The hottest titanium alloy aviation parts milling

2022-10-14
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Titanium alloy aviation parts milling tools

the design of the new Boeing 787 dream liner aircraft widely depends on the application of various composite materials, which has naturally attracted people's attention. However, the extensive application of composite materials is not this kind of aircraft. Is it certain that the elongation of the material after fracture will not change once it is 1? For example, the one I just made is the only reason why it is different in 10%. Compared with other commercial airliners, Boeing 787 also uses more titanium alloy parts. In order to meet the orders for this type of aircraft and only to process these titanium alloy parts, Boeing will need to use at least 1000 machine tools (spindles) in the next 3 to 5 years. This estimate comes from Keith young, an engineer and scientist at Boeing's advanced manufacturing technology research and development group (St. Louis, Missouri). One of Dr. Young's tasks is to help these machining machines work more efficiently for Boeing. The challenge of machining Aerospace titanium alloy parts is to make the parts lighter by thinning the side wall and base of the parts, and by reducing the additional weight of the blank left at the corners of the parts. Through experiments, Dr. young and his research team have developed processing technologies that can achieve this goal. They told the designers of Boeing that it is completely possible to make the processed titanium alloy parts have the above characteristics; At the same time, they also guide processing providers how to realize this kind of processing

some titanium alloy processing technologies have been successfully developed in the production of titanium alloy parts of military warplanes. However, there are great differences between commercial airliners and military fighter planes in terms of scale. The size of parts of airliners (especially the cavity depth) is larger. For example, the cavity depth of a military fighter part is 3 inches, while the cavity depth of Boeing 787 titanium alloy parts can reach 6 inches. However, the aspect ratio of traditional cutting tools used for machining Aerospace titanium alloy parts is usually 3:1 or 4:1, while the aspect ratio of cutting tools required for machining these new parts is 6:1 or 8:1. And these fundamental differences will affect the choice of tool system. For example, the machine clamp blade milling cutter can usually use steel, and then divide the peel strength of each punctuation point by the width of each punctuation point to make the tool handle, while the machining of deeper cavity requires the use of cemented carbide tool handle with higher rigidity, so as to reduce the bending deformation of the tool and prevent vibration

tom Talley is also an engineer and scientist of Boeing advanced manufacturing technology R & D group. Like Dr. young, he knows very well how to choose a tool system suitable for processing the latest generation of titanium alloy parts. The content of this paper is based on the recommendations of these two experts. But they also pointed out that the effectiveness of these recommendations needs to be verified. Although Boeing may have certified these processing technologies, it has not certified the tool manufacturer. Some tool manufacturers mentioned in this article are because experts believe that their products are clear examples of applicable tool types. In most cases, other tool manufacturers can also provide similar products. For a specific machining task, other tools may also be a more effective choice. The tool mentioned in this article is only used to describe the tool characteristics suitable for the machining characteristics of parts, which are increasingly important to Boeing

rough machining tool

weldon crest Kut tool is characterized by irregular geometry along the spiral groove. The important function of this irregular geometry is to eliminate chatter. In many milling processes, chatter is a limiting factor. It will intensify at a specific cutting depth, which usually restricts the tool from obtaining the larger cutting depth allowed by the tool and spindle in other cases. The chattering phenomenon is partly caused by the regular waveform reflected on the machined surface by the regular geometry of the tool. The tool spiral groove with irregular geometry will not produce such regular waves, so the "signal" that may provide chattering potential is very weak, so that this tool can cut efficiently and smoothly at the cutting depth where a high metal removal rate can be obtained

in order to obtain high metal removal rate in titanium alloy processing, another completely different method is to use insert milling rough machining. For aviation parts made of aluminum alloy, insert milling is of little significance, and conventional milling is fast enough. However, for titanium alloys, plunge milling can provide a processing method to quickly cut a large number of workpiece materials at a low cutting speed

during insert milling rough machining, the milling cutter can feed into the workpiece blank like a drill, and the material is gradually cut off through multiple overlapping insert milling, and each insert milling takes advantage of the inherent rigidity of the machine tool in the z-axis direction. Iscar's central cutting tool is an example of this kind of insert milling cutter, which can quickly cut workpiece material through z-axis feed

Dr. Yong pointed out that for titanium alloy processing, z-axis plug milling rough machining can be considered in two cases: ① machining shallow and wide cavities; ② Process narrow and deep cavities

for shallow cavities, deep cutting end mills (such as Weldon cutters) may not be able to obtain sufficient axial depth to give full play to their cutting efficiency. However, if the cavity has enough width and is suitable for continuous insert milling with large-diameter tools, the rough machining with insert milling may be more efficient. On the other hand, for narrow and deep cavities, the end milling cutter may need to spend too much time walking on the slope instead of effective milling, while the insert milling rough machining tool can use the insert milling depth of each feed to realize the efficient machining of such cavities

no matter what tool and processing method you choose to quickly cut a large number of blank materials, it is important to note that not all titanium alloy parts need rough machining. Recently, many titanium alloy parts use laser deposition near net shape workpiece, only need to finish machining. Finish machining is also a processing procedure to realize the use value of parts by machining a challenging workpiece morphology. Therefore, the choice of finishing tools is more important than that of roughing tools

bottom and corner finishing tools

data flute's finishing end mills also use irregular tool geometry (the included angle between the tool slots is not 90 °) to suppress chatter. The spatial positions of the four cutter slots are not symmetrically distributed at 90 °, but slightly changed. This irregular arrangement of the tool tips can make the tool tips in the proper machining position when finishing the bottom surface and corners

in finish machining, the harm of chattering is more serious than that in rough machining. During rough machining, chattering will only affect the machining efficiency; However, in finish machining, chattering may cause damage to the workpiece itself, because chattering may affect the accuracy and finish of the workpiece, and may even damage the precise shape structure of the workpiece (such as extremely thin ribs and side walls). Therefore, whether irregular geometry is used or not, the tool used for finishing titanium alloy parts should usually have good rigidity to minimize the impact of chatter. In addition, better rigidity can reduce the danger of deformation of the tool when machining in the deep cavity

the precision insert milling cutter of Ingersoll tool company can process small corner radius in deep cavity through z-axis feed. Dr. young pointed out that such tools may need to use cemented carbide tool holders instead of steel tool holders to maximize the rigidity of the tools

side wall and rib finishing tools

data flute is a 10 slot precision milling tool used to process thin-walled titanium alloy parts and ribs. Because the feed rate is a function of the number of tool slots and chip load, the tool can quickly cross cut the workpiece even when the chip load is very small. The spiral groove of the tool is shallow, which is conducive to increasing rigidity. Because the tool is designed for small depth cutting, it just needs a shallow groove depth, and the result is that the tool core diameter is larger and the stiffness is higher; A shorter slot length also helps maintain good rigidity

this tool has another potentially important structural feature. Mr. Talley pointed out that the tool used for finishing the side walls and ribs of titanium alloy parts should have an eccentric back angle along the spiral groove, which can reduce vibration by interacting with the machined surface to suppress vibration

the workshop that often processes the thin-walled structure of aluminum alloy aviation parts may already know how to use end mills to process the thin-walled structure of titanium alloy parts. It is obvious that the tool should adopt carburized layer "Waterline processing" mode, cutting from both sides of the thin-walled or ribbed plate, so that the thin-walled or ribbed plate can retain a balanced supporting effect from both sides during the workpiece forming process

as for the question of how much material allowance should be removed by the finishing tool, Dr. Young said that in fact, the tool itself provides a clue to solve this problem. According to experience, the height thickness ratio (height/thickness) of the finished product should match the length diameter ratio (length/diameter) of the finishing tool in the design and manufacturing process of the rough machined workpiece. In other words, if the rib is to be finely milled with a tool with a length diameter ratio of L ∶ d = 6 ∶ 1, the thickness of the rough milled rib should be about 1/6 of the length of the rib. Of course, this is only a rule of thumb and does not take into account the difference between the elastic modulus of the tool and the workpiece material. But the fundamental point is that the thin wall or rib supported by the material left after rough machining should be roughly equivalent to the stiffness of the finishing tool, not higher. If the rough machining leaves too much material allowance that needs to be cut by the finishing tool, so that the rigidity of the thin wall or rib plate is higher, it will waste processing time and affect the tool life. The excess stiffness of the workpiece is not beneficial, because the result is the same whether it is tool deformation or workpiece deformation. If it has been determined that a certain stiffness is appropriate for the tool, then the same stiffness is also appropriate for the workpiece material to be processed by the tool. (end)

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