CAM programmed in hyperMILL.

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What is CNC machining?

CNC stands for computer numerical control. CNC machining is therefore any type of machining process that is controlled by a computer. Automation allows parts to be made faster, more precisely, and with more complex geometries than parts produced via manual machining. CNC also reduces the manual machining labor that would otherwise be done by humans. Although they don't machine every part themselves, people are essential for programming and operating the machines so that every operation runs smoothly.

About the CNC machining process

CNC, or computer numerical control machining, is a subtractive manufacturing method that uses a combination of computerized controls and machine tools to remove layers from a solid block of material. The desired cuts in the metal are programmed according to the associated tools and machines, which perform the machining task automatically.

Types of CNC Machining

Depending on the type of part that needs to be machined, there are different types of CNC machines that are best suited for the job. CNC milling uses CNC mills, which consist of a multi-axis system (three, four or five axes, depending on the complexity of the part). CNC turning involves lathe machines, which generally have two axes and cut pieces with a circular motion. Electrical discharge machines (EDM) use electric sparks to mold workpieces into the desired shape. Hobbing is another type of machining process used for cutting gears, splines and sprockets. Other types of CNC machines include plasma cutters and waterjet cutters.

How does CNC machining work?

The programs used for CNC machining today are written with G-code and are usually created automatically by CAM software. CAM, or computer-aided manufacturing software, generates the G-code for a 3D model using certain tools and workpiece materials. This G-code controls the CNC machines, i.e. the movement of the tool, the workpiece and any tool changes. It even has commands to turn the coolant and other auxiliary components on or off.
CNC machining can be used on a wide variety of materials, with aluminum, steel, brass, ABS, Delrin and nylon being the most common. But in fact, almost any hard material can be CNC-milled. We will discuss the materials in more depth later.

CNC vs 3D printing

Compared to parts production via additive methods, CNC machined parts are functionally stronger and typically have superior production quality and finish. Therefore, CNC machining is typically used in the mid to late stages of development, when parts are ready to be tested for functional accuracy.

CNC design considerations

Although most of the details, such as tooling, spindle speed, cutter type, and depth of cut, are handled in the machine shop, there are some important things you can do when designing your parts to not only ensure they can be made, but ensure also ensure that you develop a streamlined product that does not cost a lot of money.

The main benefits of CNC machining include rapid prototyping and the ability to quickly produce full-scale production parts. It provides a high degree of precision and accuracy in part manufacturing and enables close tolerance machining for CNC parts of any size. It also offers maximum flexibility in terms of volume, prices, lead times and the range of materials and finishes used.

The two main CNC machining processes are CNC turning and CNC milling. Other machining processes include drilling, gear milling and electrical discharge machining.

Industries that use CNC machining include the aerospace industry, automotive parts manufacturing, medical machinery manufacturing, transportation, defense and maritime industries, along with the oil and gas and electronics industries. CNC machining has made these industries more efficient at mass-producing custom CNC parts.

The standard machining tolerance is 0.005/" or 0.13 mm. Tolerances are the allowable range for a dimension. If a CNC machining tool has a tolerance of 0.01 mm, this means that the machining tool will have a deviation of 0.01 with each cut mm. With a drawing, Fictiv's CNC machining service can produce CNC parts with a tolerance as small as 0.0002 inches. Without a drawing, all CNC parts are produced to our ISO 2768 medium standard. We can also machine with closer tolerances, 0.025 mm or 0.001/.

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