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Home - News - Discussion on the advantages of five axis cnc machining for aviation parts

Discussion on the advantages of five axis cnc machining for aviation parts

December 6, 2022

There are more than 500000 parts in an airplane, a space plane or just a flying airplane, and a large part of them must be very precise and durable. Ensuring that these parts have the best quality and cost is an important goal of industrial aerospace processing.

Problems in the production of aviation parts
There are many problems in aerospace five axis precision machining. First, a large number of aerospace components are made of a wide range of materials. The most critical engine components in aircraft work are made of heat-resistant hardening alloys that are extremely difficult to machine. The thermal conductivity of these alloys is poor, so the heat during processing will accumulate in the tools. Nickel alloys are usually aged or otherwise heat treated and therefore difficult to machine. Compared with other industries, the precision of aerospace parts is much stricter, and the geometric shape of parts is much more complex.

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In addition to direct processing problems, there are many indirect problems. One of them includes production standards. Like the medical industry, aerospace production is one of the most regulated industries in the world, and it is difficult to meet all quality requirements.
Weight is extremely important for airspace aircraft. The lighter the design, the less fuel is consumed, so aerospace engineers often design parts with thin walls, lattices, webs, etc. Traditionally, they are machined from solid cast or stamped metal blocks, and the scrap of such parts is 95%. However, low material efficiency is not the only problem. The actual problem when machining such parts is the deformation caused by high cutting force

If you increase the feed rate and cutting depth too much, especially for nickel alloys, the wall may be broken due to vibration or deformed due to overheating. The result is usually that you cut off a tiny chip when crawling, and the total processing time is impossible.
What can you do to reduce processing time and actually process competitive thin-walled aerospace parts? The first thing you must do is reduce the vibration. The vibrating tool hits the thin wall and bends or breaks. Therefore, in order to reduce vibration, it is better to reduce the feed rate but increase the number of cutting edges of the milling cutter (even using multiple cutters on the lathe). The best cutting strategy for thin-walled aerospace parts is forward milling.
This strategy uses feed in the opposite direction to the traditional milling strategy. This results in less cutting force, better surface finish, and most importantly, the milling cutter enters the material with the thickest wall thickness, so the vibration is much smaller. To deal with overheating,

Cycloidal machining path for reducing overheating of aerospace alloys
Overheating of parts due to poor heat conduction is a typical problem of aviation parts. A machining strategy to reduce heat accumulation is called cycloidal milling. It makes great use of the functions of CNC machine tools to follow complex cutting paths. The cycloid strategy uses a small milling cutter (smaller than the cutting in any case) that follows a path similar to the side projection of a spring on a plane. One curve - the cutter cuts, then returns during the second curve, and then cuts the metal again. This strategy allocates the contact time between the tool and the part so that there is time for the cutting fluid to effectively cool both.

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Cycloidal turning is similar to milling, using short cutting and pause sequences to allow the coolant to function and avoid overheating. This strategy has more empty tool runs than other strategies, but it counteracts this effect by increasing cutting speed and feed.
Select the right tool for rapid machining

Speaking of machine tools, numerical control machine tools have played a great role, and they have been widely used in aluminum processing. One of the most important ways to improve machining efficiency is to choose the right tool. If the softer alloy is well analyzed, and many manufacturers provide solutions for aluminum and other alloys. However, many aerospace materials are classified, so they must be selected on site.

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The technique of selecting effective tools for heat-resistant materials must counteract the negative characteristics of the material.
Therefore, a perfect tool must have very small vibration, must be very hard, and must be able to withstand high temperatures to have a consistent service life and efficient feeding. A perfect example of a tool for this purpose is a diamond cutting tool.
Artificial diamond blades are harder and more durable than cemented carbide blades, and can work at higher temperatures. Diamond machining has its particularity, but it can certainly be modified to meet the needs of aerospace manufacturers. In addition to diamond tools, ceramic tools have also proved to have excellent performance because they can work at the highest temperature.
In order to reduce the vibration of machined parts, it is important to use milling cutters with more cutting edges and more sharp edge angles. This type of milling cutter minimizes the time and distance that passes before the next cutting edge hits the material, reducing vibration, and you can increase cutting parameters to improve efficiency.