and bevels composites in one operation. This tool eliminated three other tools and eliminated the operation of trimming the part to match the CAD model. The tool bevels the mating surfaces and trims the part in one operation, reducing cycle time by five days,” MacArthur said.

Scott Etling, director of global product management, for indexable milling at Kennametal, explains the radial engagement of the milling cutter to the workpiece is one key component when optimising the cutting speed.