Importance of High Speed Milling Aluminum
The need for fast manufacturing, quick prototypes or custom parts in modern industry is increasing every month. Customers want their orders faster and need components to be more accurate than before. Aluminum is one of the most widely used alloys in modern production, it is light, strong, durable and corrosion-resistant.
One of the modern successful CNC aluminum machining methods is high-speed milling. The main difference compared to conventional milling is that the speeds of high-speed milling are much higher and the machinist can increase the cutting feed with them, which has many advantages.
1.Higher efficiency
By increasing the cutting speed to three times the speed of conventional milling aluminum, the feed can be increased by two times (for softer aluminum alloys). As we know, the machining feed is the parameter that defines the productivity of the entire milling process. That is, high-speed machining can be much more efficient than conventional milling. The machinability of aluminum can increase the spindle speed to 18000 rpm, or even higher.
Such high material removal rates make aluminum machining services a very profitable product for the automotive and aerospace industries. In the first case, automotive prototypes require a lot of material removal, and the milling settings are preferably as few as possible. In the second case, there are a lot of long and large parts with grooves and thin walls, and in addition, aluminum alloys are required for aircraft and rockets, which contain up to 80%.
2.Lower cutting temperature
It has been proven that the cutting temperature changes with increasing speed. First, as the speed increases, the temperature also increases. However, as the speed continues to increase, the temperature begins to drop sharply until at some point it no longer changes. Increasing the cutting speed will only reduce the temperature to a small extent. For example, when milling at 300-500 m/min, the temperature may reach 600-800 degrees. However, if the speed is increased to 1200, the temperature drops to less than 200 degrees, and at 1800 m/min the temperature is only 150 degrees. From that point on, faster cutting does not make sense.
Just think about it, only 150-200 degrees! Due to local heat treatment, the material properties of the cutting area do not change, metal grains do not increase, and the cooling requirements are much smaller. I would say this is a good advantage.
3.Longer Tool Life
It may seem strange that because the cutting speed is greater, so must the tool wear, but if we compare the amount of material removed by HSM’s aluminum cutting tools to conventional milling, instead of reducing tool life to a few minutes, we will see that the difference is obvious and can be said to be in favor of high-speed milling aluminum. What is the reason for the longer tool life? First, the cutting temperature is lower, which means the tool material is stronger. Then, the chip width is much smaller when milling at high speed (even though the feed rate is increased, the tool turns faster and manages to cut thinner chips).
In addition, one of the main problems when machining aluminum is that the aluminum is too soft and sticks to the cutting edge of the tool during machining. This reduces the sharpness of the tool and increases the cutting forces, which shortens the tool life. But this does not happen at high speeds.
4.Better Precision
We all think that higher feed rates will make the surface finish of aluminum less smooth because the cutting edge of the tool moves farther while the tool can turn and cut off. Generally, this results in wider chips, higher cutting forces, and a poorer surface finish. However, in HSM, despite the high feed rate, the tool speed is high, so the chip is actually thinner than in conventional milling.
5.Constant tool engagement angle
One of the main problems when milling a cavity with an end mill is making the cavity angle. The end mill must rotate 90 degrees to create the cavity, and at this point, the material it cuts must be doubled (from both sides of the cavity). This causes the cutting forces to increase locally and is very detrimental to tool life and part accuracy. However, HSM aluminum milling has many predetermined tool path generation strategies that include a constant tool engagement angle. This means that the tool gradually approaches this angle while machining all the material around it in a circular trajectory. This way, the cutting forces remain constant and the accuracy remains the same. In addition, tool life is extended.
6.Less use of coolant
Some HSM strategies for aluminum machining do not use coolant at all. What I mean by this is that machining at 200 degrees requires almost no cooling of the material and the tool. However, some extremely precise operations still use coolant to improve part quality, but the amount of coolant is much less than in conventional machining. Some aluminum high-speed milling processes use what is called minimum quantity lubrication. The amount of coolant applied is just enough to form a thin film, thereby reducing friction and providing some cooling.
It is therefore very clear that high-speed aluminum milling is an innovative production method for manufacturing custom parts, aluminum alloy prototypes, and small batch production.