6 High-speed Machining Tips for Milling Aluminum


Posted on August. 30th, 2019, | By WayKen Rapid Manufacturing

The modern industry needs parts done very fast. Rapid prototypes or custom parts demand to rise higher every month. The clients want their orders faster and need the components to have more accuracy than before. One of the most widespread alloys for modern production is aluminum, seemingly the best material there can be. It is lightweight, strong, durable, and resistant to corrosion. That’s why new milling aluminum strategies are developed rapidly.

One of the modern successful CNC aluminum milling methods is called High-Speed Machining. The main difference compared to conventional milling is that the speeds of high-speed milling are considerably higher, and with them, the machinists can increase cutting feeds. As a result, HSM milling aluminum is very advantageous in a number of unexpected ways. Here is what you will gain by choosing  HSM strategies for aluminum instead of using conventional milling.

The Efficiency is Much Higher

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By increasing the cutting speed up to 3 times as fast as conventional aluminum milling, it is possible to increase the feeds up to 2 times ( in cases for softer aluminum alloys ). As far as we know, machining feeds are the parameters that define the productivity of the whole milling process. That being said, high-speed machining efficiency can be much compared to conventional milling. Aluminum machinability makes it possible to increase spindle revolution speeds up to 18000 rpm and more, thus making material removal rates scary.

Such material removal rates make aluminum machining services using HSM strategies for aluminum a very lucrative offer for automotive and aerospace industries. In the first case, automotive prototypes require a lot of material removal with preferably as few milling setups as possible. In the second case, there are a lot of long and large parts that have deep pockets ( they must be lightweight so they are mostly machined down to a set of intersecting ribs) and thin walls, in addition, aluminum alloys are what planes and rockets consist of up to 80%.

The Temperature of the Cut

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It has been proved that the temperature of the cut changes with the increase of the speed. At first, as the speed grows, so does the temperature. However, as we go further, the temperature starts to go down drastically until, at some point, it stops to matter. Increasing cutting velocity will only lower the temperature to a small degree. This transition is what signifies HSM. For example, when milling aluminum at 300-500 m/min, the temperatures may reach 600-800 degrees. However, if we increase the velocity up to 1200, the temperature goes down to less than 200 degrees, and it is a mere 150 degrees at 1800 m/min. From that point on cutting faster is pointless.

Just consider, a mere 150-200 degrees! No material property change in the area of the cut due to local thermal processing, no metal grain increase, and much smaller demands to cooling. A good advantage, I’d say.

Tools Live Longer

It may seem strange because the speed of the cut is larger and so tool wear must be as well, but if we compare the amount of material that gets cut by the aluminum cutting tools at HSM with conventional milling rather than tool life in minutes, we’ll see that the difference is evident and speaks in High-speed milling aluminum favor. What’s the reason for a prolonged tool life? First, the cutting temperature is lower and that means tool material strength is higher. Then, chip width during high-speed milling is much lower ( the tool turns faster and manages to cut off a thinner chip even despite increased feeds).

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In addition, when machining aluminum, one of the main issues is that it is so soft, it sticks to the cutting edges of the tool during processing. This lowers tool sharpness and increases cutting forces hence decreases tool life. But that doesn’t happen at high speeds. Aluminum just leaves.

The Precision of High-Speed Milling Aluminum

We all think that higher feeds make the aluminum surface finish lower because the tool cutting edge travels further while the tool can make a turn and cut it off. Generally, this results in a wider chip, higher cutting force, and a worse surface finish. However, in HSM despite the feed being larges, the velocity of the tool is higher, so the chip is actually thinner than in conventional milling. In addition, vibration is lower because of a smaller cutting force.

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Constant Tool Engagement Angle

One of the major problems when milling part cavities with end mills is concerned with manufacturing pocket angles. The end mill must turn 90 degrees in order to produce the pocket and at that moment, the material it has to cut doubles ( from both sides of the pocket). This results in a local increase in cutting force and is very bad for tool life and part precision. However, HSM aluminum milling has a number of predetermined tool path generation strategies that include a constant tool engagement angle. That means the tool gets gradually closer to the angle while machining all the material around it in a circular trajectory. That way, the cutting force remains constant and so does the precision. in addition, tool life is prolonged.

Coolant Use

Some HSM strategies for aluminum machining don’t use coolants at all. I mean, machining at 200 degrees hardly requires any cooling of both the material and the cutter. However, some extremely precise operations still use coolants in order to increase part quality but the quantity of the coolant is much lower compared to conventional machining. Some aluminum high-speed milling processes use the so-called minimum quantity lubrication. The amount of coolant administered is just enough to make a thin film that lowers friction and offers some cooling.

So, it is quite evident that High-speed aluminum milling is an innovative and productive way to manufacture custom parts, prototypes, small batches, and other sets made of aluminum alloys. With high-speed machining, you will get better prices and will spend less time waiting for your order to be fulfilled.

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