Posted on May. 11th, 2020, | By WayKen Rapid Manufacturing
The pinnacle of human thought and engineering is rightfully reserved for the gigantic flying machines. Rockets, airplanes, and jets are impossibly hard to design and are even harder to produce. That is the reason why there are only 8 big companies in the world that make commercial planes in considerable volumes. An aircraft, space or just a flying one, has over 500 000 parts, a large portion of which must be extremely precise and durable. Ensuring that these parts have the best quality and cost is a vital aim of industrial aerospace machining.
Problems with the Production of Aerospace Parts
Aerospace precision machining has a lot of issues. First of all, the multitude of aerospace parts is made of a vast variety of materials. The engine elements being the most crucial in the work of the aircraft are made of heat-resistant hardened alloys that are extremely hard to machine. Those alloys conduct heat poorly and so the heat during the processing builds up in the tool. The nickel alloys are often aged or otherwise heat treated so they are very hard to machine. The precision of aerospace parts is much more strict compared to other industries while the geometries of the parts are much more complex.
Apart from direct machining issues, there are a lot of indirect problems. One of them includes production standards. Along with the medical industry, aerospace production is one of the most regulated in the world and meeting all the quality requirements is hard.
Machining Thin-walled Aerospace Parts Efficiently
Weight is extremely crucial for airspace vehicles. The lighter the design, the less fuel it will consume so aerospace engineers often design parts with thin walls, lattices, webs, and so on. Conventionally, they are machined from a solid cast or stamped block of metal and the waste material of such parts is 95%. However, low material efficiency isn't the only problem. The actual issue when machining such parts is the deformation because of high cutting forces. If you increase the feed and cut depth too much, especially with nickel alloys, you risk shattering the walls because of vibration or deforming them because of the excess heat. The result is usually that you cut a tiny chip off at a crawling feed and the total machining time is impossibly large.
What can you do to decrease the machining time and actually machine thin-walled aerospace parts competitively? The first thing you have to do is decrease vibration. The vibrating tool strikes a thin wall and it bends or cracks. So, in order to decrease vibration, it is better to decrease the feed but increase the number of cutting edges in a mill ( or even use multiple cutting tools on a lathe). The optimal cutting strategy for milling thin-walled aerospace parts is climb milling. This strategy uses a feed that goes in the opposite direction from the conventional milling strategy. This leads to a smaller cutting force, better surface finish and most importantly the mill enters the material where the wall is thickest thus the vibration is much smaller. In order to countermand the overheating, it is necessary to use progressive high-pressure coolants.
Trochoidal Machining Paths to Reduce Overheating in Aerospace Alloys
Part overheating because of poor heat conduction is a typical problem for aerospace parts. One machining strategy to reduce heat build-up is called trochoidal milling. It greatly utilizes the capabilities of CNC machines to follow complex cutting paths. The trochoidal strategy uses a small mill (smaller than the cut anyway) that follows a path similar to a spring side projection on a flat surface. One curve - the mill cuts, then it goes back during the second curve and then cuts the metal again. This strategy portions the time of contact between the tool and the part so that there is a moment for both to be efficiently cooled down by the cutting fluids. Trochoidal turning is similar to milling, using short cutting and pausing sequences to let the coolants do their work and avoid overheating. Such a strategy has much more empty tool runs compared to other strategies but it negated this effect by increasing the cutting speeds and feeds. At Wayken, we also can offer EDM Machining maybe can avoid machining parts.
Choosing the Right Tools For Fast Machining
When comes to mind the machine tools, CNC machines play a great role and it has widely applicable to Aluminum machining. One of the most important ways to increase the efficiency of machining is choosing the correct cutting tool. If softer alloys are well analyzed and a lot of manufacturers offer solutions for aluminum and other alloys. However, a lot of aerospace materials are classified and so the choice must be made on the spot.
The tricks to efficient tool choice for heat resistant materials must counteract the negative properties of the materials. So, a perfect tool must have little vibration, must be very hard, and must withstand high temperatures to have a consistent life and work at efficient feeds. A perfect example of a tool used for such purposes is the diamond cutting tool. Artificial diamonds are harder and more durable than carbide inserts and can work at higher temperatures. Diamond machining has its specifics but it can certainly be modified to suit the needs of aerospace manufacturers. Apart from diamond tools, ceramic tools prove to have a great performance as well because they can work at the highest temperatures.
In order to decrease the vibrations of the processed parts, it is important to use mills with more cutting edges and a sharper flute angle. Such mills minimize the time and distance the tool passes before the next cutting edge hits the material thus decreasing vibration and with that, you can increase cutting parameters for more efficiency.
Systems That Ensure the Quality of Machining
Before using any strategy and starting the processing, it is important to estimate whether the quality of the part can be achieved at the desired time. How can we predict the final tolerance, surface finish and the time of machining before doing it? It wasn't possible just a short while ago but it is now due to a staggering rate at which the mathematical modeling techniques develop. Finite element analysis has reached a level where you can simulate the cutting processes with good precision. So, you can upload your model and look at the actual cutting forces and heat dissipation and how it will influence the final part. You can see residual stresses, deformations and so on even before you install a blank on the CNC machine tool. This technology offers great advantages to predict the outcome of machining and decreases time left for re-runs.
How WayKen Can Help You?
Here, we have invested heavily in advanced CNC machining technology and multi-axis-machines that enable us to easily and fast process trial runs, customized short runs, or low- volume production runs. We can meet your needs for machined parts when you can upload CAD files today for a free quotation.