High-speed CNC machining, or high-speed machining (HSM), is a method of working parts in the metalworking industry that is characterised by greater efficiency, precision and quality in the parts produced, compared with conventional processes.
What is high-speed machining?
This method, increasingly used in machine shops, is valued for the great benefits it brings. Besides producing more precise parts and improving efficiency, it has been shown that this technique reduces production times and requires little human intervention. As a result, production costs fall considerably, and so do lead times.
High-speed machining uses computer numerical control (CNC) technology, so the procedures are automated and require minimal operator intervention. But what is high-speed CNC? High-speed machining can be done in a single operation or in a combination of operations, depending on the machine used.
The term can refer to the cutting speed, spindle speed, feed rate or metal removal rate. In high-speed machining the spindle reaches speeds of 3,000 to 6,000 revolutions per minute and a diameter of 25 to 30 millimetres; as for speeds, these processes can machine at cutting speeds five to ten times faster than conventional methods.
In this type of machining, the depth and speed of cut, as well as the feed rate, depend on the parts being machined (shape, material, etc.).
Applications of high-speed CNC
The type of material to be machined plays a very important role in metalworking. Machining an aluminium part is not the same as machining one in steel or titanium; the hardness of the material and the dimensions of the part also have an influence. But one of the great advantages of high-speed CNC is that it can machine all kinds of parts. The versatility of the machines that allow this type of machining has led to their use in many different industries.
Besides metalworking, high-speed CNC is used in the aerospace sector, and also in the manufacture of dies and moulds. Both industries work with very resistant metals such as titanium, stainless steel and aluminium. Remember, for example, that in the manufacture of dies and moulds, large volumes of these components must be produced, that is, serial production in large quantities. That is why machining at high speed is highly advisable.
Advantages of high-speed machining
High-speed CNC has many advantages for the metalworking industry. To begin with, it replaces deep cuts at low cutting speed (common in conventional machining) with shallower cuts at higher speed; this means that more material is removed. The high cutting speed also reduces the cutting forces and the size of the chips.
Because these cutting forces are lower, it is possible to machine very thin walls, starting at 0.2 millimetres. This type of machining also allows much greater contour accuracy and improves the surface quality of the part. High-speed CNC allows almost all the heat generated during the process to be carried away through the chips and also reduces the coefficient of friction between the chips and the cutting tool.
Another advantage of this technique is that very hard steels can be machined and the service life of the cutting tool is also extended. Finally, as mentioned, production times are shortened, which reduces lead times; there is little need for operators to be present, which also helps to lower production costs.
What should a high-speed machine be like?
To obtain all the benefits of high-speed CNC machining, the machine and its tools must meet a series of requirements. The machine has to be able to respond to the required speeds, as well as to the profile to be produced. In addition, the CNC built into the machine must be able to anticipate how the cutting tool paths will change; for example, to switch between drilling and turning very quickly, or to rotate the part to the required angle.
The tools in the head must be highly wear-resistant and suited to the processes being run. Finally, for high-speed machining to work, it is essential to use CAM and CAD software that can create designs and strategies suited to this type of machining.