When processing the most difficult materials, advanced cutting tools can maximize the metal removal rate (MRR). With the support of the latest CAM programs, these machining strategies are known as proprietary brands such as high-speed, high-efficiency, optimized roughing and Mastercam's dynamic milling. Tools such as multi-edged, solid carbide tools benefit from the latest advances in machine vision, high-speed spindles, coatings and geometric shapes.
Here is how leading tool manufacturers help customers use these tools for machining titanium, nickel-based alloys, superalloys, inconel and stainless steel.
It is important to remove the metal, and it is more important to do it fast enough to make money. National Product Manager Bryan Stusak said that in order to take advantage of the latest processing strategies for milling difficult-to-machine materials, Iscar Metals Inc. of Arlington, Texas continues to increase its multi-edge solid carbide end mill series-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 such as dynamic milling by Mastercam.
"All four strategies are essentially the same," Stusak said. "We have developed multi-edged tools, especially seven-edged tools with chip segmentation technology, which can achieve very light cutting widths based on the length of the edge on the end mill. These strategies actively manage all four attributes in the CAM system-including Radial cutting width, contact arc, chip thickness and feed rate-to optimize performance," he said.
Stusak explained that the chip separation technology reduces the radial tool pressure encountered during long cuts and helps break down the chips to produce more manageable chips for the operator or chip tray or conveyor. "The key to processing difficult-to-machine materials is radial meshing," he said. "You want to minimize the cutting width or contact arc to resist heat." By minimizing the cutting width, because the end mill has a limited cutting time, there is not much heat transferred to the tool.
There are other advantages. "By minimizing the cutting width, you can increase the surface thickness of most alloys, with the exception of nickel-based alloys," Stusak said. "You can't increase the cutting speed that much, because it is impossible to eliminate the heat during the cutting process, but for Ti6Al4V, we have a case study where we used these tools to machine cutting speeds up to 400 sfm with 4% radial engagement."
Understanding the composition of these materials is the key to understanding the cutting speed limits. "Workpiece hardness and material composition have a huge impact on workability," he explained. "Nickel-based, cobalt-based, and iron-based superalloys contain certain alloying elements that will not increase sfm, because no matter how you handle the cutting width or cutting speed. [cutting speed must] stay between 80 and 110 sfm, It depends on the hardness of the material."
PH stainless steel, some duplex stainless steels and titanium alloys are different, and the speed can be increased to increase the productivity of the tool. "Duplex stainless steels with high nickel and chromium content are more like Inconel materials because of the high nickel content. Therefore, it is important to understand the alloying elements when processing superalloys," he said.
Stusak emphasized the benefits of these machining strategies. He explained that the basic principle of metal cutting is to form chips correctly based on the edge geometry, so that you can cut the material instead of planing it. Both roughing and finishing benefit from optimized processing strategies, especially roughing, and the processing time can be greatly reduced.
"For hardened materials with hardness up to 65 HRC, a 45o spiral end mill is usually used for finishing, because a higher helix angle can cut the material more effectively," he said. "End mills with a helix angle of 60o are used for finishing applications of non-ferrous materials, such as aluminum, and even high nickel content alloys. Generally speaking, variable pitch end mills with a helix angle of 35 to 38 degrees are ours The most common in the industry, because it has a good balance between edge strength and core diameter, and is sharper when cutting. Compared with 30o spiral end mills, it can cut materials more effectively."
Iscar's range of end mills for high-speed milling includes:
ECP-H7-CF multi-blade (seven-blade) end mill has a hard matrix, IC902 ultra-fine cemented carbide grade, 9% cobalt content, and TiAlN PVD coating. According to Iscar, it is suitable for machining a variety of materials at high cutting speeds, including hard steel and cast iron.
The five-edge ECY-S5 end mill has a universal base material and AlTiCrSiN coating (IC608), which is used for shoulder or full groove high-speed milling or trochoidal milling or peeling milling. Its main use is stainless steel, but it can also be used to process nickel-based superalloys.
The ECI-H4S-CFE end mill is a short four-edged design with different helixes (35o and 37o) and variable pitch to suppress chatter vibration. It can be used for high MRR roughing and finishing, and full slot milling up to 1×D. It also provides a new AlTiCrSiN IC608 coating for high temperature processing.
The ECKI-H4R-CF four-flute end mill has a fillet radius suitable for aerospace applications and two coatings, IC300 TiCN or IC900 AlTiN. It offers variable pitch and variable helix as well as special edge preparation for machining titanium.
Jay said that as the use of high-temperature nickel-based alloys becomes more and more common, Seco Tools Co., Ltd. of Troy, Michigan focuses on using high-speed, efficient and optimized roughing strategies to maximize the metal removal rate. Ball, cemented carbide Product manager.
"Machining these materials with traditional processing techniques tends to harden them," he explained. "Using efficient milling and optimized roughing, you generate much less heat because you use a lighter radial step and depth of cut (DOC), but you don't transfer a lot of heat to the workpiece," he said. "The typical solid carbide end mills used for roughing and finishing are usually four- and five-edged. Now high-efficiency milling is taking over the industry. We have added six, seven and nine-edged tools."
The advantage of the multi-edge end mill is that the operator can use a higher feed rate, because the use of high temperature and heat resistant materials reduces the DOC and step distance. "These metals don't like to be processed in the traditional way, with large DOC, large radial steps and slow feed rates," Ball said. "Multi-edge tools can increase MRR without work hardening because you can run faster feed rates and lighter radial steps with more teeth."
He pointed out that although it is difficult to rough the material and can cause a variety of problems, optimized roughing with a maximum radial step of 6-10% is effective for heat-resistant superalloys (HRSA) and titanium. "And you can also use these same tools to finish many of these parts, so you can finish with a more traditional side mill," he said.
Seco Tools has developed specific geometries, coatings, cemented carbide substrates and edge treatments for these difficult-to-machine materials. The company's latest development in coatings is its patented HXT silicon-based coating, which has higher heat resistance and wear resistance. "We have found that these same tools can be used to cut more easily machined metals such as tool steel, stainless steel and cast iron. As a result, we are now able to use these efficient milling strategies to extend tool life and the productivity of machining more easily machined materials," Ball said.
He added: "We have started to use variable exponents and [spirals] more in multi-edge tools because they may generate greater cutting pressure due to increased tool contact with the workpiece. However, it is necessary to change [[ Spiral], rake and index to change the geometry to eliminate chatter and harmonics while still maintaining the tool’s ability to cut efficiently."
These optimized high-speed and high-efficiency machining strategies are the trend of the future. They are here today. According to Ball, 80-90% of CAM software vendors have some kind of optimized roughing and milling strategies, and 80-90% of major tool manufacturers have some kind of multi-edged products for these strategies.
Yair Bruhis, global product and applications manager at YG-1 Tool Co., Vernon Hills, Illinois, said that the goal of high-speed and efficient machining strategies is to increase MRR. Efficient processing increases cutting by limiting air cutting time. "Because these two processing strategies are very effective, people want to turn everything to them," Bruhis said. "But it all depends on the part and processing parameters. Sometimes I can look at the part and declare that due to factors such as the shape and complexity of the part, the function of the machine, the part features and programming, etc., it is not possible to process it with efficient strategies.
“I have talked to many people in the aerospace industry and trends have changed in the past 10 or 15 years,” Bruchs continued. "This is no longer the cost of the tool. Customers want to know the true cost of metal removal. In many cases, I meet with engineers or programmers and they make it clear that they don't care about the price of the tool. Cycle time and tool life are the most important considerations. factor."
He also pointed out that the trend of titanium alloy and dissimilar metal processing in the past four or five years is high-speed processing of large and medium-sized parts, because the cost of removing titanium or inconel is much higher than that of aluminum or steel.
"For example, when evaluating the processing of large aerospace parts, although I am not a programmer, in most cases, I can look at the program and say what should be changed," Bruhis said. "In recent years, between traveling and working around the world, if I can’t check the program, I will ask my customers to send simulated videos and hold online meetings to discuss possible program modifications. Through Skype interaction, I continue to simulate and modify program."
YG-1 has developed a standard tool specifically for high-speed machining of titanium alloys, but about 30% of its tools for this application are still customized, with special lengths and fillet radii. "A trend in high-speed machining is the increase in the number of chip flutes required for light cutting and fast operations," he said. "The trend in the past five years has been five, six, seven and nine flutes," he said. The advantages are longer tool life and better heat and chip control and machining performance.
“When major OEMs call me, it’s usually to improve tool life, process, or both,” Bruhis continued. "This may be a new project and they are facing a serious problem. It may be part quality, cycle time or on-time delivery of parts or total cost, but it is almost never because of the cost of tools, because YG-1 provides Very attractive performance cost ratio package."
Bruhis described his method of evaluating and determining titanium processing projects. "I usually first ask about the capabilities of the machine, whether it is three-axis, four-axis or five-axis, vertical or horizontal, fixtures and tools," he said. He added that in most cases, a specific end mill is selected based on programming for axial or radial cutting, speed and feed, and high-speed and high-efficiency machining.
The tool paths are different and can include profiling, grooving and grooving. The complexity and size of the workpieces also vary. YG-1 has tools suitable for specific materials such as titanium, inconel or aluminum, as well as general tools suitable for small shops and a variety of applications.
"We determine the process and program, run it within a certain speed and feed range, and estimate a cycle time," Bruchs said. "Once the customer has the opportunity to run the program we set, we can get feedback on the actual processing time results. If the cycle time is too long and the cost does not match the expected results, we will adjust it as needed."
Like other companies writing this article, Horn USA Inc. of Franklin, Tennessee emphasizes the importance of multi-edge tool design and customer collaboration for tool success. "I would describe us as an engineering-oriented company that provides customers with sophisticated tooling solutions," said Edwin Tonne, a training and technical expert. Horn is known for its grooving and cut-off turning tools and offers a wide range of product lines, including solid carbide end mills, drills and indexable milling cutters, as well as turning products. More than 40% of its cutting tools are special tools. Horn has developed multi-edge end mills for machining titanium, inconel, stainless steel and other high-temperature resistant metals, using high-speed and efficient machining strategies to achieve the highest MRR.
The following is a consensus report on interviews with application and sales engineers Tonne and Eric Carbone; John Kollenbroich, head of product management; and application and sales engineer Jeff Shope.
Not every part is suitable for high-speed machining. The choice of strategy is a function of part geometry and size. Some of the tests that have been seen require machining of Inconel, titanium and stainless steel with small depth of cut, high speed and low radial engagement and feed rates.
If it is a very shallow "part depth", the machinist will not be able to obtain the economy and high speed of the end mill, and will experience a lot of excessive vibration. The reason is that if the shop runs a shallower axial depth of cut, the MRR will be reduced, and the operation may not be as effective as other methods with larger radial and shallower axial steps.
These machining strategies require more than just the right carbide grades, inserts, and geometries—the approach to the material is also critical. The goal of efficient machining is to reduce the cutting width and increase the cutting length to reduce the cutting force, so as to achieve faster processing. Sometimes that will be faster, sometimes it will be faster with traditional high-feed tools. In many cases, dynamic processing may waste a lot of movement. Application It depends on the application and complexity of the features involved, such as pockets.
It is important to have the correct CAM software to avoid wasted fast movements, which will increase cycle time. Sometimes it is better to use a more traditional cutting channel. An example is when the cutting width is very short, such as using a 0.5" (12.7-mm) end mill, the purpose is to cut a part with a length of 0.5", and the process needs to remove 0.3" (7.62 mm). In this example, Horn It is recommended to remove all material in one or two passes instead of 30 passes. To improve efficiency, the tool must remain on the part and limit time-wasting retraction.
In addition to components, programming strategies and software also played a role. If the shop performs 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 expensive and wasteful actions.
Horn's solid carbide tools with 7 or 9 large DOCs and 10-15% steps (as a rule of thumb at the beginning) contribute to these strategies, but the machine must have the required acceleration and deceleration. Old machines with 600 ipm rapids are not enough. Likewise, the forward-looking nature of newer machines is also required.
Horn's DSFT end mills are part of the DS series of high-DOC, low-radial engagement tools and are specially designed for trochoidal machining. To be effective, DS tools require a robust machine spindle with tight runout and a powerful controller for programming. CAD programs can be used to create simulations of machining time estimates to determine whether traditional end milling or high-speed machining is best. In addition, there are many software tools that can be used to evaluate the economics of these tool decisions.
When using multi-edge tools for high-speed machining, the highest MRR may occur when the machining process is engaged with the entire blade length of the tool. The more grooves, the larger the core diameter for rigidity. Horn said that under normal circumstances, the first thing to consider when considering high-speed machining is the size of the part and the length of the groove to determine the diameter of the tool. A 3/8 inch (9.5 mm) diameter tool can handle an actual flute length of one inch, and a 5/8 inch (15.8 mm) diameter tool can handle a two inch actual flute.
The goal is to maximize the flute length, as this will provide the best MRR and steps of 5% and 10%. Another way to determine tool selection is to decide whether to simply switch to high-feed milling and use a traditional end mill to bevel and remove the blank.
According to Emuge of West Boylston, Massachusetts, the use of Circle Segment solid carbide end mills can reduce five-axis cycle time for molds, inserts, and other complex aerospace and medical parts by up to 90%. Machining may be familiar with using traditional ball end mills for small steps. Circular segment end mills use high step milling cutters 10 times larger than ball end mills to cut large areas of material, maximizing efficiency and maximizing To reduce the tip height.
According to the company, it saves time and costs and improves part quality. Due to the shorter tool path, tool life is increased. The tolerance deviation caused by the thermal warpage of the tool is minimized, the axial deviation of the machine is smoothed, and a higher quality surface finish is provided in a shorter time. The Circle Segment end mill has a unique shape with a large radius in the cutting area of the milling cutter, allowing a larger axial DOC during pre-finishing and finishing operations.
There are four geometric shapes for end mills: barrel, ellipse, cone and lens. Oval and tapered milling cutters are suitable for curved shapes, such as blades or straight wall grooves, which can freely engage more cutting edges. Emuge said that the barrel-shaped design milling cutter can effectively side mill the sides of spiral grooves and similar applications. Lens-shaped mills perform well in narrow passages or molds. Specific CAM system software (such as Mastercam and hyperMILL) is required to support and calculate geometric shapes.