Copper as a ductile material - or about metal machinability and CNC machining
Much depends on the chemical composition and structure of metals. These characteristics affect their mechanical and thermal strength, as well as the susceptibility of individual materials to different types of machining.
One of these is machining, which is the removal of excess material. We explain what the susceptibility of metals to machining depends on and what the machinability indexes of materials are. You will also learn what CNC machining is and what CNC processes Electris offers.
Machining and machinability
Metals can be machined by many methods - such as casting, welding and machining. Machining involves removing successive layers of machining allowance and converting it into chips using appropriate tools.
Machining can be divided into two types of machining, which differ in the size and number of blades in the tools:
- chip machining (e.g. turning, drilling, milling);
- abrasive machining (e.g. grinding, honing).
Machinability, on the other hand, is an indicator of the susceptibility of a particular material to cutting, by which we obtain the desired properties of the machined surface. Machinability, in turn, is the ability of a particular tool to cut another metal.
Machinability is determined by such material properties as, for example, its chemical composition and structure, which is influenced by the technology of manufacture and preparation of the metal for machining. Yield strength, hardness, heat conductivity and other material characteristics depend on these factors.
Why is determining the metal's machinability important for industrial production? Thanks to this parameter, we know what workpiece materials to use to achieve the desired machining time and increase productivity. This, in turn, leads to a reduction in the costs needed to manufacture metal components.
Material machinability indices
Both material machinability and tool machinability are evaluated using the same criteria. The most important machinability indicators are:
- cutting resistance - these are determined by cutting forces, cutting power and cutting torque, which are relevant to the strength of tools and machine tool components and the energy required to remove the machining allowance in a certain amount;
- the quality of the machined surface - it is related, among other things, to the roughness of the metal being cut;
- blade life at an assumed cutting speed, or periodic cutting speed at an assumed blade life;
- the shape of the chips produced in the cutting process - this affects the risk of damage to the machining tool and the material being cut, as well as the risk of causing an accident at work; it is also related to the cost of storing and moving the chips.
It is not possible to unambiguously determine the order of machinability indicators in terms of their importance - depending on the type and degree of automation of machining, other indicators may gain in importance. For example, in rough machining, the most important criteria are cutting resistance and blade life, and in fine machining - the quality of the surface after machining.
In addition to this, we also distinguish a number of absolute machinability indexes that allow us to select the right metal in terms of the best cutting parameters:
- coefficient of friction,
- amplitude and frequency of vibration,
- mechanical properties of the metal,
- chip breakage coefficient,
- temperature in the cutting zone.
Machinability indexes of copper and its alloys
Pure copper is considered difficult to cut - it forms long and difficult to evacuate chips. Its alloys are much more machinable. For example, for automated production, copper with the addition of lead is excellent - the chips are then brittle. Brass, an alloy of copper and zinc, is also a material with favorable machinability rates. The more zinc, the lower the surface roughness of the cut part. An alloy that also achieves low roughness is bronze - a combination of copper and tin or other metals (copper content of 80-90% by weight). The machined surface properties of bronze are particularly well influenced by high cutting speed.
Why do copper alloys show good machinability? On the surface of some materials, overgrowth (sticking) form during cutting, through which the forces and temperature in the machining process increase, and as a result, the resulting surface does not have satisfactory properties. In the case of copper alloys, such a problem does not occur, so cutting is carried out efficiently and effectively - both in chip and abrasive machining.
If copper has such alloying additives as lead, selenium or tellurium, chip breakage and cutting forces are lower, and the temperature accompanying the machining process is lower. All of this ultimately leads to even better machinability.
What is CNC machining and what are its advantages?
CNC machining of copper and other metals involves the use of advanced computer-controlled machines to create precision parts. The process requires careful planning, programming and setup, but offers many advantages over traditional machining methods, including greater precision, flexibility and efficiency.
- One of the primary benefits is the ability to create highly precise and complex parts with tight tolerances. This level of precision can be difficult to achieve with traditional machining methods, which rely on manual labor and are more prone to human error.
- Another advantage of CNC machining is its ability to automate the manufacturing process. Once a design file is entered into a CNC machine, it can be left to run without the need for constant supervision or manual adjustments.
- CNC machining allows for a great deal of manufacturing flexibility, as it can be used to produce large production runs as well as small, small batches and even individual pieces.
How do we perform machining at Electris?
CNC machining service at Electris machinery park, is one of the processes we offer to our customers. By machining copper and copper alloys with CNC milling, CNC turning, CNC bending on our CNC machines, we get very good cutting parameters, and thus the right properties of the machined components. We have computer-controlled CNC 3-axis (3 AX) and 5-axis (5 AX) machining machines, thanks to which we realize the most demanding projects for our customers. Modern machines allow us to reduce milling time to the minimum necessary.